不同氮磷配比施肥对烤烟生长及碳代谢的影响OA

To explore an efficient nutrient co-application fertilization mode promoting the accumulation of sweetness-related substances in tobacco leaves,a field experiment was conducted under two nitrogen(N)application levels(conventional N and increased N application)with three N-to-P ratios(1:0.7,1:1,and 1:1.3),and the effects of different N-P ratios on tobacco growth,photosynthesis,and the activities of key enzymes involved in sugar synthesis within carbon metabolism were studied.The results showed that under the same N-P ratio,increased N application promoted plant height and stem girth at the rosette stage.At the vigorous stage,it conferred no significant gain in most agronomic traits or photosynthetic indicators,except for a significant increase in leaf width.Nevertheless,under the same N level,increasing P application significantly enhanced the length and width of the largest leaf,as well as the intercellular CO2 concentration,photosynthetic rate,and stomatal conductance of the tobacco leaves.Under conventional N application,increased P application elevated the activity of sucrose phosphate synthase in the leaves but had no effect on the activity of ADP-glucose pyrophosphorylase(AGPase),a key rate-limiting enzyme in starch synthesis.Increased N application inhibited sucrose accumulation,while reducing the N:P ratio by adding P alleviated this negative effect and promoted total sugar accumulation.In conclusion,in the tobacco-rice rotation system of southern Hunan,appropriately increasing P application to reduce the N:P ratio while controlling nitrogen input can improve agronomic traits,enhance photosynthetic capacity and carbon metabolism activity,and thereby improving tobacco leaf quality.