Poster: Hormones

Abs # 612: Effects of Mineral Nutrients on The Endogenous Gibberellins Levels in Rice Plants

Presenter:	Lee, In-Jung , ijlee@knu.ac.kr
Authors	Lee, In-Jung  (A)   Jang, Soo-Won  (A)   Seo, Hye-Song  (A)   Kim, Sang-Kuk  (B)   Kang, Dong-Jin  (A)
Affiliations:	(A): Kyungpook National University (B): Kyongbuk Provincial Agri. Tech. Admin.

Influences of mineral nutrients such as nitrogen, calcium, and silica on endogenous plant hormones GAs were investigated. Three rice varieties (Oryza sativa L. cv. Daesanbyeo, Junambyeo and Dongjinbyeo) were grown under several nitrogen levels, and also grown in different type of nitrogen forms (NO₃^-, NH₄⁺, and a mixture of NH₄⁺/NO₃^-). Endogenous GA level, especially bioactive GA₁, was elevated along with increasing of nitrogen levels. However, biosynthesis of GA₁ was somewhat differently regulated with nitrogen forms within rice. In Daesanbyeo, biosynthesis of GA₁ was enhanced by ammonium form [(NH₄)₂SO₄] compared with provision of either KNO₃ or NH₄NO₃. Meanwhile, the highest GA₁ level in Dongjinbyeo was observed in which rice plant was grown under mixtures of NH₄⁺ and NO₃^-. These results implied that GA level in rice varieties are not responded with same manner whenever different nitrogen sources such as KNO₃, (NH₄)₂SO₄ and NH₄NO₃ are supplied. In addition, when nitrogen level was changed by 1mM to 2mM or 4mM, bioactive GA₁ level was significantly increased at 6h and 12h after nitrogen application. However, level of GA₂₀, a precursor of GA₁ biosynthesis, was not changed significantly. This result shown that the 3¥â-hydroxylase activity, catalyzing GA₂₀¡æGA₁ biosynthetic step, was up-regulated by enhanced supply of N, and indicating that the increasing of GA₁ content may have a key role in the regulation of development and growth accompanying with nitrogen. Furthermore, an elevated calcium and silica supplies also lead to an up-regulation of GA₁ level in the shoots of rice plants. (Supported by a grant from the APSRC(R11-2001-09203002-0) funded by KSEF)