pollinators [20]. Floral nectar composition, its quality, and chemical and physical
features varies widely between species and type of nectary and most probably are
related to different consumers and ecological factors (abiotic and biotic).
Flowers often have specialized structures that make the nectar accessible only for
animals possessing appropriate morphological structures, and there are numerous
examples of coevolution between nectarivores and the flowers they pollinate. The
main function of nectar compounds is related to the attraction of pollinating insects. It
is well-known that honey bee chemoreceptor can detect volatile substances, contained
in the nectar of crop plants at distance of about 2 km [21]. In this way, pollinators are
unintentionally mediating the transfer of pollen to receptive stigma, becoming a key
attribute for increasing cross-pollination [22, 23]. Although floral nectar production
represents a high cost for the plant, it ensures a higher possibility of fruit/seed set,
higher reproductive success and gene transfer into next generation. The production of
nectar (when starch granules in the parenchyma are broken down) often peaks when
anthers start to shade pollen and when the stigma is the most receptive. Generally
flowers secreting more nectar show more successful pollination events [24].
It is proved that secreted nectar volume correlates with flower size, which is
probably due to the pleiotropic effects, where larger flowers have larger nectaries and
more space for nectar [25, 26]. The amount of nectar reward is positively correlated
with the number of pollinator visits, the number of flowers visited within a plant, and
the duration of the visit within a flower [27]. Generally, energy received from nectar
per insect (or other pollinator) must be enough to attract pollinators, but still need to
encourage movement of the pollinator from flower/plant to another one. This means
that nectar volume is correlating with the body size of the pollinator [28].
The attractiveness of nectar to pollinators depends on taste [29], but odor and color
play an important role too [30, 31]. Characteristics such as volume, concentration,
color, and taste may be related to the concentration and composition of dissolved sugar
(especially glucose, fructose, and sucrose). But also other components, including
minerals, phenolic compounds, and amino acids, may make a cardinal contribution
to its attractiveness to honey bees [22, 32–34]. Bees prefer bright flowers, while visual
and chemical associations are pushing it to navigate within the field [35].
Nectar concentration is highly influenced by geographical distribution, thus environmental factors, especially light, water, nutrients, CO 2 concentration, temperature,
humidity, soil moisture, and wind [36]. Besides, nectar composition can vary between
the two sexual phases of a given hermaphrodite flower [37], phenology phase, among
flowers on different plants [38] and individuals, populations, cultivars, or subspecies
of the same species [39]. Physiological factors such as flower age, health of plants, and
damage to floral parts also affect the quality and composition of nectar.
3
Nectar Productions in Cherries
Cherry flowers are allogamous, actinomorphic, and are arranged in racemose clusters of 2–5 flowers. The sweet and sour cherry flowers are from 2.5 to 4.0 cm in
758
M. F. Akšić et al.
features varies widely between species and type of nectary and most probably are
related to different consumers and ecological factors (abiotic and biotic).
Flowers often have specialized structures that make the nectar accessible only for
animals possessing appropriate morphological structures, and there are numerous
examples of coevolution between nectarivores and the flowers they pollinate. The
main function of nectar compounds is related to the attraction of pollinating insects. It
is well-known that honey bee chemoreceptor can detect volatile substances, contained
in the nectar of crop plants at distance of about 2 km [21]. In this way, pollinators are
unintentionally mediating the transfer of pollen to receptive stigma, becoming a key
attribute for increasing cross-pollination [22, 23]. Although floral nectar production
represents a high cost for the plant, it ensures a higher possibility of fruit/seed set,
higher reproductive success and gene transfer into next generation. The production of
nectar (when starch granules in the parenchyma are broken down) often peaks when
anthers start to shade pollen and when the stigma is the most receptive. Generally
flowers secreting more nectar show more successful pollination events [24].
It is proved that secreted nectar volume correlates with flower size, which is
probably due to the pleiotropic effects, where larger flowers have larger nectaries and
more space for nectar [25, 26]. The amount of nectar reward is positively correlated
with the number of pollinator visits, the number of flowers visited within a plant, and
the duration of the visit within a flower [27]. Generally, energy received from nectar
per insect (or other pollinator) must be enough to attract pollinators, but still need to
encourage movement of the pollinator from flower/plant to another one. This means
that nectar volume is correlating with the body size of the pollinator [28].
The attractiveness of nectar to pollinators depends on taste [29], but odor and color
play an important role too [30, 31]. Characteristics such as volume, concentration,
color, and taste may be related to the concentration and composition of dissolved sugar
(especially glucose, fructose, and sucrose). But also other components, including
minerals, phenolic compounds, and amino acids, may make a cardinal contribution
to its attractiveness to honey bees [22, 32–34]. Bees prefer bright flowers, while visual
and chemical associations are pushing it to navigate within the field [35].
Nectar concentration is highly influenced by geographical distribution, thus environmental factors, especially light, water, nutrients, CO 2 concentration, temperature,
humidity, soil moisture, and wind [36]. Besides, nectar composition can vary between
the two sexual phases of a given hermaphrodite flower [37], phenology phase, among
flowers on different plants [38] and individuals, populations, cultivars, or subspecies
of the same species [39]. Physiological factors such as flower age, health of plants, and
damage to floral parts also affect the quality and composition of nectar.
3
Nectar Productions in Cherries
Cherry flowers are allogamous, actinomorphic, and are arranged in racemose clusters of 2–5 flowers. The sweet and sour cherry flowers are from 2.5 to 4.0 cm in
758
M. F. Akšić et al.