How zinc improves drought resistance of crops

An Indian study reveals the properties of zinc in mitigating the effects of water stress on plants. Foliar sprays offer an effective solution

by Matteo Cavallito

 

Applying zinc to plant leaves could mitigate the effects of water stress. This is supported by an study published in the journal Plant Stress. The research, conducted by a team of scientists led by Arun K. Shanker, a researcher at ICAR, the Central Research Institute for Dryland Agriculture in Hyderabad, India, specifically revealed the effectiveness of zinc foliar sprays in reducing the impact of drought on pearl millet.

“Water stress adversely affects the photosynthetic apparatus and pigment composition in plants, leading to reduced yields and compromised plant health,” the study explains. “Zinc (Zn) foliar spray in nano form presents a potential solution to ameliorate water deficit stress.”

The study on zinc

The researchers, a statement from ICRA points out, demonstrated how zinc-delivered in the form of nanoparticles (Zn Nano) and ethylenediaminetetraacetic acid (Zn EDTA)-improves the photosynthetic efficiency of plants. “We attempt here a detailed dissection of electron transport in Photosystem II (PSII) through studies on chlorophyll a fast fluorescence kinetics and non-photochemical quenching (NPQ) and pigment dynamics in response to water stress,” the authors further explain.

“We also investigated the possible changes in these processes and the regulation of it by Zn Nano and Zn Ethylenediaminetetraacetic acid (EDTA) foliar sprays that may lead to amelioration of stress.” The application of zinc as a foliar spray positively affected electron transport efficiency and reduced nonphotochemical quenching creating a better energy balance.

Protection guaranteed to pigments is crucial

The study highlights the crucial role of xanthophylls – the yellow pigments in leaves – in dissipating excess light energy. According to the researchers, zinc treatments would enhance their protective effects under stressful conditions. “Treatments with Zn Nano (particle size < 90 nm) spray with Zn concentration at 20 mg L−1 and Zn EDTA spray (solid material size ∼ 100 µm) with Zn concentration at 240 mg L−1 effectively ameliorated water deficit stress.”

The applications, in particular, “positively influenced chlorophyll content, and xanthophyll components, including violaxanthin, antheraxanthin, and zeaxanthin, and reduced non-photochemical quenching and the de-expoxidation state.”

At the same time, the scientists note, increasing the concentration of zinc nanoparticles in the foliar spray (30 mg liter) made the treatment less effective. “This lack of stress amelioration at higher concentrations”, they explain, ”may be due to physiological limitations of elemental zinc action within the plant.”

Implications for food security

The results, the researchers conclude, underscore the potential of foliar sprays, especially in nanometer form, in increasing drought resistance of crops and, as such, in paving the way for sustainable agricultural practices in water-constrained environments. This is essential, especially in the context of global warming.

“This study not only provides mechanistic insights into zinc’s role in stress tolerance but also suggests practical applications for enhancing crop resilience in the face of climate change-induced water scarcity,” the authors say. “The research has significant implications for developing low-cost, efficient foliar nutrition strategies to support global food security.”