Leaf water relations characteristics of Lupinus angustifolius and L. cosentinii.

Lupins (Lupinus angustifolius and L. cosentinii) growing in 321 containers in a glasshouse were exposed to drought by withholding water. Leaf water potential (Ψ1), and leaf osmotic potential (Ψs) were measured daily as soil water became depleted. Leaf water relations were further assessed by a pressure-volume technique and by measuring Ψs and relative water content of leaves after rehydration. Analysis by pressure-volume or cryoscopic techniques showed that leaf osmotic potential at saturation (Ψs100) decreased from -0.6 MPa in well watered to -0.9 MPa in severely droughted leaves, and leaf water potential at zero turgor (Ψzt) decreased from about -0.7 to -1.1 MPa in well watered and droughted plants, respectively. Relative water content at zero turgor (RWCzt) was high (88%) and tended to be decreased by drought. The ratio of turgid leaf weight to dry weight was not influenced by drought and was high at about 8.0. The bulk elastic modulus (ɛ) was approximately halved by drought when related to leaf turgor potential (Ψp) and probably mediated turgor maintenance during drought. The latter was found to be negatively influenced by rate of drought. Supplying the plants with high levels of K salts did not promote adjustment or turgor maintenance.