Total Pollen Grains Research Articles

Pollen‐mediated gene flow in an autogamous crop: Foxtail millet (Setavia italica)

AbstractGene How is a key concern associated with the eonlamination of seed multiplication iields and the use of transgenic crops. The release of herbicide‐resistant germplasnis and the use of male‐sterile varieties make foxtail millet (Sviaria ilalicii) an appropriate material to inves‐tigate this concern. Pollen dispersal from pollen donor sources and gene tlow in fertile and male‐slerile varieties of fortail millet were investigated in experiments in China and France. Although foxtail millel is mainly autogamous (less than 2% oiitcrossing), pollen from a 5m diameter plot could fertilize a tertile variety up to 24 ni away, and a male‐sterile variety up to 40m. Negative exponential and WeibuU fnnctions were used to tit the relationships between percentage and number i.A iubrids per cm of ear with distance from the pollen source. Wind velocity and direction resulted in variations of gene How intensity, but did nol change liie slope ofthe regression equations. Pollen competition for available target ovules was observed up to 2 m away from a 1 m diameter pollen source. The percentage of pollen grains that fertilized ovules outside the pollen donor source was 1.4% of the total pollen grain produetion. For every iflO pollen grains released under lieid conditions 1.5 seeds were produced. The probability funetion of pollen dispersal for one donor plant was calculated. It allowed predictions of gene How accord‐ing to lield shapes, estimations of isolation distances to preserve /ariety purity against pollen contamination, and the fornuiiation of efficient male/female ratios Ibr hybrid seed production.

ATOPIC ALLERGY IN ELITE RUNNERS ENHANCES EXERCISE INDUCED BRONCHOSPASM399

We studied 27 non-asthmatic elite runners, mean age 22 yrs, active competitors for 9 yrs. They had run a mean distance of 3510 km during the previous year. The runners answered a respiratory-symptom questionnaire and were subjected to an exercise challenge test (ECT) in winter at subzero temperature (from -1°C to -13°C) and in summer preceded by birch pollen season (weekly total pollen grains ranged from 11 to 538 grains/m3 during the preceding month). ECT consisted of 2000 m free running at 85% of predicted maximum heart rate without warm up and forced expiratory volume in one second (FEV1) measurements immediately before and at 4, 10 and 20 min after the run. Atopy was determined by skin prick tests (SPT) with 10 air-borne allergens. Sixteen (59%) of the runners were atopic in SPT. Five (31%) of the 16 atopic runners, but none of the non-atopics had previously reported exercise-induced bronchial symptoms. The mean maximum postexercise change was -6.0% (7.0%) for atopic and +2.5% (SD 4.3%) for non-atopic runners in winter or in summer tests (t-test, p=0.0013). Significant postexercise fall in FEV1 (≥6.0%, mean-2SD) was defined from the exercise responses of those 11 symptom-free, non-atopic runners. Nine(56%) of the atopic runners had a significant fall in either winter or summer tests, six (38%) of them in winter and four (25%) in summer. In conclusion: 1) Atopic runners have a significantly greater risk for exercise-induced bronchospasm (EIB) compared with non-atopic runners. 2) ECT for studying EIB should be performed both in winter and in summer conditions. SPT is valuable tool in assessing the risk for EIB.

Effect of Night Temperature on Pollen Characteristics, Growth, and Fruit Set in Tomato

Lycopersicon esculentum Mill. `Laura' plants were grown in the North Carolina State Univ. phytotron at 26C day temperature and 18, 22, 24, or 26C night temperatures to determine the effects of night temperature on pollen characteristics, growth, fruit set, and early fruit growth. Total and percentage normal pollen grains were higher in plants grown at night temperatures of 18 and 22C than at 24 and 26C, but germination was highest in pollen produced at 26C. Seed content was rated higher on the plants grown at 18C night temperatures than in any of the other treatments. Numbers of flowers and fruit on the first cluster were lower in the 26C night treatment than in the other night temperature treatments. Plant height was greatest but total shoot dry mass was lowest in the 22C night temperature treatments. Fruit fresh mass increased with night temperature, reflecting more rapid development, but the experiment was not continued to fruit maturity, so the effect of night temperature on final fruit size and total plant production could not be determined. Night temperatures of 26C reduced fruit number and percentage fruit set only slightly at a day temperature of 26C, even though these temperatures were above optimal for pollen production and seed formation. To separate temperature effects on pollen from direct or developmental effects on female reproductive structures, pollen was collected from plants in the four night temperature treatments and applied to stigmas of a male-sterile cultivar kept at 24-18C minimum temperatures in adjacent greenhouses. In the greenhouse-grown male sterile plants, no consistent effects of night temperature treatment given the pollen could be seen in fruit set, fruit mass, seed content (either on a rating or seed count basis), seedling germination, or seedling dry mass.

A quantitative approach to the sexual reproductive biology and population structure in some arctic flowering plants: Dryas integrifolia, Silene acaulis and Ranunculus nivalis

The population ecology of three species in northwest Greenland (Dryas integrifolia, Silene acaulis and Ranunculus nivalis) was studied in two consecutive seasons. Flowering phenology, population structure, flowering biology (including numbers of pollen grains per anther, germinated pollen grains per stigma, ovules per gynoecium, seeds per fruit), pollination and insect activity were the main features investigated.
 They were related to the micro- and macroclimatic conditions.
 The results can be summarized as follows:
 
 The unpredictability of the quality and length of the growing season makes the success of the reproductive cycle (i.e. production of mature seeds) very uncertain.
 There are seedlings at the studied sites of the three species.
 Most of the seedlings disappear.
 Population structure results indicate that seedlings become established in at least some years, but input of new individuals is episodic.
 Of the three species studied, R. nivalis allocates most resources to reproduction.
 Percentage normal pollen varies mostly between plants, less between days and sites (D. integrifolia).
 All three species are self-compatible.
 Full seed set is obtained only after insect visits.
 In S. acaulis seed set may be limited by the number of pollen grains reaching the stigmas.
 The flowers provide food (pollen and nectar) for the insects. They also provide shelter, warmth, and a mating place for them.
 There are sufficient insect visits per flower to ensure seed set, except possibly in S. acaulis.
 About 1 % of total pollen grain production is found as germinated pollen grains on stigmas.
 The utilization of pollen and stigmas varies between the three species. R. nivalis is the most efficient, whereas D. integrifolia is the most extravagant.
 A cold and rainy summer in 1976 resulted in conspicuously lower seed set in 1977 in spite of the latter summer being comparatively dry and warm.
 A 'reproductive budget' quantifying the various steps in the reproductive cycle is presented.

Inhibitors of cyanide-insensitive respiratory pathway induce male sterility in broccoli (Brassica oleracea).

(...) All three major specific inhibitors; salicylhydroxamic acid (SHAM), propyl gallate and disulfiram (tetraethylthiuram disulfide), were effective in inducing male sterility whenever they were applied to the flower buds with anthers less than about 2 mm in length, which those pollen developing stages corresponded to be earlier than early microspore stage. These chemically induced male sterile flowers which were characterized by shorter filaments and a reduction in the number of total and fertile pollen grains per flower, were similar to the cytoplasmic male sterile flowers. (...)

Influence of Triticum timopheevii Cytoplasm on Pollen Production and Dispersal in Common Wheat1

Breeders of hybrid hexaploid wheat (Triticum aestivum L. aestivum group) are developing R‐lines (pollinators) with cytoplasm and male‐fertility restorer genes derived from Triticum timopheevii (Zhuk.) Zhuk. var. timopheevii. It is important to determine if such R‐lines have reduced pollen production and dispersal compared to their respective B‐lines.The soft wheat cultivar ‘Monon’ was compared to three recovered backcross Monon‐type R‐lines with both cytoplasm and nuclear male‐fertility restorer factors derived from T. timopheevii. Pollen production and dispersal were measured by pollen collection in automatic spore traps, percent anther extrusion, and percent seed set on A‐lines.In spore trap comparisons A‐line 68846L2 dispersed significantly fewer total pollen grains than Monon, 1559 vs. 1975. The patterns of daily dispersal over the 7‐day period were generally similar for the R‐line and Monon although a significant day × pollinator interaction occurred.The three R‐lines were equal to Monon in anther extrusion with an average of 92% of the anthers extruded. The R‐lines and Monon were equally effective as pollinators in effecting seed set on three A‐lines (mean=60%). The small reduction in pollen dispersal of R‐lines was not great enough to reduce the effectiveness of the R‐lines as pollinators when compared to Monon at the 60% level of seed set for A‐lines in these experiments.