DROUGHT-INDUCED EFFECTS AND RECOVERY OF NITRATE ASSIMILATION AND NODULE ACTIVITY IN COWPEA PLANTS INOCULATED WITH BRADYRHIZOBIUM SPP. UNDER MODERATE NITRATE LEVEL

Brazilian Journal of Microbiology

Joaquim Albenísio Gomes Da Silveira²  Roberto Cezar Lobo Da Costa¹  José Tadeu Abreu Oliveira² 

[1] ,Universidade Federal do Ceará Laboratório Metabolismo e Fixação do Nitrogênio Fortaleza CE ,Brasil

关键词: glutamine synthetase;    leghemoglobin;    nitrate reductase;    N2 fixation;    water stress;    Vigna unguiculata (L.) Walp;    estresse hídrico;    fixação de N2;    glutamina sintetase;    leghemoglobina;    redutase do nitrato;    Vigna unguiculata (L.) Walp;   

DOI  :  10.1590/S1517-83822001000300005

来源: SciELO

【 摘 要 】

This study was carried out to establish comparative effects of drought and recovery on the nitrate assimilation and nodule activity related to N2 fixation in cowpea plants [Vigna unguiculata L. (Walp.)] previously inoculated with Bradyrhizobium spp. BR-3256 (CB-756) strain in the presence of 5 mol m-3 NO-3. Twenty-eight-day-old nodulated plants were submitted to water deprivation during 4 consecutive days and afterwards resupplied with nutrient solution during 2 days. The water deprivation caused a rapid increase in the nitrate content in root and a marked reduction in leaf nitrate reductase (NR) activity. In contrast nodule NR activity was slightly increased by water deprivation. Concomitantly, in nodules of water stressed plants, leghemoglobin and glutamine synthetase (GS) activity declined and a progressive reduction in ureide-N concentration in xylem sap was observed. Leaf-NR activity increased rapidly after rehydration while leaf nitrate content declined. In contrast both GS activity and soluble protein content in the nodule continued to decline in rewatered plants. In addition the concentration of leghemoglobin recovered well, while the xylem ureide-N content experienced a slight increase after rehydration. Despite the nitrate assimilation in leaves and the nodule activity had been both severely affected by water stress, the rapid recovery of nitrate reductase activity suggests that the nitrate assimilation process is less sensitive to drought/rehydration cycle when cowpea plants are nodulated in presence of moderate nitrate level.

【 授权许可】

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