Growth and Gibberellins level of Two Rice Cultivars as Influenced by Different Nitrogen Containing Compounds

Seedlings of two rice cultivars i.e. cv. Daesanbyeo and cv. Dongjinbyeo were analyzed for growth and endogenous gibberellins (GAs) in response to nitrogen nutrition applied in the forms of $KNO_3$, $(NH_4)_2SO_4$ and $NH_4NO_3$. All the growth parameters showed an increase in N applied treatments and their magnitudes of increase were different depending on different nitrogen fertilizer forms. The endogenous GAs contents were increased with N application but differentially affected by various N-forms in both rice cultivars. In cv. Daesanbyeo, maximum amount of bioactive $GA_1$ was recorded for $(NH_4)_2SO_4$, while maximum amount of bioactive $GA_1$ in cv. Dongjinbyeo was observed in $NH_4NO_3$ applied treatments. In both rice cultivars, $KNO_3$ applied rice plants contained least $GA_1$ contents. Also, $GA_{19}$ was the most abundant GA found in rice seedlings whereas $GA_4$ was absent at seedling stage. Our study indicated that different rice cultivars showed different responses for the same fertilizer depending upon the response potential of each cultivar and the pertinent physiological responses to changes of endogenous GAs in rice cultivars, which were comparatively lesser in magnitude.