Functional relationships between freezing resistance and hydraulic traits in species from patagonian forests and steppes

BUCCI SANDRA J; ARIAS NADIA; CARBONELL SILLETA LUISINA; GOLDSTEIN GUILLERMO; SCHOLZ FABIAN

Seminario; 12th International Plant Cold Hardiness Seminar; 2021

Plant species from Patagonian forests and steppes must survive low water availability during summer and subzero temperatures during winter. Several evergreen species tolerate the extracellular freezing. Different tissues and organs show different degrees of frost resistance. Leaves exhibit very low leaf damage at -25 oC. At leaf level, the temperature at which the extracellular water freezes is dependent on its relative water content and at stem level on xylem vessel size. Species with larger vessel achieve high xylem hydraulic efficiency and are more vulnerable to freezing but without the cost of reduced hydraulic safety. Thus, higher resistance to drought induced cavitation was related to higher ice nucleation temperatures. Different structural characteristic of xylem tissue and pit levels may be affecting these processes. Although some species are susceptible to extracellular freezing, which causes cell dehydration as the water potential of ice is lower than that of liquid water, those species have strategies that slow water release from the inside of the cell. Leaf and stem hydraulic capacitance were negatively correlated to ice nucleation temperature across species. Low capacitance contributed to more gradual dehydration of the leaf tissues and thus lethal damage was achieved to lower temperatures. At stem level, lower radial water movement from living cell of xylem to vessels per unit of change in the water potential may maintain the integrity of those cells while axial water transport is impaired. These results suggest a novel role for hydraulic capacitance in the survive of plants at stressful environmental. While a high capacitance contributes to drought resistance, having low capacitance can reduce the freezing damage.