Abstract
Heavy metal-polluted soil represents an important stress condition for plants. Several studies demonstrated that growth inhibition under metal stress and metal-induced damages, including genotoxicity, is particularly pronounced at the early stages of seedling growth. Moreover, it is reported that heavy metals enter the cytoplasm to exert their detrimental effect, including DNA damage. In this work, we estimated (i) metal-induced genotoxicity by ISSR molecular markers and (ii) the distribution of the metal fractions between symplast and apoplast by EDTA washing, in three cultivars of Cynara cardunculus var. altilis (L.) DC (Sardo, Siciliano, and Spagnolo), grown in hydroponics for 15 days with Cd or Pb: In line with the literature, in all cultivars, the genotoxic damage induced by Pb was more severe compared to Cd. However, a cultivar-specific response was evidenced since Spagnolo showed, under metal stress, a significantly higher genome template stability compared to the other examined cultivars. The lower genotoxicity observed in Spagnolo could depend on the lower intracellular metal concentration measured in this cultivar by chemical analysis. Accordingly, light microscopy highlighted that Spagnolo developed smaller and more numerous epidermal cells under metal stress; these cells would provide a larger wall surface offering a wider metal sequestration compartment in the apoplast.
Highlights
Plants are sessile organisms; they cannot escape from environmental stresses, being constantly exposed to both abiotic and biotic agents, which can frequently induce oxidative and genotoxic damage
We found that Cynara cardunculus cv “Spagnolo” could face Cd and Pb metal stress with multiple responses that overall safeguarded plant growth and cell structure and functions, compared to other two cultivars (“Sardo” and “Siciliano”)
As for the Spagnolo, the primers mostly contributing to the variance were 22, 23, and w843; the other primers produced a relatively low level of variance compared to the other cultivars, or even no variance, resulting in a higher Genomic template stability (GTS) calculated for Spagnolo under metal stress
Summary
Plants are sessile organisms; they cannot escape from environmental stresses, being constantly exposed to both abiotic and biotic agents, which can frequently induce oxidative and genotoxic damage. Abiotic stresses include unfavorable growth conditions, such as water, salt, and temperature stresses, and a multitude of xenobiotic substances spread in the environment, such as organic pollutants and heavy metals. All the d-block elements of the periodic table have been identified as heavy metals, based on their density higher than 5 g cm−3 [1]. Due to their specific properties, heavy metals are employed in a wide variety of industrial applications. The estimated annual Pb production is 15,000 million tons followed by Cd (22,000 tons) [2]
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