Abstract
The ability of exogenously applied glycinebetaine (GB) for the alleviation of growth inhibition and senescence resulting from NaCl stress was investigated in view of growth parameters, net PS-II efficiency, photosynthetic pigments, protein and proline contents in two rice ( Oryza sativa L.) cultivars differing in salt tolerance (salt-tolerant Pokkali, and salt-sensitive IR-28). Shoot fresh weight (FW) of Pokkali and shoot and root dry weight of IR-28 showed a decrease under salinity but an increase with exogenous GB application. NaCl treatment caused no serious decrease in F V/ F M ratio of Pokkali whereas F V/ F M ratio of IR-28 showed a remarkable decline throughout the experiment. Exogenous GB application partially preserved net PS-II efficiency of IR-28 from salt-stress. While Chl-b and carotenoid contents of IR-28 decreased, photosynthetic pigment contents of Pokkali showed no notable change under salinity. GB treatment did not show protective effect on photosynthetic pigment contents of IR-28 decreased under-salinity. Proline content significantly increased in Pokkali and IR-28 under salt-stress with a higher rate of increase in the former. When compared to NaCl-exposed groups alone, GB treatment caused an increase and a decrease in the level of proline accumulation in Pokkali and IR-28, respectively. While protein content of Pokkali enhanced with salinity, GB pre-application decreased it to control levels. Protein content of IR-28 showed a decrease under salinity but an increase with GB application. Therefore, we conclude that GB can reduce the impact of salt-stress on growth and senescence, enhance the photosynthetic efficiency of PS-II and increase the protein content of rice seedlings.
Published Version
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