Variation between plant species in pollen digestion rates in the green lacewing Chrysoperla carnea

Abstracts of Nippon Dojo-Hiryogaku Zasshi

The combined effects of high nitrogen supply, cool temperature regimes and shading on factors related to fertility in rice plants were investigated. High nitrogen supply during the period from the spikelet differentiation stage to the young microspore stage caused a decrease in the number of microspores per anther. High nitrogen supply plus cool treatment at the young microspore stage (12°C for 3 or 4 days) resulted in a conspicuous decrease in the number of engorged pollen grains per anther. Shading also decreased the number of microspores and pollen grains. The lowest numbers of microspores and pollen grains were observed in a treatment combining high nitrogen supply with shading and cooling. The number of pollen grains shed on the stigma and germinated pollen grains were decreased by cooling. These results suggested that the lower fertility due to high nitrogen supply combined with cooling resulted from 1) decrease in number of microspores, 2) large decrease in number of pollen grains per anther, and 3) decreases in number of pollen grains and germinated pollen grains on the stigma.

Наведено результати дослідження якості пилку 18 видів сосни 37-річного віку на пінетумі Старопетрівського лісництва ДП «Київська ЛНДС». Із 29 посаджених видів роду Pinus дотепер зберіглося 20. Усі види сосни, представлені на пінетумі, «цвітуть». Природно-кліматичні умови регіону сприяють утворенню життєздатного пилку (65,9–99,8 %) з незначною кількістю аномальних пилкових зерен.
 У процесі пророщування пилку виявлено відхилення від норми у вигляді двох пилкових трубок майже у всіх видів сосни. Життєздатність пилку інтродукованих видів сосни та інтенсивність росту пилкових трубок пов’язані між собою. Якість пилку не є причиною низького виходу виповненого насіння. Виявлено, що на пінетумі ДП «Київська ЛНДС» дерева-інтродуценти не утворюють достатньої кількості якісного насіння.

Low temperatures impose restrictions on rice (Oryza sativa L.) production at high latitudes. This study is related to low temperature damage that can arise mid-season during the panicle development phase. The objective of this study was to determine whether low temperature experienced by the root, panicle, or foliage is responsible for increased spikelet sterility. In temperature-controlled glasshouse experiments, water depth, and water and air temperatures, were changed independently to investigate the effects of low temperature in the root, panicle, and foliage during microspore development on spikelet sterility. The total number of pollen and number of engorged pollen grains per anther, and the number of intercepted and germinated pollen grains per stigma, were measured. Spikelet sterility was then analysed in relation to the total number of pollen grains per spikelet and the efficiency with which these pollen grains became engorged, were intercepted by the stigma, germinated, and were involved in fertilisation. There was a significant combined effect of average minimum panicle and root temperatures on spikelet sterility that accounted for 86% of the variation in spikelet sterility. Total number of pollen grains per anther was reduced by low panicle temperature, but not by low root temperature. Whereas engorgement efficiency (the percentage of pollen grains that were engorged) was determined by both root and panicle temperature, germination efficiency (the percentage of germinated pollen grains relative to the number of engorged pollen grains intercepted by the stigma) was determined only by root temperature. Interception efficiency (i.e. percentage of engorged pollen grains intercepted by the stigma), however, was not affected by either root or panicle temperature. Engorgement efficiency was the dominant factor explaining the variation in spikelet sterility. It is concluded that both panicle and root temperature affect spikelet sterility in rice when the plant encounters low temperatures during the microspore development stage.

SummaryFor basic and clinical studies of Japanese cedar (JC) pollinosis and its treatment, experimental facilities for exposure to pollen under stable environmental conditions are becoming increasingly desirable. We developed an artificial exposure chamber (OHIO Chamber) that allows the dispersal of fixed concentrations of JC pollen in stable environments with a unique pollen supply system, air flow system for fixing the concentration of JC pollen, system for monitoring the number of pollen grains, and automated pure water washing and drying system. In the chamber, temperature and relative humidity (RH) could be successfully maintained at 22±1.1 °C and 45±5%, respectively. The spatial distribution of pollen concentrations in the chamber was within 10% of target, including when subjects were present. Only a few or no pollen grains were detected in the chamber after automatic washing and drying. We conducted a pilot tolerability and safety study in 15 JC pollinosis patients who were exposed to 15 000 pollen grains/m3 for 2 h. Symptoms manifested on average 33 min after start of exposure. The subjects experienced no serious side‐effects, and pollen exposure at 15 000 grains/m3 was confirmed safe. After exposure, the number of intranasal and intraocular pollen grains was 469 and 602, respectively. The lower number of pollen grains in the nose than in the eyes was considered due to sneezing and nasal discharge. Further studies are needed to clarify the number of pollen grains required for the occurrence of symptoms in the OHIO Chamber.

This study was conducted to clarify the relationship between the number of pollen grains per anther and spikelet fertility under low temperature conditions in the rice cultivars and lines including lines with quantitative trait loci (QTL) for cold tolerance, adapted to the Tohoku region of northern Japan. Cold-water treatment decreased anther length, the number of pollen grains per anther, and spikelet fertility in all cultivars and lines. The number of pollen grains was proportional to anther length in all cultivars and lines and under all temperatures. Spikelet fertility decreased with decreasing the number of pollen grains in cold-water treatments at 18.5 and 19.3 °C. ‘Ouu 415’, with the qLTB3 QTL for cold tolerance, had 28% more pollen grains and 9% higher spikelet fertility than the recurrent parent, ‘Hitomebore’, in the 18.5 °C cold-water treatment, suggesting that qLTB3 increased both parameters. Lines with the qCTB8 QTL for cold tolerance had significantly more pollen grains in two of the three years and significantly higher spikelet fertility in all three years in the 19.3 °C cold-water treatment, suggesting that qCTB8 reinforced cold tolerance. Ctb1, a proposed cold-tolerance QTL, had no effect on the number of pollen grains or spikelet fertility. In conclusion, the cultivars and lines with more pollen grains had a higher cold tolerance. Some of QTLs were inferred to increase the number of pollen grains and reinforce cold tolerance.

In the study, structural features of flowers of the following allergenic plant species were analysed: <i>Betula verrucosa</i>, <i>Secale cereale</i>, <i>Rumex acetosella</i>, <i>Plantago major</i> and <i>Artemisia vulgaris</i>. Pollen production was established by calculating the number of pollen grains produced by the stamen, flower and inflorescence. The dates of occurrence and pollen grains concentration in the air of Lublin were determined. A positive correlation was found between the length of anthers and the number of pollen grains produced. The largest number of pollen grains per anther is produced by Secale cereale (22 360), whereas the smallest one by Plantago major (5 870). The other species produced intermediate numbers of pollen grains in the anther: <i>Betula verrucosa</i> - 11 160, <i>Rumex acetosella</i> - 10 850, <i>Artemisia vulgaris</i> - 9 580. The birch pollen season in Lublin lasts about a month, and pollen of this taxon reaches the highest airborne concentrations among the studied taxa. Low values of pollen concentrations are characteristic for rye and plantain, whereas slightly higher values are recorded for sorrel pollen. Mugwort pollen reaches high concentrations which are noted at the beginning of August.

Pollen grain germination in vitro indicates viability and consequently provides information related to fruit set. It also assists in the development of hybrids. Along with a suitable species, a standard culture medium is essential for evaluating pollen viability. It should contain a gelling agent consisting of carbohydrates and enhancer elements as well as have the correct pH, temperature, and incubation time. The objective of this study was to optimise the culture medium, determine the pollen germination capacity, and quantify the number of pollen grains per flower of certain olive tree cultivars. A basic sequential culture medium for pollen grain germination was determined, always utilizing the best result from the previous experiment to continue the sequence.The factorial treatment arrangement was: 1) agar versus boric acid; 2) pH versus sucrose; 3) calcium nitrate versus magnesium sulfate. After determining the culture medium components, two experiments were conducted evaluating temperature and incubation time. Another experiment evaluated both the germination percentage and the number of flower pollen grains of 28 cultivars. The culture medium should be composed of 4 g∙L-1 of agar, 90 g∙L-1 of sucrose, and 400 mg∙L-1 of boric acid with a pH adjusted to 5.79 and an incubation time of 60 h at 28 °C. The Manzanilla 215 cultivar had the highest germination rate while Ascolano 315 presented the highest number of pollen grains per flower.

Correlation between symptoms and the threshold for release of mediators in nasal secretions during nasal challenge with grass-pollen grains

The production of the total and stainable number of pollen grains per flower and per inflorescence of 13 olive cultivars (Olea europaea L.) has been investigated. Grains stainability was evaluated by using the acetic carmine staining method whereas the production of pollen grains was calculated by using a Bürker haemocytometer. All pollen characteristics taken into account varied significantly among the cultivars. The number of flowers per inflorescence ranged from a maximum of 31.3 (‘Cipressino’) to a minimum of 13.0 (‘Leccino’), the number of pollen grains per anther ranged from 123 346 (‘Arbequina’) to 40 975 (‘Sant'Agostino’), and the pollen stainability from 97.6% (‘Cipressino’) to 48.0% (‘Cellina di Nardò’). The number of stainable pollen grains per inflorescence averaged 2 559 512, ranging from a maximum of 3 913 678 (‘Nociara’) to a minimum of 940 143 (‘Sant'Agostino’). All parameters were positively correlated, whereas a linear negative correlation was found between stainability and total pollen grains both per anther and per inflorescence.

Characteristic air-disturbance patterns around megastrobili of Cycas, Dioon, and two species of Zamia (Z. pumila and Z. furfuracea) influence the pattern and quantity of wind-borne pollen grain deposition on ovules and surfaces of megasporophylls. The greatest number of adhering pollen grains is found on the windward profiles of cycad cones, with the density of pollen grains generally diminishing along cone surfaces oriented parallel to airflow. Cycas megastrobili preferentially deflect airflow passing over the cone toward leeward, distal surfaces, where pollen grains accumulate. Dioon cones deflect airflow and pollen grains toward leeward, proximal surfaces, where pollen grains preferentially impact with or settle on the surfaces of sterile bracts. Zamia pumila megastrobili have a fairly uniform distal to proximal distribution of pollen grain impactions. Zamia furfuracea megastrobili split longitudinally along the contact zones of orthostichous megasporophylls. Air currents carrying pollen grains into the cone through these openings circulate within the cone, centrifugally depositing pollen on ovules and megasporophyll surfaces. Statistical analyses of pollen distribution in Cycas, Dioon, and Z. pumila indicate no significant differences between the number of pollen grains adhering to surfaces of ovules and adjacent megasporophylls. Although the general pattern of pollen grains adhering to megastrobili of Cycas and Dioon is the result of nonrandom aerodynamic processes, direct wind pollination in all four taxa appears to be stochastic. The preferential concentration of pollen on the distal portions of Cycas megastrobili may aid pollination. Water, dislodging adhering pollen grains, flows along the glabrous ovule-bearing margins of megasporophylls and accumulates on or near micropyles. Similarly, air eddies may sift pollen into the cone onto ovules. By contrast, the preferential accumulation of pollen on the proximal, sterile bracts of Dioon, in conjunction with insect foraging and semidestructive burrowing into the cone, may effect pollination. We suggest that cycad pollination may have two phases: (1) the transport of wind-borne pollen grains to megastrobili (Cycas, Dioon, and Zamia), and (2) the subsequent transport of adhering pollen to ovules by water and/or passive sifting (Cycas) or insect activity (Dioon, and possibly Zamia).

Beziehungen zwischen Pollenkonzentrationen in der Luft und Pollenniederschlagswerten

In Medicago saliva L. intra‐plant variation in pollen production occurred in partially male‐sterile clones, but it was not associated with either flower position on the plant or sampling date. The variation occurred at random throughout the plant. Anthers within the same flower varied for both number of pollen grains and percentage of normal pollen grains.The average number of pollen grains per anther varied among clones from about 440 to 850. The free anther had only about two‐thirds as many pollen grains as each of the remaining nine anthers. The number of normal pollen grains correlated with visual estimates of the amount of dehisced pollen, r = .854**, 11 d.f. Pollen abortion in male‐sterile plants apparently reduced internal pressure sufficiently to prevent rupture of the anther wall and extrusion of pollen.

Amount and quality of pollen grains in four olive (Olea europaea L.) cultivars as affected by ‘on’ and ‘off’ years

Honey bees and wild bees provide critical pollination services to agricultural ecosystems; however, the relative contributions of different bee taxa are not well understood. The natural habitats surrounding farmland support food and nesting resources for wild bees and therefore play an important role in the maintenance of crop pollination. In this study, we selected Cucurbita pepo L. (squash) as a model crop to investigate the relative importance of honey bees and bumblebees in pollinating the crop. Thirteen fields, which were surrounded by a gradient of natural habitat, were investigated on the Yunnan‐Guizhou Plateau in China. We measured the visit densities of honey bees and bumblebees, the number of pollen grains deposited in a single visit by the two bee taxa, as well as the overall pollen grains deposited on stigmas during a flowering day, and then used Bayesian inference to decouple the pollen grains deposited by either the honey bees or the bumblebees. Compared with honey bees, bumblebees deposited a higher number of pollen grains on stigmas in a single visit, but had a lower visit density than honey bees. Meanwhile, the bumblebee visit density increased along the proportion of natural habitat, while the honey bee visit density was not affected by the surrounding natural habitat. Data simulations using Bayesian inference showed that on a flowering day, the number of pollen grains deposited by bumblebees increased with the proportion of natural habitat in the surrounding landscape, but the number of pollen grains deposited by honey bees did not. Moreover, the total numbers of pollen grains deposited by honey bees or bumblebees alone were all below 2000 (the critical level to satisfy the pollination requirement of this crop). Pollen calculations demonstrated that the number of pollen grains deposited by the two bee taxa was greater than 2000 in fields surrounded by more than 13% natural habitat (grasslands and forests). The results revealed that bumblebees ensured C. pepo pollination in combination with honey bees in the highland agricultural ecosystems.