Sulfate-Based Fertilizers Regulate Nutrient Uptake, Photosynthetic Gas Exchange, and Enzymatic Antioxidants to Increase Sunflower Growth and Yield Under Drought Stress

Bilal Ahamid Shafiq,Abdullah Al Mamun,Khawaja Shafique Ahmad,Tanveer Ul Haq Tanveer Ul Haq,Muhammad Aurangzaib,Fahim Nawaz,Muhammad Ahsan,Muqarrab Ali,Sadia Majeed,Muhammad Asif Shehzad,Sarfraz Hashim

doi:10.1007/s42729-021-00516-x

Abstract

The challenging impact of drought to agricultural productivity requires the adoption of mitigation strategies with a better understanding of underlying mechanisms responsible for drought tolerance. The present study aimed at investigating the effects of sulfur-based fertilizers on mitigation of drought stress in sunflower. Sulfate-containing fertilizers, viz., ammonium sulfate, zinc sulfate, magnesium sulfate, potassium sulfate, and gypsum, were initially evaluated at two different rates (10 and 20 mg kg−1 soil equivalent to 20 and 40 kg ha−1, respectively) for nutrient uptake and growth-promoting traits in sunflower seedlings (cv. Hysun-33). The best performing fertilizer (gypsum) was then selected to evaluate the response of sunflower under drought stress imposed at flowering stage for three weeks (25–30% water holding capacity). Results indicated significant amelioration of drought stress with higher activity of photosynthetic apparatus, upregulation of antioxidative enzymes, and increased achene yield by gypsum application. In comparison to control, gypsum-treated plants (20 mg kg−1 soil) exhibited higher water status (32%), leaf photosynthetic rate (29%), transpiration rate (67%), and stomatal conductance (118%) under drought stress. The antioxidant enzyme activities of catalase, guaiacol peroxidase, and superoxide dismutase were also increased by 67%, 62%, and 126%, respectively, resulting in higher achene yield (19%) under water-deficit conditions. This study indicates that the application of sulfur-based fertilizers (gypsum) can be used to induce drought tolerance and obtain high sunflower yields under drought stress, and furthermore, it is a cost-effective strategy resulting in high benefit–cost ratio with respect to no gypsum application.

Highlights

Climate extremes such as drought have become the most common and critical limiting factors affecting the productivity of food crops around the globe (Leng and Hall 2019).Low water availability impairs the germination and seedling establishment and reduces the overall fitness of the plants to withstand unfavorable environmental conditions (Anavella et al 2016)
The highest increase in shoot length (SL) (115%), SFW (95%), and SDW (135%) was noted in seedlings treated with gypsum (CaSO4. 2H2O) at 40 kg ha−1 compared to control, i.e., no S supply (0 kg ha−1)
A marked increase in these growth attributes was noted by (NH4)2SO4 application at 40 kg ha−1 that increased SL, root length (RL), SFW, and SDW by 76, 70, 54, and 40%, respectively, compared to control (Fig. 1a–d)

Summary

Introduction

Climate extremes such as drought have become the most common and critical limiting factors affecting the productivity of food crops around the globe (Leng and Hall 2019). Low water availability impairs the germination and seedling establishment and reduces the overall fitness of the plants to withstand unfavorable environmental conditions (Anavella et al 2016). Plants tend to adapt water limitations through various self-protection mechanisms, for instance, the regulation of stomatal aperture to adjust the photosynthetic capacity of mesophyll cells (Waseem et al 2021). Knowledge about the management of nutrient fertilizers and cultivation of potential drought-tolerant crop species is crucial to combat the uncertainties associated with climate change (Ma et al 2021)

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