Water and Salt Stresses, Kinetin and Protein Synthesis in Tobacco Leaves

Abstract

Sumnniary. The capacity of tobacco (Nicotiatna rutstica) leaf discs to incorporate L-leuicine "-C into proteins was measured. Leaf discs were obtained from plants which experienced soil water depletion, or which were exposed to a saline or osmotic stress in the root nmediuim. The stresses were brief of relatively short duration and water potential did not decrease below 4 bars in the root media. Leaf discs were sampled 2 hours a fter stress removal, achieved by reirrigation, or replacement of saline and osmotic solutions with normal nutrient solution. Plants were always tutrgid when leaves were sampled.All stressed tissues showed redutced capacity to incorporate L-leucine 14C into protein. The reduction was about 50 % and could not be attributed either to reduced uLptake into the discs, or to possible isotopic diluition. Incorporation decreased progressively with leaf age in control discs as well as in stressed leaf discs. At all ages tested, incorporation in stressed discs was lower than that of the control. Full recovery of incorporation capacity in stressed discs was obtained when discs were sampled 72 hours after stress removal but not earlier.Kinetin pretreatment prior to incuibation with labelled letucine partially restored incorporation in stressed discs. The differences in response to kinetin of stressed and control discs suggest a lower endogenouis level of cytokinins in the stressed discs. The results were qualitatively similar regardless of the kind of stress given to the plants dturing pretreatment and oni recovery of these rates in the presence of kinetin. Materials and MethodsSingle tobacco plants (Nicotiana rustica) were grown for about 10 weeks in a cooled greenhoulse (20°-30°) in pots containing either 3 kg of a soil-manutre mixture (3: 2 v/v)

Physiological Significance of Internal Water Relations to Crop Yield

“…Indeed, interruption of protein synthesis and proteolysis are generally observed when stress is imposed (Zholkevich and Koretskaya, 1959;Chen, Kessler, and Monselise, 1964;Shah and Loomis, 1965;Ben-Zioni, Itai, and Vaadia, 1967). Although few studies of the effects of water stress on nucl,c:ic acid metabolism have been made, the results form a fairly consistent pattern.…”

The Role of Cytokinins in Chloroplast Lamellar Development

“…These observations are in contrast to an earlier report (25) tion was eliminated. In light of these observations and previous studies of Itai and Vaadia (14,15) and Ben-Zioni et al (8) which provided evidence that exogenously applied cytokinin was capable of relieving the effects of small water deficits, it was thought that cytokinin treatment should relieve the effects of small water deficits on the greening process; namely, reduce or eliminate the lag phase in Chl accumulation. However, cytokinin was neither effective in reducing the 3-to 4-hr lag in Chl accumulation nor in eliminating the delay in lowering of the leaf Chl a/b ratio (Figs.…”

Early Effects of Salinity on Nitrate Assimilation in Barley Seedlings

“…In contrast, NaCI slinization had little effect on N uptake in winter barley but impaired its incorporation into the protein fraction (13). In leafdiscs ofNicotiana rustica, salt stress reduced both the uptake of L-leucine and its incorporation into proteins (3).…”