Exogenously Applied Gibberellic Acid Enhances Growth and Salinity Stress Tolerance of Maize through Modulating the Morpho-Physiological, Biochemical and Molecular Attributes.

Kashif Shahzad,Shahid Zamir,Christophe Hano,Saddam Hussain,Muhammad Arfan,Ejaz Ahmad Waraich,Khaled Y Kamal,Maham Saddique,Sadam Hussain,Mohamed A El-Esawi,Abdur Rauf

doi:10.3390/biom11071005

Abstract

Soil salinity is the major limiting factor restricting plant growth and development. Little is known about the comparative and combined effects of gibberellic acid (GA3) seed priming and foliar application on maize under salt stress. The current study determined the impact of different application methods of GA3 on morpho-physiological, biochemical and molecular responses of maize seedlings under three salinity stress treatments (no salinity, moderate salinity-6 dS m−1, and severe salinity-12 dS m−1). The GA3 treatments consisted of control, hydro-priming (HP), water foliar spray (WFS), HP + WFS, seed priming with GA3 (GA3P, 100 mg L−1), foliar spray with GA3 (GA3FS, 100ppm) and GA3P + GA3FS. Salt stress particularly at 12 dS m−1 reduced the length of shoots and roots, fresh and dry weights, chlorophyll, and carotenoid contents, K+ ion accumulation and activities of antioxidant enzymes, while enhanced the oxidative damage and accumulation of the Na+ ion in maize plants. Nevertheless, the application of GA3 improved maize growth, reduced oxidative stress, and increased the antioxidant enzymes activities, antioxidant genes expression, and K+ ion concentration under salt stress. Compared with control, the GA3P + GA3FS recorded the highest increase in roots and shoots length (19–37%), roots fresh and dry weights (31–43%), shoots fresh and dry weights (31–47%), chlorophyll content (21–70%), antioxidant enzymes activities (73.03–150.74%), total soluble protein (13.05%), K+ concentration (13–23%) and antioxidants genes expression levels under different salinity levels. This treatment also reduced the H2O2 content, and Na+ ion concentration. These results indicated that GA3P + GA3FS could be used as an effective tool for improving the maize growth and development, and reducing the oxidative stress in salt-contaminated soils.

Highlights

Maize (Zea mays L.) is a staple cereal crop, cultivated throughout the world for its usage as forage, and food grains for human and animal feed
Plant growth significantly differed with gibberellic acid (GA3 ) application under salinity stress (Figure 1; Table S1)
GA3 priming with foliar spray (GA3 P + GA3 FS) increased the shoot fresh and dry weight, root fresh weight and dry weight by 138.71%, 232.89%, 145.08% and 67.19%

Summary

Introduction

Maize (Zea mays L.) is a staple cereal crop, cultivated throughout the world for its usage as forage, and food grains for human and animal feed. Maize crop is subjected to various abiotic stresses under field. Biomolecules 2021, 11, 1005 conditions, such as soil salinity, drought, light and temperature, which may lead to a severe decline in its productivity [2]. Soil salinity is one of the major factors limiting crop growth and productivity. Soil salinity decreases the seed emergence and germination rates and severely reduces the growth, development and yield of field crops [4,5]. Reactive oxygen species (ROS) are continuously produced as a result of metabolic activities, with more production under environmental stress stimuli [4]. The increase in ROS production can lead to the destruction of lipids, membranes, nucleic acids and proteins, and results in malfunction of cellular machinery [9,10,11]. In order to reduce the oxidative damage, plants have developed an effective antioxidant defense system comprising of antioxidant enzymes like superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT) [14]

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