PHYSIOLOGICAL AND MOLECULAR RESPONSES OF TEXTILE HEMP (Cannabis sativa Santhica 27) TO CADMIUM AND ZINC, WITH A PARTICULAR FOCUS ON THE ANALYSIS OF SILICON-INDUCED PROTECTION MECHANISM.

Abstract

Soil contamination by heavy metals, particularly cadmium and zinc, represents a major environmental and health concern, exacerbated by industrial, mining, and agricultural activities. Phytoremediation, an ecological and cost-effective strategy, leverages plants to extract or stabilize these pollutants. Textile hemp (Cannabis sativa L. var. Santhica 27) is a promising candidate for this approach due to its deep root system, high biomass production, and non-food applications. Although silicon is not an essential element for plant growth, it has been shown to enhance tolerance to abiotic stresses. This study investigates the effect of silicon on the response of textile hemp exposed to cadmium and zinc contamination in a highly bioavailable hydroponic system. Silicon was supplied in hydroponic solution as 2 mM metasilicic acid, ensuring full phytoavailability. One week later, cadmium (20 µM) and zinc (100 µM) were introduced. A multidisciplinary approach was used, integrating molecular (proteomic), biochemical, and physiological analyses – including pigment composition, hormonal profiling, and gas exchange measurements – to better understand the adaptation and accumulation mechanisms of hemp in a phytoremediation context. Contrary to numerous studies highlighting the beneficial role of silicon in mitigating abiotic stress, our results indicate no protective effect and even potential negative impacts on certain physiological mechanisms. Specifically, silicon application led to a reduction in chlorophyll and certain carotenoid concentrations, with no significant improvements in physiological parameters. These findings suggest that silicon does not enhance the tolerance of textile hemp to cadmium and zinc stress, potentially due to the plant’s relatively low silicon accumulation capacity