Arginine and Total Free Amino Acids As Indicators of the Nitrogen Status of Grapevines1

Abstract

Abstract Growth and composition of ‘Thompson Seedless’ rootings grown in a perelite-vermiculite mixture (1:1 v/v), and receiving Hoagland nutrient solutions containing 0, ½, 1, 2, 4, or 8 mM NO3 were investigated over a 3-year period. Dry wt, no. of nodes, and total leaf area per vine, trunk circumference, and chlorophyll concn in leaves increased linearily with increasing concn of NO3 from 0 to 4 mM, and then remained relatively constant at 4 and 8 mM. Control vines (no NO3) had significantly less area per leaf blade and dry wt per unit leaf area than vines receiving ½ to 8 mM NO3. However, among vines irrigated with ½ to 8 mM NO3 differences in leaf area and leaf wt were not statistically significant. Highly significant linear (correlation coefficients 0.76 to 0.98) and 4th degree polynomial (correlation coefficients 0.92 and 0.99) regression equations were obtained between the levels of NO3 in the nutrient solution and the concn of arginine in canes, trunk, and roots at 3 different stages of vine development; i.e., mid-dormancy, budbreak, and bloom. Total free amino acids and NO3 in petioles and leaf blades were also positively correlated with the level of N in the Hoagland solutions, and with each other. The increases in concn of arginine and total free amino acids (relative to the control) in various parts of vines irrigated with different levels of NO3 were greatest at bloom, followed by budbreak and then dormancy, and were generally in the order of roots>trunk>canes>leaves. The relative increases of arginine reserves in vines following budbreak was first from canes, then from trunk, and lastly from roots.