; leaf water potential at 36, 55, 67, 75, and 90 DAS; and leaf temperature, transpiration, and stomatal resistance at 36, 55, and 90 DAS. We sampled three plants per plot for each sampling date. The gaseous exchange measurements from the porometer LI-1600
-watered citrus leaves reduces net assimilation of CO 2 (A CO2 ) by a direct biochemical inhibition of photosynthetic capacity rather by decreases in stomatal conductance ( g s ) or leaf water potential ( GarcÃa-Sánchez et al., 2006 ; Levy and Syvertsen, 2004
all the water used for any given 24-h period. However, Gucci et al. (1997) reported that A. deliciosa does not demonstrate low midday leaf water potential values under water deficit as effective stomatal closure allows water conservation. But
moved indoors for measurement. Leaf water potential was measured in a custom Scholander-type pressure chamber ( Ritchie and Hinckley, 1975 ) constructed at the University of Queensland and fitted with a digital readout. Osmotic adjustment in terms of
Abstract
Field measurements of leaf water potential were made on ‘Valencia’ orange trees subjected to varying degrees of soil water availability. During the night, leaf water potentials were reasonably well correlated with tensiometer estimates of soil matric potential. During the day, however, leaf water potentials were unrelated to matric potential because plant water balance was influenced by other factors in the shoot and root environments, including vapor pressure deficit, leaf diffusion resistance, and soil temperature.
harvested for final growth analysis. During the severe dry-down, predawn leaf water potential, leaf gas exchange, container weight (for later calculation of substrate moisture contents and daily evapotranspiration rate), and leaf relative water content (RWC
The sensitivity of leaf (ψleaf) and stem (ψstem) water potential and stomatal conductance (gs) to soil moisture availability in apple (Malus domestics Borkh.) trees and their correlation with yield components were studied in a field experiment. Two drip irrigation treatments, 440 mm (H) and 210 mm (L), were applied to a `Golden Delicious' apple orchard during cell enlargement stage (55-173 days after full bloom). Data collected included ψstem, y leaf, gs, and soil water potential at 25 (ψsoil-25) and 50 cm (ψsoil-50). No differences in midday ψleaf's were found between irrigation treatments. Stem water potential was higher in the H treatment than in the L treatment in diurnal measurements, and at midday throughout the season. Stomatal conductance of the H treatment was higher than the L treatment throughout the day. Stomatal conductance between 0930 and 1530 hr were highly correlated with ψstem. The H treatment increased the percentage of fruit >65 mm, and increased the proportion of earlier harvested fruit reaching marketable size compared to the L treatment. Fruit size in the first harvest and the total yield were highly correlated with ψstem. The degree of correlation between plant water stress indicators and yield component decreased in the following order: ψstem>ψsoil-25,>ψsoil-50>ψleaf. The data suggest that midday ψstem may serve as a preferable plant water stress indicator with respect to fruit size.
transpiration rate and leaf area ( Lazaridou and Koutroubas, 2004 ). In our study, high leaf WUE under drought stress was observed in all four cultivars ( Fig. 3 ). Leaf water potential. During the dry down, midday ψ at SMC between 20% and 35% was similar among
μL·L −1 . Plant–water relations. Midday leaf water potential and crown water potential were measured 0, 2, 4, 5, 6, 7, 9, 11, 13, and 15 d after start of treatments. Measurements of ψ leaf were carried out using a pressure chamber (Soil
that nodding needlegrass exhibited a low summer cuticular transpiration rate, suggesting a drought tolerance mechanism. This study evaluated summer soil moisture and vine leaf water potential patterns with nodding needlegrass as a cover crop compared