Warming effects on growth and photosynthetic gas-exchange during the autumn and winter in young olive trees (Olea europaea L.)

VIRGINIA CORTES MOLINA; ANDREA MISERERE; ROCIO ARGAÑARAZ; DIEGO CASTRO; M. CECILIA ROUSSEAUX; PETER SEARLES

Congreso; XXXIV Reunion de la Sociedad Argentina de Fisiologia Vegetal; 2023

Differences in air temperature are common between olive production areas in northwest Argentina due to altitude and other topographical features. Additionally, the average annual air temperature is rising due to global warming. Nevertheless, few studies have examined how autumn and winter temperatures may affect plant growth. The objective of this research was to determine the shoot growth rate and the emergence of new leaf pairs during and after either an autumn or a winter warming period. Photosynthetic gas-exchange at midday was also assessed on some dates. To conduct the experiment, young, potted olive plants of two cultivars (cvs. Arbequina, Picual) were placed in open-top chambers at either near ambient temperature or heated by four degrees Celsius for 60 days (autumn or winter). During the autumn period, the absolute shoot elongation rate and new leaf emergence were much greater in warmed plants than in the near ambient temperature controls for both cultivars. In contrast, no vegetative growth occurred during the winter period under either temperature regime. Stomatal conductance and net leaf photosynthesis at midday were generally not different between temperature regimes, although transpiration was often greater in the warmed treatment for both cultivars due to a greater atmospheric vapor pressure deficit at higher temperatures. Little difference in net photosynthesis likely reflects the fairly optimal temperatures for photosynthesis at midday under both treatments (20 – 30 degrees Celsius).