Kaolin and salicylic acid alleviate summer stress in rainfed olive orchards by modulation of distinct physiological and biochemical responses

Abstract

In a changing world, the search for new agronomic practices that help crops to maintain and/or increase yields and quality is a continuous challenge. We aim to evaluate kaolin (KL) and salicylic acid (SA) effectiveness as summer stress alleviating agents through physiological, biochemical and immunohistochemical analysis. Olive trees (Olea europaea L. cv. Cobrançosa) grown under rainfed conditions were sprayed with 5% KL and 100 μM SA, at the beginning of summer, during two consecutive years. KL enhanced relative water content (RWC), stomatal conductance (g s) net photosynthesis (A) and leaf indole-3-acetic acid (IAA) signal, and decreased leaf sclerophylly, secondary metabolites and non-structural carbohydrates accumulation and abscisic acid (ABA).The trees treated with SA showed changes on IAA and ABA dynamics, and an enhancement in RWC, g s , A, soluble proteins, and leaf P and Mg concentrations during the summer. Notably, KL and SA also allowed a faster restauration of the physiological functions during stress relief. In sum, KL and SA foliar sprays alleviated the negative effects induced by summer stress in olive trees performance, by modulation of distinct physiological and biochemical responses.

Foliar Application of Calcium and Growth Regulators Modulate Sweet Cherry (Prunus avium L.) Tree Performance

“…This relationship is established by the correlation between RWC and A, mainly in 2016 (r = 0.54, P < 0.05). Similarly with our results, a significant improvement of RWC in different crops exposed to several biotic stresses and treated with biostimulant [29,[52][53][54], GA 3 [55], ABA [56], SA [57], and GB [49,58] was previously reported.…”

Influence of Foliar Kaolin Application and Irrigation on Photosynthetic Activity of Grape Berries

“…Recently, it was verified that grapevine leaves with kaolin display the same response, i.e., an increase in F v /F m , Φ ll , and ETR, and a decrease in NPQ [18,60]. Similar results were also reported for olive leaves [61]. In this way, and in terms of photochemical processes, those kaolin-treated leaves have lower photo-inhibitory damage [17,62], and the open PSII reaction centers captured the light absorbed by PSII antenna more efficiently [17,35].…”

Drought Stress Effects and Olive Tree Acclimation under a Changing Climate

“…Usually considered the main stress hormone, ABA biosynthesis and accumulation is stimulated by drought, in association to a key role in g s regulation, but a water deficit also influences other stress signalling pathways [47]. Thus, ABA is unequally distributed within and between the different plant organs [6,7,82,83]. Under drought stress, ethylene (ET), another important stress hormone, might inhibit plant growth [84], is involved in leaf abscission, and thus, in the reduction of water loss [85], induces remobilization of minerals from the leaves [84]; recent evidence also suggests that it might increase the accumulation of compatible solutes and reduce oxidative stress damage [86].…”

“…Furthermore, some studies have shown that drought influences the local Aux concentration and distribution by changes in Aux transport, allowing to maintain a balance between vegetative growth and survival [95,96]. In fact, it was well demonstrated that the Aux was unequally distributed within and among the different plant organs [6,82,83]. In addition, it was suggested that Aux could act as a stress hormone, directly or indirectly, once it was observed that several auxin-responsive genes operate during stress signalling [97].…”