Changes on cold hardiness in acclimated and non-acclimated Olea europaea leaves

ARIAS, N; BUCCI, S.J; SCHOLZ,F.G; FIEDOROWICZ KOWAL R.; ASKENAZI J; GOLDSTEIN,G

Buzios

Congreso; XIII Congreso Brasilero de Fisiología VegetalXIV Reunión Latinoamericana de fisiología vegetal; 2011

Sociedad Brasilera de Fisiología vegetal

Cold hardiness in plants is a complex process that involves extrinsic and intrinsic ice nucleating agents, antifreeze proteins, permeability and thickness of the cell wall and anatomical or morphological physical mechanism. Like other woody plants Olea europaea undergoes supercooling, a freeze avoidance mechanism to resist frost temperatures during winter. We evaluated sensitive to low temperatures in Olea europaea (var. Arbequina) trees during summer and winter in Patagonian steppe (45º 47’S, 67º 30’W). Two- years old- plants were grown outdoor in 20-dm3 pots filled with a mixture of clay and sand soil irrigated bi- weekly. Differential thermal analysis was used to evaluate the temperature at which ice initially form in the central veins of leaves (IN) and electrolyte leakage method was used to evaluate cellular damage of mature leaves and determine LT50 that is the temperature at which 50% of the total ion leakage was measured. Osmotic potential at turgor loss point (ψTLP), bulk elasticity modulus (ɛ), solutes content (Ns) and osmotic potencial at full turgor (π0) were estimated from pressure-volume curves by 4 leaves per season. Summer olive leaves showed lowest values of ɛ (2.52 ±0.66 MPa), ψTLP (-4.31±0.13 MPa) and π0 (-3.06± 0.30MPa) while winter olive leaves showed highest values of ɛ (-4.91±0.18MPa), ψTLP (-1.40±0.89 MPa) and π0 (-0.95±1.06MPa). Active osmotically solutes and LT50 were lower in acclimated olive leaves (winter) than in non-acclimated olive leaves (summer) (0.242 ± 0.17mosmol.g-1, 0.728 ± 0.22mosmol.g-1 and -6°C, -3.8°C, respectively). Values of IN were similar in acclimated and non-acclimated leaves (-6.43°C, -7°C, respectively). Results indicate that acclimated olive leaves had rigid cell membranes that lost the cellular intactness at lowest temperatures. Non-acclimated leaves showed higher values of solutes that lower the π0 and the ψTLP, ,this could allow olive decrease minimum leaf water potentials to continue extracting water from drier soils within loss turgor, but had more elastic membrane cell that loss the cellular intactness at higher temperatures. These results suggest that acclimated leaves could maintain the integrity of the membrane plasmatic modifying the rigidity of the cell wall (elastic adjustment) and resist frost temperatures during Patagonian winter.