ISHS Acta Horticulturae 493: I ISHS Workshop on Water Relations of Grapevines
EFFECT OF IRRIGATION REGIME ON PHOTOSYNTHESIS AND LEAF WATER POTENTIAL OF VITIS VINIFERA L. (CV. ALPHONZE LAVALLÉ) IN VENEZUELA |
| Authors: | F.J. Araujo, T. Urdaneta, M. Marin, L.E. Williams |
| Keywords: | Net CO2 Assimilation rate, Leaf water potential, Grapevine, Tropics, Irrigation regime |
| Abstract:
Net CO2 assimilation rate (A) and leaf water potential (  1) were measured weekly at midday and diurnally on selected days throughout two growing cycles of grapevines grown in the tropics (Venezuela). Vines in a low and a high irrigation treatment were selected for measurements.
The average cycle Kps for the two irrigation treatments were 0.31 and 0.65. The differences in midday 1 between the high and low irrigation treatments, although consistent, were relatively small (0.14 MPa). This was probably due to the fact that midday 1 was similar in both irrigation treatments during the first third of the growing cycles.
The diurnal behavior of 1 was similar to that reported elsewhere.
For both irrigation treatments the highest values of A (18–20 μmol CO2. m-1. s-1) were obtained during the early morning hours up until 10 a.m. depending upon photon flux density (PFD) of that particular day.
Later in the day A slowly decreased for both irrigation treatments independent of further increases in PFD and/or temperature.
Stomatal conductance responded similarly to that of A. Photoinhibition of photosynthesis may be responsible for the reduction in A prior to midday for both irrigation treatments.
Further study is warranted to determine the physiological response of V. vinifera grown under tropical environmental conditions.
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