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
In order to evaluate and compare adaptability to dry sites, plant water relations and leaf gas exchange were compared in response to water stress among six birch species: monarch birch (Betula maximowicziana), river birch (B. nigra), paper birch (B. papyrifera), European birch (B. pendula), `Whitespire' Japanese birch (B. platyphylla var. japonica `Whitespire'), and gray birch (B. pendula). After 28 days without irrigation, Japanese birch maintained significantly higher stomatal conductance (gs) and net photosynthesis (Pn) than did any of the other species, despite having one of the lowest mid-day water potentials. Evaluation of tissue water relations, using pressure-volume methodology, showed no evidence of osmotic adjustment for any of these species in response to water stress. However, there was substantial variation among species in the water potential at the turgor loss point; varying from a high of -1.34 MPa for river birch to a low of -1.78 MPa for Japanese birch. Rates of Pn and gs under mild stress (mean predawn leaf water potential of -0.61 MPa) were negatively correlated with leaf osmotic potential at full turgor and the leaf water potential at the turgor loss point.
Water relation parameters were calculated from analysis of 92 pressure-volume isotherms of leaves of two olive varieties, `Leccino' and `Frantoio', measured after 4 weeks of salinity stress and 4 weeks of subsequent relief either in hydroponics or soil culture. `Frantoio' was more salt-tolerant than `Leccino', but no major differences in water relation parameters emerged between the two varieties. Increasing salinity from 0 to 200 mM NaCl decreased predawn leaf water potential from –0.5 MPa to –1.3 MPa, relative water content (RWC) from 97.6% to 89%, and leaf osmotic potential (Ψπ) from –2.0 to –3.5 MPa. Relative water content at turgor loss point (RWCtlp) was decreased from 89% to 85% (soil culture) and from 86% to 80% (hydroponic culture) in 0 to 200 mM CaCl-treated plants, respectively; a lower RWCtlp was also retained during the relief from salinity. Active osmotic adjustments induced by salinity was the result of accumulation of both inorganic ions and compatible solutes (e.g., mannitol). Maintenance of lower Ψπ and RWCtlp during relief indicated that salinized plants were better adapted to withstand further stress and that this potential might be exploited to harden olive plants to be used in arid or saline environments.
Leaf cell turgor pressure is a water status variable related to firmness, growth, and with the consumer perception of wilting and freshness. Turgor pressure measurements are usually made at a laboratory using laborious procedures. With the
starting just before application of s-ABA. Wilt status ratings were from 1 to 5 with 5 being completely turgid, 4 soft to the touch, 3 starting to wilt, 2 wilted with complete loss of turgor, and 1 wilted to the point that leaves are dry and brittle. Leaf
coordinating the vapor loss and liquid supply, as described in Eq.  . Combined with a high leaf water potential, the turgor pressure of guard cells was sufficiently high to sustain pore openness for CO 2 use in low-VPD-grown plants. Comparison of water
total water content of the saturated shoot (Vt). The relative water content at the turgor loss point (RWC tlp ), relative osmosis water content at the turgor loss point (ROWC tlp ), and the ratio of bound water to free water (V a /V p ) were calculated
upright, 2 = wilted with complete loss of turgor, and 1 = wilted to the point that leaves are dry and desiccated. Values are means ± sd of four replications (n = 4). Expt. 1: Leaf chlorosis of 11-cm finished pansies and violas treated with s
leaf area were found under moisture stress conditions in bonfire salvia ( Salvia splendens F. Sellow), which was the result of loss of turgor during dry-down cycles ( Eakes et al., 1991 ). Turgor loss has been reported to cause reductions in cell
every other day for 31 d, until the end of leaf elongation. Once per week, water, osmotic, and turgor potential were measured using individually calibrated thermocouple psychrometers (model 76-2VC; JRD Merrill Specialty Equipment, Logan, Utah) on a 5