Exogenous application of salicylic acid ameliorates salinity stress in barley (Hordeum vulgare L.)

Abstract

Barley (Hordeum vulgare L.) is a significant cereal crop belonging to Poaceae that is essential for human food and animal feeding. The production of barley grains was around 142.37 million tons in 2017/2018. However, the growth of barley was influenced by salinity which was enhanced by applying a foliar spray of salicylic acid. The current study investigated to evaluated the potential effect of SA on the barley (Hordeum vulgare L.) plants under salinity stress and its possible effects on physiological, biochemical, and growth responses. The experiment was conducted at Postgraduate Research Station (PARS), University of Agriculture; Faisalabad to assess the influence of salicylic acid on barley (Hordeum vulgare L.) under highly saline conditions. The experiment was conducted in a Completely Randomized Design (CRD) with 3 replicates. In plastic pots containing 8 kg of properly cleaned sand, two different types of barley (Sultan and Jau-17) were planted. The plants were then watered with a half-strength solution of Hoagland's nutritional solution. After the establishment of seedlings, two salt treatments (0 mM and 120 mM NaCl) were applied in combining three levels of exogenously applied salicylic acid (SA) (0, 0.5, and 1 mg L-1). Data about morphological, physiological, and biochemical attributes was recorded using standard procedure after three weeks of treatment. The morpho-physiological fresh weight of the shoot and root (48%), the dry mass of the shoot and root (66%), the plant height (18%), the chlorophyll a (30%), the chlorophyll b (22%), and the carotenoids (22%), all showed significant decreases. Salinity also decreased yield parameters and the chl. ratio (both at 29% and 26% of the total chl. leaf area index). Compared to the control parameters, the following data was recorded under salt stress: spike length, number of spikes, number of spikelets, number of tillers, biological yield, and harvest index. Salicylic acid was used as a foliar spray to lessen the effects of salinity stress, and 1 mg L-1 of salicylic acid proved more effective than 0.5 mg L-1. Both varieties show better growth by applying salicylic acid (0 mg L-1) as a control, showing normal growth. By increasing its level to (0.5 mg L-1), it shows better growth but maximized growth occurred at a higher level (1 mg L-1). Barley sultan (Hordeum vulgare L.) is the best variety as compared to Jau-17 performs more growth to mitigate salt stress (0mM and 120mM NaCl) by improving morpho-physiological parameters by enhancing plan height, Root and shoot fresh and dry weights, as well as root and shoot lengths, photosynthetic pigments, area of the leaves and their index, and yield attributes and reduce sodium ions.

Keywords: Barley; Morphology; Physiology; Salicylic acid; Salinity; Yield.

Fig. 1

Experimental design and treatment application

Fig. 2

Effects of different concentrations of salt and salicylic acid on root length (A), root fresh weight (B), root dry weight (C), shoot length (D), shoot fresh weight (E), and shoot dry weight (F), of barely varieties. Different letters over the bars are significantly different at 0.05 levels. Values are mean (± SD) of three replicates

Fig. 3

Effects of different concentrations of salt and salicylic acid on Chl. a (A), Chl. b (B), Chl. a/b (C), total Chl. (D), and carotenoids (E), of barely varieties. Different letters over the bars are significantly different at 0.05 levels. Values are mean (± SD) of three replicates

Fig. 4

Effects of different concentrations of salt and salicylic acid on 1000 g seed weight (A), number of tillers (B), plant height (C), number of spikes (D), number of spikelets (E), and spike length (F), of barely varieties. Different letters over the bars are significantly different at 0.05 levels. Values are mean (± SD) of three replicates

Fig. 5

Effects of different concentrations of salt and salicylic acid on leaf area (A), leaf area index (B), leaf specific area (C), biological yield (D), and harvest index (E), of barely varieties. Different letters over the bars are significantly different at 0.05 levels. Values are mean (± SD) of three replicates

Fig. 6

Effects of different concentrations of salt and salicylic acid on K⁺ (A), Ca²⁺ (B), and Na⁺ (C), of barely varieties. Different letters over the bars are significantly different at 0.05 levels. Values are mean (± SD) of three replicates

Fig. 7

(A) Principle component analysis of various Morphological physiological parameters of Barley (A: Sultan and B: Jau-17). Plant height (PH), Shoot fresh weight (SF), Shoot dry weight (SD), Root fresh weight (RF), Root dry weight (RD), Shoot length (SL), Root length (RL), Spike length (SP), Leaf area (LA), Leaf area index (LAI) and Specific Leaf area (SA), ionic contents: Sodium (Na⁺), Potassium(K⁺), Calcium(Ca^+ 2),. T1 = 0 mM salt + 0 mM salicylic acid, T2: = 0 mM salt + 0.5 mM salicylic acid T3 = 0 mM salt + 1 mM salicylic acid, T4 = 120 mM salt + 0mM salicylic acid, T5: 120 mM salt + 0.5 mM salicylic acid, T6 = 0 mM salt + 1 mM salicylic acid

Fig. 8

Clustered Heatmaps of various Morpho-physiological and yield parameters of Barley (A: Sultan and B: Jau-17). Shoot fresh weight (SF), Shoot dry weight (SD), Root fresh weight (RF), Shoot length (SL), Root length (RL), Spike length (SP), Leaf area (LA), Leaf area index (LAI), Physiological: Sodium (Na⁺), Potassium(K⁺), Calcium(Ca²⁺), Chlorophyll a (Cha), Chlorophyll b (Chb), Carotenoids (CAR), Yield parameters: Harvest index (HI), Biological yield (BY), Spike length (SP), T1 = 0 mM salt + 0 mM salicylic acid, T2: = 0 mM salt + 0.5 mM salicylic acid T3 = 0 mM salt + 1 mM salicylic acid, T4 = 120 mM salt + 0mM salicylic acid, T5: 120 mM salt + 0.5 mM salicylic acid, T6 = 0 mM salt + 1 mM salicylic acid