Bermudagrass ( Cynodon ) species has been identified as a dominant plant species in cadmium (Cd)-contaminated soils. Objectives of current study were to evaluate Cd tolerance of two hybrid bermudagrass ( Cynodon transvaalensis x Cynodon dactylon ) cultivars Tifdwarf and Chuannong-3 for urban greening and slope ecological restoration and further to explore the difference in Cd tolerance associated with changes in ion absorption and distribution, antioxidant metabolism, and accumulations of phytochelatins (PCs) and metallothioneins (MTs) in roots, stems, and leaves. After exposure to equal concentration and duration of Cd stress, growth, chlorophyll content, and photochemical efficiency of both cultivars reduced significantly, but Cd-induced these inhibitory effects were more pronounced in Chuannong-3. As compared to Chuannong-3, Tifdwarf maintained significantly higher Cd concentration in roots and lower Cd concentration, bioconcentration factor, and translocation factor in aboveground parts in response to Cd stress. Each plant of Tifdwarf also accumulated more Cd in leaves, stems, and roots than each plant of Chuannong-3 due to larger biomass under Cd stress. Cd stress also significantly inhibited uptake and partitioning of iron, sodium, and potassium in two cultivars. In addition, Tifdwarf exhibited better antioxidant defense for reactive oxygen species (ROS) scavenging than Chuannong-3 under Cd stress, as reflected by higher antioxidant enzyme activities and antioxidant metabolites involved in ascorbic acid (ASA)glutathione (GSH) cycle. Tifdwarf also accumulated more PCs in leaves, stems, and roots and more MTs in leaves and stems than Chuannong-3, which could help to chelate Cd to reduce cytotoxicity of Cd. Moreover, strong antioxidant property of MTs was beneficial for maintaining ROS homeostasis in plants. Therefore, better Cd tolerance of Tifdwarf could be mainly due to the inhibition of Cd uptake and partitioning, enhanced ASA-GSH cycle, and more accumulations of PCs and MTs. Tifdwarf showed better potential for Cd remediation or urban greening in Cd-polluted soils.

Soil cadmium (Cd) contamination poses a significant threat to global food security and the environment. Astaxanthin (AX), a potent biological antioxidant belonging to the carotenoid group, has been demonstrated to confer tolerance against diverse abiotic stresses in plants. This study investigated the potential of AX in mitigating Cd-induced damage in wheat seedlings. Morpho-physiological, ultrastructural, and biochemical analyses were conducted to evaluate the impact of AX on Cd-exposed wheat seedlings. Illumina-based gene expression profiling was employed to uncover the molecular mechanisms underlying the protective effects of AX. The addition of 100 mu M AX alleviated Cd toxicity by enhancing various parameters: growth, photosynthesis, carotenoid content, and total antioxidant capacity (T-AOC), while reducing Cd accumulation, malondialdehyde (MDA), and hydrogen peroxide (H 2 O 2 ) levels. RNA sequencing analysis revealed differentially expressed genes associated with Cd uptake and carotenoid metabolism, such as zinc/iron permease (ZIP), heavy metal-associated protein (HMA), 3 -beta hydroxysteroid dehydrogenase/isomerase (3-beta-HSD), and thiolase. These findings suggest that AX enhances Cd tolerance in wheat seedlings by promoting the expression of detoxification and photosynthesis-related genes. This research offers valuable insights into the potential use of AX to address Cd contamination in agricultural systems, highlighting the significance of antioxidant supplementation in plant stress management.