ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
MODIFICATION OF THE HYDRAULIC CONDUCTIVITY IN VITIS VINIFERA L. BY MANIPULATING SHOOT ORIENTATION. |
| Authors: | C. Lovisolo, G. Lubraco, A. Schubert |
| Keywords: | Sap flow, Stem Heat Balance technique, stem water potential, transpiration, xylem, water transport, embolism. |
| Abstract:
The grapevine can respond to environmental and agronomic-imposed conditions with modifications of shoot transport systems. The objective of this work was to manipulate shoot orientation in order to modify water conductivity and to assess the effects of such manipulations on water transport in the plant. Conductivity was modified by inverting the orientation of the central shoot portion in potted single-shoot grapevines. Three decreasing levels of conductivity were obtained by increasing the length of the inverted portion. Conductivity was checked in vivo by calculation of the ratio between water flow along the shoot and the respective gradient of shoot water potential, and it was assessed at the end of the growing season by direct measurements using pressure-induced flow in excised shoots. Water flow was measured in whole shoots by the Stem Heat Balance method, and evaluated in each shoot portion using transpiration rates obtained by gas exchange measurements. The three decreasing levels of conductivity, found in the inverted shoot portions, caused a progressive reduction of water transport through the whole shoot in manipulated plants. Shoot inversion caused a proportionately greater reduction in transpiration from leaves in the inverted segments than for the whole shoot. In contrast, in distal shoot portions, when the apex grew again upwards, the transpirative flow was slightly higher than in homologous portions of the control plants. Water flow modifications were not due to a significant decrease in water tension gradient which was not different among the manipulated vines. Reduced hydraulic conductivity was therefore the main cause of decreased water and nutrient transport to the leaves through the shoot. The role of hydraulic conductivity in controlling water losses and its relation with the growth of differently oriented grapevine shoots are discussed. | |
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