D. Eisikowitch

On the Pollination Ecology of Ficus Sycomorus in East Africa

Pollination and seed setting in ficus sycomorus have been investigated in East Africa. Ficus sycomorus is monoecious, each fig bearing both male and female flowers. Inside the figs 6 sycophilous wasps develop: Ceratosolen arabicus, Ceratosolen galili and sycophaga sycomori (primary sycophiles), and Apocrypta sp., Eukoebelea sp. and Sycoryctes sp. (secondary sycophiles). The structure and behavior of these wasps and their bearing on pollination and seed productionare studied. Ceratosolen arabiacus is the legitimate pollinator of Ficus sycomorus. It oviposits chiefly into short—styled female flowers, thus ensuring seed setting in the long—styled ones. It is a mutualistic symbiont of the fig. Sycophaga sycomori oviposits into both short— and long—styled flowers, and does not cause seed setting. It is a competitor of Ceratosolen, but a parasite of the fig. Eukoebelea, Apocrypta and Sycoryctes are inquilines, making use of galls induced by the activity of the primary sycophiles. They do not interfere with seed production in pollinated flowers not occupied by Ceratosolen or Sycophaga.

Amygdalin in almond nectar and pollen – facts and possible roles

Abstract. Nectar and pollen within flowers are usually the primary attractants to floral visitors. Chemical analysis of almond nectar and pollen in this study revealed that they contain the secondary compound amygdalin. Floral display often reflects pollinator characters, and almond flowers are accordingly designated as “bee flowers”. A previous study in Israel showed that when almonds bloom early in the season they attract honeybees, but later in the season the bees shift toward other species that start blooming. In this study, we offered honeybees sugar solutions containing various concentrations of amygdalin. These preference experiments revealed that in mid-summer bees were not selective, whereas early in the summer they were more discriminating, and consumed faster the sugar solutions with the lower amygdalin concentrations. Possible roles of amygdalin in almond nectar and pollen are discussed.

Some aspects of pollination of oil-seed rape ( Brassica napus L.)

The self-fertile cultivar of swede rape ( Brassica napus ) Maris Haplona does not usually autopollinate. The entomophilie pollen grains cannot be transferred by wind alone; anthers when flicked by insects or artificially under dry conditions behave like catapults raising a cloud of pollen grains. Variability in the concentration of sugar in its two types of nectaries (within a single flower) may increase the range of visiting insects. All visiting insects, including honey bees, carried out pollination; it is suggested that beehives should be placed in fields of oil-seed rape in order to increase pollination.

The role of electrostatic forces in pollination

This paper reviews research on the role of electrostatic forces in pollination, both in natural and in agricultural systems. Researchers from various fields of biological studies have reported phenomena which they related to electrostatic forces. The theory of electrostatically mediated pollen transfer between insect pollinators and the flowers they visit is described, including recent studies which confirmed that the accumulated charges on airborne honey bees are sufficient for non-contact pollen detachment by electrostatic forces (i.e., electrostatic pollination). The most important morphological features in flower adaptiveness to electrostatic pollination were determined by means of two theoretical models of a flower exposed to an approaching charged cloud of pollen; they are style length and flower opening. Supplementary pollination by using electrostatic techniques is reported, and its possible importance in modern agriculture is discussed.

Sequential introduction of honeybee colonies and doubling their density increases cross-pollination, fruit-set and yield in ‘Red Delicious’ apple

Summary The ‘Red Delicious’ apple exhibits full self-incompatibility, therefore its fruit production depends totally on cross pollination, especially by honeybees, which are the ultimate apple pollinators. In the present study, the technique of sequential introduction of honeybee colonies and doubling their density was applied to determine effects on yield. In three consecutive season it was found that sequentially increasing the density of colonies in the apple orchards from 2.5 colonies per ha., as recommended previously, to 5.0 colonies per ha, and introducing them sequentially (half at the 10% full bloom (FB) and half at FB), increased the number of bees per tree, their mobility among the rows, and the proportion of “topworkers” compared with “sideworkers” . It seems that a large number of foragers per tree directly increases the amount of pollination, high bee mobility between rows increases the amount of cross-pollination, and a high proportion of “topworkers” increases pollination efficiency. All the above effects were expressed in higher fruit set and higher yield (50–100%) in the treatment plots.

Volatiles of two chemotypes of Majorana syriaca L. (Labiatae) as olfactory cues for the honeybee

SummaryA study of olfactory discrimination by honeybee has been set up in order to understand the role of volatiles of the aromatic plant Majorana syriaca in attracting pollinating insects. The honeybees response to volatiles from leaves and inflorescences of two M. syriaca chemotypes, which differ in the thymol carvacrol ratio of their volatiles, was tested using a bioessay method based on associative conditioning and recruitement techniques. Behavioural data show that a honeybee identifies and reacts selectively to olfactory signals from leaves and from inflorescences of the two chemotypes. Such data suggest that the volatiles from all parts of the aromatic plant M. syriaca may have a role in attracting pollinators. The vegetative parts produce a volatile emission which attracts the pollinators from a distance towards the whole plant. At close range these are directed by the flower signal which is amplified by the volatiles of bracts and leaves in the inflorescence.

The behaviour of honey bees (Apis mellifera) visiting avocado (Persea americana) flowers and their contribution to its pollination

SUMMARYObservations of honey bee (Apis mellifera) foraging behaviour on five cultivars of avocado (Persea americana) were carried out in 1982–1984 and 1990–1992 in Galilee, Israel. Examination of the morphology of avocado flowers showed that the pistillate and staminate flower stages have similar structures. Bees collecting nectar, or nectar and pollen, visited both pistillate and staminate flowers, and due to the flower structure they were forced to touch both pistil and anthers. Only limited sites on a bees body contacted the anthers, and these ‘collection sites’ also contacted the stigma, which occupied the same position as the anthers of the inner stamens. Most avocado pollen grains on bees visiting staminate flowers were clumped at the ‘collection sites’ and constituted the main pollen available for pollination. Some pollen grains randomly distributed over the entire bodies of bees visiting either pistillate or staminate flowers could have been acquired inside the hive, and did not play an important...

THE NECTAR-INHABITING YEASTS AND THEIR EFFECT ON POLLEN GERMINATION IN COMMON MILKWEED, ASCLEPIAS SYRIACA L.

ABSTRACT In Asclepias, nectar is secreted by the stigmatic chamber and has two functions: (i) it is a carbohydrate reward for pollinating insects required by the plants for sexual reproduction and (ii) it is the germination medium for pollen at the onset of pollen tube growth. The nectar easily becomes infected by yeasts, mostly Metschnikowia reukaufii Griiss, which are vectored by pollinators. Nectar from flowers which opened in the laboratory was yeast-free and did not inhibit pollen germination, but samples of nectar from older, open flowers from the field were almost always (94–98%) inhibitory and supported populations of yeast When nectar samples from buds which opened in the laboratory or artificial nectars (solutions of D-glucose and sucrose which normally support vigorous germination of pollen) were contaminated with yeast-infected nectar, they did not support pollen germination. Yeast-infected nectar or sugar solutions were inhibitory even when filtered to remove the yeast cells. Laboratory yeast...

THE ROLE OF NECTAR IN THE GERMINATION OF POLLEN IN ASCLEPIAS SYRIACA L.

The nectary of Asclepias syriaca is in the stigmatic chamber. Nectar flows from there by a capillary system to the nectar reservoirs (cuculli). The fluid connection from the stigmatic chamber to the cuculli allows quick mixing of liquids in the system. Nectar in the stigmatic chamber is the germination medium for the pollen. Pollinia do not germinate in dry stigmatic chambers. The nectar must contain 5%-30% sugars for pollen germination. The nectar in the cuculli is the reward taken by insect pollinators and may become altered by physical (e.g., evaporation or dilution) or biotic (e.g., microbes, enzymes) factors.

The role of dark flowers in the pollination of certain Umbelliferae.

Summary The dark purple flower in the umbel of Daucus and the black spot on the umbel of Artedia have been shown to play a significant role in the pollination of these umbelliferae, because they attract the fly pollinators by their mimicry of resting insects.