Comparison of photosynthesis and antioxidant performance of several Citrus and Fortunella species (Rutaceae) under natural chilling stress

Abstract

International audienceCitrus plants originate from southeastern Asia, in a large area with various climates characterized by a broad range of temperatures. Some species have been diversified in temperate climates, others in subtropical climates. Temperature is assumed to be a key factor in citrus species adaptation and diversification of basic cellular functions. In a field experiment, the tolerance of the three fundamental Citrus species C. medica L., C. reticulata Blanco and C. maxima (Burm.) Merr., and Fortunella japonica (Thunb.) Swing. to photooxidative stress caused by seasonal climatic changes was evaluated on adult trees by measuring net photosynthesis (Pnet), stomatal conductance (Gs), maximum photosynthesis (Pmax) and chlorophyll fluorescence (Fv/Fm). In addition, seasonal changes in oxidative status, antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase) and antioxidant metabolites (ascorbate and glutathione) were monitored. Mandarin and pummelo appeared to be the most tolerant, showing the lowest down-regulation of photosynthetic parameters, and the lowest accumulation of oxidized compounds associated with efficiency of their antioxidant system. Kumquat showed intermediate behaviour, with a large diminution of photosynthetic parameters and marked accumulation of hydrogen peroxide, whereas the malondialdehyde content remained low, with a strong induction of glutathione synthesis. Finally, citron appeared to be the most sensitive genotype with a marked decrease in photosynthetic performance, the largest accumulation of oxidative parameters, insufficient induction of antioxidant enzymes and down-regulation of ascorbate and glutathione synthesis

Triploid Citrus Genotypes Have a Better Tolerance to Natural Chilling Conditions of Photosynthetic Capacities and Specific Leaf Volatile Organic Compounds

“…Net photosynthesis rate (P net ) and stomatal conductance (g s ) were measured using an LC-PRO-SD portable infra-red gas analyzer (ADC, BioScientific Ltd., Hoddeston, United Kingdom). During the experiment, photosynthetically active radiation (PAR) was applied at the leaf surface and fixed at 1400 µmol.m −2 .s −1 (Santini et al, 2013;Oustric et al, 2017;Ruiz et al, 2018). Leaf temperature was set at 25 • C and ambient carbon dioxide concentration (CO 2 ) was used (390 µmol.…”

“…Each biochemical sample was obtained by pooling 15 fully expanded leaves selected from one individual tree for each variety and for each period. Harvested samples were immediately immersed in liquid nitrogen, ground to a fine powder, and then stored at −80 • C. Malondialdehyde content was assayed according to Hodges et al (1999) and adapted to citrus samples as described by Santini et al (2013). Eighty milligrams of leaf powder were homogenized in 2 mL of 80% ethanol (v/v).…”

“…For antioxidant enzymatic activities, leaf powder (54 mg) was homogenized in 2 mL of extraction buffer (0.1 M potassium phosphate, pH 7.5) and the homogenates were centrifuged at 13,000 × g for 30 min at 4 • C. The supernatant was collected and was used for all enzymatic assays and for protein determination (Bradford, 1976). Superoxide dismutase, catalase, ascorbate peroxidase, and dehydroascorbate reductase assays were performed as described by Santini et al (2013). Time-course measurements were monitored using a V-630 spectrophotometer (Jasco Inc., Tokyo, Japan).…”

“…Plants have developed a complex defense system that includes enzymes and antioxidant molecules to avoid or reduce chilling injuries. The key role of these antioxidant mechanisms that provide plants with their cold tolerance has been largely described (Santini et al, 2013;Oustric et al, 2017;Agurla et al, 2018;Hussain et al, 2018). Abiotic stresses also modify the biosynthesis and emission of volatile organic compounds (VOCs) (Loreto and Schnitzler, 2010;Peñuelas and Staudt, 2010;Vieira et al, 2016).…”

Effect of diurnal irradiance on night-chilling tolerance of six rubber cultivars

“…Stomatal closure might be a protective response to chilling stress. The reduction of P max was probably limited by the decreased enzyme activity and/or photosynthetic electron transport efficiency due to night chilling (Allen and Ort 2001, Bertamini et al 2005, Huang et al 2010a, Santini et al 2013, Zhang et al 2014. The significantly positive correlation of P max and F v /F m with soluble protein content (Fig.…”