EFFECT OF OXYGEN AND SODIUM THIOGYCOLLATE ON GROWTH OF RICE

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Abstract
Rice seedlings were grown for 60 to 108 hrs. in closed chambers through which air mixtures containing the following concs. of O2 were continuously passed, 0.2, 1.2, 5.2, 10.2, 20.8 and 50.1%. The dry wts. of both shoots and roots increased with increasing O2 conc. up to the highest conc. used, 50.1% The greatest increase was shown by the roots, the shoot/root ratios decreased at the higher O2 conc. A similar increase in total growth with increasing O2 was shown by wheat but with less marked effects on shoot/root ratios. The response to increasing O2 for rice was similar in both continuous light and in darkness. Studies were also made of the interrelation among aeration, N nutrition, iron nutrition and the presence of a reducing substance, Na thioglycollate. Plants supplied with NO3 in unchanged soln. developed severe chlorosis with or without aeration of the culture soln. Those supplied with NH4 in unchanged soln. developed severe tip-burn of lower leaves with or without aeration. With continuous flow of the culture soln. no chlorosis developed in the NO3 cultures and tip-burn was reduced in the NH4 cultures. When Na thioglycollate was present at 250 ppm. in the unchanged solns., either NO3 or NH4, the plants developed neither chlorosis nor tip-burn. NO3 was more favorable for root growth than NH4. No marked differences in growth were evident between Fe supplied as ferrous sulphate and as ferric tartrate.