In a changing world, where is expected the temperatures rising and the reduction in
precipitation in some semi-arid areas of the globe, the search for new agronomic practices that
help crops to maintain and/or increase yields and quality is a continuous challenge. Kaolin (KL)
exogenous application has been considered a short-term solution to alleviate the adverse effects
of summer stress. The formed particle film increases the reflection of excess radiation reducing
the risk of leaf damage from heat load accumulation and solar injury. Olive trees (Olea europaea
L.) cultivated under rainfed conditions were sprayed with KL (5%) during two consecutive years
in the beginning of the summer season. In general, relatively to the control group, KL-sprayed
plants showed an enhancement in leaf water status, stomatal conductance and photosynthetic
capacity and a reduction in leaf sclerophylly. In the severest period analyzed, at the end of the
second-year summer, KL has lost the effectiveness of keeping gas exchange above the control
measurements. However, in both years, allowed a faster restauration of the physiological
functions in early autumn and contributed to higher crop yield. Overall, the results of the present
investigation revealed that KL were effective in preventing the adverse effects of summer stress
on crop performance and yield.Doctoral fellowship under the Doctoral Program “Agricultural Production Chains –
from fork to farm” (PD/00122/2012) provided by the FCT-Portuguese Foundation for Science and
Technology to C. Brito (PD/BD/52543/2014). Institution CITAB, for its financial support through the
European Investment Funds by FEDER/COMPETE/POCI– Operational Competitiveness and
Internationalization Program, under Project POCI-01-0145-FEDER-006958 and National Funds by FCT -
Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2013.info:eu-repo/semantics/publishedVersio
