Biochemical Impact of Microplastic Exposure on Seed Enzyme Activation During Early Germination

Microplastics (MPs) constitute a pervasive environmental contaminant with demonstrable phytotoxic effects. This review synthesizes cutting-edge research (up to 2025) elucidating the specific biochemical mechanisms by which MPs disrupt critical enzymatic pathways during the highly vulnerable early germination phase (imbibition to radicle emergence). We detail how MPs, through physical interference, chemical leachates, and induction of oxidative stress, directly modulate the activity, structure, and expression of key enzymes governing metabolic reactivation (α-amylase, proteases, lipases), energy production (glycolytic enzymes, G6PDH), ROS homeostasis (SOD, CAT, APX, POD), and cell wall remodeling (expansins, XTHs). Advanced methodologies (proteomics, real-time activity monitoring, spatiotemporal mapping) reveal significant alterations in enzyme kinetics (Km, Vmax), post-translational modifications, and subcellular localization. These disruptions impair reserve mobilization, energy metabolism, antioxidant capacity, and radicle emergence, directly linking MP exposure to reduced germination percentage, rate, and seedling vigor. This work establishes MPs as potent biochemical disruptors at the seed level, with profound implications for plant establishment, agricultural productivity, and ecosystem resilience.