Influence of nitrogen fertilization on water relations, photosynthesis, carbohydrate and nitrogen metabolism of diverse pearl millet genotypes under arid conditions

Effects of nitrogen fertilization (80 kg N/ha) were studied on pearl millet (Pennisetum glaucum) genotypes including hybrids (MH-179 and HHB-67), composites (CZ-IC-923 and CZP-9604) and land races (Barmer population and CZ-IC-718) grown for 2 consecutive years (1997 and 1998) under rainfed conditions of the Indian and zone. Nitrogen application significantly increased the grain and stover yields in all the genotypes, particularly in the hybrids during both the years but more so in 1997, characterized by late onset of rains followed by adequate precipitation (299.5 mm). Notwithstanding lower plant water potential and leaf relative water content, N fertilized plants displayed significantly higher photosynthetic rates, leaf area, levels of total chlorophyll, starch, reducing sugars, soluble protein and free amino acids and nitrate reductase activity as compared with unfertilized control plants in all the genotypes during both the years. Genotypes HHB-67 and Barmer population during 1997 and HHB-67 and CZ-IC-718 during 1998 provided significantly higher grain yields than other genotypes whereas dry matter production was highest in cv. Barmer population during both the years. These genotypes generally maintained higher rates of photosynthesis, more efficient carbohydrate metabolism and higher nitrate reductase activity leading to better performance. Relatively higher yields of land races than composites and comparable with those of hybrids indicated adaptation of these cultivars to and conditions and maintenance of several characteristics for their superior performance which could be further augmented by N application. Fertility induced improvement of metabolic efficiency, coupled with higher photosynthesis and nitrate reductase activity for efficient N utilization seem to be the control mechanisms, for enhanced growth and yield of diverse pearl millet genotypes under limited water conditions.