Dry matter production and root system development of rice cultivars under fluctuating soil moisture

Abstract

Rice plants in the rainfed areas are mostly grown under fluctuating soil moisture. We examined responses in dry matter production, root development and water use to changing soil moisture in diverse rice cultivars. Rice plants were grown in polyvinyl chloride tubes under glasshouse conditions. Progressive drought right after planting greatly inhibited the shoot dry matter production, tiller development, nodal root development and water uptake in all cultivars tested. When the plants experienced soil submergence before being exposed to drought, all the cultivars exhibited higher dry matter production than their well-watered counterparts. Cultivar differences were clearly noted in the growth responses to rewatering after these plants were droughted. With well-watered control as basis, IRAT 109 and KDML 105 plants increased efficiency in converting available dry matter to increase their total root length by means of enhanced lateral root development. In the latter, however, the dry weight of roots also increased and so did root water uptake. In Dular, droughted plants did not show a clear response in terms of root development and water uptake to rewatering while its shoot growth was much more severely inhibited than the other cultivars. These findings suggest that phenotypic plasticity in the root system structure exhibited by promoted lateral root development and new nodal root production play a key role in the growth of rice under changing moisture level in the soil.