Intracanopy hydraulic responses induced by wind in cold desert shrubs

IOGNA PA; BUCCI SJ; SCHOLZ FG; GOLDSTEIN G

Athens

Conferencia; 6th IInternational COnference IUFRO Section 8.03.06; 2011

IUFRO

The physiology of plant´s organs within the canopy is not constant, and can vary depending on their position within the plant and to the different environmental stimulus that the organ is exposed. Plants respond to stimulus presenting alternative phenotypes suitable for each particular environmental condition. The hydraulic efficiency is a determinant factor for whole plant conductance, which imposes a limit to the maximal stomatal conductance and consequently to the photosynthetic rate and growth. Argentinean Patagonian steppe (45 57’S; 67 31’W) is an arid region where winds are strong and dry and blow througthout of the year originating different microenvironment conditions at leeward (LW) and windward (WW) of the plants. We evaluated intraindividual wind effects on leaf-and-stems hydraulic traits of two shrubby species (Colliguaja integerrima and Berberis heterophylla). Leaf hydraulic conductance (KLeaf), specific (KS) and leaf (KL) hydraulic conductivity, wood density, leaf and stem vessel diameter and density, leaf vein density, stomatal density, stomatal pore index and leaf water potential (Ymín) were measured on 10 samples per specie at WW and LW. At stem level vessel diameter was higher at WW, while vessel density was lower at this side for both species. Wood density was significantly higher at WW for C. integerrima. KS tended to be lower and KL higher at WW for both species. At leaf level vessel diameter was higher at WW than at LW for both species whereas vessel and vein density showed significant differences in both species (lower at WW). KLeaf was significantly higher at WW for C. integerrima. Stomatal density increased and stomatal pore index decreased significantly at WW for both species. Cuticular conductance decreased at WW in both species. There were no differences in Ymín between WW and LW. The results indicate phenotypic plasticity in wood anatomic traits, where changes in vessels diameter and density contributed to decrease KS but increasing water transport efficiency to leaves at WW as a consequence of a lower leaf area in this position. Consistently, leaf characteristics at WW lead to higher leaf hydraulic capacity that could allow a quick recovery of water status when wind stress ceases. In adittion, the plastic responses of the stomatal morphology and the lower cuticular conductance support the idea of a better control of the loss of water due to wind stress at WW. Keywords: intracanopy plasticity, hydraulic traits, Patagonia, wind stress.