Effect of chromium (VI) toxicity on morpho-physiological characteristics, yield, and yield components of two chickpea (Cicer arietinum L.) varieties

Abstract

The ever-increasing industrial activities over the decades have generated high toxic metal such as chromium (Cr) that hampers the crop productivity. This study evaluated the effect of Cr on two chickpea (Cicer arietinum L.) varieties, Pusa 2085 and Pusa Green 112, in hydroponic and pot-grown conditions. First, growth parameters (seed germination, seedling growth, and biomass production) and physio-biochemical parameters (oxidative stress and the content of antioxidants and proline) were measured to evaluate the performance of both varieties grown hydroponically for 21 days at concentrations of 0, 30, 60, 90 and 120 μM Cr in the form of potassium dichromate (K2Cr2O7). In both varieties, significantly deleterious effects on germination and seedling growth parameters were observed at 90 and 120 μM, while growth was stimulated at 30 μM Cr. Significant increases in malondialdehyde and hydrogen peroxide content and electrolyte leakage demonstrated enhanced oxidative injury to seedlings caused by higher concentrations of Cr. Further, increasing concentrations of Cr positively correlated with increased proline content, superoxide dismutase activity, and peroxide content in leaves. There was also an increase in peroxisomal ascorbate peroxidase and catalase in the leaves of both varieties at lower Cr concentrations, whereas a steep decline was recorded at higher Cr concentrations. In the pot experiments conducted over two consecutive years, growth, yield, yield attributes, grain protein, and Cr uptake and accumulation were measured at different Cr concentrations. Pusa Green 112 showed a significant reduction in plant growth, chlorophyll content, grain protein, pod number, and grain yield per plant when compared with Pusa 2085. Overall, our results indicate that Pusa 2085 has a higher Cr tolerance than Pusa Green 112. Therefore, Pusa 2085 could be used to further elucidate the mechanisms of Cr tolerance in plants and in breeding programmes to produce Cr-resistant varieties.

Fig 1. A schematic outlining of mechanism of chromium (Cr) toxicity in soil and the potential deleterious effects of Cr pollution on morphological and physiological aspects of chickpea plants.

Fig 2. Germination performance of seeds in two chickpea varieties under different chromium (Cr) treatments.

(a) Pusa 2085. (b) Pusa Green 112.

Fig 3. Effects of various chromium (Cr) concentrations on the morpho-physiological traits of two chickpea varieties under hydroponic conditions.

(a) Pusa 2085. (b) Pusa Green 112.

Fig 4. Effects of the various chromium (Cr) concentrations on two chickpea varieties (Pusa 2085 and Pusa Green 112) 21 days after treatment (DAT).

(a) root length (cm). (b) shoot length (cm). (c) plant fresh weight (g). (d) plant dry weight (g). Values are means ± standard errors from three independent experiments. Error bars with the same letters are not significantly different at p ≤ 0.05.

Fig 5. Effects of various chromium (Cr) concentrations on two chickpea varieties (Pusa 2085 and Pusa Green 112).

(a) Malondialdehyde (MDA), roots. (b) MDA, shoots. (c) H₂O₂, roots. (d) Hydrogen peroxide (H₂O₂), shoots. (e) electrolyte leakage (EL), roots. (f) electrolyte leakage, shoots.

Fig 6. Effects of the various chromium (Cr) concentrations on the proline contents in roots and shoots of two chickpea varieties (Pusa 2085 and Pusa Green 112) 21 days after treatment (DAT).

Values are means ± standard errors from three independent experiments. Error bars with the same letters are not significantly different at p ≤ 0.05.

Fig 7. Effects of the various chromium (Cr) concentrations on the activities (units mg^-1 protein) of antioxidative enzymes: Superoxide dismutase (SOD), Peroxidase (POD), Catalase (CAT), and Ascorbate Peroxidase (APX) in the leaves of two chickpea varieties (Pusa 2085 and Pusa Green 112) 21 days after treatment (DAT).

Values are means ± standard errors from three independent experiments. Error bars with the same letters are not significantly different at p ≤ 0.05.

Fig 8

Fig 9. Violin plots showing the distributions of three plant growth parameters examined in two chickpea varieties, Pusa 2085 and Pusa Green 112, grown in pots under different chromium (Cr) concentrations.

(a–b) plant height (PH) (cm). (c–d) plant fresh weight (PFW) (g). (e–f) plant dry weight (PDW) (g).

Fig 10. Violin plots showing the distributions of the number of primary branches per plant (NPBPP) and the number of secondary branches per plant (NSBPP) in two chickpea varieties, Pusa 2085 and Pusa Green 112, grown in pots under different chromium (Cr) concentrations.

Fig 11. Violin plots showing the distributions of the number of pods per plant (NPPP) and the yield-related traits in two chickpea varieties, Pusa 2085 and Pusa Green 112, grown in pots under different chromium (Cr) concentrations.

Fig 12. Effects of various chromium (Cr) concentrations on the seeds per pod in two chickpea varieties grown under potted conditions.

(a) Pusa 2085. (b) Pusa Green 112.

Fig 13. Effects of the chromium (Cr) treatments (control and 120 μM) on plant growth, above-ground biomass, and plant productivity in two chickpea varieties grown in pots.

(a) Pusa 2085. (b) Pusa Green 112.

Fig 14. Effects of various chromium (Cr) concentrations on chlorophyll (Chl) contents of leaves in two chickpea varieties (Pusa 2085 and Pusa Green 112), grown in pots, 95 days after treatment (DAT).

(a) Chl a. (b) Chl b. (c) Total Chl. Values are means ± standard errors from three independent experiments. Error bars with the same letters are not significantly different at p ≤ 0.05.

Fig 15. Chromium (Cr) accumulation in roots, stems, leaves, and seeds of Pusa 2085 and Pusa Green 112 chickpea seedlings grown in pots under different Cr concentrations (0, 30, 60, 90 and 120 μM).