Metabolism in orange fruits is driven by photooxidative stress in the leaves

Abstract

In plants, stress signals propagate to trigger distant responses and thus stress acclimation in non-exposed organs. We tested here the hypothesis that leaves submitted to photooxidative stress may influence the metabolism of nearby fruits and thus quality criteria. Leaves of orange trees (Citrus sinensis (L.) Osbeck cv. 'Navelate') were acclimated to shade for 1 week and then submitted to full (FL) and medium light (ML) conditions. As expected, photoinhibition was detected in leaves of both FL and ML treatments as revealed by stress indicators (Fv /Fm , Performance Index) for at least 99 h after treatments. In the fruits near the stressed leaves, we then determined the activities of enzymes related to oxidative stress, superoxide dismutase, catalase and the enzymes of the ascorbate (AA)/glutathione cycle, as well as the contents in sugars, organic acids and carotenoids. Ascorbate peroxidase and monodehydroascorbate reductase activities in the pulp of fruits were dramatically higher in both treatments when compared to the control. AA and total sugars were not affected by the photooxidative stress. However, the FL treatment resulted in a 16% increase in total organic acids, with succinic acid being the major contributor, a shift towards less glucose + fructose and more sucrose, and a 15% increase in total carotenoids, with cis-violaxanthin being the major contributor. Our observations strongly suggest the existence of a signal generated in leaves in consequence of photooxidative stress, transmitted to nearby fruits. Exploiting such a signal by agronomic means promises exciting perspectives in managing quality criteria in fruits accumulating carotenoids.

Tolerance to clomazone herbicide is linked to the state of LHC, PQ-pool and ROS detoxification in tobacco (Nicotiana tabacum L.)

“…This result agrees with the findings of Darwish et al (2013), who reported that clomazone more significantly affects the function of the PSII reaction center (F v /F m parameter) in Virginie than in Xanthi. However, the decrease in F v /F m could be due as well to PSII photoinhibition (Krause et al, 1990;Osmond et al, 1993;Maxwell and Johnson, 2000;Poiroux-Gonord et al, 2013;Darwish et al, 2014).…”

γ-Aminobutyric acid (GABA) priming enhances the osmotic stress tolerance in Piper nigrum Linn. plants subjected to PEG-induced stress

“…SOD and GPX act in concert with other enzymes of the ascorbate glutathione cycle and scavenge ROS to reduce the negative impact of oxidative stress (Poiroux-Gonorda et al 2013;Li et al 2015). The early sensing of stress for effective detoxification of ROS as a result of GABA treatment was evident from induction of GPX activity at an early stage (5 days), followed by exorbitant increase during 10 and 15 days of stress.…”

Ecophysiological and phytochemical characterization of wild populations of Inula montana L. (Asteraceae) in Southeastern France

“…Initial fluorescence (F0) is obtained from dark adapted samples and maximum fluorescence (Fm) is measured under a saturation pulse (Maxwell and Johnson, 2000;Rohaçek, 2002). PI is an integrative parameter that reflects the contribution to photosynthesis of the density of reaction centers and both the light and the dark reactions (Poiroux-Gonord et al, 2013). All of the parameters were calculated from the measured fluorescence of leaves under saturating pulsed light (1 s at 3500 μmol m −2 s −1 ) after 20 min adaptation to the dark.…”