Magnesium deficiency decreases biomass water-use efficiency and increases leaf water-use efficiency and oxidative stress in barley plants

Abstract

Aims In water-scarce agro-environments a clear understanding of how plant nutrients like magnesium (Mg) affect plant traits related to water-use efficiency (WUE) is of great importance. Magnesium plays a crucial role in photosynthesis and is thus a major determinant of biomass formation. This study investigated the effect of Mg deficiency on leaf and whole plant water-use efficiency, δ 13 C composition, hydrogen peroxide (H 2 O 2 ) production and the activity of key enzymes involved in ROS scavenging in barley. Methods Barley (Hordeum vulgare) was grown in hydroponic culture under three different levels of Mg supply (0.01, 0.1, 0.4 mM Mg). WUE was determined on the leaf-level (leaf-WUE), the biomass-level (biomass-WUE) and via carbon isotope discrimination (δ 13 C). Additionally, concentrations of Mg, chlorophyll and H 2 O 2 , and the activities of three antioxidative enzymes (ascorbate peroxidase, glutathione reductase and superoxide dismutase) in youngest fully expanded leaves were analyzed. Results Dry matter production was significantly decreased (by 34 % compared to control) in Mg deficient barley plants. Mg deficiency also markedly reduced leaf Mg concentrations and chlorophyll concentrations, but increased H 2 O 2 concentrations (up to 55 % compared to control) and the activity of antioxidative enzymes. Severe Mg deficiency decreased biomass-WUE by 20 %, which was not reflected regarding leaf-WUE. In line with leaf-WUE data, discrimination against 13 C (indicating time-integrated WUE) was significantly reduced under Mg deficiency. Conclusions Mg deficiency increased oxidative stress indicating impairment in carbon gain and decreased biomass-WUE. Our study suggests that biomass-WUE was not primarily affected by photosynthesis-related processes, but might be dependent on effects of Mg on night-time transpiration, respiration or root exudation.

Organic fertilizer application and Mg fertilizer promote banana yield and quality in an Udic Ferralsol

“…In addition, leaf Mg concentration was significantly and positively correlated with shoot growth (Table 1). Magnesium is the central atom of chlorophyll [71] and Mg deficiency results in lower chlorophyll contents and thus affects plant growth [72]. In our experiment, leaf SPAD values in the control (34.7) and the Lime (41.6) treatments were significantly lower than in the CMP (49.8), OF (51.5) and OFC (52.7) treatments.…”

Functioning of potassium and magnesium in photosynthesis, photosynthate translocation and photoprotection

“…Chlorophyll a and b are the major pigments for the absorption of light energy and synthesis of both pigments requires Mg. A common response to Mg deficiency is the reduction of chlorophyll concentrations as demonstrated in numerous studies (Mengutay et al , Faust and Schubert , Tränkner et al ). However, considering chlorophyll a and b separately, the response is not uniform.…”

“…As a consequence, photoprotective mechanisms are up-regulated. deficiency the extent of H 2 O 2 production exceeded the scavenging capacity (Tränkner et al 2016).…”

“…Numerous studies show decreased Rubisco activity or CO 2 assimilation rates under Mg deficiency in various plant species such as spinach (Yuguan et al ), citrus (Tang et al , Li et al ), maize (Jezek et al ), sunflower (Lasa et al ) and P. radiata (Laing et al , Sun et al ). The Rubisco activity is sensitive to the Mg status as observed by a decline in CO 2 assimilation rates in Mg‐deficient sugar beet and barley already 7 and 8 days, respectively, after onset of Mg deficiency in nutrient solution trials (Terry and Ulrich , Tränkner et al ). Rubisco catalyzes the carboxylation and/or the oxygenation of ribulose‐1,5‐bisphosphate (RuBP) and thereby initiates the sugar producing or photorespiratory pathway.…”

“…Similarly, barley leaves suffering severe Mg deficiency had up to 55% higher H 2 O 2 concentration compared to control, though the activity of APX, GR and SOD were substantially increased. Under mild deficiency, the activity of APX, GR and SOD were still increased, but the concentration of H 2 O 2 was decreased to the same level as the control, indicating that under severe Mg deficiency the extent of H 2 O 2 production exceeded the scavenging capacity (Tränkner et al ).…”