共查询到20条相似文献,搜索用时 15 毫秒
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Petkus winter rye seed was subjected to ultrasonic vibrations of i Mcyc./sec. frequency in order to test the possibility of their having a vernalizing action. Seed which had not been soaked, fully imbibed seed, germinating seed (radicle showing) and seedlings with about 2 mm. long coleoptiles were treated with two intensities of ultrasonics for two periods of exposure.
There is a slight favourable effect on germination rate of the unsoaked seed, but injury or death is caused by higher doses applied to the imbibed or germinated seed. Time to flowering was not affected by this treatment and no vernalization resulted. 相似文献
There is a slight favourable effect on germination rate of the unsoaked seed, but injury or death is caused by higher doses applied to the imbibed or germinated seed. Time to flowering was not affected by this treatment and no vernalization resulted. 相似文献
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Wllla Nehlsen 《American journal of botany》1979,66(5):601-603
Protonemata of Polytrichum juniperinum were grown in the dark, in sucrose- and cytokinin-supplemented media. Under these conditions gametophore buds form shortly after spore germination. Of the cytokinins tested, DMAAP was most effective in bud induction. This system holds much promise for study of cytokinin action. 相似文献
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《Lichenologist (London, England)》1999,31(6):603-612
Dispersal patterns from seven terricolous lichen species, with a high capacity for asexual reproduction by fragmentation (Cetraria muricata, Cladonia species), were studied in differing vegetation types in north-eastern Germany. Marked lichen thalli were fragmented by trampling. After 15 days the spread of thallus fragments was monitored. Whereas most of the fragments that were dispersed by wind remained within a 20-cm radius from the source, the maximal dispersal distance was 57 cm in a dry sand grassland and 68 cm in an open pioneer pine forest. Dispersal was negligible in a closed old-growth pine forest. Several fragmented lichen cushions were disturbed and removed by animals, and led to a maximal dispersal distance of 9·70 m. These results suggest that: (a) thallus fragments provide good short-distance dispersal in open vegetation, but are inefficient for long-distance dispersal, and (b) wind and animals are important factors for the dispersal of thallus fragments. For restoration management of man-made substrata, artificial introduction of lichen thalli is proposed. 相似文献
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MODERN POLLEN RAIN IN FINNISH LAPLAND INVESTIGATED BY ANALYSIS OF SURFACE MOSS SAMPLES 总被引:2,自引:2,他引:0
SHEILA HICKS 《The New phytologist》1977,78(3):715-734
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取食辽东栎(Quercus liaotungensis)叶片的植食性昆虫有丰富的多样性和重要的生态功能,昆虫取食叶片留下的形状变化多,易观察,可以作为昆虫物种多样性监测的手段之一。研究北京西部东灵山地区辽东栎叶片被植食性昆虫取食状况,发现昆虫对辽东栎叶片的危害非常普遍,叶片被食频率约为90%,被食面积约5%,取食状可分为9类,其中以缘食和孔食为主,共记录20余种植性昆虫,其中蛾类幼虫和甲虫是主要取食种类,植食性昆虫集中出现在叶片发育的早期阶段(5-6月份),7月份后,大多数幼虫发育成熟,取食叶片的面积减少。各取食状所涉及昆虫种类的组成不同,面积呈不同的季节变化模式,其中缘食状和孔食状之间有显著的正相关关系;辽东栎叶片在展叶初的叶面积最低,在7月底均达到最大值,然后呈下降趋势,单位面积重量也在展叶初最低,在6月底接近最大值,不同坡向的辽东栎林和叶片面积,单位面积重量及叶片被食面积均有显著差异,偏阳坡(东南坡) 高于偏阴坡(西北坡)。以上结果表明,辽东栎叶片维持了昆虫物种多样性,昆虫的生长发育与辽东栎的物候规律相互协调,昆虫种类的取食呈季节和空间变化。 相似文献
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TIME FACTOR IN UTILIZATION OF MINERAL NUTRIENTS BY HEMP 总被引:1,自引:0,他引:1
Tibeau SM 《Plant physiology》1936,11(4):731-747
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Pure antibodies to nerve growth factor have been isolated from sheep nerve growth factorantiserum by affinity chromatography using 2.5 S nerve growth factor linked to Sepharose 4B by means of cyanogen bromide. The elution of the antibodies was accomplished either at low pH (pH 2) or by high salt concentration (4.5 wMgC12). The purity of the antibodies was established by SDS-gel electrophoresis. Their immunological activity was tested by imrnunoprecipitation and their biological activity in a tissue culture assay using embryonic chick dorsal root ganglia. 相似文献
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PATTERNS OF PIRACY BY PERUVIAN SEABIRDS: A DEPTH HYPOTHESIS 总被引:1,自引:0,他引:1
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IDENTIFICATION OF CHLOROPLAST COUPLING FACTOR BY FREEZE-ETCHING AND NEGATIVE-STAINING TECHNIQUES 总被引:3,自引:1,他引:2 下载免费PDF全文
Identification of chloroplast coupling factor particles, by the freeze-etching and negative-staining techniques, was made utilizing chloroplast thylakoids isolated from spinach leaves. Complete removal of particles, comparable in diameter to purified coupling factor particles, from the outer surface of freeze-etched thylakoids was achieved by treatment with 0.8% silicotungstate. Reappearance of particles, comparable in diameter to purified coupling factor particles, on the outer surface of freeze-etched thylakoids was demonstrated by combining silicotungstate-treated thylakoids with purified chloroplast coupling factor. Negative-staining results were in agreement with the freeze-etch data. The results demonstrate that the chloroplast coupling factor particles are exposed on the outer surface. 相似文献
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Diana K. Hews 《Evolution; international journal of organic evolution》1990,44(8):1956-1966
I examined sexual selection in the iguanid lizard Uta palmeri by measuring phenotypic selection in a cohort of males. Relative fitness was estimated by copulation rate from one breeding season, and I analyzed selection on five morphological traits (snout–vent length, mass, jaw length, head width, and head depth) and on male territory quality. Only territory quality and head depth were identified as direct targets of selection in a linear selection gradient analysis. Head depth was suggested to also be subject to quadratic selection. All traits exhibited significant directional selection differentials, suggesting indirect selection also was present because of the correlation of these traits with direct targets of selection. I used these results to generate hypotheses about the mechanisms of selection. For traits not identified as direct targets of selection (snout–vent length, mass, head width, jaw length), I could accept the null hypothesis of no female preference for the analyzed male traits; if these morphological traits were preferred by females in mate choice, they would have been identified as direct targets of selection. Exploring possible functional relationships within the cohort, I found that all five morphological traits contributed to explaining variation in territorial status. And in staged aggressive interactions between males that were similar in snout–vent length and mass, winning was associated only with greater head depth and not with head width or jaw length. Several possible interpretations of these results are presented. This study suggests that differential mating success arising from variation in territory quality gives rise to indirect selection on morphology. The possible mechanisms giving rise to the proposed direct selection on head depth require further study. 相似文献
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TAKEO KISHIMOTO JUNKO KUBOTA HARUO KANATANI 《Development, growth & differentiation》1977,19(4):283-288
In starfish, cytoplasm taken from maturing oocytes is capable of inducing breakdown of the germinal vesicle and subsequent maturation when injected into immature oocytes. The cytoplasmic factor has been designated as "maturation-promoting factor" (MPF). Ooplasm was stratified by centrifugation of maturing oocytes in density-graded Ficoll-seawater, without disrupting the cell. Three strata were distinguished beginning with the centripetal side: oil cap, hyaline layer and yellow layer. MPF activity was shown to be localized in the hyaline layer. Electron microscopic observation revealed that the hyaline layer contains Golgi complexes, many lucent vesicles and multi-vesicular bodies as distinct organelles, but seldom contains such inclusions as the lipid droplets forming the oil cap, mitochondria, yolk and pigment granules contained in the yellow layer. Based on these observations, a possible cytoplasmic component with MPF activity is discussed. 相似文献
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免疫酶双重染色法显示再生神经中的神经生长因子与睫状节神经营养因子 总被引:1,自引:0,他引:1
本研究以成人正中神经切割伤后2~3个月的神经干为材料,冰冻切片,用免疫双重染色技术显示了神经生长因子与睫状节神经营养(诱向)因子在再生的周围神经组织中的表达与分布。神经生长因子选用APAAP法.其阳性产物呈红色;睫状节神经营养(诱向)因子选用ABC系统,4氯-1-萘酚显色,阳性产物为褐色。光镜下观察:神经生长因子的阳性反应产物出现在正中神经切割伤后再生的神经纤维中,高倍镜下可见其阳性产物分布在轴索,而在雪旺氏细胞中没能见到呈红色的阳性反应产物;睫状节神经营养(诱向)因子分布在一些细胞体积大、核大呈增生活跃状态的雪旺氏细胞中。红与褐双色反应产物色调清晰,效果较好。研究结果提示:睫状节神经营养(诱向)因子与神经生长因子在人周围神经再生过程中起着十分重要的作用。 相似文献