Protective effect of potassium and chitosan supply on growth, physiological processes and antioxidative machinery in sunflower (Helianthus annuus L.) under drought stress

• Published in: Ecotoxicology and environmental safety 2020-01, Vol.187, p.109841, Article 109841
• Main Authors: Shehzad, Muhammad Asif, Nawaz, Fahim, Ahmad, Fiaz, Ahmad, Naveed, Masood, Shahid
• Format: Article
• Language: English
• Subjects: Antioxidants - metabolism; Biomass; Chitosan - pharmacology; Chlorophyll - metabolism; Climate Change; Crops, Agricultural - drug effects; Crops, Agricultural - growth & development; Crops, Agricultural - metabolism; Droughts; Helianthus - drug effects; Helianthus - growth & development; Helianthus - metabolism; Helianthus annuus; Osmotic adjustment; Oxidative stress; Potassium - pharmacology; Stress, Physiological - drug effects; Water - metabolism; Yield
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2019.109841

Drought stress is one of the extreme effects of climate change causing large losses in production of crop plants. The risk of recurrent droughts has increased in next decades hence, the development of shot-gun, inexpensive and effective approaches is essential to ensure high yield of crops in drought-prone areas of the world. Exogenous application of nutrients such as potassium (K) has been reported to increase abiotic resistance and improve yield in crops however, knowledge regarding interaction of K with osmoprotectants like chitosan (Ct) still remains elusive. Here, we report the effects of individual or combined K (using K2SO4 as a source) or Ct application on growth, physiological processes and antioxidative defense system of sunflower under drought stress. At first, various doses of K (0, 5, 10, 15, 20, 25 g/l) and Ct (0, 0.1, 0.2, 0.3, 0.4, 0.5 g/l) were foliar applied to evaluate their role in improving plant biomass, water status and total chlorophyll in drought-induced seedlings of sunflower. The optimized K (11.48 g/l) and Ct (0.28 g/l) doses were further tested in second experiment to understand the underlying mechanisms of drought tolerance. Foliar K + Ct spray markedly enhanced the leaf gas exchange characteristics, increased proline, soluble proteins, and free amino acids, upregulated antioxidant defense system and helped to maintain plant water status in sunflower exposed to drought stress. The impact of drought stress was more pronounced at vegetative than reproductive stage and positive effects of combined K and Ct application were related to improved physiological and metabolic processes to improve yield and quality of sunflower under drought stress. •Exogenous K and Ct supply affects sunflower growth and yield under drought stress.•The combined K + Ct treatment contributes to better drought tolerance in sunflower.•Enhanced drought tolerance was attributed to regulation in physiological processes.•Drought at vegetative than reproductive stage results in more deleterious effects.