Magnesium in the Dynamics of Carbohydrates and Antioxidant Metabolism of Coffee Seedlings in Two Irradiance Levels

Abstract

The aim of this study was to verify the physiological impacts and the carbohydrate dynamics of Coffea arabica, seedlings subjected to increasing concentrations of magnesium (Mg) and two irradiance levels. Methods: The experiment was carried out in growth chambers with nutrient solution. The treatments were five concentrations of Mg (0, 48, 96, 192, and 384 mg L-1) and two irradiance levels (80 and 320 µmol of photons m-2 s-1). The coffee seedlings were under the treatments for 90 days. Results: The leaves with deficiency or excess of Mg exposed to the irradiance of 320 µmol of photons m-2 s-1 accumulated more carbohydrates than those exposed to 80 µmol of photons m-2 s-1. The accumulation of carbohydrates in the leaves increased the activity of antioxidant enzymes due to the increased production of reactive oxygen species (ROS). Leaves exposed to 320 µmol of photons m-2 s-1 exhibited symptoms of scald by the sun caused by photo-oxidation. The scald was more intense in plants with abnormal concentrations of Mg. The antioxidant system of the coffee tree is closely relates to the Mg supply and irradiance levels. Concentrations of Mg between 48 and 96 mg L-1 functioned as a mitigating agent of oxidative stress under stressful conditions caused by high irradiance level.

Comparative Physio-Biochemical and Transcriptome Analyses Reveal Contrasting Responses to Magnesium Imbalances in Leaves of Mulberry (Morus alba L.) Plants

“…Our results agree with [18] who opine that CAT activity decreased in Mg-deficient treated mulberry plants. An increase in CAT activity under low and excessive Mg supply has been reported [46], which agrees with our current results. However, our transcriptome analysis identified the CAT1 (Catalase isozyme 1; EXC51646.1) gene to be upregulated, with a low expression level exclusively under Mg deficiency (Figure 11A), suggesting possible safeguarding of plant cells against oxidative stress.…”

“…However, our transcriptome analysis identified the CAT1 (Catalase isozyme 1; EXC51646.1) gene to be upregulated, with a low expression level exclusively under Mg deficiency (Figure 11A), suggesting possible safeguarding of plant cells against oxidative stress. The elevation of antioxidant enzymes in response to excessive Mg levels can be attributed to the physiological imbalances caused by the surplus of this nutrient, the hindrance in the assimilation of other nutrients, particularly potassium (K), and the escalation in the salinity of the solution [46]. Peroxidase (POD) is an essential antioxidant whose activity level can be used as a biomarker to determine plant membrane integrity.…”

The possible role of extra magnesium and nitrogen supply to alleviate stress caused by high irradiation and temperature in lemon trees

“…Under low levels of Mg, wheat and maize plants are prone to heat stressassociated damages caused by elevated ROS levels (Mengutay et al 2013). A correlation between Mg supply and antioxidant system in coffee seedlings was observed under controlled conditions, where the activity of such enzymes as catalase (CAT) and ascorbate peroxidase (APX) were greater in plants grown with low Mg supply, as well as those enzyme activities were dependent of the radiance level that the plants were exposed (Dias et al 2018).…”

Magnesium as a Promoter of Technological Quality in Sugarcane

“…The discrepancy found between our results and other reports may be due to duration of the experiment. In our experiment, the plants were grown for 65 days, while most studies reporting Mg 2+ deficiency had evaluated younger plants (up to 35 days) (Cakmak et al 1994a;Guo et al 2015;Hermans et al 2010a;Dias et al 2018). Thus, due to Mg 2+ deficiency first affecting phloem loading, leading to long-term accumulation of sucrose and starch in the leaves, lack of Mg 2+ also affects photosynthesis by reducing sucrose production (Cakmak and Kirkby 2008).…”