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Nectar of camellia
Orange-yellow nectaries and greenish nectar in buckwheat flowers
An Australian painted lady feeding on a flower's nectar
Gymnadenia conopsea flowers with nectar-filled spur

Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide herbivore protection. Common nectar-consuming pollinators include mosquitoes, hoverflies, wasps, bees, butterflies and moths, hummingbirds, honeyeaters and bats. Nectar is an economically important substance as it is the sugar source for honey.

Nectar is also useful in agriculture and horticulture because the adult stages of some predatory insects feed on nectar. For example, a number of predacious or parasitoid wasps (e.g., the social wasp species Apoica flavissima) rely on nectar as a primary food source. In turn, these wasps then hunt agricultural pest insects as food for their young.[1]

Nectar is most often associated with flowering plants (angiosperms), but it is also produced by other groups, including ferns.[2]

Etymology

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Nectar is derived from Greek νέκταρ, the fabled drink of eternal life.[3] Some derive the word from νε- or νη- "not" plus κτα- or κτεν- "kill"[citation needed], meaning "unkillable", thus "immortal". The common use of the word "nectar" to refer to the "sweet liquid in flowers", is first recorded in AD 1600.[3]

Floral nectaries

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A nectary or honey gland is floral tissue found in different locations in the flower and is one of several secretory floral structures, including elaiophores and osmophores, producing nectar, oil, and scent respectively. The function of these structures is to attract potential pollinators, which may include insects, including bees and moths, and vertebrates such as hummingbirds and bats. Nectaries can occur on any floral part, but they may also represent a modified part or a novel structure.[4] The different types of floral nectaries include:[5]

  • receptacle (receptacular: extrastaminal, intrastaminal, interstaminal)
  • hypanthium (hypanthial)
  • tepals (perigonal, tepal)
  • sepals (sepal)
  • petal (petal, corolla)
  • stamen (staminal, androecial: filament, anther, staminodal)
  • pistil (gynoecial: stigmatic, stylar)
    • pistillodes (pistillodal, carpellodial)
    • ovaries (ovarian: non-septal, septal, gynopleural)

Most members of Lamiaceae have a nectariferous disc which surrounds the ovary base and derived from developing ovarian tissue. In most Brassicaceae, the nectary is at the base of the stamen filament. Many monocotyledons have septal nectaries, which are at the unfused margins of the carpels. These exude nectar from small pores on the surface of the gynoecium. Nectaries may also vary in color, number, and symmetry.[6] Nectaries can also be categorized as structural or non-structural. Structural nectaries refer to specific areas of tissue that exude nectar, such as the types of floral nectaries previously listed. Non-structural nectaries secrete nectar infrequently from non-differentiated tissues.[7] The different types of floral nectaries coevolved depending on the pollinator that feeds on the plant's nectar. Nectar is secreted from epidermal cells of the nectaries, which have a dense cytoplasm, by means of trichomes or modified stomata. Adjacent vascular tissue conducts phloem bringing sugars to the secretory region, where it is secreted from the cells through vesicles packaged by the endoplasmic reticulum.[8] The adjacent subepidermal cells may also be secretory.[4] Flowers that have longer nectaries sometimes have a vascular strand in the nectary to assist in transport over a longer distance.[9][4]

Pollinators feed on the nectar and depending on the location of the nectary the pollinator assists in fertilization and outcrossing of the plant as they brush against the reproductive organs, the stamen and pistil, of the plant and pick up or deposit pollen.[10] Nectar from floral nectaries is sometimes used as a reward to insects, such as ants, that protect the plant from predators. Many floral families have evolved a nectar spur. These spurs are projections of various lengths formed from different tissues, such as the petals or sepals. They allow for pollinators to land on the elongated tissue and more easily reach the nectaries and obtain the nectar reward.[6] Different characteristics of the spur, such as its length or position in the flower, may determine the type of pollinator that visits the flower.[11]

Defense from herbivory is often one of the roles of extrafloral nectaries. Floral nectaries can also be involved in defense. In addition to the sugars found in nectar, certain proteins may also be found in nectar secreted by floral nectaries. In tobacco plants, these proteins have antimicrobial and antifungal properties and can be secreted to defend the gynoecium from certain pathogens.[12]

Floral nectaries have evolved and diverged into the different types of nectaries due to the various pollinators that visit the flowers. In Melastomataceae, different types of floral nectaries have evolved and been lost many times. Flowers that ancestrally produced nectar and had nectaries may have lost their ability to produce nectar due to a lack of nectar consumption by pollinators, such as certain species of bees. Instead they focused on energy allocation to pollen production. Species of angiosperms that have nectaries use the nectar to attract pollinators that consume the nectar, such as birds and butterflies.[13] In Bromeliaceae, septal nectaries (a form of gynoecial nectary) are common in species that are insect or bird pollinated. In species that are wind pollinated, nectaries are often absent because there is no pollinator.[14] In flowers that are generally pollinated by a long-tongued organism such as certain flies, moths, butterflies, and birds, nectaries in the ovaries are common because they are able to reach the nectar reward when pollinating. Sepal and petal nectaries are often more common in species that are pollinated by short-tongued insects that cannot reach so far into the flower.[15]

Secretion

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Nectar secretion increases as the flower is visited by pollinators. After pollination, the nectar is frequently reabsorbed into the plant.[16] The amount of nectar in flowers at any given time is variable due to many factors, including flower age,[17] plant location,[18] and habitat management.[19]

Extrafloral nectaries

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See also: Myrmecophily and Plant defenses against herbivory
Extrafloral nectaries with droplets of nectar on the petiole of a wild cherry (Prunus avium) leaf
Extrafloral nectaries on a red stinkwood (Prunus africana) leaf

Extrafloral nectaries (also known as extranuptial nectaries) are specialised nectar-secreting plant glands that develop outside of flowers and are not involved in pollination, generally on the leaf or petiole (foliar nectaries) and often in relation to the leaf venation.[20][21] They are highly diverse in form, location, size, and mechanism. They have been described in virtually all above-ground plant parts—including stipules, cotyledons, fruits, and stems, among others. They range from single-celled trichomes to complex cup-like structures that may or may not be vascularized. Like floral nectaries, they consist of groups of glandular trichomes (e.g., Hibiscus spp.) or elongated secretory epidermal cells. The latter are often associated with underlying vascular tissue. They may be associated with specialised pockets (domatia), pits or raised regions (e.g., Euphorbiaceae). The leaves of some tropical eudicots (e.g., Fabaceae) and magnoliids (e.g., Piperaceae) possess pearl glands or bodies which are globular trichomes specialised to attract ants. They secrete matter that is particularly rich in carbohydrates, proteins and lipids.[20][22][23]

Ants on extrafloral nectaries in the lower surface of a young Drynaria quercifolia frond

While their function is not always clear, and may be related to regulation of sugars, in most cases they appear to facilitate plant insect relationships.[20] In contrast to floral nectaries, nectar produced outside the flower generally has a defensive function. The nectar attracts predatory insects which will eat both the nectar and any plant-eating insects around, thus functioning as "bodyguards".[24] Foraging predatory insects show a preference for plants with extrafloral nectaries, particularly some species of ants and wasps, which have been observed to defend the plants bearing them. Acacia is one example of a plant whose nectaries attract ants, which protect the plant from other insect herbivores.[20][21] Among passion flowers, for example, extrafloral nectaries prevent herbivores by attracting ants and deterring two species of butterflies from laying eggs.[25] In many carnivorous plants, extrafloral nectaries are also used to attract insect prey.[26]

Loxura atymnus butterflies and yellow crazy ants consuming nectar secreted from the extrafloral nectaries of a Spathoglottis plicata bud

Charles Darwin understood that extrafloral nectar "though small in quantity, is greedily sought by insects" but believed that "their visits do not in any way benefit the plant".[27] Instead, he believed that extrafloral nectaries were excretory in nature (hydathodes). Their defensive functions were first recognized by the Italian botanist Federico Delpino in his important monograph Funzione mirmecofila nel regno vegetale (1886). Delpino's study was inspired by a disagreement with Darwin, with whom he corresponded regularly.[27]

Extrafloral nectaries have been reported in over 3941 species of vascular plants belonging to 745 genera and 108 families, 99.7% of which belong to flowering plants (angiosperms), comprising 1.0 to 1.8% of all known species. They are most common among eudicots, occurring in 3642 species (of 654 genera and 89 families), particularly among rosids which comprise more than half of the known occurrences. The families showing the most recorded occurrences of extrafloral nectaries are Fabaceae, with 1069 species, Passifloraceae, with 438 species, and Malvaceae, with 301 species. The genera with the most recorded occurrences are Passiflora (322 species, Passifloraceae), Inga (294 species, Fabaceae), and Acacia (204 species, Fabaceae).[22] Other genera with extrafloral nectaries include Salix (Salicaceae), Prunus (Rosaceae) and Gossypium (Malvaceae).[25]

Nylanderia flavipes ant visiting extrafloral nectaries of Senna

Foliar nectaries have also been observed in 101 species of ferns belonging to eleven genera and six families, most of them belonging to Cyatheales (tree ferns) and Polypodiales.[28][22] Fern nectaries appear to have evolved around 135 million years ago, nearly simultaneously with angiosperms. However, fern nectaries did not diversify remarkably until nearly 100 million years later, in the Cenozoic, with weak support for a role played by arthropod herbivore diversifications.[29][30] They are absent in bryophytes, gymnosperms, early angiosperms, magnoliids, and members of Apiales among the eudicots.[22] Phylogenetic studies and the wide distribution of extrafloral nectaries among vascular plants point to multiple independent evolutionary origins of extrafloral nectaries in at least 457 independent lineages.[22]

Components

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The main ingredients in nectar are sugars in varying proportions of sucrose, glucose, and fructose.[31] In addition, nectars have diverse other phytochemicals serving to both attract pollinators and discourage predators.[32][7] Carbohydrates, amino acids, and volatiles function to attract some species, whereas alkaloids and polyphenols appear to provide a protective function.[32] The Nicotiana attenuata, a tobacco plant native to the US state of Utah, uses several volatile aromas to attract pollinating birds and moths. The strongest such aroma is benzylacetone, but the plant also adds bitter nicotine, which is less aromatic, so may not be detected by the bird until after taking a drink. Researchers speculate the purpose of this addition is to discourage the forager after only a sip, motivating it to visit other plants, therefore maximizing the pollination efficiency gained by the plant for a minimum nectar output.[7][33] Neurotoxins such as aesculin are present in some nectars such as that of the California buckeye.[34] Nectar contains water, essential oils, carbohydrates, amino acids, ions, and numerous other compounds.[16][7][35]

Similar attractive substances

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Some insect pollinated plants lack nectaries, but attract pollinators through other secretory structures. Elaiophores are similar to nectaries but are oil secreting. Osmophores are modified structural structures that produce volatile scents. In orchids, these have pheromone qualities. Osmophores have thick domed or papillate epidermis and dense cytoplasm. Platanthera bifolia produces a nocturnal scent from the labellum epidermis. Ophrys labella have dome-shaped, papillate, dark-staining epidermal cells forming osmophores. Narcissus emit pollinator specific volatiles from the corona.[4]

See also

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References

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Bibliography

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Nectar

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Nectar is a sweet, viscous liquid secreted by specialized glands called nectaries in , primarily consisting of water and sugars such as , glucose, and , along with trace amounts of , proteins, , vitamins, and secondary metabolites. It is produced mainly in flowers to attract pollinators like and birds, facilitating through , but can also occur in extrafloral structures for defensive purposes. The composition and concentration of nectar vary widely among species, influenced by environmental factors and pollinator preferences, with sugar concentrations typically ranging from 10% to 70% . In terms of production, nectaries are glandular tissues located within flowers (floral nectaries) or on leaves, stems, and other vegetative parts (extrafloral nectaries), where metabolic processes involving enzymes like sucrose synthase and generate the nectar's sugary content. Floral nectar, the most common type, rewards pollinators for transferring between , enhancing cross-pollination and . Extrafloral nectar, by contrast, attracts predatory such as to deter herbivores, providing an indirect defense mechanism for the . Ecologically, nectar plays a crucial role in mutualistic interactions between plants and animals, supporting biodiversity by sustaining pollinator populations and serving as the primary source material for honey production in bees. Its chemical profile, including non-sugar components like alkaloids and phenolics, can influence pollinator behavior, visitation rates, and even plant fitness by deterring microbial contamination or nectar robbers. Recent studies highlight how evolutionary pressures from specific pollinators shape nectar's sugar ratios and nutrient content, underscoring its adaptive significance in plant-pollinator coevolution.

Fundamentals

Definition and Characteristics

Nectar is a sugar-rich secreted by from specialized structures called nectaries, primarily functioning as a reward to attract pollinators and, in some cases, plant defenders. It consists predominantly of water, which makes up 30-90% of the solution depending on sugar levels, and dissolved sugars such as , glucose, and , with concentrations typically ranging from 10% to 70% by weight. Physically, nectar exhibits variable that rises exponentially with increasing concentration, resulting in a that can range from dilute and watery to thick and syrupy. It is generally clear or colorless, though some species produce yellowish or vividly colored variants to enhance visibility to pollinators. Per-flower volumes vary widely, from less than 1 microliter in many insect-pollinated blooms to several milliliters in flowers adapted for or visitation. Unlike sap—the nutrient-transporting fluid circulating through a plant's vascular tissues—or latex, a milky emulsion exuded from laticifers for defense, nectar is a specialized exudate tailored for mutualistic interactions with animals. Nectar secretion occurs in roughly 74% of animal-pollinated angiosperms, representing over 223,000 species, and is also present in select gymnosperms and ferns.

Etymology

The term "nectar" originates from the Ancient Greek word νέκταρ (néktar), referring to the mythical drink consumed by the gods on , believed to confer and eternal youth. This etymology likely derives from a compound of Proto-Indo-European roots *nek- ("death" or "perish") and *tar- ("overcoming" or "ferrying across"), literally meaning "overcoming death," which aligned with its symbolic role in as a substance defying mortality. In classical literature, such as Homer's and , nectar is depicted alongside as the divine sustenance that sustained the Olympian deities, distinguishing them from mortals. The word entered Latin as nectar, retaining its mythological connotation as the "drink of the gods" or a sweet, pleasurable beverage, and was adopted into English in the mid-16th century, around 1555, initially in literary and classical contexts. By the , as botanical studies advanced, "nectar" began to describe the sweet, sugary fluid secreted by plants, marking a shift from its divine origins to a scientific term for a biological substance attractive to pollinators. This transition reflected broader Enlightenment-era efforts to demystify natural phenomena, replacing ancient views of nectar as a celestial with empirical observations of its role in . The related term "nectary," denoting the glandular structure in that produces nectar, was coined in 1735 by the Swedish botanist in his work Critica Botanica, where he identified specialized tissues dedicated to nectar secretion. Derived from New Latin nectarium (a or form of Latin nectar with the -arium indicating a place or instrument), it formalized the anatomical distinction in . Early misconceptions persisted into the , with some naturalists viewing nectar as a remnant of divine essence or a honey-like from the heavens, rather than a product of specialized cellular activity, until microscopic examinations clarified its organic origins.

Nectary Types

Floral Nectaries

Floral nectaries are specialized glandular tissues within the flowers of angiosperms, primarily functioning to secrete nectar that attracts pollinators essential for . These structures are present in approximately 74% of animal-pollinated angiosperm , underscoring their widespread role in biotic systems. Anatomically, floral nectaries consist of modified epidermal cells overlying secretory , with a subnectary layer providing ; they are often vascularized, particularly by strands that supply carbohydrates for nectar production. The may feature specialized stomata or pores for nectar release, while the cells exhibit dense and wall ingrowths in transfer cells to facilitate solute transport. Common types include gynoecial nectaries, located on the carpels or their margins; septal nectaries, embedded in the septa between fused carpels, often in monocots with subtypes such as infralocular (basal to locules), interlocular (mid-ovary), and supralocular (distal to locules); and septal-intrusive forms where the nectary tissue extends into the ovarian locules. Other variants encompass receptacular nectaries on the floral receptacle and androecial types on stamens. These nectaries occur in diverse locations within the flower, such as at the bases of petals or sepals, on stamen filaments, surrounding the ovary, or on the receptacle, adapting to the flower's architecture to optimize pollinator access. For instance, in Asteraceae like Echinacea purpurea, they form an annular collar atop the inferior ovary, encircling the style base. In approximately 66% of flowering plants, their positioning aligns with reproductive organs to ensure nectar availability coincides with pollen presentation. The diversity of floral nectaries reflects evolutionary adaptations to specific pollinators, with morphological variations enhancing attraction efficiency. In orchids, elongated spur nectaries extend from petals or sepals, housing nectar at depths suited to long-tongued like hawkmoths, promoting precise . In contrast, passionflowers ( spp.) feature a ring-like floral nectary at the base of the floral tube, sometimes with scale-like elevations that facilitate nectar pooling for shorter-tongued bees. Such variations, including trichomatic types (glandular hairs) in or epithelial forms in , correlate with pollinator morphology and behavior, driving across lineages. Developmentally, floral nectaries originate from floral meristems during , with their formation specified by transcription factors that pattern glandular identity amid surrounding tissues. In , genes such as CRABS CLAW (CRC) establish nectary fate on the receptacle, while BLADE-ON-PETIOLE1/2 (BOP1/2) regulate elaboration and vascular integration in . Similar genetic modules, including signaling, underpin nectary development in diverse clades, enabling repeated independent origins and losses in angiosperm evolution. This developmental plasticity contributes to the structural diversity observed, linking anatomy to reproductive ecology.

Extrafloral Nectaries

Extrafloral nectaries (EFNs) are specialized glandular structures located on vegetative and non-reproductive parts of , distinct from floral nectaries by their role in indirect defense rather than attraction. These nectaries secrete sugar-rich rewards to recruit predatory , primarily , for protection against herbivores. Anatomically, EFNs are often simpler than their floral counterparts, manifesting as food bodies, trichome-like glands, or embedded secretory tissues. They typically comprise a single-layered overlying nectary rich in secretory cells, sometimes subtended by a subnectary layer, and may or may not be vascularized by or both and . Non-vascularized forms, such as cuplike or scurfy trichomes, predominate in many , facilitating rapid nectar release without extensive vascular support. EFNs occur on various plant organs, including leaves, petioles, stems, stipules, and bracts, with positions often strategically placed to maximize accessibility for defending arthropods. In Acacia species, such as the bullhorn acacia (Acacia cornigera), prominent EFNs are situated on leaflet petioles and rachises, integrated into myrmecophytic structures that house ant colonies. Similarly, passionvines (Passiflora spp.) feature paired EFNs at the petiole base and along leaf margins, enabling efficient ant patrolling. These locations enhance the defensive efficacy by positioning nectar sources near vulnerable tissues. As of a 2013 analysis, EFNs have been documented in approximately 3941 species across 745 genera and 108 families of vascular plants (including 4 fern families), representing about 1–2% of all vascular plant species but up to 21% of angiosperm families. Recent estimates (as of 2024) suggest nearly 4,000 species across over 90 families. The diversity of EFNs spans tropical trees to temperate herbs, reflecting multiple independent evolutionary origins—estimated at least 457 times across plant lineages. In tropical myrmecophytes like certain and Senna species, EFNs form complex, elevated glands or bowl-like depressions optimized for access, often co-occurring with domatia for symbiotic housing. Temperate examples include herbaceous plants such as broad bean (), where inconspicuous trichome-based EFNs on stipules provide modest rewards in lower-herbivore-pressure environments. EFNs are particularly prevalent in woody plants, comprising at least 25% of the flora in savanna-like habitats such as the Brazilian , where they deter herbivores in resource-limited conditions. This distribution underscores their adaptive value in high-predation ecosystems, with structural variations like porous slits or raised cups facilitating nectar exposure to ground-foraging ants.

Secretion and Production

Process of Secretion

Nectar secretion in plants involves a series of biophysical and cellular processes that enable the production and release of this sugary fluid from specialized nectary tissues. The primary sugars in nectar, such as , glucose, and , originate from photosynthetic products transported via the to the nectary cells, where they are synthesized and modified. In these cells, serves as a key precursor, accumulating in amyloplasts before being broken down into soluble sugars through enzymatic activity, including phosphate and other carbohydrate-metabolizing enzymes. The sugars then move symplasmically through plasmodesmata by passive toward the secretory , driven by concentration gradients. At the cellular level, the transition from symplasm to apoplasm is mediated by mechanisms to overcome concentration gradients, as nectar sugars often exceed intracellular levels. is primarily exported via /H⁺ symporters or facilitators like the SWEET9 transporter, which uses the proton motive force generated by plasma membrane H⁺-ATPases to co-transport with protons into the . Once in the , cell wall invertases hydrolyze into glucose and , increasing and facilitating osmosis-driven exudation of nectar. This process requires energy from by proton pumps, which maintain the essential for activity; without this, sugar loading into the would not occur against the gradient. rates vary widely by and nectary size, from 0.01 μL/h to several μL/h per nectary, reflecting the metabolic investment in this energy-dependent transport. The secretion process unfolds in distinct phases: synthesis and accumulation followed by release. During synthesis, sugars accumulate in the intercellular spaces of the nectary and subepidermal layers, forming a pre-nectar that expands due to osmotic influx of . This accumulation occurs in subcuticular or intercellular pockets, often supported by unloading directly into these spaces. Release then happens through modified stomata, which open to allow nectar passage, or via rupture or across a reticulate in nectar-producing epidermal cells. In some cases, pressure from osmotic buildup drives mass flow out of these openings without further active intervention. Nectar secretion modes differ between active glandular processes and passive osmotic exudation. Active secretion, prevalent in glandular nectaries, relies on metabolic for transmembrane . In contrast, passive secretion involves primarily osmotic forces after initial sugar loading, with nectar exuding through unmodified pathways like pores without ongoing ATP expenditure, as seen in some extrafloral nectaries. These modes ensure efficient nectar delivery tailored to the nectary's anatomical structure.

Factors Affecting Secretion

Nectar secretion in is modulated by various environmental factors that influence its volume, timing, and composition. plays a critical role, with optimal ranges typically between 20°C and 30°C for many , promoting higher nectar volume and content; temperatures exceeding this threshold, such as above 30°C, often reduce secretion rates and alter concentration due to physiological stress on nectary tissues. affects the component of nectar, where higher relative humidity increases exudation of from nectaries without significantly impacting secretion, leading to more dilute nectar under moist conditions. , particularly photoperiod and intensity, influences nectar production through in nectary cells; for instance, longer photoperiods enhance secretion timing by activating light-responsive pathways, including those involving 2 (CRY2), which integrates light signals to synchronize developmental processes. Physiological triggers, such as hormonal regulation and circadian rhythms, further control the dynamics of nectar . primarily regulates extrafloral nectar production, where its application induces rapid increases in volume as part of defense responses, while , such as GA3, promote floral nectar by enhancing sugar accumulation and overall yield in species like . Circadian rhythms govern the temporal patterns of , with peaks often occurring at dawn to align with activity; this rhythmicity is mediated by clock genes that oscillate nectar synthesis and release, ensuring coincides with optimal times. Genetic factors underpin the variability in nectar production through transcription factors that modulate nectary activity and development. The CRABS CLAW (CRC) gene, a YABBY family transcription factor, is essential for specifying nectary identity and promoting secretion; mutations in CRC lead to nectarless phenotypes by disrupting nectary formation and function in . Similarly, SHATTERPROOF (SHP1/2) genes, encoding proteins, regulate nectary development by controlling CRC expression. Stress responses, particularly to drought and herbivory, can dramatically alter extrafloral nectar secretion as an adaptive strategy. Under drought conditions, extrafloral nectar production can vary by species and genotype; for example, in quaking aspen, low water availability often reduces secretion rates. Herbivory triggers similar elevations, often mediated by jasmonic acid signaling, leading to significant increases in nectar volume to bolster indirect defenses; this response varies by species but enhances ant recruitment during heightened herbivore pressure.

Composition

Carbohydrates

Nectar carbohydrates primarily consist of three sugars: the disaccharide and the monosaccharides and , which together account for the majority of its dry mass and serve as the principal energy source for pollinators. These sugars are present in varying proportions across plant species, with typically comprising 20–60% of total sugars, 10–40%, and 10–40%. Ratios differ by plant family; for instance, species often exhibit sucrose dominance up to 85%, while tend toward hexose dominance with only about 27% sucrose. and are usually in near-equal amounts (approximately 1:1 ratio) in hexose-rich nectars. Sugar ratios reflect adaptations to pollinator preferences and floral morphology, with hexose-dominant compositions (glucose and fructose exceeding 50% combined) common in open-access flowers like those in buzz-pollinated species, facilitating quick energy acquisition during short visits. Sucrose-dominant nectars (>50% sucrose), prevalent in tubular flowers visited by long-tongued pollinators such as bees and hummingbirds, provide higher energy density but require enzymatic hydrolysis for digestion. These variations arise from phylogenetic constraints and evolutionary pressures, with shifts toward sucrose-rich profiles observed in older plant families and warmer historical climates. Freshly secreted nectar has a high concentration, often 10–70% w/w (median ~40%), corresponding to an osmotic pressure of 1–2 MPa that aids in within the nectary. Post-secretion, concentrations can dilute to as low as 17–24% due to , rain, or , reducing and improving drinkability while maintaining energetic accessibility. This dynamic prevents over-concentration in exposed flowers. High-sucrose nectars (>50%) risk in arid conditions if not rapidly consumed, potentially deterring repeated visits. Nectar's energetic value stems from its content, yielding 0.7–3.6 cal/μL depending on concentration and composition, with offering slightly higher density (~17 kJ/g) than hexoses (~15.6 kJ/g). This fuels essential activities like flight; a honeybee worker requires ~40 μL of typical nectar daily to obtain ~11 mg dry , equivalent to its metabolic demands. Such provisioning underscores carbohydrates' role as primary attractants, optimized evolutionarily to match needs without excess.

Amino Acids, Proteins, and Other Compounds

The non-sugar fraction of nectar typically constitutes 1-10% of its dry mass, encompassing , proteins, , vitamins, and secondary metabolites, with higher proportions often observed in extrafloral nectar to enhance defensive roles against microbes and herbivores. Amino acids represent a minor but bioactive component of nectar, generally comprising 0.01-0.5% of dry weight and occurring at concentrations of 0.1-13 mM, though up to 20 proteinogenic types have been identified across species, with non-essential amino acids like proline, serine, glutamine, and alanine predominating. These compounds serve primarily as phagostimulants influencing pollinator foraging preferences and as supplementary nitrogen sources, potentially fulfilling 5-10% of protein requirements for certain pollinators like bees through metabolic utilization, such as proline for flight energy. Proteins in nectar, present at concentrations of 0.1-1 mg/ml, include enzymes known as nectarins, such as nectarin V (a flavin-containing bridge enzyme-like protein) and nectarin I (a ), which generate via activity to inhibit microbial growth. Additional proteins like and pathogenesis-related (PR) proteins, including chitinases and glucanases, further contribute to nectar's defensive properties by targeting fungal and bacterial pathogens, particularly in extrafloral nectaries. Other compounds in nectar include at 0.1-1% of dry mass, which may aid in microbial inhibition, and volatiles such as phenolics that contribute to scent profiles attracting pollinators. Metals like occur in trace amounts and can confer toxicity to deter nectar robbers, while secondary metabolites, including alkaloids, are found in approximately 20% of plant species and serve dual roles in pollinator attraction and defense.

Functions

Attraction of Pollinators

Nectar serves as a primary reward in plant-pollinator mutualisms, providing pollinators with essential carbohydrates and other nutrients in exchange for transfer, thereby enhancing plant . Floral nectar is strategically positioned within flowers near reproductive organs, where visual cues such as colorful patterns and guides, combined with scents from volatile compounds, direct pollinators to access it efficiently. This reciprocal arrangement ensures that pollinators, while foraging for the energy-rich reward, inadvertently facilitate cross-pollination by contacting stamens and stigmas. Plants exhibit specificity in nectar traits to attract particular pollinator guilds, tailoring sugar compositions and secretion patterns to match visitor preferences and behaviors. For instance, flowers pollinated by and moths often produce -dominant nectar (typically >50% relative to hexoses), which aligns with these ' rapid digestion capabilities, whereas bee-pollinated species tend to offer hexose-rich nectar ( and glucose >60%), better suited to their enzymatic processing. Hummingbird-visited flowers similarly favor -rich profiles to meet high-energy demands during hovering. Additionally, nectar volume and timing are synchronized with pollinator activity; bat-pollinated flowers secrete large volumes of dilute nectar (often <15% sugars) at night to accommodate the bats' inability to hover and their nocturnal . Nectar production promotes pollination efficiency by maintaining standing crops that incentivize repeated visits, though non-pollinating robbers can reduce this benefit by depleting rewards without aiding transfer. In some systems, nectar robbers account for 10-20% of floral visits, leading to decreased legitimate if replenishment lags. Pollinator visits typically remove 50-90% of the available nectar standing crop per flower, as modeled in depletion studies, which underscores the dynamic balance plants strike to sustain attraction amid high foraging pressure. A representative example is found in hummingbird-pollinated Salvia species, where concealed nectaries at the base of long tubular corollas necessitate legitimate visitation for access, thereby promoting effective transfer via the staminal mechanism. In these flowers, nectar is retained by structural barriers like papillae, ensuring that hummingbirds must probe deeply and contact reproductive parts, which minimizes and maximizes cross-pollination efficiency.

Attraction of Ants and Defense

Extrafloral nectar serves as a key resource in mutualisms, where recruit as indirect defenders against herbivores. In this protective interaction, forage on the nectar and in return patrol surfaces, deterring or preying upon potential herbivores, thereby reducing damage to tissues. A of 59 species pairs found that presence mediated by extrafloral nectar decreases herbivory by an average of 62%, with benefits varying by and species. This bodyguard strategy is particularly prevalent in tropical and subtropical regions, where extrafloral nectaries are abundant on leaves, stems, and petioles. The effectiveness of this mutualism relies on strategic placement and compositional adjustments of the nectar to optimize recruitment and retention. Nectaries are often located on exposed vegetative parts, such as margins or young stems, facilitating easy access for while positioning them near vulnerable tissues prone to herbivory. To prolong visitation, modulate nectar quality; for instance, higher concentrations of in the nectar enhance its attractiveness to certain , encouraging longer durations and more thorough defense. This induced response can be triggered by damage, increasing nectar production via signaling to bolster attendance during periods of threat. Prominent examples include species in Central American ant-gardens, where extrafloral nectar sustains obligate colonies housed in swollen thorns, enabling continuous protection against browsers and folivores. In these systems, s aggressively defend the host plant, removing herbivores and even pruning encroaching vegetation. The energetic cost to the plant is notable, representing a targeted in defense over . Despite these advantages, the ant defense provided by extrafloral nectar has limitations, particularly against specialist herbivores that possess chemical defenses or behaviors resistant to ant predation, such as certain lepidopteran larvae. In such cases, ant recruitment may fail to significantly reduce damage, as specialists can tolerate or counter ant attacks. Additionally, evolutionary trade-offs exist, where heightened nectar production for defense may divert resources from pollination services, potentially reducing reproductive success in pollinator-dependent plants. Recent studies (as of 2025) further indicate that ants can disrupt pollination by deterring legitimate pollinators like bees from flowers.

Interactions and Ecology

Pollinator Behavior

Pollinators detect nectar sources through a combination of visual and olfactory cues that guide them to rewarding flowers. Bees, for instance, perceive ultraviolet (UV) patterns on flowers, which often feature UV-absorbing centers surrounded by UV-reflecting peripheries, serving as nectar guides that enhance attraction and landing precision. These visual signals are particularly effective for bee-pollinated species, increasing visitation rates compared to flowers lacking such patterns. Olfactory cues, including volatile organic compounds emitted by flowers, complement visual signals by attracting pollinators from a distance, with studies showing synergistic effects that improve foraging efficiency in hawkmoths and bees. Additionally, pollinators like bees rapidly learn to associate specific scents with nectar rewards, memorizing floral odors after just one to three visits to prioritize profitable sources in future foraging. Consumption patterns among pollinators are shaped by nectar volume, viscosity, and handling requirements, influencing overall foraging efficiency. Bumblebees typically extract small volumes of nectar per flower, ranging from 0.5 to 4 microliters, depending on the plant species and flower age. Higher nectar viscosity, often due to elevated sugar concentrations, increases handling time as bees must expend more energy to lap or suck the fluid, leading to trade-offs between reward quality and extraction speed. For example, in viscous nectars, bumblebees adjust their tongue movement frequency to optimize intake, but this can extend per-flower visit duration by up to 30% compared to less viscous rewards. Nectar quality, particularly its content, influences and beyond immediate energy provision. in nectar contribute to the nutritional balance that can extend lifespan by supporting protein synthesis and reducing . However, excessive or imbalanced may have neutral or negative effects on survival. Behavioral responses include , where pollinators bypass reproductive structures to access nectar directly, occurring in approximately 9% of interactions in some systems and reducing legitimate . In broader ecological contexts, competition among pollinators for nectar resources alters visitation dynamics and community structure. High nectar depletion rates, often exceeding 80% in seasonal grasslands, intensify exploitative , leading to reduced per-species visitation and shifts toward generalist foraging strategies. For instance, dominant species like honeybees can suppress native pollinator visits by 50% or more through resource monopolization, thereby influencing overall efficiency in plant communities. Recent studies as of July 2025 indicate that honeybees can remove up to 80% of available in a single day, exacerbating resource and threatening native populations. Such interactions highlight how nectar availability mediates coexistence and specialization among pollinator guilds.

Microbial Inhabitants

Floral nectar serves as a for diverse microbial communities, primarily consisting of and yeasts, with fungi such as Metschnikowia species being prominent among the latter. Common bacterial inhabitants include species, such as A. nectaris and A. boissieri, alongside genera like Rosenbergiella, , and . These microbes are typically introduced into initially sterile nectar through dispersal mechanisms involving pollinators, wind, or rain, with animal vectors like bees and hummingbirds playing a key role in community assembly. Microbial densities start low but can rapidly increase to 10^5 cells/μl for yeasts and up to 10^7 cells/μl for bacteria within hours of colonization. The dynamics of these microbial communities in nectar are influenced by plant-derived antimicrobials that limit initial growth, yet successful colonizers alter nectar chemistry significantly. and yeasts ferment sugars, shifting profiles toward higher proportions and reducing overall concentrations, often within hours of establishment. This process also lowers nectar to acidic levels (typically 3-5) and modifies volatile organic compounds, enhancing or altering floral scents to influence detection. Such changes reflect priority effects and interactions within metacommunities, where local nectar habitats are connected across plants via dispersal, and environmental factors like temperature and nectar composition shape community structure and persistence. Microbial presence impacts nectar quality and ecology, often reducing attractiveness to pollinators; for instance, bacterial colonization can decrease hummingbird visits and lower nectar consumption compared to uncolonized controls. Yeasted nectar similarly deters some bees, with bumblebees avoiding certain bacterial species like Asaia astilbes. However, microbes offer potential benefits, such as yeasts suppressing the bumblebee gut pathogen Crithidia bombi by up to 50%, thereby reducing infection transmission. Recent research highlights metacommunities shaped by environmental gradients, like urbanization influencing bird-vectored bacterial diversity in nectar. Regarding pollinator health, nectar yeasts like Metschnikowia reukaufii can act as probiotics, enhancing bumblebee colony growth and foraging, while others may function as opportunistic pathogens, potentially shortening lifespan depending on context and species interactions.

Evolutionary History

Origins in Plants

The origins of nectar production in plants are rooted in ancient glandular structures that predate modern nectaries. The earliest evidence comes from the late Paleozoic era, where glandular hairs and internal glands on prepollen organs and ovules of Carboniferous seed ferns (medullosans), dating to approximately 300 million years ago, likely served as nutritional rewards for early arthropods. Similarly, hyathodes—water-secreting structures—in Lower Permian marattialean tree ferns secreted fluids that may have attracted insect visitors, representing potential proto-nectaries in fern lineages. These features suggest an early evolutionary experimentation with secretory tissues for plant-arthropod interactions, though true nectar secretion as a sugar-rich reward emerged later. Nectar production is phylogenetically restricted, being largely absent in gymnosperms, which primarily rely on drops rather than dedicated nectaries for reproductive interactions. In contrast, it evolved convergently in ferns and angiosperms during the Cretaceous period, with origins estimated at around 135 million years ago in ferns (across 5 families in 3 orders) and 132 million years ago in angiosperms (across 119 families in 42 orders). This timing aligns closely with the diversification of and the rise of ant-plant mutualisms around 115 million years ago, facilitating the of as defensive bodyguards through extrafloral nectaries. While rare in ferns (affecting about 1% of species), nectaries are more prevalent in angiosperms, particularly like , reflecting multiple independent gains and losses across lineages. Genetically, floral nectaries in angiosperms originated through the co-option of the ABC model of floral organ identity, where C-lineage genes such as (in ) and its orthologs pMADS3 and FBP6 (in ) redundantly activate nectary development, often in conjunction with the CRABS CLAW (CRC) gene family, which specifies nectary positioning and elaboration. This regulatory network, conserved across and , allows nectaries to form independently of other floral whorls but within defined domains. Extrafloral nectaries, meanwhile, derive from co-option of developmental pathways, exhibiting serial homology to leaf margin structures like teeth or glands; for example, in , they evolve from shared genetic programs governing foliar serrations, enabling defensive secretion outside reproductive contexts. The fossil record underscores these evolutionary patterns, with amber-preserved Eocene flowers (circa 50 million years ago) from Baltic and other deposits revealing early associations between floral structures and insect pollinators, implying nectar-mediated interactions despite rare direct preservation of nectaries. The oldest unequivocal extrafloral nectary fossil, from late Eocene leaves (approximately 34 million years ago), confirms the antiquity of ant-attracting glands in angiosperms. These records highlight how nectar production diversified post-Cretaceous, building on precursors to support complex ecological partnerships.

Adaptations and Diversity

Nectar production exhibits remarkable diversification across taxa, with floral nectaries evolving independently multiple times and displaying diverse structural organizations that cater to specific guilds. These structures include three major types—mesophyllary, trichomatic, and epithelial—along with variations in position, size, and nectar composition that respond to preferences, such as larger nectaries in hummingbird-pollinated species compared to bee-adapted ones. For instance, in orchids, long nectar spurs exceeding 5 cm have evolved in moth-pollinated species to match the pollinators' lengths, promoting specialized interactions and contributing to . Such morphological shifts, including nectar spurs, are associated with increased species diversification rates in clades where they occur, acting as key innovations that enhance efficiency. At the genetic level, nectar production is regulated by conserved genes that have undergone duplications and adaptations, enabling nectary development and secretion. Key regulators include the transcription factor CRABS CLAW (CRC) and its MADS-box relatives, which control nectary formation in eudicots, with loss-of-function mutants resulting in absent nectaries. The sucrose transporter SWEET9 is essential for nectar secretion in mesophyllary nectaries, showing evolutionary conservation across lineages. In contrast, nectar production is frequently lost in wind-pollinated plants, such as those in Fagales and Poales, due to the energetic costs of secretion when pollinators do not require rewards. These genetic losses also occur in self-pollinating species, reflecting shifts away from animal-mediated pollination. Ecological factors drive variations in nectar composition, though patterns can vary by species and tissue. In high-elevation environments, such as the , concentrations of phenolic acids (e.g., caffeic and chlorogenic acids) in plant tissues often decrease, potentially due to reduced herbivory pressure and energy allocation trade-offs. Invasive species introductions can alter nectar chemistry, as seen in , where toxin levels like I are lower in introduced ranges compared to native ones, possibly from relaxed selection by enemies or pollinators. These changes may disrupt native plant-pollinator dynamics by affecting reward quality. Recent research highlights of nectaries in ferns, with at least three major ancestral origins across families like and , plus independent gains in several other lineages, spanning 149 in 12 genera. This evolution occurred around 135 million years ago during the , paralleling angiosperm nectary origins and facilitating recruitment for defense against herbivores. Additionally, nectar microbiomes show co-adaptation with host traits, as like evolve reduced genomes and osmotic tolerance to thrive in nectar, altering its pH and sugar profiles to influence behavior.

Similar Plant Secretions

In carnivorous such as sundews ( spp.), glandular secretions from tentacle-like trichomes produce a sticky that attracts and traps prey, containing and sugars like and glucose at concentrations around 4%, lower than typical nectar levels. These mucilaginous exudates, with 96–98.5% water content, mimic the sweetness of nectar to lure victims but primarily serve predatory functions rather than mutualistic ones. Associated osmophores in some species, such as Heliamphora, release volatile monoterpenes to enhance prey attraction through scent, integrating olfactory cues with the sticky resin-like secretion. Guttation fluid represents another non-nectar plant exudate, consisting of watery drops secreted through hydathodes at margins and tips, derived from and rather than glandular activity. This fluid contains sugars at low concentrations, typically up to 1%, along with proteins and other nutrients, and exhibits diurnal patterns with peak exudation around noon under conditions of high and . Unlike nectar, primarily aids in excess water and mineral regulation, though its sugars can incidentally support nutrition without promoting structured mutualisms. These secretions differ from true nectar in lacking dedicated nectaries—specialized glandular tissues—and instead arise from general epidermal or vascular structures, emphasizing functions like prey immobilization or hydraulic balance over or defender attraction. For instance, the in sundews traps and digests prey directly, while facilitates passive nutrient release without evolutionary adaptations for . Extrafloral resins in genera like exemplify similar ant-attracting exudates, where milky or sugary secretions from laticifers or glands draw protective to deter herbivores, mirroring nectar's role but originating from wound-responsive or constitutive resin-producing tissues. In species, these resins enhance ant-plant defenses without the floral context of true nectar, providing carbohydrates that sustain ant colonies in exchange for herbivory control.

Non-Plant Analogues

Honeydew is a sugary excretion produced by and other sap-feeding , such as scale insects, when they ingest sap and excrete the excess sugars after processing. This substance primarily consists of sucrose-derived carbohydrates, including glucose, , and trisaccharides like melezitose, with total concentrations typically ranging from 30% to 35% by . Unlike plant nectar, honeydew generally lacks significant protein content, though it contains free at levels around 2-3%, and its composition is influenced by the host 's chemistry, leading to variations in secondary metabolites such as cardenolides. actively farm for honeydew by tending colonies, protecting them from predators and parasitoids, which increases aphid populations and, in turn, amplifies ecological impacts like the spread of plant viruses transmitted during aphid feeding. Additionally, honeydew often harbors a higher microbial load due to its origin and exposure, fostering fungi like sooty molds that grow on the sticky residue. Animal secretions can also mimic nectar in function or composition, providing alternative sugar sources in ecosystems. For instance, female hummingbirds regurgitate nectar mixed with small insects to feed their chicks, creating a nutrient slurry that delivers carbohydrates and proteins directly into the nestlings' mouths multiple times per hour during early development. This regurgitated mixture serves as a processed analogue to raw nectar, adapted for avian digestion, but it remains biologically tied to floral origins rather than being independently produced by the birds. These animal-derived analogues differ ecologically from nectar by supporting predator-prey dynamics instead of mutualistic , and their chemical profiles may include higher concentrations in cases like honeydew to sustain mutualisms. Artificial nectars, commonly used in wildlife feeders, represent human-made non-plant analogues designed to replicate floral rewards. These solutions are typically prepared as 20% sucrose in (a 1:4 ), mimicking the average sugar concentration of many natural nectars to attract hummingbirds and other nectarivores without introducing proteins or secondary compounds. While effective for supplemental feeding, such mixtures lack the diverse and volatiles found in genuine nectar or honeydew, potentially altering foraging behavior if over-relied upon. In human applications, nectar analogues appear in beverages like sweetened sodas or energy drinks, where sucrose solutions provide but hold no biological relevance to ecology or plant-animal interactions.

References

  1. https://royalsocietypublishing.org/doi/10.1098/rstb.2021.0163
  2. https://www.cell.com/trends/plant-science/fulltext/S1360-1385%2811%2900006-9
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC9058545/
  4. https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-024-05630-3
  5. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nectar-plants
  6. https://botanic-garden.bristol.ac.uk/2014/05/27/the-science-of-nectar/
  7. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.987145/full
  8. https://www.nature.com/articles/s41598-024-64755-5
  9. https://www.nature.com/articles/s41598-020-58102-7
  10. https://plecevo.eu/article/124295/
  11. https://www.biologydiscussion.com/plants/secretory-structures-in-plants-botany/69129
  12. https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19940
  13. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nectar-secretion
  14. https://www.merriam-webster.com/dictionary/nectar
  15. https://www.etymonline.com/word/nectar
  16. https://www.oed.com/dictionary/nectar_n
  17. https://par.nsf.gov/servlets/purl/10095388
  18. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nectary
  19. https://www.merriam-webster.com/dictionary/nectary
  20. https://pmc.ncbi.nlm.nih.gov/articles/PMC2803364/
  21. https://link.springer.com/article/10.1007/s00709-019-01412-z
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC12095991/
  23. https://plants.sdsu.edu/simpson/pdfs/Simpson1993-SeptalNectary-Haemodorac.pdf
  24. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.70141
  25. https://bsapubs.onlinelibrary.wiley.com/doi/10.1002/j.1537-2197.1981.tb07789.x
  26. https://pmc.ncbi.nlm.nih.gov/articles/PMC3662527/
  27. https://www.redalyc.org/pdf/1871/187131652009.pdf
  28. https://pmc.ncbi.nlm.nih.gov/articles/PMC4247069/
  29. https://www.sciencedirect.com/science/article/pii/S0254629921002994
  30. https://academic.oup.com/aob/article/111/6/1251/151279
  31. https://www.nature.com/articles/s41467-024-48646-x
  32. https://pubmed.ncbi.nlm.nih.gov/18761504/
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC10610396/
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC2826252/
  35. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00622/full
  36. https://link.springer.com/article/10.1007/s13592-018-0578-y
  37. https://academic.oup.com/aobpla/article/17/4/plaf037/8185587
  38. https://www.mdpi.com/2223-7747/14/11/1718
  39. https://pmc.ncbi.nlm.nih.gov/articles/PMC6030359/
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC11072124/
  41. https://pmc.ncbi.nlm.nih.gov/articles/PMC3115044/
  42. https://pmc.ncbi.nlm.nih.gov/articles/PMC5647282/
  43. https://journals.biologists.com/dev/article/126/11/2387/40285/CRABS-CLAW-a-gene-that-regulates-carpel-and
  44. https://www.sciencedirect.com/science/article/pii/S1360138520303381
  45. https://www.researchgate.net/publication/262875090_The_influence_of_water_availability_and_defoliation_on_extrafloral_nectar_secretion_in_quaking_aspen_Populus_tremuloides
  46. https://pmc.ncbi.nlm.nih.gov/articles/PMC3736772/
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC11180116/
  48. https://pmc.ncbi.nlm.nih.gov/articles/PMC6397631/
  49. https://faculty.eeb.ucla.edu/Nobel/people/Erick/peru/Nectar.PDF
  50. https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-023-04344-2
  51. https://www.pollinationecology.org/index.php/jpe/article/view/821
  52. https://www.sciencedirect.com/science/article/am/pii/S0168945216308184
  53. https://pmc.ncbi.nlm.nih.gov/articles/PMC2802787/
  54. https://baynature.org/article/whats-the-secret-of-nectar/
  55. https://www.nature.com/articles/s41598-019-51170-4
  56. https://pmc.ncbi.nlm.nih.gov/articles/PMC10780904/
  57. https://pmc.ncbi.nlm.nih.gov/articles/PMC316325/
  58. https://www.sciencedirect.com/science/article/abs/pii/S2214574521000304
  59. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01063/full
  60. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00205/full
  61. https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.4696
  62. https://www.researchgate.net/publication/227698930_Effect_of_Pollinators_and_Nectar_Robbers_on_Nectar_Production_and_Pollen_Deposition_in_Hamelia_patens_Rubiaceae
  63. https://nsojournals.onlinelibrary.wiley.com/doi/10.1111/oik.10495
  64. https://pmc.ncbi.nlm.nih.gov/articles/PMC2735312/
  65. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014308
  66. https://pubmed.ncbi.nlm.nih.gov/19370376/
  67. https://www.pnas.org/doi/10.1073/pnas.1009007107
  68. https://www.sciencedirect.com/science/article/pii/S0960982223001410
  69. https://academic.oup.com/aob/article/112/4/751/132906
  70. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.13135
  71. https://phys.org/news/2025-09-ants-defend-herbivores-hinder-pollination.html
  72. https://pubmed.ncbi.nlm.nih.gov/25703147/
  73. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2435.12242
  74. https://www.sciencedirect.com/science/article/pii/S0003347202940108
  75. https://www.jneurosci.org/content/15/3/1617
  76. https://academic.oup.com/aobpla/article/13/4/plab029/6287644
  77. https://www.cell.com/iscience/pdf/S2589-0042%2823%2902148-X.pdf
  78. https://pmc.ncbi.nlm.nih.gov/articles/PMC5372980/
  79. https://www.nature.com/articles/s41598-021-90895-z
  80. https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.4077
  81. https://www.sciencedirect.com/science/article/pii/S2666515824000234
  82. https://www.sciencedaily.com/releases/2025/07/250707073349.htm
  83. https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.11531
  84. https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.20369
  85. https://pmc.ncbi.nlm.nih.gov/articles/PMC9058548/
  86. https://royalsocietypublishing.org/doi/10.1098/rspb.2012.2601
  87. https://web.stanford.edu/~fukamit/jacquemyn-et-al-2021.pdf
  88. https://pmc.ncbi.nlm.nih.gov/articles/PMC3899272/
  89. https://enviromicro-journals.onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.16159
  90. https://pmc.ncbi.nlm.nih.gov/articles/PMC9058548
  91. https://pmc.ncbi.nlm.nih.gov/articles/PMC6181019/
  92. https://sites.tntech.edu/skrosnick/evolution-of-extrafloral-nectaries-in-passifloraceae/
  93. https://pmc.ncbi.nlm.nih.gov/articles/PMC8620889/
  94. https://royalsocietypublishing.org/doi/10.1098/rspb.1995.0215
  95. https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2022.864728/full
  96. https://www.researchgate.net/publication/298790407_Plant_toxin_levels_in_nectar_vary_spatially_across_native_and_introduced_populations
  97. https://web.stanford.edu/~fukamit/Quevedo-Caraballo-et-al-2025.pdf
  98. https://www.researchgate.net/publication/229203421_Physical_and_chemical_properties_of_the_mucin_secreted_by_DroSera_capensis
  99. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/drosera
  100. https://www.researchgate.net/publication/258996764_Sweet_but_dangerous_nectaries_in_carnivorous_plants
  101. https://pmc.ncbi.nlm.nih.gov/articles/PMC7542811/
  102. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.70087
  103. https://pmc.ncbi.nlm.nih.gov/articles/PMC4242560/
  104. https://www.pgro.org/ipm-aphids-and-viruses2/
  105. https://www.perkypet.com/articles/the-mother-hummingbird
  106. https://www.audubon.org/magazine/hummingbird-feeding-faqs
  107. https://www.birdsandblooms.com/birding/attracting-hummingbirds/hummingbird-nectar-recipe/
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