Exploring the Potential Enhancing Effects of Trans-Zeatin and Silymarin on the Productivity and Antioxidant Defense Capacity of Cadmium-Stressed Wheat

Abstract

Pot trials were performed to explore the impacts of seed priming (SPr) plus leaf treatment (LTr) with trans-zeatin-type cytokinin (tZck; 0.05 mM) and silymarin (Sim; 0.5 mM) on growth, yield, physio-biochemical responses, and antioxidant defense systems in Cd-stressed wheat. tZck + Sim applied as SPr + LTr was more effective than individual treatments, and the impacts were more pronounced under stress conditions. Cd stress (0.6 mM) severely declined growth and yield traits, and photosynthesis efficiency (pigment contents, instantaneous carboxylation efficiency, and photochemical activity) compared to the control. These negative impacts coincided with increased levels of Cd2+, O2•‒ (superoxide), H2O2 (hydrogen peroxide), MDA (malondialdehyde), and EL (electrolyte leakage). Non-enzymatic and enzymatic antioxidant activities, and tZck and Sim contents were also increased. However, tZck + Sim increased photosynthesis efficiency, and further boosted antioxidant activities, and contents of tZck and Sim, while minimizing Cd2+ levels in roots, leaves, and grains. The levels of O2•‒, H2O2, MDA, and EL were also minimized, reflecting positively on growth and productivity. tZck + Sim applied as SPr + LTr was highly effective in promoting antioxidants and photosynthesis machineries, minimizing oxidative stress biomarkers and Cd2+ levels, boosting tolerance to Cd stress, and improving wheat productivity under Cd stress.

Interplay of silymarin and clove fruit extract effectively enhances cadmium stress tolerance in wheat (Triticum aestivum)

“…Cd degrades chlorophyll, restricts nutrient uptake, and reduces photosynthetic activity due to Cd toxicity-induced oxidative burst and over-ROS accumulation in plant cells, leading to reducing plant performance (Alzahrani et al, 2018;Haider et al, 2022). Furthermore, Cd toxicity may decrease dry matter accumulation due to the inhibition of root growth caused by Cd accumulation at a higher rate in roots than in shoots (Ali et al, 2022;Zeshan et al, 2022).…”

“…On the other hand, CFE contains microelements that can enhance plant tolerance to drought by improving root growth and promoting nutrient uptake (Abou El-Nour, 2002). In addition,silymarin-fortified biostimulants improved crop growth and productivity by regulating adaptive mechanisms via modulation of physio-biochemical and molecular processes under Cd stress (Ali et al, 2022). Cd uptake and accumulation in plants produce ROS by substituting cofactors for basic metal ions in metalloproteins via the Fenton reaction, which destroys membrane cells via lipid peroxidation and prevents the biosynthesis of cellular molecules necessary for plant growth (Jung et al, 2021).…”

“…Silymarin is the primary bioactive substance extracted from all parts of the S. marianum; Milk thistle. plant (Ali et al, 2022). Silymarin comprises flavonolignans and a flavonoid mixture such as silibinin, silydianin, isosilychristin, isosilybin, silychristin, and taxifolin (Marmouzi et al, 2021).…”

“…Accumulating such active substance (i.e., silymarin) in plant tissues highly interacts with environmental stresses, having antioxidant properties, directly detoxifying and preventing ROS formation via inhibiting ROS production (Surai, 2015). As a result, silymarin or silymarin-fortified biostimulants have been used recently to help plants withstand environmental stresses (Ali et al, 2022). Additionally, silymarin helps maintain mitochondrial integrity and cell redox homeostasis by activating nonenzymatic and enzymatic antioxidants (Ali et al, 2022).…”

“…As a result, silymarin or silymarin-fortified biostimulants have been used recently to help plants withstand environmental stresses (Ali et al, 2022). Additionally, silymarin helps maintain mitochondrial integrity and cell redox homeostasis by activating nonenzymatic and enzymatic antioxidants (Ali et al, 2022). Under severe water stress, milk thistle (silymarin) accumulates more silymarin and related components, associated with increased enzymatic antioxidants activity and chalcone synthase gene expression, inducing drought stress tolerance (Elsayed et al, 2019).…”