Hubungan Antara Aktivitas Nitrat Reduktase Pada Akar Dan Tajuk Dengan Akumulasi Dan Asimilasi N Pada 16 Inbred Jagung

Abstract

The relationships between nitrate reductase activity (NRA) in the shoots and roots, NRA versus net nitrate uptake, and NRA versus accumulation of nitrate and reduced N were studied in 15-day-01d greenhouse-qrown seedlings of 16 corn (Zea mays L.) inbreds. The distributions of NRA, total N (TN), nitrate, and reduced N (RN) between roots and shoots were determined. The observed genotypic differences in accumulated N per plant were related to differences in root size, but factors other than root size also affected nit.rate absorption. Results of the present study are comparable to earlier results obtained with 12-week-01d plants. Both studies indicate that selection for genotypic variation in maize inbreds for uptake or accumulation of nitrate is possib1eo On the average, root NRA was 10.0\ and 3.0\ of shoot NRA on a gram fresh weight basis and on a per plant basiS, respectively. These data indicate that shoot NRA plays a greater role in N assimilation in corn seedlings than does root NRA. A positive relationship was observed in the 16 inbreds between root and shoot NRA as indicated by a highly significant correlation (r = 0.786**) based on a gram fresh weight basis. When total NRA per shoot was compared to total NRA per root, the correlation was also highly significant (r = 0.787**). The data suggest that root and shoot NR are both induced in paralle1 when high levels of nitrate are provided to corn seedlings. Corn genotypes with high shoot and root NRA also had high TN (r = 0.772** and r = 0.727**, respectively). On a per plant basis, genotypes with high NRA also had high TN and RN (r = 00 775** and r = 00 781**, respectively).