Abstract
BackgroundThis study assessed the effects of 24-epibrassinolide (EBL, 10–7M) and silicon (2 mM) on the alleviation of cadmium (Cd, 150 mg L–1) toxicity in Pisum sativum L. seedlings via the modulation of growth, antioxidant defense, glyoxalase system, and nutrient uptake.ResultsShoot and root lengths declined by 46.43% and 52.78%, respectively, following Cd stress. Shoot and root dry weights also declined with Cd toxicity. Biochemical and physiological aspects exhibit significant decline including total chlorophyll (33.09%), carotenoid (51.51%), photosynthetic efficiency (32.60%), photochemical quenching (19.04%), leaf relative water content (40.18%), and gas exchange parameters (80.65%). However, EBL or Si supplementation alone or in combination modulates the previously mentioned parameters. Cadmium stress increased proline and glycine betaine (GB) contents by 4.37 and 2.41-fold, respectively. Exposure of plants to Cd stress increased the accumulation of H2O2, malondialdehyde content, electrolyte leakage, and methylglyoxal, which declined significantly with EBL and Si supplementation, both individually and in combination. Similarly, Cd stress adversely affected enzymatic and non-enzymatic antioxidants, but EBL and/or Si supplementation maintained antioxidant levels. Glyoxalase I (GlyI) accumulated after Cd stress and increased further with the application of EBL and Si. However, GlyII content declined after Cd stress but increased with supplementation of EBL and Si. Cadmium accumulation occurred in the following order: roots > shoots>leaves. Supplementation with EBL and Si, individually and in combination reduced Cd accumulation and enhanced the uptake of macronutrients and micronutrients in shoots and roots, which declined with Cd toxicity.ConclusionThe application of 24-EBL and Si, individually and in combination, alleviated the adverse effects of Cd by improving growth, biochemical parameters, nutrient uptake, osmolyte accumulation, and the anti-oxidative defense and glyoxalase systems in Pisum sativum seedlings.
Highlights
This study assessed the effects of 24-epibrassinolide (EBL, 10–7M) and silicon (2 mM) on the alleviation of cadmium (Cd, 150 mg L–1) toxicity in Pisum sativum L. seedlings via the modulation of growth, antioxidant defense, glyoxalase system, and nutrient uptake
Several studies have shown that Cd toxicity alters nitrogen metabolism, reduces photosynthetic efficiency caused by impaired chlorophyll synthesis, and reduces carbon fixation [8, 9]
In Cd-stressed seedlings, shoot and root lengths increased by 28.89% and 41.71%, respectively, with EBL, and by 34.70% and 51.31%, respectively, with Si, relative to seedlings exposed to Cd alone (Fig. 1a, b)
Summary
This study assessed the effects of 24-epibrassinolide (EBL, 10–7M) and silicon (2 mM) on the alleviation of cadmium (Cd, 150 mg L–1) toxicity in Pisum sativum L. seedlings via the modulation of growth, antioxidant defense, glyoxalase system, and nutrient uptake. Heavy metal contamination causes morphological, physiological, biochemical, and ultra-structural alterations in plants [4]. Cd toxicity reduces plant growth, biomass, photosynthesis, yield, and quality [11, 12]. It impairs mineral nutrition in plants [13, 14]. Increased Cd accumulation hampers root morphology, resulting in stunted growth [15], and causes oxidative stress in vegetables via the generation of reactive oxygen species (ROS), which damage the antioxidant enzyme system [1, 16]. Leafy vegetables accumulate more Cd than vegetable roots and tubers [25]
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