The temperature dependence of shoot hydraulic resistance: implications for stomatal behaviour and hydraulic limitation

Abstract

Recent soil pressurization experiments have shown that stomatal closure in response to high leaf-air humidity gradients can be explained by direct feedback from leaf water potential. The more complex temperature-by-humidity interactive effects on stomatal conductance have not yet been explained fully. Measurements of the change in shoot conductance with temperature were made on Phaseolus vulgaris (common bean) to test whether temperatureinduced changes in the liquid-phase transport capacity could explain these temperature-by-humidity effects. In addition, shoot hydraulic resistances were partitioned within the stem and leaves to determine whether or not leaves exhibit a greater resistance. Changes in hydraulic conductance were calculated based on an Ohm's law analogy. Whole-plant gas exchange was used to determine steady-state transpiration rates. A combination of in situ psychrometer measurements, Scholander pressure chamber measurements and psychrometric measurements of leaf punches was used to determine water potential differences within the shoot. Hydraulic conductance for each portion of the pathway was estimated as the total flow divided by the water potential difference. Temperature-induced changes in stomatal conductance were correlated linearly with temperature-induced changes in hydraulic conductance. The magnitude of the temperature-induced changes in whole-plant hydraulic conductance was sufficient to account for the interactive effects of temperature and humidity on stomatal conductance.

PHOTOSYNTHETIC PERFORMANCE AND LEAF WATER POTENTIAL OF GULUPA (Passiflora edulis Sims, PASSIFLORACEAE) IN THE REPRODUCTIVE PHASE IN THREE LOCATIONS IN THE COLOMBIAN ANDES

“…1d) did not favor an adequate water recovery because they could generate cavitation in the xylem (Schultz and Matthews, 1997), which is evidenced in the water potential values during the day and the night, despite registering low transpiration rates. The low water potential values before morning that were registered in plants grown in Chia in the fruiting stage, could result from a low temperature during the night that decrease the permeability of the roots and its water conductivity (Matzner and Comstock, 2001;Norisada et al, 2005); these values were close to those reported for grapevines (Vitis vinifera) under water deficit conditions (Tay et al, 2007).…”

Hydraulic Analysis of Water Flow through Leaves of Sugar Maple and Red Oak

“…The greater-than viscosity temperature response of R leaf is consistent with the flow path including a transcellular component (Haines, 1994). This temperature response is the first to be reported for steady-state water flow through individual leaves; previously, milder effects (but still greater than those expected for viscosity) have been reported for leafy shoots (Fredeen and Sage, 1999;Cochard et al, 2000;Matzner and Comstock, 2001). Responses greater than expected from viscosity have also been found for the dehydration of shoots and leaves using the pressure bomb (Tyree et al, 1973(Tyree et al, , 1975Boyer, 1974;Tyree and Cheung, 1977).…”

Do we know how plants sense a drying soil?

“…SALIENDRA et al, 1995;FUCHS & LIVINGSTON, 1996;COMSTOCK & MENCUCCINI, 1998). However, interestingly this argument has no support of a recent study by MATZNER & COMSTOCK (2001) who assumed that stomata indeed respond to leaves water status leaves in a drying soil for an herbaceous species (Phaseolus vulgaris L.). Are these evidences for returning to an emphasis away from the soil and towards the shoot of the plant again?…”