Impact of heat waves during the spring on the ecophysiology of young olive trees (Olea europaea L.).

ARGAÑARAZ, ROCÍO; MISERERE, ANDREA; AGÜERO ALCARAS, L. MARTÍN; ROJAS BARRIONUEVO, FEDERICO; CASTRO, D. N.; HERRERA, CARLOS J.; CORTÉS MOLINA, VIRGINIA; ROUSSEAUX, M. CECILIA; SEARLES, P.S.

Congreso; XXXIV Argentinian Meeting of Plant Physiology; 2023

The frequency and intensity of heat waves have increased in recent years with climate change. Understanding olive tree responses to these events in Northwest Argentina, where very warm air masses are common during the spring, may play a crucial role in planning production strategies. Thus, the objective of this study was to evaluate the ecophysiological responses of young olive trees to experimentally imposed heat waves during the spring in La Rioja, Argentina. One-year-old cv Coratina plants were placed in either near-ambient control (C) or heated (T+) open top chambers (OTCs) for periods of seven days. The air temperature was near-ambient in the control OTCs and increased by around 8°C during the day and 5°C at night in the T+ OTCs. Photosynthetic gas exchange and vegetative growth variables were measured for three individual heat waves conducted in September, October, and November. Measurements were carried out prior to each heat wave (-2 days), during the heat wave (days 3 and 6), and after each heat wave (+2 days). And, different plants were used in each heat wave. Net photosynthesis was similar between the C and T+ plants during all three heat waves, but foliar transpiration was greater on day 6 of the September and October heat waves. No differences were apparent during the third heat wave when air temperatures were very high in both C and T+ OTCs (>35 °C). Stem elongation was significantly greater in T+ than in C during the first wave when air temperatures were mild, but no differences occurred in the second and third waves. Overall, the results suggest that heat waves will not adversely affect net photosynthesis during the spring unless very high temperatures are reached, but leaf transpiration will likely be increased. Further studies will assess whether the thermal tolerance to extreme temperatures changes after exposure to heat waves.