Physiological and growth response in Quillaja saponaria and Cryptocarya alba plants under restricted water conditions

Abstract

Central Chile is characterized by a Mediterranean Climate. Some of the tree species that grows in this zone (e.g. Quillaja saponaria (quillay) and Cryptocarya alba (peumo)) have developed physiological mechanisms to tolerate drought periods during the summer. The aim of this study was to quantify physiological and growth parameters in two-year-old quillay and peumo saplings, maintained under controlled water restricted conditions during one summer season. The plants were assigned to two different experimental treatments: well watered (control-WW) and restricted irrigation (RI). Saplings in RI had an average predawn water potential (ψ_pd) near to -3.5 MPa. At the end of the water restriction period, plant gas exchange parameters were determined and biomass distributions in leaves, branches, stems and roots were analyzed. During the period of high water deficit, quillay did not showed a clear mechanism of adjustment to water deficit, but a reduction in 55 % of leaf biomass decreased the evapotranspiration rate. Peumo showed an osmotic adjustment. Net photosynthesis, stomatal conductance and transpiration rate of quillay and peumo plants were significantly reduced in the RI treatment when compared to control saplings. Quillay saplings showed a significant reduction in the above/below biomass ratio under the restricted irrigation treatment (2.3 to 1.4). In contrast peumo saplings did not change signifcantly this ratio (1.3).