Cadmium Toxicity Affects Morpho-Physiological and Biochemical Attributes in Gladiolus grandiflorus L.: The Mitigating Roles of Exogenous Strigolactone (GR24)

Abstract

Cadmium (Cd) is one of the most toxic heavy metals to living organisms including floricultural crops. Strigolactone (SL), a relatively recent plant growth regulator, mediates plant growth under heavy metal stress. This study aimed to investigate whether exogenous SL could effectively alleviate Cd toxicity in Gladiolus grandiflorus by increasing morphological and physiological attributes and decreasing oxidative stress. A pot experiment was conducted to explore the alleviating potential of Gladiolus grandiflorus cv. Rose Supreme to Cd toxicity (0.5 mM) damage by foliar supplementation of SL (4 μM). Cadmium stress significantly reduced morphological traits, photosynthetic pigments, soluble proteins, and vase life of gladiolus plants. However, exogenous SL supplementation resulted in an enhanced number of leaves (27%), spike length (33%), spike diameter (23%), florets numbers (17%), root length (21%), contents of chlorophyll (101%), and carotenoids (25%) in Cd-polluted plants. Likewise, the increment in photosynthetic rate, transpiration rate, total soluble proteins, and the vase life of gladiolus plants increased by 22%, 39%, 71%, and 37%, respectively, under Cd toxicity compared with non-stressed plants. Similarly, contents of free proline, and the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) were also regulated due to SL foliar spray in Cd-polluted sword lily plants. The application of SL also remarkably reduced glycinebetaine (18%), malondialdehyde (23%), and hydrogen peroxide (31%), triggered by Cd toxicity. Additionally, the Cd contents were also reduced in roots, leaves, and flowers by 28%, 34% and 46%, respectively, in SL supplied Cd-polluted plants. These results enhance our understanding of the potential of SL in mitigating Cd stress in gladiolus cut flower plants, providing valuable insights for plant resilience improvement. This study suggests that foliar supplementation of SL could be a potential eco-friendly and cost-effective approach for enhancing Cd resistance in ornamental geophytes like Gladiolus grandiflorus.