Growth responses of mutants of spring barley to fumigation with SO₂ and NO₂in combination

Abstract

SUMM.ARYThis study was undertaken to evaluate the range of variation in growth responses of sodium azide-induced Mm utants (stocks SI and S2) of spring barley, Hordeum vulgare. L. cv. Maris Mink, in relation to air pollution tolerance or sensitivity. The preliminary screening experiment with 150 nl I"' concentrations of SO^ and NOg in combination for 10 d, yielded well-defined sensitive and tolerant lines in both the stocks. However, the percentage frequency distribution of plants in different injury classes varied and stock S2 sbowed a better segregation of different lines. In a subsequent experiment, treatment with a mixture of each gas at lQO nl 1"' concentration for 22 d caused a variable degree of growth reduction. As a result of air pollution treatment, most of the growth parameters were significantly {P < 0-001) reduced in the sensitive lines of both the stocks, whereas the tolerant lines showed a marked resistance to the growth inhibitory effect of the pollutants. The magnitude of the difference between the sensitivities of different lines was usually double or more, and the effects were, more pronounced in stock S2 than in stock SI. Root dry weight was more adversely affected than shoot dry weight in sensitive lines of both the stocks. The results indicated that inter-line differences in growth responses of these mutants were wide ranging, distinct and consistent. In conclusion, this study clearly demonstrates that artificial mutations may cause a markedly broad base of variation in air pollution sensitivity of crop plants which may be used in future piant breeding progranritnes of pollution tolerant cultivars.