Growth and Reproduction of Junglerice (Echinochloa colona) in Response to Water Stress

Abstract

Junglerice is one of the most serious grass weeds of rice in the tropics. Greenhouse studies were conducted to evaluate growth and reproduction of junglerice in response to water stress. Plant height, biomass, and seed production of junglerice grown alone were reduced with increasing water stress. However, most stressed plants (irrigated at 12.5% of field capacity) still produced considerable biomass (8.5 g plant−1) and seeds (>1,600 seeds plant−1). When junglerice and rice were grown together under water-stressed condition, junglerice was taller than rice. The junglerice-to-rice biomass ratio also increased from 4.7 at 100% of field capacity to 7.6 at 12.5% of field capacity, indicating the greater junglerice vigor in water-stress conditions. In another study, the influence of the duration of water stress at intervals between 3 and 15 d on growth and seed production of junglerice was evaluated. Plant height, biomass, and seed production decreased with increasing water-stress duration. However, the weed produced an average of 400 seeds plant−1 in the most stressed treatment (i.e., when irrigation was applied at 15-d intervals). Water-stressed treatments did not affect germination of junglerice seeds in the laboratory. Growth and seed production of junglerice at all moisture levels ensures survival of the population in an unpredictable environment and contributes to the weedy nature of this species. The joint effect of enhanced weed competition and drought stress could severely harm crop yield; therefore, it is important to control such weeds in the early stages of crops and save stored moisture for the crops.