Ethylene inhibitors promote male gametophyte survival in rice

Rice (Oryza sativa L. cv. Lalat) was grown in pots under open field conditions during the wet season of 1997. Attempts were made to manipulate the growth and development of the male gametophyte, located on the basal region of the panicle, by exogenous application of chemicals regulating formation/action of ethylene and compare grain setting in the spikelets bearing few grain. Application of ethylene action (AgNO3) and synthesis inhibitor (Co(NO3)(2); paclobutrazol and uniconazole) improved grain setting in the spikelets and the ethylene releasing substance 2-chloroethyle phosphonic acid (CEPA) depressed it compared to the control. The ethylene inhibitors promoted dry mass accumulation and concentrations of starch and reducing sugars in the anthers of the basal spikelets, while CEPA reduced the level of these carbohydrates significantly. The ethylene inhibitors helped in the survival of more numbers of pollen in these anthers, but CEPA depressed their number significantly. Promotion of growth of the basal anthers was accompanied by a concomitant reduction in the concentration of nonreducing sugars and enhanced activities of acid invertase and sucrose synthase enzymes. It is concluded that male gametophyte development of the basal spikelets of rice is susceptible to ethylene at the stage of pollen mitosis. The possibility of the hormone interfering in carbohydrate metabolism of the anther during this stage of development is discussed.