Contribution of leaf water uptake to transpiration and water status in arid ecosystems

BUCCI SANDRA; CAVALLARO AGUSTIN

Workshop; XI INTERNATIONAL WORKSHOP OF SAP FLOW; 2019

Foliarwater uptake (FWU) could be relevant for the plants, allowing them to usealternative water sources than the primary one that is soil water uptake andthus prevent dehydration especially during the dry season in arid/semiaridecosystem characterized by small and erratic water pulses. The main objectiveof this study was to evaluate the effects of FWU on leaf water status and itscontribution to daily transpiration in an arid ecosystem in southern Argentina.Eight dominant species, including shrubs and grasses, with different rootingdepth (< 0.5 m, <1 m, <2 m and > 2 m) and thus different soil wateraccess, were selected. We hypothesized that FWU is higher in species withshallow roots than in species with permanent water sources and thus FWUenhances plant water availability.  Wedetermined FWU capacity by changes in leaf mass after spraying with deionizedwater. The water potential (YLeaf) wasdetermined in the field before and after small water experimental application.Leaf transpiration (E) was measured using a portable photosynthesis system. Allstudy species exhibited leaf water uptake capacity, but it was lower in specieswith deep roots than in the species with shallow roots during the growingseason however the effects on YLeaf were different. Duringthe dry season, only grasses had a substantial enhancement of water statusafter an experimental water application. A linear negative relationship betweenFWU and the changes in YLeaf after anexperimental water pulse was observed during the spring season (R2 =0.80) and an inverse relationship during summer (R2 = 0.59).  Species with higher FWU were those withhigher transpiration rate (R2 = 0.66) suggesting that FWU contributeto plant water balance allowing stomata to remain open, thus enhancing tocarbon assimilation during the growing season.