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Abstract

An experiment was conducted to investigate the physio! logical and biochemical responses of two hexaploids viz[\ C 295 "water stress tolerant# and Hira "water stress sus! ceptible#\ and two tetraploids\ HW 13 "Triticum dicoccum# and A 8!29!0 "Triticum durum# wheat genotypes to water stress under pot culture condition[ Water stress was imposed for a uniform period of 09 days at 49\ 59 and 69 days after sowing "DAS# and observations were recorded at 59\ 69 and 79 DAS[ Total dry matter and plant height were recorded at harvest[ Water stress caused a decline in relative water content "RWC#\ chlorophyll and carotenoid content\ membrane stability and nitrate reductase activity and increased accumulation of proline at all stages and abscisic acid "ABA# at 79 DAS in all the genotypes[ Both the tetraploids showed a lower reduction in RWC and highest ABA accumulation under water stress[ Among the hexaploids Hira showed the most decline in RWC and the lowest ABA accumulation[ The tetraploids also showed comparatively higher carotenoid content and membrane stability\ closely followed by C 295\ while Hira showed the minimum response under water stress[ Nitrate reductase activity and chlorophyll content under irrigated conditions were highest in Hira but under water stress the lowest per cent decline was observed in C 295\ followed by HW 13\ A 8!29!0\ and Hira[ Proline accumulation under water stress conditions was highest in hexaploids C 295 and Hira and lowest in tetraploids HW 13 and A 8!29!0[ Tetraploids HW 13\ followed by A 8!29!0 maintained higher plant height and total dry matter "TDM# under water stress and also showed a lower per cent decline under stress than hexaploids C 295 and Hira[ From the results it is clear that proline accumulation did not contribute to better drought tolerance of tetraploids than hexaploids[ It is also apparent that water stress tolerance is the result of the cumulative action of various physiological processes\ and all the parameters:processes may not be positively associ! ated with the drought tolerance of a particular tolerant genotype[