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Journal of Agronomy
Year: 2004  |  Volume: 3  |  Issue: 1  |  Page No.: 1 - 10

Effect of Salinity on Growth of Some Modern Rice Cultivars

M.Z. Alam, T. Stuchbury, R.E.L. Naylor and M.A. Rashid    

Abstract: Ten rice cultivars (Oryza sativa L.) were tested for their salt tolerance at three levels of salinity, 4.5, 8.5 and 12.5 dS m-1 electrical conductivity (EC) and tap water as control. A 4x10 factorial experiment in split-plot design was used with three replications. Data taken 6 weeks after salt application were reported. Severe effects of salt on rice plant growth were seen even at 4.5 dSm-1. Growth was arrested immediately after application of 12.5 dS m-1 salt but not in other lower salt treatments (8.5 and 4.5 dS m-1). However, with time, salt injury symptoms were clearly visible in all plants growing in all levels of salt and showing different symptoms. The degree of injury was greater in the highest salt concentration (12.5 dS m-1). The symptoms appeared mostly in older leaves and the upper portion of the leaves rolled in and withered away. The emerging leaf blades were tightly rolled; the tips were severely withered and necrotic. However, the younger leaves of the affected plant remained succulent and looked darker green. The affected plants looked stunted and most of the young tillers gradually died. Salt injury symptoms varied with concentration of salt and between cultivars. The relative salt sensitivity of cultivars was not consistent across salt levels indicating cultivar differences in threshold levels of salt tolerance. All plant parameters decreased significantly in all cultivars with increasing salinity. However, leaf area, shoot and root fresh weight were relatively more affected and the magnitude of reduction varied between cultivars. Limited differences between cultivars for salt tolerance were seen during vegetative growth. An index combining all plant parameters measured, suggested that V2, V3, V5 and BR23 were relatively tolerant of salinity than others. Neither reduced photosynthetic capacity nor reduced turgor appeared to be the major reason for the reduced growth. Rather, reduced growth may be the result of disturbed mineral nutrition. There was no correlation between sensitivity at germination and later growth stages. The results suggested that screening of rice cultivars for salt tolerance should be at salt sensitive stages.

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