Alkaline and acidic soil constraints on iron accumulation by Rice cultivars in relation to several physio-biochemical parameters

Abstract

Agricultural production is severely limited by an iron deficiency. Alkaline soils increase iron deficiency in rice crops, consequently leading to nutrient deficiencies in humans. Adding iron to rice enhances both its elemental composition and the nutritional value it offers humans through the food chain. The purpose of the current pot experiment was to investigate the impact of Fe treatment in alkaline (pH 7.5) and acidic (pH 5.5) soils to introduce iron-rich rice. Iron was applied to the plants in the soil in the form of an aqueous solution of FeSO₄ with five different concentrations (100, 200, 300, 400, and 500 mM). The results obtained from the current study demonstrated a significant increase in Fe content in Oryza sativa with the application of iron in both alkaline and acidic pH soils. Specifically, Basmati-515, one of the rice cultivars tested, exhibited a notable 13% increase in iron total accumulation per plant and an 11% increase in root-to-shoot ratio in acidic soil. In contrast to Basmati-198, which demonstrated maximum response in alkaline soil, Basmati-515 exhibited notable increases in all parameters, including a 31% increase in dry weight, 16% increase in total chlorophyll content, an 11% increase in CAT (catalase) activity, 7% increase in APX (ascorbate peroxidase) activity, 26% increase in POD (peroxidase) activity, and a remarkable 92% increase in SOD (superoxide dismutase) in acidic soil. In alkaline soil, Basmati-198 exhibited respective decreases of 40% and 39% in MDA and H₂O₂ content, whereas Basmati-515 demonstrated a more significant decrease of 50% and 67% in MDA and H₂O₂ in acidic soil. These results emphasize the potential for targeted soil management strategies to improve iron nutrition and address iron deficiency in agricultural systems. By considering soil conditions, it is possible to enhance iron content and promote its availability in alkaline and acidic soils, ultimately contributing to improved crop nutrition and human health.

Keywords: Fe accumulation; Iron biofortification; Iron fertlizer; Soil fertility; Soil pH.

Fig. 1

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on selected O. sativa cultivars under alkaline and acidic pH. Plant height (A, B), root fresh weight (C, D), shoot fresh weight (E, F), and total dry weight per plant (G, H). According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 2

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on selected O. sativa cultivars under alkaline and acidic pH. Chlorophyll a (A, B), chlorophyll b (C, D), total chlorophyll content (E, F), and carotenoids (G, H). According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 3

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on selected O. sativa cultivars under alkaline and acidic pH. Fe accumulation in shoot (A, B), Fe accumulation in roots (C, D), Fe total accumulation in plant (E, F), and root to shoot Fe ratio (G, H). According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 4

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on selected O. sativa cultivars under alkaline and acidic pH. CAT activity (A, B), APX activity (C, D), POD activity (E, F), and SOD activity (G, H). According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 5

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on increasing the level of antioxidants (GPX (A, B); DPPH (C, D)) and reducing oxidative stress levels (MDA (E, F); H₂O₂ (G, H)) in selected Oryza sativa cultivars under alkaline and acidic pH. According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 6

Effect of Fe (0, 100, 200, 300, 400, and 500 mM) on selected O. sativa cultivars under alkaline and acidic pH. Soluble sugar (A, B), flavonoids (C, D), free amino acids (E, F), and total carbohydrates (G, H). According to DMRT, bars with distinct alphabet letters are substantially (p < 0.05) different from one another. All data in the graph are the averages of six replicates (n = 6)

Fig. 7

Impact of iron fertilizer treatment on iron accumulation in rice plants and pH-dependent solubility