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.e., 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 > vacuoles > chloroplast > 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, helpi