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. 2021 Apr 1;10(4):684.
doi: 10.3390/plants10040684.

Antioxidant Adjustments of Olive Trees (Olea Europaea) under Field Stress Conditions

Márcia Araújo  1   2   3 , João Prada  2 , Nuno Mariz-Ponte  2 , Conceição Santos  2 , José Alberto Pereira  4 , Diana C G A Pinto  5 , Artur M S Silva  5 , Maria Celeste Dias  1   5
Affiliations

Antioxidant Adjustments of Olive Trees (Olea Europaea) under Field Stress Conditions

Márcia Araújo et al. Plants (Basel). .

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.

Keywords: Olea europaea; climate change; drought; flavonoids; rainfed olive groves; secoiridoids.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
O2•– (A), H2O2 (B), SOD (C), CAT (D), APX (E) and GPOX (F) activities, and MDA (G) contents in Cobrançosa’ olive trees leaves from hydrated and dry areas. Values are mean ± standard deviation (n = 9). Asterisk (*) indicates significant differences (p ≤ 0.05) between conditions.
Figure 2
Figure 2
General overview of the responses of olive trees to field conditions. Parameters analyzed are present in boxes surrounded by a green, red, and grey square that indicates a significant increase, decrease, and no significant difference in the abiotic stress response, respectively. Between black arrows occurs multiple reactions. DAHP, 3-deoxy-D-arabino-heptulosonate-7-phosphate; ACP, acyl carrier protein; GPP, geranyl pyrophosphate.
Figure 3
Figure 3
Color rectangles are correlation coefficients; green means a positive correlation coefficient, and red means a negative correlation coefficient. Significant differences (p ≤ 0.05) are indicated by a white asterisk (*). Alkane, long-chain alkane; Lut.-7-O-gluc., luteolin-7-O-glucoside; Lut.-7-O-glucor., luteolin-7-O-glucuronide; Lut.-4-O-gluc., luteolin-4-O-glucoside; Lut.-4-O-gluc. (i), luteolin-4-O-glucoside (isomer); Querc.-3-O-rut., quercetin-3-O-rutinoside; Apig.-7-O-gluc., apigenin-7-O-glucoside; Apig.-7-O-hex., apigenin-7-O-hexosyl rhamnosides; 6’-O-[8-hyd.], 6’-O-[8-hydroxy-2,6-dimethyl-2-octenoyloxy] secologanoside; Oleos.-11-met., oleoside-11-methyl ester; Oleos.-11-met. (i), oleoside-11-methyl ester (isomer); Oleu. aglyc., oleuropein aglycone; ac., acid; Lupeol der., lupeol derivative.
Figure 4
Figure 4
(A) Monthly average precipitation, monthly maximum air temperature from January to October of 2017 in the local of the olive orchard. (B) Branch of olive trees from the dry area; and (C) branch of olive trees from the hydrated area.
See this image and copyright information in PMC

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