Effects of exogenous zinc on the photosynthesis and carbonic anhydrase activity of millet (Setaria italica L.)

Abstract

This study aimed to evaluate the effects of Zn on the growth safety and activity of carbonic anhydrase (CA) in foxtail millet (Setaria italica L.). The photosynthetic characteristics, CA activity, and relative gene expression of different varieties of millet at the seedling stage were studied by spraying Zn solution under pot experiment and indoor culture conditions. Results showed that spraying low-concentration Zn solution (20, 40, and 60 mg L −1) reduced malondialdehyde content and intercellular CO2 concentration (Ci) but increased antioxidant enzyme activity, pigment content, and photosynthetic gas-exchange parameters (net photosynthetic rate, stomatal conductance, transpiration rate, except for Ci); meanwhile, spraying high Zn concentration (80 and 100 mg L −1) exerted opposite effects. The optimal growth of millet was achieved when the Zn concentration was 40 mg L −1. At this concentration, CA activity increased and β-CA family expression was upregulated, which exerted little or no effect on other CA families. Compared to Zhangzagu 10 (zinc-resistant variety), Jingu 21 (zinc-sensitive variety) showed a more significant change. This study may serve as a reference for further research on the function of CA and physiological processes, such as photosynthesis in millet, and a theoretical basis for the effective use of Zn fertilizer in millet.

Potential of Integrated Use of <i>Bacillus</i> sp. AZ6 and Organic Waste for Zinc Bio-Activation to Improve Physiological Attributes of Maize

“…Zinc solubilizing bacteria play an important role in plant growth, owing to the direct or indirect mechanisms that involve the production of Indole Acetic Acid (IAA), organic acids, Hydrocyanic acid (HCN), ACC deaminase, siderophores, mineralization of various minerals such as P liquefaction and Zn solubilization, all of which are important for plant development [42,43]. The increase in gas exchange attributes, CA activity, chlorophyll contents due to increased uptake of Zn was previously supported by Jan et al [44], Cao et al [45], Aslam et al [46], Wang et al [47] and documented the improvement of wheat's physiological qualities under drought stress through the application of endophytic bacteria containing CA activity. Thus, ZnO bio-activation with ZSB may serve as an effective and cost-effective technique to improve the physiological parameters of maize.…”