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

Abstract

Selenium (Se) is considered a beneficial element for plants; however, in high concentrations, it causes negative effects on plant physiology and development. This study reports the first physiological, nutritional, and ultrastructural description of Se toxicity in cowpea growing under field conditions. Selenium was supplied as a foliar application of sodium selenite at varying concentrations (0, 50, 100, 200, 400, 800, 1200, and 1600 g ha −1). An increased yield was observed with the application of 50 g ha −1 Se. Application of concentrations higher than 50 g ha −1 caused leaf toxicity. Increased lipid peroxidation and hydrogen peroxide concentration and reduced total sugars, sucrose, and carotenoid concentration were observed at highest doses tested (1200 and 1600 g ha −1). Applications of more than 50 g ha −1 Se reduced the phloem diameter, caused chlorosis of the leaf blade with a coalescence of lesions, and caused pink salt deposits to appear. Lesions were observed mainly near the trichomes on the adaxial surface of the leaf blade. An analysis of the element distribution with microprobe Xray fluorescence spectrometry (μ-XRF) revealed accumulation of Se, calcium (Ca), potassium (K), copper (Cu), and manganese (Mn) near the primary vein and in the necrotic brown areas of the leaf lesions. In contrast, Na was homogeneously distributed in the leaf tissue.

Agronomic biofortification with selenium impacts storage proteins in grains of upland rice

“…According to the Köppen classification scheme, the climate of the region is type Aw, humid tropical, with a rainy season in the summer and a dry season in the winter. The average annual rainfall is 1232 mm, and the average temperature is 24.5 °C . During the experiment, the average daily temperature varied between 27.2 and 15.3 °C; the average rainfall was 3.0 mm d −1 ; and the average relative humidity was 86%.…”

“…Since most Se in the human diet is derived directly or indirectly from edible plants, Se deficiency in humans is attributed to agricultural production on soils with little phytoavailable Se . Despite the consequences of Se deficiency having been recognized for decades, strategic interventions to meet the shortfall of Se in food are still limited . Biofortification is the process of enriching edible crops with mineral nutrients based on management strategies that increase the phytoavailabilty of nutrients and / or genotypes that partition more nutrient into their edible portions .…”

“…In the case of Se, biofortification of crops can be achieved through the application of Se fertilizers and / or adopting cultivars that partition more Se to their edible portions . Previous studies have indicated that the application of low concentrations of Se does not lead to a loss of crop productivity or harvest index . In addition, fertilization with Se at low concentrations can mitigate oxidative stress and increase photosynthetic activity, thereby resulting in greater plant growth .…”

“…6,7,[12][13][14][15] Despite the consequences of Se deficiency having been recognized for decades, strategic interventions to meet the shortfall of Se in food are still limited. 16,17 Biofortification is the process of enriching edible crops with mineral nutrients based on management strategies that increase the phytoavailabilty of nutrients and / or genotypes that partition more nutrient into their edible portions. 18 In the case of Se, biofortification of crops can be achieved through the application of Se fertilizers and / or adopting cultivars that partition more Se to their edible portions.…”

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 .…”