Browsing by Author "Mariz-Ponte, Nuno"
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- Antioxidant adjustments of olive trees (Olea europaea) under field stress conditionsPublication . Araújo, Márcia; Prada, João; Mariz-Ponte, Nuno; Santos, Conceição; Pereira, J.A.; Pinto, Diana; Silva, Artur; Dias, Maria CelesteExtreme 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 con-ditions. 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 lipo-philic 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†glucu-ronide) that may act as reactive oxygen species scavengers. Secoiridoids adjustments may also con-tribute to stress regulation. This work highlights for the first time the protective role of some metabolite in olive trees under field drought conditions.
- Effect of photo-selective nets on yield, fruit quality and Psa disease progression in a ‘hayward’ kiwifruit orchardPublication . Moura, Luísa; Pinto, Rui; Rodrigues, Raúl; Brito, Luís Miguel; Rego, Rute; Valin, Maria Isabel; Mariz-Ponte, Nuno; Santos, Conceição; Mourão, IsabelThe influence of the colour of photo-selective nets on Actinidia deliciosa yield, fruit quality and progression of the bacterial kiwifruit canker (Pseudomonas syringae pv. actinidiae, Psa) need to be characterised due to increasing use of these nets, mainly to protect from hail and storms. From May 2019 onwards, pearl (Pn), yellow (Yn) and grey (Gn) nets were installed permanently in a ‘Hayward’ kiwifruit orchard in NW Portugal and uncovered plants were used as the control. Compared to outside conditions for both seasons, the blue:red ratio and the mean air temperature were higher (mean increase of 12.7% and 0.6 °C, respectively) and the photosynthetic active radiation (PAR) was lower (10.8% less between budbreak and bloom) under the Pn. Crop yield, compared to the control, decreased by 40.3% under the three nets in 2020, and by 23.9% under the Yn and Gn in 2021. Yield and fruit grade under the Pn were similar to that of uncovered crops in 2021, and fruit grade was overall higher under the Pn compared to the Yn and Gn. Photo-selective nets did not affect the fruit quality parameters. Psa progression decreased under the Pn compared to the control during two months in both seasons, although this beneficial impact needs further evaluation.