Abstract

Rice genotypes of varying salt tolerance [tolerant (T), semi-tolerant (ST) and sensitive (S)] were evaluated in field lysimeters that contained saline soil of EC_e 4 and 8 mS cm^-1 and alkali soil of pH  9.5 and 9.8 in Karnal, North India. Tolerant rice genotypes accumulated lesser Na⁺ and higher K⁺, which led to lower Na/K ratios inshoot; and they showed non-significant reduction in Zn content even at EC_e 8 whereas they were significantly reduced in ST and S groups even at EC_e 4 mS cm^-1_. Alkalinity had no significant effect on Zn content of any group. There was significant increase in shoot P with increasing stress in T and ST groups. Zn/P ratio in shoot reduced with salinity stress in all the tolerance groups but there were no marked effects of alkalinity. A Na/K ratio of <1.1 at high salinity and < 0.8 at high alkalinity in the shoots served to distinguish the tolerant ricegenotypes from the sensitive. The T genotypes had a shoot Zn/P ratio of >0.03 whereas the sensitive had < 0.02 under salinity stress. Results suggested that in addition to Na/K ratio, shoot Zn/P ratios can be used as additional criteria for identifying rice genotypes with higher tolerance under salinity (but not alkalinity) stress.

Key words: Potassium, salt stress, salinity, alkalinity, sodium.