EFFECT OF IRRIGATION REGIME ON PHOTOSYNTHESIS AND LEAF WATER POTENTIAL OF VITIS VINIFERA L. (CV. ALPHONZE LAVALLÉ) IN VENEZUELA

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 K_ps 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.

I ISHS Workshop on Water Relations of Grapevines

F.J. Araujo, T. Urdaneta, M. Marin, L.E. Williams

Net CO₂ Assimilation rate, Leaf water potential, Grapevine, Tropics, Irrigation regime

https://doi.org/10.17660/ActaHortic.1999.493.22