Land plants need water to replace the evaporation that occurs while atmospheric CO2 is diffusing into photosynthetic tissue. The water-for-carbon exchange rate is poor, and evolutionary history indicates a progression of innovations for cheap water transport—beginning in order with capillary suction at cell walls, stomatal regulation, hydroids, tracheids, secondary xylem, endodermis, and vessel...

erophylla (Raf.) Sarg.) seedlings experience water stress and declining xylem pressure potential (Ψx). Low Ψx can result in xylem cavitation and embolism formation, causing a decline in hydraulic conductance. This study focused on the relationship between Ψx, xylem cavitation and transpiration (E) of newly planted seedlings. Leaf specific hydraulic conductance (kAB) declined from 0.56 to 0.09 m...

Following planting, western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings experience water stress and declining xylem pressure potential (Psi(x)). Low Psi(x) can result in xylem cavitation and embolism formation, causing a decline in hydraulic conductance. This study focused on the relationship between Psi(x), xylem cavitation and transpiration (E) of newly planted seedlings. Leaf specifi...

A number of recent observations have indicated a role for abscisic acid in maintaining water balance. Treatment with ABA reduces the transpiration rate (3, 5), probably by bringing about stomatal closure (2, 4). Furthermore, water stress leads to a significant increase in ABA concentration in leaves (5, 7). On the other hand, ABA increases the rate of root exudation (6). The present communicati...

Anatomical and physiological acclimation to water stress of the tree hydraulic system involves trade-offs between maintenance of stomatal conductance and loss of hydraulic conductivity, with short-term impacts on photosynthesis and long-term consequences to survival and growth. Here, we study the role of variations in root and branch maximum hydraulic specific conductivity (k(s-max)) under high...

Heat shock (HS) at 40 degrees C was given to the root system of Nicotiana tabacum wild type (WT) and to HSIPT transgenic plants transformed with the bacterial cytokinin biosynthesis gene isopentenyltransferase (ipt) cloned behind the heat shock 70 promoter from Drosophila melanogaster. HS increased cytokinin concentrations in roots and leaves of transgenic plants. The effect was smaller in WT p...

A clear understanding of hydraulic regulation in cultivated plants is crucial for addressing challenges to forest water cycling due to climate changes in low subtropical China. Experiments were conducted to determine the hydrologic balance of a Eucalyptus urophylla plantation in response to periodic drought. Trees displayed lower stomatal conductance (GS) and leaf water potentials (ΨL) during t...

Increasing the rate of leaf photosynthesis is one important approach for increasing grain yield in rice (Oryza sativa). Exploiting the natural variation in CO2 assimilation rate (A) between rice cultivars using quantitative genetics is one promising means to identify genes contributing to higher photosynthesis. In this study, we determined precise location of Carbon Assimilation Rate 8 (CAR8) b...

Effects of sodium naphthenates (NAs) on root hydraulic conductivity (Lp) and gas exchange processes were examined in aspen (Populus tremuloides Michx.) seedlings grown in solution culture. Exposure of roots to NAs for 3-5 weeks significantly decreased Lp and stomatal conductance. Root-absorbed NAs also decreased leaf chlorophyll concentration, net photosynthesis and leaf growth. Short-term (< o...