Morphological and physiological characteristics of several rice types under optimum nitrogen conditions

High-yielding rice varieties are associated with specific morphological and physiological characteristics, and their optimal performance depends on sufficient nutrient supply, particularly nitrogen. As an essential nutrient, nitrogen plays a crucial role in plant growth and development. Therefore, it is necessary to conduct further studies on the effects of nitrogen application on different rice varieties. This study aimed to investigate the morphophysiological responses and assimilate dynamics of several rice types under different nitrogen supply conditions. The research was conducted in a plastic house located in Maros Regency, South Sulawesi, from May 2022 to November 2022. A randomized block design was employed, consisting of two treatment factors: rice varieties and fertilizer dosage. The variety factor included four varieties: IPB 3S (new plant type), Inpari 33 (new high-yielding variety), Mentik Wangi (local variety), and Hipa 21 (hybrid). The dosage factor consisted of two levels: 0 kg ha-1 and 90 kg ha-1 of nitrogen. The results showed that optimal nitrogen application significantly influenced various morphological and physiological characteristics of the rice plants. IPB 3S and Mentik Wangi varieties exhibited higher net assimilation rates from the primordial stage to the heading stage, enabling them to produce larger assimilates for allocation to grain filling. The non-structural carbohydrates (NSC) of Inpari 33 and Hipa 21 at the heading stage were much lower than the NSC at harvest, while the sink demand was high, indicating a hindrance in assimilate translocation from vegetative parts to the grains.