Characteristic water status in dwarf pea in relation to drought resistance

Dwarfism in pea (Pisum sativum L.) manifests itself more conspicuously in the light, and light-induced epicotyl growth inhibition in relation to water status was studied. NMR spin-lattice relaxation times (T ₁)s of epicotyls of no-elongation zone were markedly longer than those of elongation zone of the seedlings of both cultivars, tall type cv. Alaska and dwarf type, cv. Progress No. 9. T ₁ of GA ₁-dose response in dwarf pea, which grows normally, decreased in elongation zone while T ₁s in no-elongation zone increased. The changes in T ₁ of light- and dark-grown pea epicotyls were not simply attributable to a change in water content. Water of dwarf control and no-elongation zone of GA ₁-treated cv. Progress No. 9 grown under light condition was more sustained during three-hours air drying compared to those of cv. Alaska. Osmotic concentrations in elongation zones were higher than those of no-elongation zone. In addition, there was no relationship between osmotic concentration and cell length. It seems that the epicotyl tissues of dwarf pea phenotype were high T ₁ values accompanied by low osmotic values while water uptake was not changed. In conclusion, T ₁ of the pea seedlings will be useful for an evaluation of the dwarfism and GA ₁ dose-response to drought stress.