Photooxidative damage to plastids affects the abundance of nitrate-reductase mRNA in mustard cotyledons

It was found previously that in the mustard (Sinapis alba L.) seedling (Schuster et al. 1989, Planta 177, 74–83) the action of nitrate and phytochrome on the appearance of cytosolic nitrate reductase (NR) is abolished if the plastids are damaged by photooxidation. In the present study this finding has been corroborated by the following results: (i) the appearance and disappearance of NR activity are strictly correlated with the appearance and disappearance of immunoresponsive NR protein; (ii) the appearance of NR correlates with the appearance of translatable NR mRNA; (iii) photodestruction of the plastids strongly reduces the level of NR mRNA. It is concluded that the dependence of the NR level on the state of the plastids can be detected at the level of its mRNA and is not attributable to an inactivation of the enzyme.Abbreviations NR nitrate reductase (EC 1.6.6.1) This research was supported by a grant from the Deutsche Forschungsgemeinschaft. We are greatly indebted to Dr. Ann Oaks (University of Guelph, Ontario, Canada) for the gift of antiserum.     

Induction of nitrate reductase by cytokinin and ethylene in Agrostemma githago L. embryos

In dark-grown, isolated embryos of Agrostemma githago, a transient period of nitrate-reductase (NR) (NADH: nitrate oxidoreductase, EC 1.6.6.1) activity occurred from 6 to 36 h after the start of imbibition. During this period, NR activity was enhanced by nitrate, 6-benzylamino-purine and ethylene. Ethylene and 6-benzylamino-purine acted synergistically, whereas ethylene had no effect on nitrate induction. Aminoethoxyvinyl-glycine, an inhibitor of ethylene biosynthesis, inhibited the cytokinin-induced increase of NR activity, but had no effect on the nitrate-induced increase. The inhibition by aminoethoxyvinylglycine was overcome completely by ethylene. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid had the same effect on NR activity as ethylene. Our data indicate that NR induction by cytokinins only occurs in the presence of ethylene, and that nitrate enhances NR activity through a mechanism which is distinct from the induction by hormones.Abbreviations ACC 1-aminocycloproparte-1-carboxylic acid - AVG aminoethoxyvinylglycine - BAP 6-benzylaminopurine - c.p. cotyledonary pair - NR nitrate reductase This article was finalized by the second author two weeks before his death. It was translated and adapted by Dr. G.J. de Klerk, Research School of Biological Sciences, Australian National University, Canberra. Reprint requests should be sent to Dr. de Klerk at his present address: Bulb Research Centre, Vennestraat 22, 2160 AB Lisse, The NetherlandsDeceased 4 September 1985     

濒危植物翅果油树种群的叶绿素和硝酸还原酶活性的研究

濒危植物翅果油树是集中分布于山西南部的一种珍稀油料木本植物。以生物化学手段测定了翅果油树三个种群的叶绿素含量和硝酸还原酶活性,并用统计学方法,欧氏距离、Word’s聚类分析及主因子分析进行了分析。结果表明：翅果油树在三个种群间已有遗传分化,种群内个体间的遗传变异也有明显差异,自然种群与其生境有密切关系。从而为翅果油树的选种育苗和森林营造提供科学依据。     

Populations of Myriophyllum alterniflorum L. as bioindicators of pollution in acidic to neutral rivers in the Limousin region

Myriophyllum alterniflorum D.C. (Haloragaceae) was studied in the acidic to neutral rivers Vienne and Gartempe (Limousin region, France). Two complementary levels of organisation were evaluated to determine their usefulness for pollution assessment: morphological traits of river populations, and eco-physiological responses to ammonium enrichment in indoor experiments. Inter-node length, stem diameter and leaf length were measured and their ratio calculated for 100 selected plants collected in 20 homogeneous areas. Using multidimensional analysis, their ecological significance for trophic assessment was demonstrated: stem diameter was linked to conductivity, and leaf length/stem diameter ratio to phosphates. Nitrate reductase activity was measured in three populations (upstream, median and downstream populations) after experimental enrichment with ammonium. Ammonium enrichment decreased activity starting at very low concentrations. However, inhibition levels depended on tested populations, with upstream populations being less sensitive due to natural ammonium content in water. The differences could be explained by an eco-adaptation to the trophic level of water. The relationships between the two levels of organisation are discussed. These results could help to distinguish different ecotypes using Myriophyllum alterniflorum.