Einfluß der Wasserversorgung auf Wachstum, Gaswechsel und Substanzproduktion traubentragender Reben <p>III. Die Substanzproduktion</p>

Abstract

The influence of water supply of fruit-bearing and vegetatively growing vines on dry matter production and on yield and quality has been investigated during the years 1979 and 1980.

1. Dry matter production is significantly reduced by soil drought, root growth being less influenced than shoot growth. Comparing weil watered plants with dry-cultivated ones, no differences are found in the total production of vegetatively growing and fruit-bearing vines. The fruit, however, reduced the dry matter production of all vegetative organs, particularly root growth under drought conditions. Despite reduction of the vegetative growth the total amount of shoot and cluster weight of fruit-bearing vines is in all cases higher than shoot weight of vegetatively growing plants.
2. The different effect of drought and fruit production on shoot and root growth caused a pronounced alteration of the shoot-to-root ratio : This ratio being low at a low water supply, and high in fruit-bearing plants.
3. A significant correlation between net photosynthesis and net assimilation rates was obtained. The correlation coefficients range between r = +0.90 and r = +0.95.
4. An optimum water supply during growth stage I of the grape berry results in a significant increase of yield via increased single-berry weight whereas no increase in yield (Müller-Thurgau) or only a slight increase (Bacchus) occurs when drought conditions during stage III of berry growth are counteracted by a surplus watering.
5. A sufficient water supply, particularly in stage I of berry growth, leads to an increased acid content of the berry.