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831.
对芸苔族8种2变种的花粉进行了光镜和扫描电镜观察。其中4种2变种为首次报道。研究表明,芸苔族植物花粉形态特征基本一致。但在花粉大小、萌发孔类型以及外壁纹饰上种间存在一定的差异。同时发现该族植物的花粉大小与其染色体数有一定的相关性。 相似文献
832.
Endogenous levels of polyamines and abscisic acid in pepper fruits during growth and ripening 总被引:4,自引:0,他引:4
Maria Serrano María Concepción Martínez-Madrid Fernando Riquelme Félix Romojaro 《Physiologia plantarum》1995,95(1):73-76
The levels of polyamines (PA) and abscisic acid (ABA) in the pericarp of California variety pepper fruit ( Capsicum annuum L.) were analyzed during development and ripening. Putrescine level was 2.75 μmol g−1 fresh weight 7 days after fruit set and fell during the exponential stage of growth to 1.05 μmol g−1 fresh weight. During the second growth stage. PA and ABA levels remained stable and fell sharply at the beginning of maturation. The levels of spermidine and spermine decreased throughout fruit development and maturation from 0.61 to 0.05 and 0.31 to 0.02 μmol g−1 fresh weight, respectively, but no changes were associated with the onset of maturation. ABA levels remained high (0.70-0.80 μg g−1 fresh weight) during the stages of fruit growth and fell at the beginning of maturation to 0.12 μg g−1 fresh weight, before rising again during the last stages of maturation and senescence. The decrease in putrescine and ABA levels and the subsequent increase in the latter may be responsible for controlling the processes of ripening in pepper fruit. 相似文献
833.
834.
Treatment of maize pollen to reduce nuclease activity 总被引:2,自引:0,他引:2
Recently it has been reported that maize (Zea mays L.) pollen can be stored up to several hours in a hypertonic aqueous medium at 0°C without losing its germinability (Broglia and Brunori 1994). We found that both release and activity of pollen nucleases are diminished in a cold hypertonic aqueous medium. Nucleases can be washed off while preserving germination ability and thus preserving the possibility of passive uptake of exogeneous DNA into germinating pollen grains. Alternatively, active DNA transfer into non-germinating pollen grains in the storage medium itself may be facilitated, due to the very reduced nuclease activity in this medium. 相似文献
835.
Nuclear DNA amount during sporogenesis and gametogenesis in sexual and aposporous buffelgrass 总被引:2,自引:0,他引:2
R. T. Sherwood 《Sexual plant reproduction》1995,8(2):85-90
Nuclear DNA amounts (C values) were measured in Feulgen-stained sections of anthers and ovules of sexual plant B-2s (genotype aaaa) and aposporous cultivar Higgins (genotype AAaa) of buffelgrass (Pennisetum ciliare). The mass of the unreplicated nuclear genome of a gamete equals 1C DNA. In both lines, pollen mother cell nuclei were 4C before leptotene; anther wall, dyad, 1-nucleate pollen, and generative cell nuclei were 2C; microspore tetrad, enlarging microspore, and sperm nuclei were 1C. The tapetum persisted as uninucleate cells with 4C DNA. Archespores (2-4C) of both lines initiated meiosis to form megaspore tetrad nuclei with 1-2C DNA. In B-2s, chalazal megaspores (2-4C) formed reduced 8-nucleate Polygonum type embryo sacs, and sacs at 2- and 4-nucleate stages showed distributions with peaks near C1 and C2, corresponding to G1 and G2 cell cycle phases; this is characteristic of active mitosis. Nuclei of 8-nucleate sacs and of eggs and polars were 1C, indicating chromosomes were not duplicated before fertilization. Antipodal nuclei had levels from 1 to 36C, possibly due to polyteny or endopolyploidy. In Higgins, aposporous initials and 2-nucleate embryo sacs showed bimodal distributions of 2n nuclei with peaks at 2C and 4C DNA. Nuclei of newly formed 4-nucleate Panicum type aposporous sacs and of polars were 2C; aposporous eggs stained too faintly for reliable measurement.Names of products are included for the benefit of the reader and do not imply endorsement or preferential treatment by USDA 相似文献
836.
Michel Debarle Arlette Martinage Pierre Sautiere Philippe Chevaillier 《Molecular reproduction and development》1995,40(1):84-90
During mouse spermiogenesis, two protamines, mP1 and mP2, are synthesized in replacement of histones. One of them (protamine mP2, 63 residues) appears at first in elongating spermatid nuclei as a pro-protamine of 106 residues (pmP2) with an amino-terminal extension that is progressively excised. The two protamines were previously described as the only proteins associated with DNA in sperm chromatin. This paper shows that the nuclear proteins of mouse spermatozoa are indeed heterogeneous: at least six minor polypeptides in addition to protamines can be identified. The primary structure of four of them has been established. They are intermediate in the maturation of the precursor of protamine mP2 and correspond to polypeptides pmP2/11, pmP2/16, pmP2/20, and pmP2/32, characterized previously in mouse testis. Therefore, these intermediates of proteolysis generated from pmP2 inside spermatid nuclei persist in mature sperm, whereas the largest precursors, pmP2 and pmP2/5, disappear. These findings clearly indicate that limited proteolysis events still occur outside of the testis. © 1995 Wiley-Liss, Inc. 相似文献
837.
Environmental monitoring of pollen grains in the atmosphere of Melbourne has been achieved using Burkard volumetric traps. Twenty-two families of flowering plants and confiers were identified in the pollen counts. About 62% of these pollen grains belonged to trees, 20% to grasses and 9% to herbs and weedy plants. During spring and summer, the atmosphere contained about 70% of the total annual pollen count. Tree pollen, predominantly elm and cypress, occurred abundantly in late winter and spring, with grass pollen predominantly in spring and early summer. These three types of pollen grains occurred in significant amounts, together accounting for more than 60% of the total annual catch. A seasonal incidence chart (pollen calendar) for Melbourne based on 2 years observation has been constructed. This pollen calendar is useful in identifying sources of allergies against particular seasonal airborne pollen types. Comparison of the time of occurrence of a particular pollen type using the pollen calendar and the time of allergic symptoms, can lead to accurate diagnosis and preventive measures being taken. This study has confirmed that grass pollen is the major source of allergenic pollen in the external environment triggering hay fever and allergic asthma in spring and early summer in Melbourne, Australia. 相似文献
838.
美味猕猴桃和软枣猕猴桃种间杂交花粉管行为和早期胚胎发生的观察 总被引:4,自引:0,他引:4
美味猕猴桃(Actinidia deliciosa No.26)和软枣猕猴桃(A. arguta)杂交,观察了花粉管在花柱内的行为和早期胚胎发生,结果如下: 花粉粒在柱头的乳突细胞表面萌发,在开放型的V 形花柱道内生长,生长速度比对照的缓慢, 到达胚珠珠孔处的时间延迟50 到60 h。当花粉管生长到花柱基部时出现波纹状弯曲;顶端膨大或尖细;部分花粉管的直径发生变化;少数花粉管生长极不规则。花粉管中胼胝质沿管壁不规则沉积, 有的不形成胼胝质塞,或整个管壁被胼胝质所覆盖。约有26.74% 的胚珠受精, 并发育成种子,其中正常种子占68.50% ;败育种子占31.50% ,其中约有11.41% 为空瘪种子;未受精胚珠占61.45% 。正常种子及其胚均较对照的小。胚发育为茄型,胚乳为细胞型,合子保持休眠十几天后开始分裂形成胚,传粉后50d 见到子叶胚 相似文献
839.
烟草花粉发育过程及不同组织中的内源GUS活性 总被引:1,自引:0,他引:1
以 X- gluc作为葡糖苷酸酶 ( GUS)酶反应底物 ,用酶组织化学方法检测了烟草 ( Nicotianatabacum L.)不同组织细胞的内源 GUS。在幼苗的根、茎、叶不同发育时期的花药壁、柱头、胚珠分离的生殖细胞和胚囊中 ,均未检测到内源 GUS活性。不同发育时期的烟草花粉内源GUS活性存在差异 ,在小孢子分裂前后和成熟花粉萌发前后有两个活性高峰。检测花粉内源GUS活性的适宜 p H为 5 .0 ;p H7.0的条件下未检测到内源 GUS。用 2 0 %甲醇或 0 .2mmol/L葡糖二酸内酯处理不能完全抑制内源 GUS活性 相似文献
840.
Pollen morphology of Gyrostemonaceae, Bataceae, andKoeberlinia, which have been affiliated with glucosinolate-producing taxa, was examined by field emission scanning and transmission electron
microscopy. Pollen grains of Gyrostemonaceae are tricolpate with scabrate-spinulate surface and have a thick, unstratified
exine, while those of Bataceae are tricolporoidate with granular surface and have a thin exine with a single, outermost granular
layer. Gyrostemonaceae and Bataceae, which had often been considered sister taxa based on palynological similarity and now
are considered more distantly related, have a similar spongy ektexine, but differences between them are evident.Koeberlinia, which is recently considered a sister group to Bataceae+Salvadoraceae (with no spongy ektexine), has tricolporoidate pollen
composed of a plesiomorphic, stratified exine with columellae. The totality of evidence indicates that, contrary to earlier
observations, pollen of Gyrostemonaceae and Bataceae does not closely resemble each other, and that the spongy ektexine, which
looks to be similar in TEM sections, is a homoplasy that evolved independently in the two families.
Dedicated to the late Prof. Emer. Kankichi Sohma (August 28, 1926–June 26, 1995), who supervised us for our M. Sc. and D.
Sc. programs at Tohoku University, Sendai. He died after his 40 years career in palynology; his wide range of interests and
enthusiasm for research, and his unfailing encouragement for students are greatly missed. 相似文献