Role of silicon in alleviating boron toxicity and enhancing growth and physiological traits in hydroponically cultivated Zea mays var. Merit

Abstract

Background: Boron (B) is a micronutrient, but excessive levels can cause phytotoxicity, impaired growth, and reduced photosynthesis. B toxicity arises from over-fertilization, high soil B levels, or irrigation with B-rich water. Conversely, silicon (Si) is recognized as an element that mitigates stress and alleviates the toxic effects of certain nutrients. In this study, to evaluate the effect of different concentrations of Si on maize under boron stress conditions, a factorial experiment based on a randomized complete block design was conducted with three replications in a hydroponic system. The experiment utilized a nutrient solution for maize var. Merit that contained three different boron (B) concentrations (0.5, 2, and 4 mg L^-1) and three Si concentrations (0, 28, and 56 mg L^-1).

Results: Our findings unveiled that exogenous application of B resulted in a substantial escalation of B concentration in maize leaves. Furthermore, B exposure elicited a significant diminution in fresh and dry plant biomass, chlorophyll index, chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids, and membrane stability index (MSI). As the B concentration augmented, malondialdehyde (MDA) content and catalase (CAT) enzyme activity exhibited a concomitant increment. Conversely, the supplementation of Si facilitated an amelioration in plant fresh and dry weight, total carbohydrate, and total soluble protein. Moreover, the elevated activity of antioxidant enzymes culminated in a decrement in hydrogen peroxide (H₂O₂) and MDA content. In addition, the combined influence of Si and B had a statistically significant impact on the leaf chlorophyll index, total chlorophyll (a + b) content, Si and B accumulation levels, as well as the enzymatic activities of guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and H₂O₂ levels. These unique findings indicated the detrimental impact of B toxicity on various physiological and biochemical attributes of maize, while highlighting the potential of Si supplementation in mitigating the deleterious effects through modulation of antioxidant machinery and biomolecule synthesis.

Conclusions: This study highlights the potential of Si supplementation in alleviating the deleterious effects of B toxicity in maize. Increased Si consumption mitigated chlorophyll degradation under B toxicity, but it also caused a significant reduction in the concentrations of essential micronutrients iron (Fe), copper (Cu), and zinc (Zn). While Si supplementation shows promise in counteracting B toxicity, the observed decrease in Fe, Cu, and Zn concentrations warrants further investigation to optimize this approach and maintain overall plant nutritional status.

Keywords: Antioxidant capacity; Boron exceeds; Minerals; Performance; Silicon; Sweet corn.

Fig. 1

Effect of different concentrations Si on a) fresh weight and b) dry weight and different concentrations of B on c) fresh weight and d) dry weight of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 2

Effect of different concentrations of B on leaf MSI of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 3

Interaction effect of different concentrations of Si and B on leaf chlorophyll of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 4

Interaction effect of different concentrations of Si and B on a) Chl a + b and the effect of B concentration on b) carotenoids of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 5

Effect of Si on a) total carbohydrate and b) total protein of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 6

Interaction effect of different concentrations of Si and B on H₂O₂ content of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 7

Effect of a) Si and b) B in nutrient solution on MDA content of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 8

Effect of a) Si and b) B in nutrient solution on CAT activity of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 9

Interaction effect of different concentrations of Si and B on a) GPX and b) APX activity of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 10

Effect of different concentrations of Si on a) Fe; b) Cu; c) Zn, and different concentrations of B in nutrient solution on d) Zn content of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01

Fig. 11

Interaction effect of different concentrations of Si and B on a) Si and b) B concentration in leaves of maize var. Merit. Means not sharing the same letter do not differ significantly at p ≤ 0.01