NITROGEN METABOLISM IN POTERIUM SANGUISORBA DURING WATER STRESS

Abstract

SUMMARYWater stress, produced either by the addition of polyethylene glycol 4000 to water culture-grown Poterium sanguisorba or by withholding water from vermiculite-grown material, reduced nitrate reductase activity, but increased the level of glutamine synthetase in shoots, in roots the levels of all the nitrogen-assimilating enzymes studied were reduced. In both tissues these changes were accompanied by a fall in soluble protein and water content and by an increase in the total a-ammo and proline pools. Marked changes in shoot individual amino acids were also induced by water stress, but were reversed when stress was relieved. The significance of these changes are discussed in relation to nitrogen assimilation and the mechanism of proline accumulation durmg drought.

Glutamate dehydrogenase activity in normal and vitrified plants of Agave tequilana Weber propagated in vitro

“…The results presented here suggest that, as has been shown for other systems [24][25][26][27] GDH could play a role in ammonium assimilation during stress. The low water potential of the culture medium (~<-4.5bars) produces an osmotic stress in the explant.…”

Responses of growth and primary metabolism of water-stressed barley roots to rehydration

“…Nitrogen metabolism has considerable importance during water stress in plants (Taylor et al, 1982). In the current study 8 amino acids increased, 8 decreased and 2 were unchanged by drought (Fig.…”

“…The reversal of chemical and morphological changes in roots due to desiccation is crucial to plant survival and crop productivity. It was previously reported (Taylor et al, 1982;Prasad et al, 1982) that a limited number of stress-related root metabolites reverted to control levels 3 d after desiccated plants were re-watered. Effects of rehydration on a broader array of root metabolites have not been examined in detail.…”

“…A second role of primary metabolites during plant stress is the mitigation of oxidative stress (Shen et al, 1997;Taji et al, 2002) due to the formation of reactive oxygen species in roots in response to desiccation (Roach and Kranner, 2011). Water deficits decrease the uptake of nutrients from the soil and impede the distribution of nutrients within the plant via the transpiration stream (Taylor et al, 1982). Consequently, nutritional imbalances have been observed in plants subjected to water stress (Heckathorn et al, 1997).…”

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

“…During water stress nitrate reductase (NR) activity is lost more rapidly than most enzymes (Huffaker et al 1970). The other enzymes of the pathway of nitrate assimilation, nitrite reductase and glutamine synthetase (Taylor et al 1982), are relatively unaffected. Huffaker et al (1970) suggested that a rapid loss of NR activity could be part of a biochemical adaptation to water deficit; shutting off the nitrate assimilation pathway at the first step would reduce energy requirements during periods of stress and prevent accumulation of nitrite and ammonium.…”