Effect of Nitrogen and Silicon Nutrition on Bioactive Gibberellin and Growth of Rice under Field Conditions

다국어 초록 (Multilingual Abstract)

Gibberellins are growth hormones that play a pivotal role in the growth and development of plants. Present investigations were carried
to check the effect of nitrogen (N) and silicon (Si) on bioactive GA1 and its immediate precursor GA20 at different growth stages
of two rice cultivars with different maturity traits. It was observed that the endogenous bioactive GA1 level gradually increased during
vegetative stage and anthesis stage of both Junghwabyeo (early flowering cultivar) and Daesanbyeo (late flowering cultivar).
However, the GA1 and GA20 content start decreasing during the seed filling stage in both rice cultivars, which indicated a possible
relationship of bioactive GA1 and floral development. Our results also confirmed that early 13-hydroxylation pathway was operated
at all developmental stages of rice plant. Variation in the levels of the endogenous gibberellins in rice shoots were measured by GCMS-
SIM using 2H2-labeled gibberellins as internal standards. Combined application of N and Si enhanced growth parameters and
reduced lodging index of both rice cultivars. It was thus concluded that the level of physiologically active GA1 increased during vegetative
and early reproductive stage, but starts declining at seed filling stage.

다국어 초록 (Multilingual Abstract)

Gibberellins are growth hormones that play a pivotal role in the growth and development of plants. Present investigations were carried
to check the effect of nitrogen (N) and silicon (Si) on bioactive GA1 and its immediate precursor GA20 at different growth stages
of two rice cultivars with different maturity traits. It was observed that the endogenous bioactive GA1 level gradually increased during
vegetative stage and anthesis stage of both Junghwabyeo (early flowering cultivar) and Daesanbyeo (late flowering cultivar).
However, the GA1 and GA20 content start decreasing during the seed filling stage in both rice cultivars, which indicated a possible
relationship of bioactive GA1 and floral development. Our results also confirmed that early 13-hydroxylation pathway was operated
at all developmental stages of rice plant. Variation in the levels of the endogenous gibberellins in rice shoots were measured by GCMS-
SIM using 2H2-labeled gibberellins as internal standards. Combined application of N and Si enhanced growth parameters and
reduced lodging index of both rice cultivars. It was thus concluded that the level of physiologically active GA1 increased during vegetative
and early reproductive stage, but starts declining at seed filling stage.