Effects of Na2WO4 on 15N absorption and utilization,13C accumulation of apple seedling, and fruit quality

Abstract

Pot culture and field experiments were carried out with one-year-old apple rootstock M9T337 seedlings and five-year-old 'Yanfu3'/SH6/M. hupehensis Rehd. as test materials respectively. Combined with 15N and 13C isotope tracer technology, we examined the effects of different concentrations of NR inhibitor Na2WO4(0, 0.5, 1, 1.5 mmol·L-1, expressed by CK, T1, T2 and T3 respectively) on 15N absorption and 13C accumulation of seedling and apple quality. The results showed that 0.5-1.0 mmol·L-1 Na2WO4 significantly inhibited shoot growth but not root growth of seedling in the pot experiment. Root growth was significantly inhibited when the concentration of Na2WO4 reached 1.5 mmol·L-1. The NR activity of each treatment was negatively correlated with the concentrations of Na2WO4 in the same period, with an order of CK>T1>T2>T3. The content of nitrate in leaves showed the trend of first rising and then decreasing with the extension of processing time. Nitrate content was positively correlated with Na2WO4 concentration in the same period, with an order of T3>T2>T1>CK. Spraying Na2WO4 reduced the 15N absorption of each organ and 15N utilization rate, with such effects increasing with the amount of spraying. With the increases of Na2WO4 concentration, 13C accumulation on the ground increased first and then decreased, with highest value in T2 treatment. The 13C accumulation of whole plant showed a similar pattern. The results of field experiment showed that Na2WO4 application reduced nitrogen contents of leaves and fruits at maturity stage, and increased the anthocyanin content in peel, soluble solids, soluble sugar content and sugar acid ratio in fruits. The T2 treatment showed the best effect. In summary, T2 treatment (1.0 mmol·L-1 Na2WO4) could inhibit shoot growth of seedlings, reduce 15N absorption and utilization, improve 13C accumulation, which would improve apple quality.