Nitrogen dose dependent changes in leaf greenness, crop phenology, grain nitrogen content and yield in rice (Oryza sativa L.) sub-species

In the present study, 30 diverse genotypes of rice sub-species were evaluated for variations in phenology, grain protein content, grain morphology and yield under field conditions with different nitrogen (N) regimes i.e., N deficient (N=0) and N sufficient (N=120 kg ha-1). N deficiency decreased the leaf greenness, panicle yield, grain protein content, altered grain morphology and grain-related parameters. Significant variations in grain morphology-related parameters such as grain length and grain width among rice genotypes were observed for different N treatments. Changes in grain morphology related parameters were correlated with yield. The study identified Sahbhagi Dhan, BAM-759, BVD-109, Pusa Sugandh-5, and Kalinga-1 that maintained higher vegetative greenness, while Sahbhagi Dhan, Vandana, Nerica-L-44, Kalinga-1 and APO that showed higher panicle yield under N0 condition. Rice genotypes APO, Nerica-L-42 and Kalinga-1 performed well under N0 with a lesser impact on crop phenology and grain morphology. Grain protein content was found higher in BAM-759, Anjali, Thurur Bhog, IR-64, Rasi, and Kalinga-1under both the treatments. Flag leaf Soil Plant Analysis Development (SPAD) and Normalized Difference Vegetation Index (NDVI) measurements were significantly correlated with grain yield, and grain protein content. The trait specific donors suitable for low N conditions identified in the study will pave the way forward to the research in understanding underlying mechanisms and in crop improvement programs

Variation in nitrogen partitioning and reproductive stage nitrogen remobilization determines nitrogen grain production efficiency (NUEg) in diverse rice genotypes under varying nitrogen supply

Nitrogen (N) is an important macronutrient needed for grain yield, grain N and grain protein content in rice. Grain yield and quality are significantly determined by N availability. In this study, to understand the mechanisms associated with reproductive stage N remobilization and N partitioning to grain 2 years of field experiments were conducted with 30 diverse rice genotypes during 2019-Kharif and 2020-Kharif seasons. The experiments were conducted with two different N treatments; N deficient (N0-no external N application, available soil N; 2019-234.15 kgha-1, 2020-225.79 kgha-1) and N sufficient (N120-120 kgha-1 external N application, available soil N; 2019-363.77 kgha-1, 2020-367.95 kgha-1). N application increased the NDVI value, biomass accumulation, grain yield, harvest index and grain N accumulation. Post-anthesis N uptake and N remobilization from vegetative tissues to grain are critical for grain yield and N harvest index. Rice genotypes, Kalinga-1, BAM-4234, IR-8384-B-B102-3, Sahbhagi Dhan, BVD-109 and Nerica-L-42 showed a higher rate of N remobilization under N sufficient conditions. But, under N deficiency, rice genotypes-83929-B-B-291-3-1-1, BVD-109, IR-8384-B-B102-3 and BAM-4234 performed well showing higher N remobilization efficiency. The total amount of N remobilization was recorded to be high in the N120 treatment. The harvest index was higher in N120 during both the cropping seasons. RANBIR BASMATI, BAM-832, APO, BAM-247, IR-64, Vandana, and Nerica-L-44 were more efficient in N grain production efficiency under N deficient conditions. From this study, it is evident that higher grain N accumulation is not always associated with higher yield. IR-83929-B-B-291-3-1-1, Kalinga-1, APO, Pusa Basmati-1, and Nerica-L-44 performed well for different N use efficiency component traits under both N deficient (N0) and N sufficient (N120) conditions. Identifying genotypes/donors for N use efficiency-component traits is crucial in improving the fertilizer N recovery rate and site specific N management

Nitrogen dose dependant changes in grain morphology parameters are correlated with grain protein and yield traits in field-grown diverse rice genotypes

Nitrogen (N) deficiency alters grain morphology and reduces yield and quality rice (Oryza sativa L.). This study investigates the impact of nitrogen (N) deficiency on grain morphology, yield, and quality in 30 diverse rice genotypes. The genotypes were grown under field conditions during the 2019 and 2020-kharif seasons, subjected to two N regimes: N deficient (N0) and N sufficient (N120). Nitrogen deficiency resulted in reduced grain weight and protein content. Variations in grain morphology-related traits were observed among rice genotypes under different N applications, and these changes were correlated with yield. Certain genotypes, like APO, Nerica-L-42, and Kalinga-1, exhibited better performance under N0, indicating their tolerance to low N environments. Additionally, specific genotypes showed higher grain protein content under both N0 and N120 treatments. The study highlights the relationship between grain N content, grain morphology, and yield traits in rice under varying N conditions

Photosynthetic machinery under salinity stress: Trepidations and adaptive mechanisms

Chloroplasts and photosynthesis are the physiologically fateful arenas of salinity stress. Morphological and anatomical alterations in the leaf tissue, ultrastructural changes in the chloroplast, compromise in the integrity of the three-layered chloroplast membrane system, and defects in the light and dark reactions during the osmotic, ionic, and oxidative phases of salt stress are conversed in detail to bring the salinity-mediated physiological alterations in the chloroplast on to a single platform. Chloroplasts of salt-tolerant plants have evolved highly regulated salt-responsive pathways. Thylakoid membrane remodeling, ion homeostasis, osmoprotection, upregulation of chloroplast membrane and stromal proteins, chloroplast ROS scavenging, efficient retrograde signalling, and differential gene and metabolite abundance are the key attributes of optimal photosynthesis in tolerant species. This review throws light into the comparative mechanism of chloroplast and photosynthetic response to salinity in sensitive and tolerant plant species