Effects of the combined application of ethephon and gibberellin on growth of rice (Oryza sativa L.) seedlings

Improvement of early seedling growth, such as seedling emergence and vigor is one of the most important agronomic traits in direct seeding rice cultivation. The effects of two plant growth regulators (PGRs), gibberellic acid (GA(3)) and ethephon (ET), on seedling growth tinder flooded soil conditions at different temperatures and water depths were investigated. The PGRs were applied during the seed soaking process. A single treatment with GA3 or ET increased seedling growth. However, combined application of GA3 and ET was more effective than that of GA(3) or ET alone in many cases at both growing temperatures (15 and 20 degrees C). The growth of different organs in the rice seedlings, such as the coleoptiles, first leaves, and second leaves was also increased by PGR treatment. The nitrogen concentration of the shoot and the ratio of shoot dry weight to shoot length did not differ significantly among the treatments. The results of our study show that rice seedling growth in direct seeding cultivation may be improved by treatment with GA(3) and ET in combination.