TIGHE NEIRA, RICARDO MARCELO
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Response of sink manipulation in Lapins sweet cherry (Prunus avium L.) branches to late-deficit irrigation
Photosynthetic traits, leaf soluble sugars and fruit yield and size were evaluated in order to identify the role of early sink manipulation (girdling and fruiting spur thinning applied in winter) in modulating the effect of late-deficit irrigation (recovering 60% of crop evapotranspiration during 36 days pre-harvest) in Lapins sweet cherry branches. Photosynthesis (PN), stomatal conductance (gs), and fruit weight were affected by both treatments, whereas intercellular CO2 concentration of leaves (Ci), mesophyll conductance (gm), Rubisco carboxylase activity (Vcmax), electron transport rate (Jmax), leaf soluble sugars and branch yield were exclusively affected by sink manipulation. The effect of sink manipulation on PN was mainly observed in the girdling treatment as it was not altered by thinning. In girdled branches, PN dropped by 34%, accompanied by a two-fold increase in leaf soluble sugars, indicating that sink feedback regulation of carbon assimilation occurred. Irrespective of the irrigation, the higher PN observed in the controls were not sufficient to achieve the fruit weight and yield of the girdled branches, indicating that fruit carbon demand in control branches was source-limited. The depressed PN by girdling was associated with significant reductions in gs, gm, Vcmax and Jmax. Since lowered PN by deficit irrigation was neither attributable to a gs-associated decrease in Ci nor to changes in any other photosynthetic variable, further research is needed to clarify this point. Results showed that irrigation deficit was sufficient to reduce PN in girdled branches, whereas it had no effect in control and thinned branches. Thus, the depressive effect of deficit irrigation on PN appeared to be exacerbated by the sink effect. © 2022 Elsevier B.V., All rights reserved.
Characterization of physiological and antioxidant responses in Run1Ren1 Vitis vinifera plants during Erysiphe necator attack
Grapevine is a fruit crop of major significance worldwide. Fungal attacks are one of the most relevant factors affecting grapevine yield and fruit quality, and powdery mildew caused by Erysiphe necator is one of the most harmful fungal diseases for this fruit-bearing species. Incorporating resistance genes such as Run1 and Ren1 in new vine selections offers a sustainable alternative to control the disease. These combined loci produce an immune response that prevents the development of the disease. However, to date studies are lacking concerning whether this response generates alterations in the physiological and antioxidant parameters of resistant plants in the presence of the fungus or if it has an associated energy cost. Therefore, the main goal of our research was to determine if Run1Ren1 plants present alterations in their physiological and biochemical parameters in the presence of the fungus. To achieve this target, a previously characterized resistant Run1Ren1 genotype and the susceptible Carmenere cultivar were analyzed. We evaluated photochemical parameters (Fv'/Fm', phi PSII and ETR), net photosynthesis (Pn), photosynthetic pigments, transpiration (E), stomatal conductance (g(s)), oxidative stress parameters (MDA), antioxidant activity, and phenols. Our results show that the physiological parameters of Run1Ren1 plants were not negatively affected by the fungus at 10 days post-inoculation, contrasting with alterations observed in the susceptible plants. Therefore, we propose that the resistance response triggered by Run1Ren1 is physiologically and biochemically advantageous to grapevines by preventing the development of powdery mildew infection.
Phytochemical characterization and antioxidant properties of Prumnopitys andina fruits in different ripening stages in southern Chile
The native conifer lleuque (Prumnopitys andina (Poepp. ex Endl.) de Laub.) grows in southern Chile, and has an edible and fleshy ovoid fruit. Some species of the genus Prumnopitys are valuable for the medicinal value of their edible fruits. Thus, the aim of this research was to characterize the phytochemical and antioxidant compounds in four ripening stages of P. andina fruits from La Araucanía Region, Chile. Fruit quality related parameters, bromatological, antioxidant and phenolic compounds analyses were performed in order to highlight their potential for human consumption. Our study showed that fresh weight, equatorial diameter, and soluble solid content significantly increased (P < 0.05) in P. andina fruits during ripening, reaching 4.02 ± 0.2 g, 17.9 ± 0.6 mm, and 23.7 ± 0.5 °Brix, respectively, per fruit at stage IV. Our bromatological analyses showed that P. andina fruits had 1.17 ± 0.1 g 100 g-1 DW protein, 1.55 ± 0.2 g 100 g-1 DW crude fiber, and 10.76 ± 2.2 g 100 g-1 DW fruit of ash at fruit ripe. Likewise, we found 2.6 ± 0.2 mg g-1 FW total phenols, 2.2 ± 0.2 mg trolox equivalent g-1 FW of antioxidant activity, and 6.4 ± 0.2 mg rutin equivalent g-1 FW total flavonoid in P. andina fruits. Interestingly, ripening stages I and II showed higher antioxidant compound levels compared to stages III and IV, with the exception of total anthocyanins, which did not change throughout the ripening process. This study shows that P. andina has great potential as a fruit with significant functional properties, which could help promote the propagation, care, and use of this native conifer. © 2022 Elsevier B.V., All rights reserved.
Physiological and molecular effects of TiO2 nanoparticle application on UV-A radiation stress responses in Solanum lycopersicum L.
Nanoparticles (NPs) of titanium dioxide (TiO2) alter photosynthetic and biochemical parameters in Solanum lycopersicum L., possibly due to their photocatalytic properties given by energy absorption in the UV-A range; however, the joint effects TiO2 NPs and UV-A radiation are not well understood. This work evaluates the combined responses of TiO2 NPs and UV-A radiation at the physiological and molecular levels in S. lycopersicum. In a split growth chamber, the presence (UV-A +) and absence (UV-A ?) of UV-A were combined with 0 (water as a control), and 1000 and 2000 mg L?1 of TiO2 NPs applied at sowing. At the end of exposure (day 30 after sowing), the photosynthetic performance was determined, and biochemical and molecular parameters were evaluated in leaf tissues. Better photochemical performance in UV-A + than UV-A ? in control plants was observed, but these effects decreased in 1000 and 2000 mg TiO2 L?1, similar to net CO2 assimilation. A clear increase in photosynthetic pigment levels was recorded under UV-A + compared to UV-A ? that was positively correlated with photosynthetic parameters. A concomitant increase in total phenols was observed on adding TiO2 in UV-A ? conditions, while a decreasing trend in lipid peroxidation was observed for the same treatments. There was an increase in psbB gene expression under TiO2/UV-A + treatments, and a reduced expression of rbcS and rbcL under UV-A ?. These results suggest that the reduction in photosynthetic performance on applying high doses of TiO2 NPs is probably due to biochemical limitation, while UV-A achieves the same result via the photochemical component. © 2023 Elsevier B.V., All rights reserved.