Immunocytochemical Localization of Phosphoribulose Kinase in the Cyanelles of Cyanophora paradoxa and Glaucocystis nostochinearum

The distribution of phosphoribulose kinase (PRK) in the cyanelles of Cyanophora paradoxa Korschikoff and Glaucocystis nostochinearum Itzigsohn was studied by protein A-gold immunoelectron microscopy. In both endocyanomes, antiserum against PRK heavily labeled the thylakoid region of the cyanelles, whereas little or no label was present over the carboxysomes. Antiserum against ribulose 1,5-bisphosphate carboxylase/oxygenase by contrast heavily labeled the carboxysomes of each endocyanome. In vitro studies of PRK distribution in cell-free extracts of C. paradoxa showed that 93% of the enzyme was in the soluble fraction. Quantitative immunoelectron microscopy showed that more than 99% of the PRK in the cyanelle of C. paradoxa was localized in the thylakoid region. We conclude that the carboxysomes of cyanelles like the carboxysomes of autotrophic prokaryotes and the pyrenoids of green algal chloroplasts do not contain phosphoribulose kinase.     

Bright ideas about parasites

The Hamilton-Zuk hypothesis for parasite-mediated sexual selection in animals has generated much controversy. To resolve the arguments it will be necessary to incorporate many more details of the biology, ecology and evolution of hosts and parasites into studies of sexual selection.     

麦田冠层气孔导度的分层研究

小麦灌浆期和乳熟期冠层各层叶片上、下表面的气孔导度之间呈正相关关系;冠层不同层的叶片气孔导度从早到傍晚有平行变化的趋势,数值上存在较大的差异,一般从冠层上到下递减。经分析,这主要与冠层叶片接受的光强自上而下递减有关,且这时所对应的叶片水势自冠层上到下递增的幅度大。测算结果表明,冠层气孔导度白天亦呈明显的日变化,灌浆期的值大于乳熟期的值。     

大麦染色体银带的研究

本文以六棱、四棱和二棱大麦为材料,用去壁低渗火焰干燥法制备染色体标本,标本在60℃恒温下经70—80％AgNO_3水溶液处理12—14小时,可在核仁组成区、着丝粒和端粒出现黑色银染区。细胞化学反应说明这些不同区域的银染物质具有相同的性质。银染带型与C带型和N带型迥然不同,3种大麦的银染带型也有差别。试验还证明染色体标本制备技术对银染效果影响极大,只有合适的酶解和火焰干燥处理才能促使着丝粒和端粒显示出银染正反应。