Effects of a brassinosteroid and an ecdysone analogue on pollen germination of rice under heat stress

Heat stress is associated with a reduction in pollen germination and seed setting of rice. Brassinosteroids have been reported to counteract some stresses on plant growth and development. We investigated the effects of an exogenously applied brassinosteroid, (24-epibrassinolide; EBR) and an ecdysone analogue (7,8-dihydro-8 alpha-20-hydroxyecdysone; DHECD) against heat stress on pollen viability of rice (Oryza sativa L.) cv. Pathum Thani 1. The plants were treated with either EBR or DHECD and exposed to a day/night heat stress regime of 40/30 degrees C for 7 days. The results demonstrated that 0.001 mu M of either chemical was effective for increasing pollen viability and reducing pollen bursting. Furthermore, these chemical treatments conferred resistance to heat stress in in vivo pollen germination and seed setting. Consequently, these results suggest EBR and DHECD should alleviate the detrimental effects of heat stress by improving pollen germination and seed setting and enable rice to withstand high temperature stress. Pesticide Science Society of Japan