Nizar Mereen, Shaukat Kanval, Zahra Noreen, Hafeez Muhammad Bilal, Raza Ali, Samad Abdul, Ali Qasim, Siddiqui Manzer H, Ali Hayssam M
Department of Botany, University of Balochistan, Quetta, Pakistan.
Department of Botany, University of Agriculture, Faisalabad, Pakistan.
Front Plant Sci. 2022 Jan 27;12:809183. doi: 10.3389/fpls.2021.809183. eCollection 2021.
Cadmium (Cd) is a potential and widespread toxic environmental pollutant, mainly derived from a rapid industrial process that has inhibitory effects on growth, physiological, and biochemical attributes of various plant species, including medicinal plants such as L. Gaertn commonly known as milk thistle. Plant signaling molecules, when applied exogenously, help to enhance/activate endogenous biosynthesis of potentially important signaling molecules and antioxidants that boost tolerance against various abiotic stresses, e.g., heavy metal stress. The present study documented the protective role of salicylic acid (SA;0.25 μM) and hydrogen peroxide (HO; 10 μM) priming, foliar spray, and combinational treatments in reducing Cd toxicity (500 μM) in milk thistle grown at two diverse ecological zones of Balochistan Province of Pakistan i.e., Quetta (Qta) and Turbat (Tbt). The morpho-physiological and biochemical attributes of milk thistle were significantly affected by Cd toxicity; however, priming and foliar spray of SA and HO significantly improved the growth attributes (root/shoot length, leaf area, and root/shoot fresh and dry weight), photosynthetic pigments (Chl , , and carotenoids) and secondary metabolites (Anthocyanin, Soluble phenolics, and Tannins) at both altitudes by suppressing the negative impact of Cd. However, the oxidative damage parameters, i.e., MDA and HO, decreased astonishingly under the treatment of signaling molecules, thereby protecting membrane integrity under Cd stress. The morphological variations were profound at the low altitude (Tbt) as compared to the high altitude (Qta). Interestingly, the physiological and biochemical attributes at both altitudes improved under SA and HO treatments, thus hampered the toxic effect of Cd. These signaling compounds enhanced tolerance of plants under heavy metal stress conditions with the consideration of altitudinal, and ambient temperature variations remain to be the key concerns.
镉（Cd）是一种潜在的、广泛存在的有毒环境污染物，主要来源于快速的工业生产过程，它对包括药用植物水飞蓟（俗称奶蓟）在内的各种植物物种的生长、生理和生化特性具有抑制作用。植物信号分子在外部施用时，有助于增强/激活潜在重要信号分子和抗氧化剂的内源性生物合成，从而提高对各种非生物胁迫（如重金属胁迫）的耐受性。本研究记录了水杨酸（SA；0.25 μM）和过氧化氢（H₂O₂；10 μM）引发处理、叶面喷施及组合处理在降低巴基斯坦俾路支省两个不同生态区（即奎达（Qta）和图尔巴特（Tbt））种植的水飞蓟镉毒性（500 μM）方面的保护作用。镉毒性对水飞蓟的形态生理和生化特性有显著影响；然而，SA和H₂O₂的引发处理和叶面喷施通过抑制镉的负面影响，显著改善了两个海拔高度下的生长特性（根/茎长度、叶面积以及根/茎鲜重和干重）、光合色素（叶绿素a、叶绿素b和类胡萝卜素）和次生代谢产物（花青素、可溶性酚类和单宁）。然而，在信号分子处理下，氧化损伤参数（即丙二醛和H₂O₂）惊人地降低，从而在镉胁迫下保护了膜的完整性。与高海拔（Qta）相比，低海拔（Tbt）的形态变化更为显著。有趣的是，在SA和H₂O₂处理下，两个海拔高度的生理和生化特性均得到改善，从而减轻了镉的毒性作用。考虑到海拔和环境温度变化，这些信号化合物增强了植物在重金属胁迫条件下的耐受性，这仍是关键问题。
