Abstract
Three grapevine (Vitis vinifera L.) cultivars, Chardonnay, Malbec, and Zinfandel were grown in sand culture at four different levels of solar radiation (100%, 50%, 28%, and 8% of full sunlight) in combination with three different levels of nitrogen (16, 4, and 1 mM nitrate).
Nitrate in petioles and blades was inversely related to light availability and directly related to nitrogen level. Dry matter per unit length of shoot growth, total cane dry wt./vine and nitrate reductase (NR, the enzyme that catalyzes the reduction of NO3 to NO2) activity of leaf blades were related directly to light intensity, decreasing sharply under reduced solar radiation. The influence of solar radiation on the level of arginine was variable. The concentration of arginine in dormant cane tissues depended mainly on cultivar and on the concentration of nitrogen in the nutrient solution.
Nitrate reductase activity was related inversely to petiole nitrate concentration and correlated highly with weight per centimenter of cane. The level of nitrate accumulated in petioles and leaf blades was modulated, at least in part, by the activity of nitrate reductase.
It is concluded that where climate is variable, especially during the bloom sampling period, petiole nitrate may not reflect the true nitrogen status of vineyards.
- Received November 1981.
- Accepted December 1981.
- Copyright 1982 by the American Society for Enology and Viticulture
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Vol 33 Issue 2
