Photosynthesis is differently regulated during and after copper‐induced nutritional stress in citrus trees

Abstract

Antioxidant enzymatic responses in Citrus leaves under Cu-induced stress depends on rootstock genotypes. However, there is a lack of information about how woody plants recover growth capacity after exposure to elevated Cu and whether growth is affected by the redistribution of the metal to new vegetative parts and consequently whether photosynthesis is affected. Therefore, the biomass of plants and Cu concentrations in new leaf flushes were determined in young citrus trees grafted onto contrasting rootstocks [Swingle citrumelo (SW) and Rangpur lime (RL)]. Photosynthetic rate, chlorophyll fluorescence and antioxidant enzymatic systems were evaluated in plants previously grown in nutrient solution with Cu varying from low to high levels and with no added Cu. Both rootstocks exhibited reduced plant growth under Cu toxicity. However, trees grafted onto RL exhibited better growth recovery after Cu excess, which was dependent on the modulation of antioxidant enzyme activities in roots and leaves that maintained the integrity of the photosynthetic apparatus. In contrast, plants grafted onto SW exhibited a lower photosynthetic rate at the lowest available Cu concentration. Although the highest accumulation of Cu occurred in citrus roots, the redistribution of the nutrient to new vegetative parts was proportional to the Cu concentration in the roots.

Copper excess reduces nitrate uptake by Arabidopsis roots with specific effects on gene expression

“…7 ). The activity of this enzyme has previously been reported to be affected by Cu toxicity in vines ( Llorens et al, 2000 ) and citrus ( Hippler et al, 2016 , Hippler et al, 2018 ). In this study, the reduction of NR1 could be a direct effect of Cu excess by increasing either metal active effects or ROS accumulation in the cell, as well as by a reduction of nitrate uptake resulting after down-regulation of the LATs transporters expression ( Fig.…”

“…Differences in proton pump activity in membrane vesicles of cucumber ( Cucumis sativus L.) exposed to Cu and Cd have been reported, with the former causing less damage to plants ( Janicka-Russak et al, 2012 ). This would be possible considering that, even though excess Cu or Cd increases ROS accumulation and cellular damage, up to a certain level, Cu also enhances the activity of antioxidant enzymes, such as superoxide dismutase (Cu/Zn-SOD) and catalase, reducing superoxide radical and hydrogen peroxide in cells ( Janicka-Russak et al, 2012 ; Hippler et al, 2016 , Hippler et al, 2018 ).…”

“…High Cu levels also inhibit the synthesis of proteins and their function with irreversible linkages established between the metal and sulfhydryl groups. As an overall process, photosynthesis rate decreases ( Drzewiecka et al, 2017 ; Hippler et al, 2018 ) and plant growth is affected ( Mattos Jr et al, 2010 ). Nutritional disorders caused by Cu excess include an interference in the reduction of nitrate to ammonium, primarily by inhibiting the activity of nitrate reductase.…”

Effects of exogenous methyl jasmonate on the synthesis of endogenous jasmonates and the regulation of photosynthesis in citrus

“…Gas exchange parameters were measured with an infrared gas analyzer open system LI‐COR 6400XT. Measurements were taken between 09:00 and 11:00 h on fully expanded sunlit leaves from the top third of the plant (Hippler et al 2018). The photosynthetically active radiation and CO 2 concentrations were set at 1200 and 400 μmol m −2 s −1 , respectively (Xiong et al 2019).…”

Boron modulates the plasma membrane H+‐ATPase activity affecting nutrient uptake of Citrus trees

“…Citrus rootstocks exhibit distinct absorption and demand for B, which results from different physiological and anatomical traits of trees (Boaretto, Quaggio, Mourão Filho, Giné, & Boaretto, 2008; Mattos Jr., Hippler, Boaretto, Stuchi, & Quaggio, 2017; Mesquita et al, 2016) and which also affects water uptake and transport (Mesquita et al, 2016). The most common rootstock genotypes used in the Brazilian citrus industry have been replaced in the last few decades by new ones exhibiting improved resistance/tolerance to diseases or highest adaptation to adverse environmental conditions (Hippler et al, 2018; Mattos Jr. et al, 2017; Zambrosi, Mesquita, Tanaka, Quaggio, & Mattos Jr., 2013).…”