Menadiol diacetate mediated subcellular Cd accumulation and nutrients uptake alleviates Cd toxicity and increases growth and yield of summer squash

Cadmium (Cd) has shown toxicity to reduce growth and productivity in different plants. The Present study investigated the efficacy of menadiol diacetate (MD) to reduce Cd stress on growth and yield of summer squash plants. The experiment was performed under saturated Hoagland’s nutrient solution (control) while the other group was supplemented with 0.1 mM CdCl₂ (Cd stress). Surface sterilized seeds of summer squash were primed in different concentrations (10, 20 µM) of MD as well as in distilled water for 24 h and sown in the pots. Different morphological and physio-biochemical attributes were determined after 35 d of growth whereas the data for yield attributes was collected after 70 d. Cd concentration was determined in various subcellular compartments <i>i.e.,</i> cell walls and cell wall debris, chloroplast, cell membrane and other organelles including vacuoles. The Cd stress decreased photosynthetic pigments, osmoprotectants and ultimately caused reduction in the yield attributes. Further, it increased the secondary metabolites and oxidants (MDA and H₂O₂) in the summer squash tissues. Cd exposure also altered ions accumulation in the summer squash tissues by increasing the root and shoot Ca²⁺ (24–93%) and Fe (4–18%) ions while decreasing the Mg²⁺ (31–39%) ions. The MD-priming, particularly at 10 µM concentration mediated increase in the total phenolics, ascorbic acid, and anthocyanins concentration, and thus enhanced growth and yield attributes of summer squash exposed to Cd toxicity. Further, 10 µM MD-priming facilitated Cd compartmentalization in the subcellular compartments mainly in the cell wall (58%) rather than in the chloroplast (18%), cell membrane (7%) and soluble fractions (18%). In this context, cell wall and vacuole were the key compartments for Cd sequestration. This study highlights MD-priming as a potential strategy to counter Cd toxicity in summer squash plants. Schematic diagram showing the effects of MD-priming on the uptake, transport and the subcellular compartmentalization of Cd in summer squash under 0.1 mM Cd stress. The plants raised from MD-primed seed accumulated higher Cd concentration in the cell wall and vacuoles rather than in the chloroplast and membranes. The order of Cd accumulation was; cell wall &gt; vacuoles &gt; chloroplast &gt; membranes. Overall, MD-priming mitigated the Cd toxicity by compartmentalization of Cd in the metabolically less active compartments. Some subcellular compartments may serve as storage sites for Cd, helping to decrease the Cd toxicity by sequestering it away from more sensitive cellular components. The present study explains the innovative role of MD to mitigate Cd toxicity in the summer squash by decreasing its subcellular accumulation in the metabolically active compartments of the cell. The exogenous MD not only reduced Cd toxicity but also significantly enhanced growth and yield of summer squash by increasing photosynthetic pigments and antioxidative potential. MD-priming increased chlorophyll pigments and especially enzymatic antioxidants to cope with Cd stress. Exogenous MD caused accumulation of Cd mainly in the metabolically inactive subcellular compartments. Low MD level increased growth and yield attributes in summer squash irrespective of growth conditions. The results suggested MD-priming a potential strategy to counter Cd toxicity in summer squash plants.