Towards soil management with Zn and Mn: estimates of fertilisation efficacy of Citrus trees

Abstract

Nutrient management recommendations for fruit crops lack the understanding of the efficiency of soil fertilisation with manganese (Mn) and zinc (Zn), which could substitute, in part, the traditional foliar applications. Fruit yield of trees in response to Zn and Mn supply via soil may be limited either by sorption reactions with soil colloids or low solubility of fertilisers. We investigated the effects of fertiliser sources and rates of Mn and Zn applied to soils with different sorption capacities on nutrient uptake, biochemical responses and biomass of Citrus. Two experiments were carried out with 2-year-old sweet orange trees that received applications of Mn or Zn. The first experiment evaluated the application of Mn fertilisers (MnCO 3 and MnSO 4 ) at three levels of the nutrient (0, 0.7 and 3.5 g plant −1 of Mn) in two types of soil (18.1% and 64.4% of clay, referred to as sandy loam and clay soils, respectively). The second experiment, likewise, evaluated Zn fertilisers (ZnO and ZnSO 4 ) and nutrient levels (0, 1.0 and 5.0 g plant −1 of Zn). Application of Mn and Zn increased nutrient availability in the soils as well as leaf nutrient concentrations in the trees. The lowest rates, 0.7 g plant −1 of Mn and 1.0 g plant −1 of Zn, both as sulphate, were sufficient to supply these micronutrients to sufficient levels in leaves, flowers and fruits. Metal toxicity to plants occurred with higher doses of both nutrients and to a large extent in the sandy soil. In this case, protein bands lower than 25 kDa were observed as well a decrease on leaf chlorophyll content. In the clay soil, despite increased micronutrient concentrations in the plant, responses were less pronounced because of higher adsorption of metals in the soil. Superoxide dismutase (SOD, EC 1.15.1.1) isoenzyme activity was determined by non-denaturing polyacrylamide gel electrophoresis (PAGE). The Cu/Zn-SOD isoenzymes increased with increased Zn rates, but in contrast, when Mn was applied at the highest rate, the activity of Cu/Zn-SODs decreased. The SOD activity pattern observed indicated increased production of superoxide and consequently an oxidative stress condition at the highest rates of Zn and Mn applied. The results demonstrated that the soil application of Mn and Zn can supply nutrient demands of orange trees, however the low solubility of fertilisers and the high sorption capacity of soils limit fertilisation efficiency. On the contrary, application of sulphate source in sandy soils may cause excess uptake of Mn and Zn and oxidative stress, which impairs the photosynthetic apparatus and consequently tree growth.

Cadmium stress antioxidant responses and root-to-shoot communication in grafted tomato plants

“…8), since Mn can be found as a cofactor of superoxide dismutase (SOD, EC 1.15.1.1) enzyme, which dismutates O -2 to H 2 O 2 (Azevedo et al 1998). Hippler et al (2015) reported that the Cu/Zn-SOD isoenzymes of citrus plants increased with increased Zn application in the soil, but in contrast, when Mn was applied at the highest rate, the activity of Cu/Zn-SOD isoenzymes were decreased.…”

“…Although grafting is a widely used technique and well established for a large number of economically important crops such as tomato or citrus (Hippler et al 2015), one of the possible applications of grafting in plants can be the mitigation of stress caused by toxic metals in the root environment because the root structure can exert control over signals arising from the shoot (Rouphael et al 2008;Savvas et al 2010). Moreover, the grafting technique can be used to study stress signaling, in particular the antioxidant stress responses, which has been neglected when compared to the number of studies published on this topic (Arruda and Azevedo 2009).…”

“…The excessive production of H 2 O 2 may be detoxified to H 2 O by the action of a number of enzymes such as ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, 1.11.1.6), and guaiacol-type peroxidases (GPOX, EC 1.11.1.7) (Hippler et al 2015;Liu et al 2015;Roychoudhury et al 2012), as well as non-enzymatic mechanisms of ROS detoxification involving ascorbate (AsA), glutathione (GSH) (Foyer and Noctor 2013), organic acids , stress proteins, proline, flavonoids, alkaloids and carotenoids (Ahmad et al 2010;Gratão et al 2005). The regeneration of glutathione (GSH) from oxidized glutathione (GSSG) is catalyzed by glutathione reductase (GR, EC 1.6.4.2) using NAD(P)H as a reducing agent (Gratão et al 2012;Nogueirol et al 2015).…”

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

“…). In leaves of citrus trees, the activity of Cu/Zn‐SOD was more responsive to the different supply of Zn sources, while Mn‐SOD and Fe‐SOD slightly varied with different supplies of Mn (Hippler et al ).…”

Nutritional status of orange tree ‘Pêra Rio’ variety after Huanglongbing disease infection, leaf spray fertilization and application of resistance-inducing bioinductors

“…This is mainly purposed to achieve a nutritional program for citrus cultivation, which can reflect on high fruit productivity and quality and sustainability of citrus industry (Hippler et al, 2015a;Rozane et al, 2015). In Brazilian literature, there are several reports about significant gains in citrus tissue micronutrients content related to leaf fertilization (Boaretto et al, 2003;Malavolta et al, 2006).…”