Xylem tension, lower apoplastic water content and high tissue rigidity in olive trees improve supercooling capacity during winter.

ARIAS NADIA SOLEDAD; BUCCI SANDRA JANET; SCHOLZ FABIAN; GOLDSTEIN GUILLERMO

Potsdam

Simposio; ISHS Symposium 2016 "Sensing Plant Water Status"; 2016

Leibniz Institute

Olive is an evergreentree considered high drought resistant and moderate resistant to lowtemperatures. Olivetissues don´t tolerate ice formation and presented supercooling as a mechanismto resist low temperatures. Temperatures below ?12°C are related with ice formationsand thus with serious damage to the. In irrigatedorchards during winter olive trees showed very low water potentials compared tosummer time. The aim of this work was to evaluated water relations and frostresistant mechanisms in five olive cultivars growing in pots during winter andsummer in the patagonian steppe. We measured pressure volume curves, midday (Ψmin)and pre-dawn (Ψmax) leaf water potentials, ice nucleationtemperature (INT) and flux density (δ) in truncks. All cultivars exhibited (Ymin) and (Ymax) significative lower in winterthan in summer. In winter Ymin varied between -2,68 MPa(Hojiblanca) y -3,21MPa (Frantoio) and in summer none cultivar presented Ymin lower than -2,1 MPa. Bulkelastic modulus (e) increased in winter in all cultivars. The apoplastic water fractiondid not show seasonal differences in Manzanilla and Frantoio cultivars, whilein the other three cultivars it was lower in winter compared to summer. In winter the observed range of p0 between cultivars was -1,2 to -1,7 MPa, while in summer was -4,1 to-4,7 MPa. The same pattern was observed in water potencial at full turgor (π100).During winter INT ranged between -10°C and -13°C, while in summer rangedbetween -2°C and -6°C. We founded a strong correlation in all cultivars duringwinter between INT and (Ymin), (e), AWF and p0 . Flux density was significant lowerin winter than in summer. The results suggests that the water tension observedduring winter, the lower apoplastic water content and the higher tissuerigidity helps olive cells to maintain water in un unfrozen state and improvesupercooling capacity.