Increases in Water Potential Gradient Reduce Xylem Conductivity in Whole Plants. Evidence from a Low-Pressure Conductivity Method1
AUTOR(ES)
Brodribb, Tim J.
FONTE
American Society of Plant Physiologists
RESUMO
A new method using hydrostatic suctions (less than 0.02 MPa) was used to measure whole-root conductivity (Kr) in saplings of two angiosperm pioneer trees (Eucalyptus regnans and Toona australis) and two rainforest conifers (Dacrycarpus dacrydioides and Nageia fleurii). The resultant Kr was combined with measurements of stem and leaf hydraulic conductivity to calculate whole-plant conductivity and to predict leaf water potential (Ψl) during transpiration. At normal soil temperatures there was good agreement between measured and predicted Ψl during transpiration in all species. Changes in the soil-to-leaf water potential gradient were produced by root chilling, and in three of the four species, changes in Ψl corresponded to those expected by the effect of increased water viscosity on Kr. In one species, however, root chilling produced severe plant wilting and a decline in Ψl significantly below the predicted value. In this species Ψl decreased to a value close to, or below, the Ψl at 50% xylem cavitation. It is concluded that decreased whole-plant conductivity in T. australis resulted from a decrease in xylem conductivity due to stress-induced cavitation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=59065Documentos Relacionados
- Rotational Steady Waves in a Low-pressure Region
- Low-Pressure UV Inactivation and DNA Repair Potential of Cryptosporidium parvum Oocysts
- Effect of furosemide in canine low-pressure pulmonary edema.
- Global model simulations of low-pressure oxygen discharges
- Experimental study of low-pressure nitrogen dielectric barrier discharge