Breaking strengths of pollen grain walls

50% breaking point pressures of pollen grain walls of eleven species were determined. The breaking point pressures of most pollen grain walls are equivalent to those reported in the literature for other types of living cell walls such as bacterial spore coats, algal cell walls, mold sporophyte cells, and dicot suspension culture cells. The strongest pollen grain walls are two or three orders of magnitude stronger, however. Pollen grain walls are proportionately very thick in comparison to other types of cell walls. It is this thickness, not the construction or physical properties of the pollen grain wall, that most probably accounts for their strength.     

花粉抗辐射损伤的动物实验研究

花粉对动物辐射损伤研究的结果为：花粉能提高辐射动物外周血粒细胞,保护骨髓、脾脏、胸腺等组织结构,增加辐射动物血浆超氧化物歧化酶（ＳｕｐｅｒｏｘｉｄｅＤｉｓｍｕｔａｓｅ,ＳＯＤ）的活力,降低脂质过氧化物（ｍａｌｏｎｉｃｄｉａｌｄｅｈｙｄｅ,ＭＤＡ）含量,此外,对辐射动物睾丸的生精作用有一定的保护。这些结果均说明花粉具有多方面的抗辐射损伤效应。     

Sugar composition of pollen grain and pollen tube cell walls

The sugar composition of pollen grain and pollen tube cell walls was studied for Camellia japonica, C. sasanqua, C. sinensis, Tulipa gesneriana and Lilium longiflorum. In all species, the main components of pollen grain walls were arabinose, galactose, glucose and uronic acid. On the other hand, the pollen tube walls consisted mostly of glucose. The pollen tube wall of C. japonica was fractionated into hemicellulose, α-cellulose and pectic substance fractions in yields of 61, 19 and 3 %, respectively. The hemicellulose fraction was composed essentially of glucose. The sugar composition of the pollen tube wall was not influenced by the nature of exogenously supplied sugars. Rapid growth of the pollen tube seemed to correlate with the synthesis of hemicellulosic glucan.     

A hematoxylin staining procedure for maize pollen grain chromosomes

Studies of postmeiotic chromosome behavior have been impeded by the thick exine and abundant starch grains of maize pollen. Staining pollen grain chromosomes with acetocarmine is tedious and gives inconsistent, often unsatisfactory results. A hematoxylin stain, used in conjunction with the clearing agent chloral hydrate, has been successfully used by the authors to stain chromosomes, nuclei and sperm cells of the maize pollen grain. An ethanol-formaldehyde fixing fluid is used to fix and preserve the pollen samples. The procedure, which is rapid and simple, gives excellent preparations with both fresh and fixed material. Stained preparations do not get darker with time, as is typical of other hematoxylin stained materials.     

Seasonal trends in honey bee pollen foraging revealed through DNA barcoding of bee-collected pollen

Insectes Sociaux - Recent declines in the abundance and diversity of wild bee species have made it important to understand how introduced species such as honey bees contribute to pollinating native...     

Utilization of alkali-treated grain. 1. Alkali-treated grain in complete diets for steers and lambs

In one experiment, 32 lambs were offered (ad libitum) diets based on whole or NaOH-treated barley, or whole or NaOH-treated oats. The live-weight gains from 17 to 35 kg live weight were 371, 290, 258 and 229 g/day, respectively, while the calculated carcass weight gains were 190, 161, 86 and 118 g/day, respectively. There were large differences in the gut contents at slaughter which were 5.0, 3.3, 9.2 and 3.0 kg for the four diets, respectively.Forty-eight, Hereford-cross steers were allocated to six dietary treatments which consisted of unrestricted access to one of the following diets: NaOH-treated barley; rolled barley; NaOH-treated oats; rolled oats; NaOH-treated wheat; or NaOH-treated maize. The steers were fattened from 325 to 425 kg live weight. The average live weight gains were 1.56, 1.91, 1.37, 1.38, 1.49 and 1.42 kg/day, respectively. The steers receiving rolled barley achieved the greatest live weight gains (P < 0.05). The rumen contents at slaughter were 19.8, 32.2, 24.2, 46.0, 20.8 and 18.4 kg, respectively. Because of differences in gut contents, the only significant differences in carcass weight gain were found for the steers receiving rolled oats, for which carcass gain was lower than that for any other treatment (P < 0.001).Sixteen, Hereford-cross steers were allowed free access to diets containing either NaOH-treated barley alone, or NaOH-treated barley mixed with 10% of chopped straw. The live weight gains from 325 to 425 kg live weight were 1.55 and 1.07 kg/day, and food conversion was 5.7 and 8.4 kg feed/kg gain respectively.     

Development of the pollen grain wall in Canna

During the tetrad period spinules form on the Canna L. plasma membrane at intervals of 1–2 μm on a microspore surface of ca. 100 μm². The isolated spinules represent all that there is of a primexine-like nature. Immediately following loss of the callosic tetrad envelope a channeled, oncus-like zone forms on the plasma membrane over the entire microspore surface, elevating the spinules. The oncus-like zone becomes ca. 4 μm thick by microspore mitosis. Intine introduction during the pollen grain period coincides with substantial thinning of the oncus-like zone and pollen grain enlargement. In the final phases of maturation grains increase further in diameter and become packed with starch and lipoidal material. The oncus-like zone more than doubles in height necessitating a migration of the boundary of the oncus-like zone and intine. At pollen grain maturity the thin (ca. 200 nm) surface layer of the oncus-like zone appears to be compacted or filled in.     

The potential for adaptive evolution of pollen grain size in Mimulus guttatus

We tested whether pollen grain size (PGS) shows heritable variation in three independent populations of Mimulus guttatus by imposing artificial selection for this character. In addition, we looked for correlated responses to selection in a range of 15 other floral characters. Heritable variation in PGS was found in all three populations, with heritabilities of between 19 and 40% (average 30%). After three generations, upward and downward lines differed on average by 30% in pollen volume. No consistent patterns of correlated response were found in other characters, indicating that PGS can respond to selective forces acting on PGS alone. Possible selection mechanisms on PGS in this species could include intermale selection, if large pollen grains produce more competitive gametophytes; or optimization of patterns of resource allocation, if local mate competition varies.     

PCR and sequencing from a single pollen grain

In order to eliminate the laborious step of DNA extraction preceding all studies within the field of plant molecular biology we attempted to do PCR amplifications directly on pollen grains. Successful PCR amplification was obtained in reactions including a single pollen grain from Hordeum vulgare or Secale strictum. Both the plastid gene encoding ribulose-1,5-biphosphate carboxylase/oxygenase (rbcL) and the nuclear-encoded internal transcribed spacer regions (ITS) and the 5.8S rDNA region were amplified and sequenced to verify PCR amplification.     

Airborne pollen grain concentrations at two different heights

The present study describes the airborne pollen grain concentrations at two different heights (1.5 m and 15 m, respectively). The survey was carried out in 1991 and 1992, using two Burkard spore-traps, both set up at the University of Córdoba, Faculty of Sciences. Generally, and for all herbaceous plants, pollen detection started and ended around the same date on both samplers. However, in the case ofOlea europaea, the pollen was detected in advance by the sampler located at 1.5 m compared with the one located at 15 m, probably due to the fact that olives growing close to the low sampler flower before the great olive plantations located some 60 km south of the city. No significant differences between the counts of both samplers have been observed, except in the case of Urticaceae, where the sampler situated on top of the building recorded higher pollen concentrations in both years. Similar annual peaks of Urticaceae are probably due to the buoyancy of their small, light grains and the explosive pollination mechanism which liberates pollen grains from the anthers of the Urticaceae family, includingUrtica andParietaria.     

Electron microscopic ammonical silver reaction forTradescantia pollen grain

Summary The postformalin ammonical silver reaction (ASR) for basic nuclear proteins was applied to both the generative and vegetative nuclei ofTradescantia pollen grains and examined with the electron microscope. The ASR deposit was usually observed mainly in the dense chromatic regions of both the generative and vegetative nuclei. Since a large amount of dense chromatic regions was observed in the generative nucleus than the vegetative ones in late or mature pollen grains, as a results, the increased amount of the ASR deposit was revealed in the generative nucleus.     

Generation of reactive oxygen species during pollen grain germination

The formation of reactive oxygen species in pollen at the early germination stage, which precedes the formation of the pollen tube, was studied. During this period, pollen grain is being hydrated, abruptly increasing its volume, and it passes from the resting state to active metabolism. Fluorescent methods have made it possible to reveal reactive oxygen species in the cytoplasm and inner layer of the pollen wall, intine. The cytoplasmic reactive oxygen species were mostly found in mitochondria, while extracellular ones were localized in aperture zones of intine, as well as in the solution surrounding pollen grains in vitro. The content of extracellular reactive oxygen species decreased after superoxide dismutase (100 units per ml) and diphenylene iodonium (100 μM), which indicates NADPH oxidase as one of possible producent of them. In conditions of suppression of extracellular reactive oxygen species production (100 μM diphenilene iodonium) or their promoted removal (after addition of 10 to 100 μM ascorbic acid), the number of germinating pollen grains increased. This effect disappeared after further increase in the concentration of the listed reagents. The result is evidence of the significance of processes of generation/removal of extracellular reactive oxygen species for pollen germination.     

Feeding performance in broiler chickens fed diets containing DAS-59122-7 maize grain compared to diets containing non-transgenic maize grain

Event DAS-59122-7 is a maize (Zea mays) genetically modified to contain cry34Ab1 and cry35Ab1 genes from Bacillus thuringiensis (Bt) strain PS149B1 and the pat (phosphinothricin acetyltransferase) gene from Streptomyces viridochromogenes. In planta, co-expression of the Cry34Ab1 and Cry35Ab1 proteins confer resistance to corn rootworms (Diabrotica virgifera virgifera LeConte and Diabrotica barberi Smith and Lawrence, respectively; CRW), a major pest of maize. Expression of the PAT protein confers tolerance to herbicides containing glufosinate-ammonium. The current study was conducted to evaluate the nutritional value of grain containing event DAS-59122-7 (59122) by comparing the growth performance and carcass yield of broiler chickens fed diets prepared with 59122 maize grain as the sole source of corn with that of broiler chickens fed diets containing near isoline maize grain (control) and three non-transgenic reference maize-grain controls (Pioneer hybrids 33P66, 33J56, and 33R77). Diets produced with 59122 or non-transgenic maize grain were fed to broilers (n = 120/group) for a period of 42 days in three phases: Starter, Days 0–21 [530 g maize grain per kg of diet], Grower, Days 22–35 [580 g maize grain per kg of diet] and Finisher, Days 36–42 [700 g maize grain per kg of diet] in accordance with standard commercial poultry farming practice. Performance and standard carcass yield data were determined at the end of the feeding trial. Differences between 59122 maize and near isoline control maize-grain means were evaluated with statistical significance at P<0.05. Performance and carcass traits from broilers consuming diets produced with 59122 and near isoline were compared to tolerance intervals constructed using data from broiler groups fed diets produced with reference maize grains. No statistically significant differences were observed in mortality, weight gain, feed efficiency (corrected for mortalities), and carcass yields between broilers consuming diets produced with 59122 maize and those consuming diets produced with near isoline control grain. Additionally, all response variables evaluated in both groups fell within the tolerance intervals of the values observed in broilers fed diets produced with the reference maize grains. Based on the results from this study, it was concluded that 59122 maize was nutritionally equivalent to non-transgenic control maize.