Dry matter and nitrogen partitioning and root growth of young field-grown Thompson Seedless grapevines

Abstract

Seasonal changes in dry weight and nitrogen distribution were quantified on 2-year-old pruned and unpruned Thompson Seedless grapevines grown in the field. Entire vines were harvested several times during the growing season from budbreak to fruit harvest. Vine dry weight and N coptent increased throughout the season for both treatments, however, the accumulation of both parameters was delayed and of a smaller magnitude for the pruned vines. The increase in root dry weight of the pruned vines occurred later in the season when compared to the unpruned vines, but there was no difference in root dry weight between treatments at the end of the study. Root N content remained constant early in the growing season followed by a significant increase later in the season for both treatments. The root N concentration decreased as a result of an increase in root dry weight, then it leveled off at about 1.2 % for both treatments due to similar rates of root dry matter and N accumulation. The results do not support the role of roots as the major storage organ of N to supply the rest of the plant early in the season for young grapevines. However, N from other permanent structures of the vine supplied between 14 and 26 % of that required for shoot growth shortly after budbreak.