Respiration and soluble sugar metabolism in sugar pine embryos

Embroys excised from dormant seeds of sugar pine ( Pinus lambertiana Dougl.) incubated at 25°C (non-dormancy-breaking) or stratified at 5°C (dormancy-breaking) were analyzed to determine temperature effects on the relative activities of respiration and fermentative metabolism, the levels of soluble sugers and the activities of the hydrolytic enzymes, invertase and sucrose synthase, as related to the release of dormancy and germinatio. At 25°C, despite a sharp drop in embryo oxygen uptake after 48 h, a simultaneous decline in acetaldehyde and ethanol concentrations indicated that there was not a shift to fermentative metabolism. The concentrations of soluble sugars showed no treatment effects. Embryo invertase (EC 3.2.1.26) activity changed only slightly at either temperature, while stratification was accompanied by a 4-fold increase in sucrose synthase (EC 2.4.1.13) activity (cleavage direction). Upon transfer of stratified seeds to 25°C, embryo sucrose synthase activity rapidly increased almost 10-fold, with the increase beginning prior to germination, while mvertase activity increased 20-fold, concomitant with germination.     

Induction by antimycin A of cyanide-resistant respiration in heterotrophic Euglena gracilis: Effects of growth,respiration and protein biosynthesis

The addition of antimycin A during the logarithmic phase of growth of heterotrophic Euglena gracilis cultures (in lactate or glucose medium) was immediately followed by decreased respiration and a cessation of grwoth. Induced cyanideresistent respiration appeared 5 h after the addition of the inhibitor then the cells started to grow again and could be cultured in the presence of antimycin A. Thus the cells exhibited a cyanide-and antimycin-resistant respiration which was, in addition, sensitive to salicylhydroxamic acid and propylgallate. Antimycin-adapted Euglena and control cells were compared for their biomass production and protein synthesis. The difference in growth yield between control and antimycin-adapted cells was not as high as would be expected if only the first phosphorylation site of the normal respiratory chain was active in the presence of antimycin A. Furthermore, the ability to incorporate labelled valine into proteins, under resting-cell conditions, was not changed. Strong correlations were established between the effects of respiratory effectors on O₂ consumption and valine incorporation. These results suggest that sufficient energy for protein synthesis and growth is provided by the operation of the cyanide-resistant respiratory pathway in antimycin-adapted Euglena.Abbreviations DNP dinitrophenol - PG propylgallate - SHAM salicylhydroxamic acid     

Monensin inhibits the secretion of α-amylase but not polysaccharide slime from seedling tissues ofZea mays

Summary The effect of monensin on polysaccharide slime secretion by root tips of corn (Zea mays) was studied. Various treatment times and ionophore concentrations were tested: none resulted in inhibition of slime secretion. Because monensin changes the pH of the medium, its effect was also monitored in strongly buffered media and at different pH's. Even in such media, monensin did not inhibit slime secretion. We also measured the effect of the drug after a pulse with [³H]fucose or a pulse followed by a chase. The amount of labeled slimed secreted was not altered by the ionophore. However, 10M monensin affected the development of root tips and drastically reduced their growth. We showed that monensin inhibits the secretion of -amylase by the scutellum of the same plantlet. The importance of the nature of the secretory compound in relation to monensin inhibition of its secretion is discussed.Abbrevations Hepes N-2-hydroxyethylpiperazine-N-2-ethane-sul-fonic acid - Mes 2-(N-morpholino)ethane-sulfonic acid     

Xenopus spermatozoon: Is there any correlation between motility and oxygen consumption?

The motility status of Xenopus laevis spermatozoa does not affect their respiration rate. Oxygen consumption for 10⁹ spermatozoa is approximately 0.4 μmol/minute. Oxygen consumption is not increased by gramicidin D, an uncoupler, and it is not blocked by KCN or NaN₃. The adenosine triphosphate (ATP) content of spermatozoa that have been activated is definitely less than that in the spermatozoa that remained immotile. Incubation in KCN, NaN₃, and gramicidin decreases the ATP content and impairs motility. The conclusions of the present study are that in Xenopus spermatozoa motility and oxygen consumption are not correlated, and the composition of the respiratory chain of these spermatozoa presents noteworthy peculiarities.     

Effects of spring and autumn fires on the composition of Chionochloa rigida tussock grassland,New Zealand

Two areas of Chionochloa rigida tussock grassland on Flagstaff Hill were burnt in autumn and spring 1976, respectively. Plant species cover and frequency were recorded in 1977 and 1985. Initially, plant cover and frequency were lower, and the area of bare ground was greater, on the autumn burnt site. After nine years, cover and frequency values were similar for most species, and bare ground was rare, on both sites. Over this period, recovery in size of indigenous tussock-forming physiognomic dominants resulted in suppression of intertussock sub-shrubs, herbs and grasses that were initially favoured by reduction of competition after fire. Plant species most tolerant of fire have features that protect the meristem, for instance an underground perennating organ or dense tillering.     

采后预处理控制甜橙褐斑病的效应

采后预处理使甜橙果皮含水量减少,改善理化性状,降低果实对低温的敏感性,从而控制了福斑病的发生,使发病率从61.7～66.0％降至4.7～6.7％。低温贮藏的呼吸强度和内源乙烯的生成也受到明显的抑制,但对果实的主要内含物和质量并无影响。控制褐斑病发生的适宜的预处理,是在10～15℃和85～90％相对湿度下处理7～10d,使果实重耗约2.5～4.0％。     

微量元素对虫草蝠蛾幼虫生长发育的影响

按月采样,分析测定虫草蝠蛾幼虫体微量元素的组成。应用Q模式系统聚类方法,分析了幼虫受环境影响引起的元素代谢变化。结果表明虫体所含元素与环境温度的变化及自身的生理活动密切相关。5、10月份幼虫组的元素含量相近,前者正当幼虫结束休眠后恢复活动的时期,后者是幼虫处于准备进入越冬的前期,两组幼虫此时均处于取食高峰期。3、4月份组的亦较接近,幼虫正渐恢复活动但不取食。8月份幼虫蜕皮前后,消耗较大,需摄取大量食物。计算结果表明7、9月份的元素含量接近,这与上述现象有一定联系;应用对应因子分析法得到的结果是:元素Fe、P对10、11月份幼虫组的贡献值显著;Na、Ca、Mg对8、9月份的贡献值显著;Cu、Zn、Co、Cd、Si对4、5月份的贡献值显著。     

银额果蝇的B染色体研究 2.昆明群体的生活力和B染色体的关系

本文分析了钮额果蝇的生活力和B染色体的关系。结果表明,银额果蝇的B染色体在其生长和发育过程中具双重性调节作用。一方面,B染色体以单一的形式存在于单雌系核型中,即1B或2Bs,可刺激生长、发育,增强生活力。另一方面,在单雌系的细胞中存在多条B染色体,并形成核型多态性,这似乎对生长和发育又有一定的抑制作用而减弱其生活力。     

Neurosecretion of the mediodorsal cells of the central nervous system of the snail Helisoma duryi

Summary The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.