Effects of zinc and influence of Acremonium lolii on growth parameters, chlorophyll a fluorescence and antioxidant enzyme activities of ryegrass (Lolium perenne L. cv Apollo)

Abstract

The effects of zinc on growth, mineral content, chlorophyll a fluorescence, and detoxifying enzyme activity (ascorbate peroxidase (APX), EC 1.11.1.11; superoxide dismutase (SOD), EC 1.15.1.1) of ryegrass infected or not by Acremonium lolii, and treated with nutrient solution containing 0-50 mM ZnSO(4) were studied. The introduction of zinc induces stress with a decrease in growth at 1, 5 and 10 mM ZnSO(4) and a cessation of growth at 50 mM ZnSO(4), in ryegrass plants infected by A. lolii or not. This decrease in growth may be due to an accumulation of zinc in leaves. Nevertheless, symbiotic plants showed higher values in tiller number, an advantage conferred by the fungus. After 24 d of Zn exposure, leaf fresh weights and leaf water content were lower in plants growing with Zn in the culture medium and no advantage was conferred by the fungus to its host. An increase in Zn supply resulted in a decrease of the Ca, K, Mg, and Cu content of the leaves, a reduction in the quantum yield of electron flow throughout photosystem II (DeltaF/F(1)(m))and a lowering of the efficiency of photosynthetic energy conversion (F(v)/F(m)), compared to control plants. To counter this zinc stress, detoxifying enzymes APX and SOD increased (100%) when Zn reached the value of 50 mM in the nutrient solution. At 10 mM ZnSO(4), the presence of the fungus in the plant led to an increase in the threshold toxicity of plants to zinc by a diminution of APX activity.

The Effect of Silicon on Photosynthesis and Expression of Its Relevant Genes in Rice (Oryza sativa L.) under High-Zinc Stress

“…In the present experiment, a high Zn level induced a chlorophyll deficiency (Figure 4), which was closely correlated with a decreasing P n (Figure 6). Similar results have been observed in ryegrass and rapeseed [43], [60]. Furthermore, the ultrastructure of the chloroplasts was greatly changed and exhibited disturbed shapes under the high-Zn stress (Figure 7).…”

Changes caused by heavy metals in micronutrient content and antioxidant system of forage grasses used for phytoremediation: an overview

“…Zinc participates in enzymes that work in the fixation of C and in the synthesis of proteins, among other activities (MARSCHNER, 2012). In view of these functions, it is evident that the alterations brought about by heavy metals in the Cu, Fe, Mn, and Zn uptake will have an impact on plant growth (BONNET et al, 2000).…”

“…This occurs because some heavy metals are more toxic to plants than others, due to components to which they bind (metals that bind to O-rich compounds are less toxic than metals that bind to N-rich compounds) and to the molecular processes in which they participate (production of reactive species by autoxidation, displacement of essential metal ions to biomolecules, and blocking of essential functional groups), with Pb and Hg normally being more toxic than Ni and Zn for most plants (NIEBOER & RICHARDSON, 1980;SCHUTZENDUBEL & POLLE, 2002;KOPITTKE et al, 2010b,c). For instance (Table 1), the activities of enzymes APX, CAT, GPX, and SOD from plants exposed to Zn increased, but the activities of enzymes CAT and SOD of forage grasses exposed to Pb were reduced (BONNET et al, 2000;WEIHONG et al, 2009;LI et al, 2012). This fact demonstrates that the generation of ROS and the inactivation of enzymes in plants exposed to Pb are greater than in plants exposed to Zn (HU et al, 2015).…”

The effect of zinc on the growth and physiological and biochemical parameters in seedlings of Eruca sativa (L.) (Rocket)

“…Excess Zn can also affect the uptake of other nutrient elements. Thus, deficiency of the other elements may cause oxidative stress (del Río et al 1991;Bonnet et al 2000). These oxygen species are highly reactive and cause the death of plants by damaging membrane lipids, proteins, pigments and nucleic acids (Chaoui et al 1997;Weckx and Clijsters 1997;Bonnet et al 2000;Cuypers et al 2002 (Nakano and Asada 1981;Mitler 2002).…”

“…Thus, deficiency of the other elements may cause oxidative stress (del Río et al 1991;Bonnet et al 2000). These oxygen species are highly reactive and cause the death of plants by damaging membrane lipids, proteins, pigments and nucleic acids (Chaoui et al 1997;Weckx and Clijsters 1997;Bonnet et al 2000;Cuypers et al 2002 (Nakano and Asada 1981;Mitler 2002). Ascorbate (AsA) is an ubiquitous soluble antioxidant in photosynthetic organisms, and the most important reducing substrate for H 2 O 2 detoxification and plays an important role in detoxification of toxic metal ions in combination with other antioxidants like non-protein thiols, cysteine and proline (Singh and Sinha 2005).…”