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31.
Selection and characterization of tobacco plants with novel o(2)-resistant photosynthesis 总被引:2,自引:2,他引:0
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Zelitch I 《Plant physiology》1989,90(4):1457-1464
Plants were obtained with novel O2-resistant photosynthetic characteristics. At low CO2 (250-350 μL CO2 L−1) and 30°C when O2 was increased from 1% to 21% to 42%, the ratio of net CO2 uptake in O2-resistant whole plants or leaf discs compared to wild type increased progressively, and this was not related to stomatal opening. Dihaploid plantlets regenerated from anther culture were initially screened and selected for O2-resistant growth in 42% O2/160 μL CO2 L−1 and 0.18% of the plantlets showed O2-resistant photosynthesis. About 30% of the progeny (6 of 19 plants) of the first selfing of a fertile plant derived from a resistant dihaploid plant had O2-resistant photosynthesis, and after a second selfing this increased to 50% (6 of 12 plants). In 21% O2 and low CO2, net photosynthesis of the resistant plants was about 15% greater on a leaf area basis than wild type. Net photosynthesis was compared in leaf discs at 30 and 38°C in 21% O2, and at the higher temperature O2-resistant plants showed still greater photosynthesis than wild type. The results suggest that the O2-resistant photosynthesis described here is associated with a decreased stoichiometry of CO2 release under conditions of rapid photorespiration. This view was supported by the finding that leaves of O2-resistant plants averaged 40% greater catalase activity than wild type. 相似文献
32.
14C-Ethylene was metabolized by etiolated pigweed seedlings (Amaranthus retroflexus L.) in the manner similar to that observed in other plants. The hormone was oxidized to 14CO2 and incorporated into 14C-tissue components. Selected cyclic olefins with differing abilities to block ethylene action were used to determine if ethylene metabolism in pigweed is necessary for ethylene action. 2,5-Norbornadiene and 1,3-cyclohexadiene were effective inhibitors of ethylene action at 800 and 6400 microliters per liter, respectively, in the gas phase, while 1,4-cyclohexadiene and cyclohexene were not. However, all four cyclic olefins inhibited the incorporation and conversion of 14C-ethylene to 14CO2 by 95% with I50 values below 100 microliters per liter. The results indicate that total ethylene metabolism does not directly correlate with changes in ethylene action. Additionally, the fact that inhibition of ethylene metabolism by the cyclic olefins did not result in a corresponding increase in ethylene evolution indicates that ethylene metabolism does not serve to significantly reduce endogenous ethylene levels. 相似文献
33.
In renal sac nephrocytes of Helix aspersa, intracellular calcium has been localized using the oxalate-pyroantimonate (OPA) and phosphate-pyroantimonate (PPA) methods. Pyroantimonate precipitates are preferentially localized in the excretory spherule and in vesicles located in the basal and lateral regions of the nephrocyte. Such vesicles appear to release their content into the excretory vacuole. Calcium may interact with diverse types of molecules present in the excretory vacuole, thus favouring stabilization and packaging of the excretory spherule. 相似文献
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35.
家兔面神经后核内侧区在呼吸节律起源中的作用 总被引:36,自引:8,他引:28
从腹侧面暴露家兔延髓,脑内微量注射1%普鲁卡因阻滞面神经后核内侧区(mNRF),全部动物(n=20)一次注射(0.3—1.0μl)后即能可逆地消除呼吸节律。区域对照显示此区非常局限,范围约1.0×1.0×1.0mm。组织学检查表明为面神经后核内侧区。本文分析了 mNRF的呼吸相关神经元(RRNs)的放电形式。在 mNRF 有较多的呼气(E)神经元和呼气-吸气跨时相(E-IPS)神经元。在阻滞 mNRF 引起呼吸停止期间,观察到低位延髓背侧呼吸群(DRG)和腹侧呼吸群(VRG)尾端区 RRNs 放电的节律性消失,表现连续放电或停止放电。电刺激DRG,VRG 尾端区,只能诱发短串的膈神经放电,而不能产生节律性发放。说明这些区域的RRNs 无自动节律性活动的能力。结果表明,面神经后核内侧区与呼吸节律发生有关,它可能是呼吸节律发生器的一个重要的所在部位。 相似文献
36.
本文报道了岩羊小肠的祁连毛圆线虫,新种Trichostrongylus qilianensis sp. nov., 其形态与已发表的39种毛圆线虫均有明显区别。 相似文献
38.
Three-dimensional structure of the regular surface glycoprotein layer of Halobacterium volcanii from the Dead Sea 总被引:2,自引:0,他引:2
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A three-dimensional reconstruction from electron micrographs of negatively stained cell envelopes of Halobacterium volcanii has revealed the structure of the surface glycoprotein to a resolution of 2 nm. The glycoprotein is arranged on a p6 lattice with a lattice constant of 16.8 nm. It forms 4.5 nm high, dome-shaped, morphological complexes with a narrow pore at the apex opening into a `funnel' towards the cell membrane. The polarity of the structure was derived from freeze-etching experiments and `edge' views. Six radial protrusions emanate from each morphological complex and join around the 3-fold axis to provide lateral connectivity. Using the primary structure of the surface glycoprotein of the closely related species Halobacterium halobium (Lechner and Sumper, 1987) and the cell envelope profile from a previous X-ray analysis of the same species (Blaurock et al., 1976) we have integrated our reconstruction into a model of halobacterial cell envelope. 相似文献
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40.
Brent Heath I 《Trends in ecology & evolution》1988,3(7):167-171
Herbivores consume large quantities of cellulose and other plant cell wall (fibre) carbohydrates yet generally lack the enzymes to digest them. This has led to the evolution of specialized portions of the gut, such as the rumen and caecum, which contain large populations of digestive anaerobic microorganisms. Diverse bacteria and protists from this environment have been studied for over a hundred years but it is only recently that a significant population of highly specialized flagellate fungi have been identified. These fungi are important in fibre digestion. Their diversity, properties, activities, phylogeny and possible economic significance are the subjects of this review. 相似文献