Effects of dietary cobalt on testicular structure

Adult male rats were maintained on a diet containing 265 ppm cobalt for up to 98 days. Three rats were sacrificed weekly and assayed for testicular damage by light and electron microscopy. Testicular damage was first apparent after 70 days of treatment, followed by a progressive deterioration of cell architecture and decrease in testicular volume. The degenerative changes were of a very general nature; e.g., thickening of basal lamina and basement membranes, increased packing of red blood cells in veins and arteries, formation of "giant" cells, loss of sperm tail filaments, and degeneration of sperm mitochondria. No cobalt residues could be detected by energy dispersive x-ray microanalysis. These data indicate that testicular degeneration was not a primary response to cobalt and suggest that the testes become hypoxic due both to blockage of veins and arteries by red blood cells and to changes in permeability caused by thickening of basal lamina and basement membranes.     

Trichodermin: Effects on plants

Trichodermin, 4ß-acetoxy-12,13-epoxy-⁹ -trichothecene,a fungal metabolite from Trichoderma viride, is a potent inhibitorof plant growth and produces other phytotoxic effects. It inhibitswheat coleoptile growth, is phytotoxic to tobacco at high concentrationsand inhibits growth at lower concentrations. Bean and corn plantsare also affected by the metabolite. (Received June 22, 1977; )     

Effects of ozone on wild plants

Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting/grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems.     

Effects of sodium chloride on tobacco plants

Abstract The effect of salinity on the growth and ion concentrations in a number of tobacco cultivars is described. Sodium chloride, at a concentration of 200 mol m^?3, hardly affected the fresh weight, but significantly reduced the dry weight. The difference in the response of fresh and dry weights to salt was due to a change in succulence (water per unit leaf area); the latter increased with increasing leaf Na⁺ and Cl^? concentration. Under saline conditions, increasing the external Na⁺: Ca^? ratio by decreasing the Ca²⁺ concentration increased the accumulation of Na⁺ and Cl^? into the leaf tissue.     

植物外来种对土壤理化特性的影响

植物外来种对土壤特性可产生深刻的影响。植物外来种可影响土壤的温度、湿度、土壤侵蚀等土壤物理特性 ;同样会影响土壤的含氮量、有机质、金属元素等化学特性。植物外来种对土壤特性的影响是十分复杂的 ,在不同的环境里同一植物外来种可产生不同的影响。总的来说 ,植物外来种对土壤特性的影响有正面、中性和负面 3种效应     

Effects of microgravity and clinostating on plants

Abstract

Results of many space flight and clinostate experiments performed with growing and developing lower and higher plants, tissue and protoplast cultures are presented. Biological effects of gravity changes on organism, cellular, subcellular and membrane levels are described. Regularities of rearrangements of organelle structural-functional organizations and cell metabolism as well as possible cell mechanisms of the adaptation to microgravity are discussed.     

气候变暖对陆生植物的影响

温度是影响植物生长、发育和功能的重要环境因子,是调节许多陆地生态系统生物地球化学过程的关键因素之一.全球气候持续变暖直接或间接地对陆生植物产生不同程度的影响.本文从不同方面分析了植物对温度升高及其它生态环境因子变化交互作用下的生理生态适应机制,包括生态系统的土壤呼吸、植物的气体交换、水分关系、生物量和生产力的响应等方面的研究进展,并就未来开展陆生植物对气候变暖响应研究提出加强和改进的设想.     

Effects of metals on enzyme activity in plants

Abstract. Uptake of phytotoxic amounts of metal by higher plants or algae can result in inhibition of several enzymes, and in increase in activity (= induction) of others. Two mechanisms of enzyme inhibition predominate: (1) binding of the metal to sulphydryl groups, involved in the catalytic actionor structural integrity of enzymes, and (2) deficiency of an essential metal in metalloproteins or metal-protein complexes, eventually combined with substitution of the toxic metal for the deficient element. Metal accumulation in the cellular compartment of the enzyme is a prerequisite for enzyme inhibition in vivo. The induction of some enzymes is considered to play a significant role in the stress metabolism, induced by metal phytotoxicity. Peroxidase induction is likely to be related to oxidative reactions at the biomembrane; several enzymes of the intermediary metabolism might be stimulated to compensate for metal-sensitive photosynthetic reactions. The induction of enzymes and metal-specific changes in isoperoxidase pattern can be used as diagnostic criteria to evaluate the phytotoxicity of soils, contaminated by several metals. Lines for future research on metal phytotoxicity are proposed, involving the study of inhibition and induction of enzymes at the different cell membranes (especially the plasmamembrane) in vivo.