ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Diurnal and seasonal changes in nitrate reductase activity and nitrogen content of grapevines: effect of canopy management.

Hunter, J. J.; Ruffner, H. P.;

Vitis Year: 1997 Vol: 36 Issue: 1 Pages: 1-6 Ref: 35 ref.

1997

บทคัดย่อ

Diurnal and seasonal variations in in vivo nitrate reductase activity (NRA) and N contents of leaves, fruits and roots and the effect of canopy management (combination of suckering, shoot positioning and leaf removal) were determined in grapes cv. Cabernet Sauvignon CS46 grafted on 99 Richter RY 30, growing in South Africa. Peak NRA in leaves occurred from mid-morning to midday. Young leaves had almost the same NRA as mature leaves before fruits reached pea size stage, but subsequent to that displayed higher activity. Leaf NRA increased during the postharvest period. Differences in NRA patterns between leaves conformed with classic source:sink behaviour. Canopy management stimulated nitrate reduction in basal source leaves, most likely through its favourable effect on canopy light microclimate and photosynthetic activity. NRA in fruits generally increased with development; canopy management affected NRA only slightly. Peak root NRA corresponded to seasonal root growth patterns. In contrast to le

aves and fruits, NRA in roots increased from the morning to the afternoon. Effect of canopy management on root NRA was minor. Leaf and fruit N contents declined during the season, whereas reasonably stable concentrations were maintained in the roots. An involvement of nitrate reductase in N assimilation and in the energy supply pathways of the grapes was substantiated. NRA proved to be a good indicator of fluctuations in N assimilation during growth, suggesting its determination to be instrumental in defining the N status and fertilization needs of the grapes.