Abstract
Extreme climate events are increasingly frequent, and the 2017 summer was particularly critical in the Mediterranean region. Olive is one of the most important species of this region, and these climatic events represent a threat to this culture. However, it remains unclear how olive trees adjust the antioxidant enzymatic system and modulate the metabolite profile under field stress conditions. Leaves from two distinct adjacent areas of an olive orchard, one dry and the other hydrated, were harvested. Tree water status, oxidative stress, antioxidant enzymes, and phenolic and lipophilic metabolite profiles were analyzed. The environmental conditions of the 2017 summer caused a water deficit in olive trees of the dry area, and this low leaf water availability was correlated with the reduction of long-chain alkanes and fatty acids. Hydrogen peroxide (H2O2) and superoxide radical (O2•–) levels increased in the trees collected from the dry area, but lipid peroxidation did not augment. The antioxidant response was predominantly marked by guaiacol peroxidase (GPOX) activity that regulates the H2O2 harmful effect and by the action of flavonoids (luteolin-7-O-glucuronide) that may act as reactive oxygen species scavengers. Secoiridoids adjustments may also contribute to stress regulation. This work highlights for the first time the protective role of some metabolite in olive trees under field drought conditions.
Highlights
The Mediterranean basin is the world’s leading region of olives and olive oil production [1]
The frequency of climate change events is increasing, and the year 2017 was atypical in several regions of the Mediterranean, with scarce precipitation and prolonged heatwaves
Dithiothreitol (DTT), nitroblue tetrazolium (NBT), H2O2, titanium dioxide, dichloromethane, pyridine, N,O-bis(trimethylsilyl) trifluoroacetamide, trimethylsilyl chloride, sodium azide, thiobarbituric acid (TBA), methionine, catalase, peroxidase, cholesterol, maltose, octadecane, phenol, palmitic acid, sorbitol, ammonia and potassium phosphate buffer were purchased from Sigma-Aldrich (Saint Louis, MO, USA)
Summary
The Mediterranean basin is the world’s leading region of olives and olive oil production [1]. The nature of these climate change-associated extreme episodes and the predictions of their increase in frequency and intensity in the decade [2] represent a new threat to olive cultivation. This threat may potentially lead to significant losses in olive productivity and fruit and oil quality [4,5,6,7,8,9]
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