ISHS Acta Horticulturae 493: I ISHS Workshop on Water Relations of Grapevines
EXPERIENCE WITH GRANIER-TYPE SENSORS FOR SAP FLOW MEASUREMENTS IN GRAPEVINES |
| Authors: | J. Schmid, W. Bettner |
| Abstract:
The Granier system for measuring sap flow in intact plants was adapted to grapevines. Measurements were carried out over a 3 months period in 1994 and 1995 on 10-year old, field-grown Vitis vinifera L. c.v. White Riesling clone 198 Gm grapevines, grafted on 5 C clone 6–13 Gm rootstocks at the Research Institute in Geisenheim, Germany (50° North, 8° East). CO2 gas exchange was measured on the same plants with an open system gas exchange apparatus without environmental control (Walz, Effeltrich, Germany) using a Binos infrared gas analyzer (Leybold Hereaeus, Hanau, Germany) operating in differential mode. Results were compared with sap flow measured in the trunk. Large differences were found in water use between different vines in the field. However, when calculating water loss on the basis of leaf area, differences between vines disappeared. Sap flux density was thus directly related to leaf area of individual vines. Stem cross sectional area did not restrict water use. The daily course of sap flow was closely related to climatic factors of which light and vapour pressure deficit had the largest influence. High rates of sap flow were always correlated with high rates of photosynthesis. Water stress inhibited both, sap flow and photosynthesis. A high rate of sap flow at night was always correlated with high respiration rates. The effect of soil water deficits together with high temperatures and high vapor pressure deficits on transpiration was higher than on photosynthesis. However, during the day, global radiation, VPD, air temperature and wind speed explained 80% of the variance in transpiration. In comparison to that global radiation alone explained 75% of the photosynthesis. Results show that Granier type sensors can be adapted to grapevines and are well suited to study various aspects of plant water relations. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
