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Pak. J. Bot., 45(SI): 35-40, 2013.

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GAS EXCHANGE ATTRIBUTES CAN BE VALUABLE SELECTION CRITERIA FOR SALINITY TOLERANCE IN CANOLA CULTIVARS (BRASSICA NAPUS L.)

ERUM MUKHTAR, EJAZ HUSSAIN SIDDIQI, KHIZAR HAYAT BHATTI*, KHALID NAWAZ AND KHALID HUSSAIN

Abstract: Present study was carried out to access inter-cultivar variation for salt tolerance in canola (Brassica napus L.) by using photosynthetic attributes including photosynthetic pigments as selection criteria. Four cultivars of canola viz., Oscar, Ac Excel, Cyclone and Dunkled were screened at 120 mM NaCl at vegetative stage. Salt stress reduced photosynthetic rate (A), transpiration rate (E), stomatal conductance (g_s), sub-stomatal CO₂ (Ci) conc. and water use efficiency (WUE) at different growth stages. Salt stress also markedly reduced chlorophyll a, chlorophyll b and total chlorophyll contents. Generally, plant biomass declined under the salt regime of all the cultivars. Nevertheless, cultivar Dunkled had higher, Oscar and Ac Excel intermediate while; Cyclone had lower shoot and root fresh weight under saline conditions. However, cultivar Cyclone was lower in chlorophyll a and chlorophyll b under the salt stress in contrast to Ac Excel. A significant variation was also shown in gas exchange attributes under the stress. Photosynthetic (A) and transpiration rates (E) was higher in Dunkled than of Oscar and Cyclone under the stress. On the basis of data, it may be concluded that fresh weight of shoots and roots had positive correlation with physiological photosynthetic rate (A) among all the four cultivars; thus, photosynthetic rate (A) can be an effectual selection criteria for salt tolerance under salt regime.

Department of Botany, Institute of Chemical and Biological Sciences, University of Gujrat, Gujrat-50700, Pakistan.

*Corresponding author’s E-mail: khizar.hayat@uog.edu.pk