Calcium Oxalate Crystals, the Plant 'Gemstones': Insights into Their Synthesis and Physiological Implications in Plants.

This article focuses on calcium oxalate (CaOx) crystals in plants, examining their origin, biosynthesis, regulation, and multifunctional roles. CaOx crystals are widespread biominerals formed through genetically regulated pathways involving calcium uptake and oxalate synthesis, with ascorbic acid identified as a primary precursor. Their proposed functions include bulk calcium regulation, heavy metal detoxification, plant defense against herbivory, light reflection and gathering for photosynthesis (notably through a process termed "Alarm Photosynthesis"), and excretion of excess calcium via senescing tissues. Despite extensive occurrence, many aspects of CaOx crystal metabolism, genetic control, and ecological significance remain unresolved, highlighting the need for integrative research to harness their potential in crop improvement, phytoremediation, and adaptation to climate stress.