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Application of phytohormones during seed hydropriming and heat shock treatment on sunflower (Helianthus annuus L.) chilling resistance and changes in soluble carbohydrates

Górnik, Krzysztof, Lahuta, Lesław B.
Acta physiologiae plantarum 2017 v.39 no.5 pp. 118
Helianthus annuus, catalase, cold stress, cold tolerance, cold treatment, heat stress, jasmonic acid, metabolism, physiological response, plant hormones, roots, salicylic acid, seedlings, seeds, sugars
The objective of this study was to analyze the mechanism of some physiological processes accompanying acquisition of sunflower (Helianthus annuus L.) chilling resistance due to seeds hydropriming in the presence of salicylic acid, jasmonic acid, 24-epibrassinolide followed exposition of seeds to short-term heat shock treatment. The seeds were hydroprimed at 25 °C in limited amounts of water or solution of salicylic or jasmonic acid at 10⁻², 10⁻³ and 10⁻⁴ M concentration, 24-epibrassinolide at 10⁻⁶, 10⁻⁸ and 10⁻¹⁰ M concentration. The seeds were incubated for 2 days, subjected to short-term heat shock (45 °C, 2 h) and chilled for 21 days at 0 °C. Sunflower chilling susceptibility and physiological responses were evaluated according to the inhibition of radicle growth, the inhibition of the number of lateral roots formation, the activity of catalase and changes in soluble carbohydrates in seedlings developing for 72 h at 25 °C. Hydropriming and short-term heat shock application explicitly reduced inhibition of roots as well as lateral roots development by allowing the germinating seeds to recover from the growth-inhibiting effects of chilling. Seeds hydropriming in solutions containing salicylic acid, jasmonic acid and 24-epibrassinolide followed heat shock treatment additionally promoted the activity of catalase and sugars metabolism, which stimulated seedlings development and alleviated the decrease of F ᵥ/F ₘ caused by chilling conditions. These beneficial effects contributed to increased resistance of sunflower seedlings to chilling stress. The present study demonstrated that the most profitable effect on reducing negative effect of chilling may be achieved by short-term heat shock applied during hydropriming in water supplemented with 24-epiBL (10⁻⁸ and 10⁻¹⁰ M) or salicylic acid (10⁻³ and 10⁻⁴ M).