Response of Pinus pinaster Ait. provenances at early age to water supply. I. Water relation parameters

Abstract

The seasonal evolution of tissue water relations was assessed in 1-year-old seedlings of four Pinus pinaster Ait. provenances growing in a nursery and subjected to two water supply regimes. Seedlings were also submitted to water stress cycles in a controlled environment chamber. Water relation parameters were deduced from pressure-volume curves. Significant differences were found between water supply regimes and measurement dates and sometimes among provenances. For the lowest water availability treatment, osmotic potential at full turgor decreased by 0.4 MPa in some provenances, whereas well-watered seedlings showed almost no osmotic adjustment. Provenances originating from hotter sites demonstrated a larger and more rapid acclimation to water stress conditions than provenances from colder sites. Osmotic adjustment, as an initial or short-term reaction, together with longerterm changes in cellular elasticity, are both observed in P. pinaster in response to water shortage. These physiological adaptations complement known morphological adaptations to drought stress in this species. With caution, assessment of these parameters in young seedlings can be used as a tool for early selection and prediction of future performance under conditions of water limitations.