Leaf conductances and xylem pressures of the host/mistletoe pair Eucalyptus behriana F. Muell. and Amyema miquelii (Lehm. ex Miq.) Tiegh. at permanently low plant water status in the field

1432-2285

Amyema miquelii ; Eucalyptus behriana ; Leaf conductance ; Porometry ; Xylem pressure

Springer Online Journal Archives 1860-2000

Biology

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Summary Over several days at permanently low plant water status in the field, where predawn xylem pressures (Ψ) were never higher (less negative) than −1.2 MPa even after extended rain, leaf conductances (g) and transpiration rates of host trees, Eucalyptus behriana F. Muell., were higher than in mistletoes, Amyema miquelii (Lehm. ex Miq.) Tiegh., which contrasts with most studies known from the literature. Mistletoes influenced Ψ but not g of host leaves distal to the haustorium. Releasing xylem tension by cutting a host stem under water raised Ψ from about −3.5 MPa to about −0.5 MPa in both plants indicating that factors in the root zone were responsible for the low Ψ in the host. In all cases, with a freely transpiring or non-transpiring parasite at low and at artificially raised Ψ, mistletoe xylem pressure was lower than that of the host. Possible reasons are discussed.

Electronic Resource