Effects of various environmental and medium conditions on the response of Indica and Japonica rice plants to ammonium and nitrate nitrogen

Abstract

The responses of two subspecies of rice, Oryza sativa subsp. Indica and Oryza sativa subsp. Japonica, to NH₄ ⁺ and NO₃ ^- under various environmental and medium conditions were studied by the water culture method. The results obtained indicated different effects of seasonal variations, particular of temperature and light intensity, on the responses of both rice subspecies to NH₄ ⁺ and NO₃ ^-. In summer, when the temperature and light intensity were high, the Indica rice plant fed with NO₃ ^- was definitely superior to that fed with NH₄ ⁺ or NHN⁺+NO₃ ^-, while the Japonica showed a better response to NH₄ ⁺+NO₃ ^- than to NH₄ ⁺ or NO₃ ^-. However, as the season progressed to autumn, the response of the Indica rice plant to NH₄ ⁺ and NO₃ ^- followed the same trend as that of the Japonica. In contrast, the growth of both rice subspecies fed with NH₄ ⁺ relative to that of plants grown in NH₄ ⁺+NO₃ ^- was better in autumn than in summer. On the other hand, although the responses of both rice subspecies to NH₄ ⁺ and NO₃ ^- were also influenced by the medium pH, and the ratio of NH₄ ⁺ to NO₃ ^- in the culture solution, the Indica always showed a better growth with NO₃ ^- than the Japonica. The uptake of NH₄ ⁺ and NO₃ ^- by both rice subspecies exhibited the same trend as the growth response.