Journal of Experimental Botany, Vol. 54, No. 391, pp. 2323-2330,
October 1, 2003
© 2003 Oxford University Press
Kinetics of recovery of leaf hydraulic conductance and vein functionality from cavitation-induced embolism in sunflower
Received 7 March 2003; Accepted 8 July 2003
1 Dipartimento di Biologia, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italia
2 UD Anatomía, Fisiología y Genética Vegetal, ETSI Montes, Ciudad Universitaria s/n, 28040 Madrid, España
* To whom correspondence should be addressed. Fax: +39 040 568855. E-mail: salleo{at}univ.trieste.it
The kinetics of leaf vein recovery from cavitation-induced embolism was studied in plants of sunflower cv. Margot, together with the impact of vein embolism on the overall leaf hydraulic conductance (Kleaf). During the air-dehydration of leaves to leaf water potentials (
L) of –1.25 MPa, Kleaf was found to decrease by about 46% with respect to values recorded in well-hydrated leaves. When leaves, previously dehydrated to L= –1.1 MPa (corresponding to the turgor loss point), were put in contact with water, Kleaf recovered completely in 10 min and so did leaf water potential. Functional vein density was estimated in both dehydrating and rehydrating leaves in terms of total length of red-stained veins infiltrated with a Phloxine B solution per unit leaf surface area. Veins were found to embolize (unstained) with kinetics showing a linear relationship with Kleaf so that about a 70% loss of functional veins corresponded with a Kleaf loss of 46%. Cavitated veins recovered from embolism within 10 min from the beginning of leaf rehydration. These data indicate that: (a) leaves of sunflower underwent substiantial vein embolism during dehydration; (b) vein embolism and leaf hydraulic efficiency apparently recovered from dehydration completely and rapidly upon rehydration; (c) vein refilling occurred while conduits were still at more negative xylem pressures than those required for spontaneous bubble dissolution on the basis of Henry’s law. The possible consistent contribution of vital mechanisms for vein refilling is discussed.
Key words: Helianthus annuus, hydraulic conductance, leaf, refilling, sunflower, vein embolism, xylem pressure.
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