A glimpse into the physiological, biochemical and nutritional status of soybean plants under Ni-stress conditions

Abstract

Nickel (Ni) toxicity has been reported to decrease productivity in soybean (Glycine max L.). However, soybean responses to Ni toxicity are not well understood. The aim of the present study was to describe Ni toxicity in soybean plants through physiological, nutritional, and ultrastructural analyses. Plants were grown in nutrient solution containing increasing Ni concentrations (0, 0.05, 0.1, 0.5, 10, and 20 μmol L −1), and nutritional, anatomical, physiological and biochemical features were determined. The results revealed previously unreported detrimental effects of Ni toxicity on soybean plants. CO 2 assimilation rates, stomatal conductance and transpiration decreased, resulting in lower biomass in soybean plants exposed to the highest Ni levels. Nitrate reductase activity increased with up to 0.05 μmol L −1 Ni and then decreased, indicating halted N-metabolism. Urease activity increased with increasing Ni availability in the nutrient solution, and peroxidase and superoxide dismutase activities were higher in plants grown at higher Ni levels. Leaf epidermal thickness (abaxial and adaxial), as well as root xylem and phloem diameter, decreased starting at 0.1 μmol L −1 Ni. Mean Ni concentrations varied from 77.5 to 17,797.4 mg kg −1 in roots and 2.3 to 16,774.5 mg kg −1 in shoots. Soybean plants exhibited symptoms of Ni toxicity starting at 0.1 μmol L −1 Ni, presenting mean shoot Ni concentration of 28.9 mg kg −1 , along with leaf water loss until complete drying. The results contribute to our understanding of several physiological, biochemical and histological mechanisms of Ni toxicity in soybean, which is still poorly understood.

Agronomic biofortification of cowpea with selenium: effects of selenate and selenite applications on selenium and phytate concentrations in seeds

“…In plants Se can promote growth, and combat oxidative stress, but is generally not required for most plants to complete their life‐cycle. Hence, it is considered a beneficial element in plant nutrition, and may not commonly be present at high levels in edible plant material . It is estimated that more than one billion people may suffer from Se deficiency .…”

“…Hence, it is considered a beneficial element in plant nutrition, and may not commonly be present at high levels in edible plant material. [8][9][10] It is estimated that more than one billion people may suffer from Se deficiency. 11 Selenium deficiency presents the third highest deficiency risk of any mineral micronutrient in Africa.…”

Physiological, biochemical, and ultrastructural characterization of selenium toxicity in cowpea plants

“…It is involved in thyroid function and the immune system and is also an antioxidant (Fairweather-Tait et al, 2011). In plants, Se is considered a beneficial trace element that can promote growth and help resist oxidative, biotic, and abiotic stress (White, 2016;Reis et al, 2017aReis et al, , 2017b.…”

“…Se concentrations tend to be very low (below 1 mg kg −1 ) in plants growing in acidic and weathered conditions such as tropical soils (Pilon-Smits et al, 2009) and the Se deficiency is estimated to be a problem for more than 1 billion people (Combs, 2001;Schiavon and Pilon-Smits, 2017). Therefore, Se supplementation to plants might be an important strategy for increasing the daily intake of this element by humans and animals (White and Broadley, 2009;Chilimba et al, 2012;White, 2016;Reis et al, 2017aReis et al, , 2017b.…”

“…ROS are an indicative of stress in plants, indicating the damage to the plant cell but also act as signaling molecules in response to stressful compounds in the plant tissues (Wrzaczek et al, 2013;Shi et al, 2016;Luo et al, 2016). The abiotic stress in plants is evaluated also by the increase of antioxidative enzymes such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in response to high levels of heavy metal exposure (Reis et al, 2017a(Reis et al, , 2017bSantos et al, 2017).…”