Abstract
Potassium (K) deficiency damaged membrane stability through irregular reactive oxygen species (ROS) caused by K deficiency stress while osmotic adjustment and antioxidant capacities play an essential role in preventing plants from osmotic stress and oxidative damages. To investigate the difference of osmoprotectants and antioxidant enzyme activities in the root, two representative maize varieties, 90-21-3 (K-tolerant) and D937 (K-sensitive), were hydroponically cultivated under normal K (+K) and K deficiency (-K) treatments in Shenyang Agriculture University, China. The results showed that root accumulation, soluble protein in root of 90-21-3 and D937 were decreased under K deficiency stress, but the root to shoot ratio, proline, free amino acid, soluble sugar, reactive oxygen species (ROS) in root for both genotypes were increased. Compared with the root of D937, the root of 90-21-3 was able to swiftly accumulate more proline, free amino acid and soluble sugar in the root when encountering K deficiency. The antioxidant enzyme activity in the root of 90-21-3, including superoxide dismutase (SOD), and catalase (CAT), peroxidase (POD), were significantly increased to counter increased levels of O2·- and H2O2 under K deficiency stress. The presented results indicated that osmotic regulator and antioxidant enzyme were actively responded to K deficiency stress, 90-21-3 (K-tolerant maize) accumulated more osmoprotectants and enhanced the activity of antioxidant enzymes to degrade ROS, alleviating oxidative stress.
Highlights
K, as a major mineral element, plays an essential role in process of crop growth and development, involved in function of osmoregulation, enzyme activation, ion homeostasis, and transport of metabolites in plants [1]
The results showed that root accumulation, soluble protein in root of 90-21-3 and D937 were decreased under K deficiency stress, but the root to shoot ratio, proline, free amino acid, soluble sugar, reactive oxygen species (ROS) in root for both genotypes were increased
Total dry weight of 90-21-3 and D937 were decreased by 13.62% and 27.83% under K deficiency stress at 7 d, respectively (Figure 1(a))
Summary
K, as a major mineral element, plays an essential role in process of crop growth and development, involved in function of osmoregulation, enzyme activation, ion homeostasis, and transport of metabolites in plants [1]. An ongoing downward trend of negative K balance of about 60 kg ha–1∙yr–1 appeared in intensive agricultural production areas starting in the late 1990s due to improper fertilization [2]. Osmoregulators can improve stress tolerance in plants by actively increasing levels of materials that can adjust the osmotic cellular conditions, including inorganic ions and organic solutes [4]. Inorganic ions and organic solutes are primary components that participate in osmotic adjustment in response to stress and contribute to stress tolerance in plants [5] [6]. The accumulated proline, soluble sugar, and phenol could reduce the osmotic stress caused by Fe2+, Zn2+, and Mn2+ deficiency, and improve plant tolerance [8]
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