; Kozlowski, 1997 ). Such changes can cause citrus trees to respond to flooding by reducing leaf water potential and g S ( Islam et al., 2003 ; Li et al., 2007 ; Ruíz-Sánchez et al., 1996 ). When flooding is prolonged, the A CO2 can also be reduced ( Vu
harvesting fruits that met market quality when ripe (≈50% of fruit exterior had turned red) throughout the study period. Photosynthetic parameters, transpiration rate, and leaf water potential. Photosynthetic rate, g S , transpiration rate (LI-6200; LI
appropriate plant for a set of specific site conditions, the tolerances of the species or cultivar should be well documented. In the case of drought, the leaf water potential at the turgor loss point (Ψ P0 ) is a valuable measurement for characterizing the
= nonphotochemical quenching; F v /F m = photochemical efficiency of PSII; ETR = electron transport rate; g S = stomatal conductance; Ψ wf = leaf water potential; PC = principal component. Comparative analysis of vascular wilt and waterlogging mitigation by
calculated with the image analysis software for plant disease quantification ASSESS 2.0 (University of Manitoba, Winnipeg, Canada). Leaf potentials. Midday leaf water potential (Ψ hmd ), midday leaf ψ S (Ψ omd ), and midday leaf turgor potential (Ψ pmd
The effect of wind stress on growth, net CO2 assimilation (A), and leaf water potential of eighteen-month-old, containerized carambola (Averrhoa carambola cv. Arkin) and seedling sugar apple (Annona squamosa) trees was investigated. In a glasshouse, trees were exposed to fan-generated wind speeds of 0 (control), 4 (low wind; LW), or 7 (high wind; HW) m sec-1 for 4 hr/day (1000-1400 hr) for 30 days. No differences in A, stomatal conductance, transpiration, and fresh and dry wt of mature carambola or sugar apple leaves or shoots were observed among treatments. In contrast, as wind speed increased, fresh wt of immature carambola leaves and shoots decreased. For carambola and sugar apple, no significant relationship was found between mid-day leaf water potentials and wind speed. However, after 30 days, leaf water potential of carambola subjected to HW (-1.2 MPa) was lower than those of LW (-1.1 MPa) and control (-1.1 MPa) trees. For sugar apple, leaf water potential of control trees was generally higher than those of trees in the LW and HW treatments. The data indicate that exposure to wind speeds of 4 or 7 m sec-1 for as little as 4 hr/day for 30 days reduces new leaf and shoot growth of carambola trees.
Low- and high-K pretreated ‘York Imperial’ apple seedlings (Malus domestica Borkh.) were grown in nutrient solution cultures. Addition of polyethylene glycol (PEG) to the nutrient solution to reduce water potential to −1.0 bar reduced water consumption, fresh weight, specific leaf weight (SLW), and leaf water potential and increased the amount of water consumed per unit of fresh weight gain. High-K pretreatment increased water consumption of unstressed seedlings but decreased water consumption of PEG-stressed plants. Daily sprays with 0.5% KCl applied in early afternoon had no effect on water consumption rate in apple seedlings. However, sprays probably induced wider stomatal opening, since K-sprayed trees had lower leaf water potential when measured at noon than unsprayed trees. This effect was not observed when water potential was measured in the morning (0800 hr). High-K plants had higher leaf water potential than low-K plants in the morning. Potassium pretreatment and PEG stress as well as K-sprays had numerous effects on plant mineral composition. The K-pretreatment or K-sprays did not alleviate the detrimental effects of PEG-induced water stress despite the effects of K-pretreatment and K-sprays on mineral composition and leaf water potential.
Eleven-year-old ‘Golden Delicious’/M. 26 apple (Malus domestica Borkh.) trees were left unthinned (483 fruit/tree), thinned to one fruit/spur (370 fruit/tree), or completely defruited. Leaf water potential, leaf stomatal conductance, and leaf water content were monitored during the growing season. From 3 weeks after thinning and continuing to harvest, trees with an average of 483 or 370 fruit had significantly lower leaf water potentials than defruited trees. Trees thinned to 370 fruit had consistently higher leaf water potentials than unthinned trees with 483 fruit. Leaves on unthinned or one fruit/spur trees had higher stomatal conductances than leaves on completely defruited trees, although these differences were detected later in the season than those for leaf water potentials. No treatment differences in leaf water content were observed. Defruited trees had higher specific leaf weights, longer shoot extension, and greater increases in trunk cross-sectional area than those not defruited. Fruit size was greatest on trees thinned to one fruit/spur.
I wish to point out a discrepancy in the conclusion on the value of the J-14 hydraulic press by A.H. Markhart, III, and B. Smit-Spinks [HortScience 19(l):52–54, Feb. 1984] that the J-14 readings prevent reliable predictions of the Scholander pressure bomb for leaf water potential measurements.
In chlorotic, K-deficient leaves of prune (Prunus domestica L. cv. Agen), leaf water potentials were greater and transpiration less than in green, K-sufficient leaves. These results bring into question the role of leaf desiccation as the primary factor in the browning of K-deficient leaves.