Untapped potential of calcium and nano-calcium to develop abiotic stress resilience in photosynthetic machinery: The primary source of plant food and fuels

• Plant growth and development require calcium as a necessary ingredient in both non-stressed and stressed environments. • Nanotechnology offers innovative approaches to enhance photosynthetic activity and increase crop yield. • Cutting-edge applications of NPs in agriculture are explored, focusing on their role as protective messenger for nutrient management and stress mitigation. • Calcium and nano-calcium mitigate environmental harm from abiotic stresses. Photosynthesis is a special mechanism that has formed life on earth and created the conditions for all known life. The function of calcium (Ca) as a secondary messenger in plants has been the subject of substantial research in recent decades. Due to their sessile nature, plants are subject to a variety of abiotic stresses, such as pesticide pollution, heavy metals, salt, drought, nutrient deficiencies, light intensity, and severe temperatures. Abiotic stresses mainly lower plants' photosynthetic efficiency because they have detrimental effects on gas exchange parameters, electron transport processes, photosystem performance, and chlorophyll production. The decline in photosynthetic capacity of plants due to these stresses is directly associated with reduction in yield. Therefore, detailed information of the role of calcium (Ca) and nano-Ca on photosynthetic machinery and better understanding of the photosynthetic machinery could help in developing new strategies with higher yield even under stressed environments. Interestingly, in this review, we provide an overview of insight into mechanism affecting photosynthesis under abiotic stresses. The present review explains how several abiotic stressors can negatively affect the photosynthesis mechanism and Ca and nano-Ca mediated-regulation in plant photosynthesis. The review also highlights the advantages of using nano-Ca to increase photosynthetic efficiency.