Effect of saline irrigation water on gas exchange and proline metabolism in ber (Ziziphus).

An experiment was conducted in pots of 25 kg capacity to study the effect of saline irrigation (EC 0,5,10,15 and 20 dSm-1) prepared by mixing NaCl, NaSO4, CaCl and MgCl2 in 3:1 ratio of chloride and sulphate on gas exchange traits, membrane stability, chlorophyll stability index and osmolytic defense mechanism in Ziziphus rotundifolia and Ziziphus nummularia species of Indian jujube (Z.mauritiana). Result showed that net photosynthetic rate (PN), transpiration (e) and stomatal conductance were comparatively lower in Ziziphus nummularia, which further declined with increasing level of saline irrigation water. Chlorophyll stability and membrane stability also declined significantly in salt stress, with higher magnitude in Ziziphus nummularia. The activity of proline anabolic enzymes; Δ1-Pyrrolline-5-carboxylate reductase, Δ1-Pyrrolline-5-carboxylate synthetase and Ornithine-δ-aminotransferase were recorded higher in Ziziphus rotundifolia with decrease in proline dehydrogenase. The sodium content was observed higher in roots of Ziziphus rotundifolia and leaves of Ziziphus nummularia. Therefore, it is suggested that salt tolerance mechanism was more efficiently operative in Ziziphus rotundifolia owing to better management of physiological attributes, osmolytic defense mechanism and restricted translocation of sodium from root to leaves along with larger accumulation of potassium in its leaves.

Real time PCR expression analysis of gene encoding p5cs enzyme and proline metabolism under NaCI salinity in rice.

Regulation of proline accumulation in seedlings of rice (Oryza sativa L. cv. Lunishree) was investigated. The increasing concentration of NaCl from 85 mM to 425 mM NaCl progressively increased proline content in rice. The maximum increase in proline content was recorded at 425 mM NaCl concentration as compared to control and other concentrations of NaCl. The highest significant activity of proline synthesizing enzymes, delta1-Pyrrolline-5-carboxylate synthetase, delta1-Pyrrolline-5-carboxylate reductase and Ornithine-δ- aminotransferase with lowest activity of proline hydrolysis enzymes;Proline dehydrogenase was also recorded at 425 mM NaCl salinity over control and other concentrations of NaCI with insignificant increase in the activity of delta1-Pyrrolline-5-carboxylate synthetase and Ornithine-δ-aminotransferase at 85 mM NaCI over control. It was found that the transcript of gene encoded with p5cs is up regulated about 1.35 folds under salinity stress. This gene synthesis an osmo protectant to help the plant resist the change in osmotic imbalances. Externally addition of MnCl2 at 300 mg/220 ml 1/2 strength Hoagland solution, having 1% NaCI, was also seen to increase 893.9% proline content of this variety as compared to control.

Analysis of proline metabolic enzymes in Oryza sativa under NaCl stress.

The regulation of proline accumulation in seedlings of rice (Oryza sativa L. cv. Badami) was investigated. The increasing concentration of NaCl from 0.5 to 2.5% progressively increased the proline content in rice. Proline accumulation caused by NaCl was related to protein proteolysis, an increase in OAT, P5CS, PSCR activity, a decrease in PDH activity. The maximum increase in proline content was recorded at 2.5% NaCl concentration as compared to control and other concentrations of NaCl. The highest significant activity of proline synthesizing enzymes, Delta1-Pyrrolline-5-carboxylate synthetase, Delta1-Pyrrolline-5-carboxylate reductase and Ornithine-delta-aminotransferase with a lowest activity of proline hydrolysis enzymes; Proline dehydrogenase were also recorded at 2.5% salinity over control and other concentrations of NaCl with a in-significant increase in the activity of Delta1-Pyrrolline-5-carboxylate synthetase and Ornithine-delta-aminotransferase at 0.5 % concentration of NaCl over control. Externally the addition of 300mg MnCl2, 220 ml(-1) 1/2 strength Hoagland solution, having 1% NaCl, was seen to increase a 893.9% in proline content of this variety as compared to control.