Int.J.Curr.Microbiol.App.Sci (2020) 9(10): 841-849 841 Review Article https://doi.org/10.20546/ijcmas.2020.910.100 Physiology of Calcium Nutrition in Plants Mainu Hazarika 1* and Praveen Kumar 2 1 Department of Horticulture, Assam Agricultural University, Jorhat-785 013, Assam, India 2 Department of Genetics and Plant Breeding, Lovely Professional University, Phagwara- 144 411, Punjab, India *Corresponding author ABSTRACT Introduction Calcium is a chemical element with the symbol Ca and atomic number 20. Ca is the 5 th most abundant element in the earth’s crust after oxygen, silicon, aluminium and iron and the third most abundant metal, after iron and aluminium. Ca is under Group 2 in the periodic table. Calcium is a soft grey alkaline earth metal. Calcium is an essential macronutrient in plants, with concentrations in the shoot ranging from 0.1 to over 5% of International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 9 Number 10 (2020) Journal homepage: http://www.ijcmas.com Calcium is an essential macro-nutrient in plants, with concentrations in the shoot ranging from 0.1 to 5% of dry wt.Ca 2+ is taken up by the root and transported to the shoot in a mainly apoplastic way to avoid interference with its function as second messenger. To circumvent the casparian strip, it has to enter the cytosol of the endodermal cells via channel proteins and subsequently be exported into the apoplast via Ca 2+ -ATPases or Ca 2+ /H + anti porters. H + /Ca 2+ anti porters and Ca 2+ -ATPases, which actively deliver Ca 2+ into the apoplast or intracellular stores. These channels maintain a low (Ca 2+ ) cyt in the resting (un-stimulated) cell appropriate for Cytoplasmic metabolism,restore (Ca 2+ ) cyt to resting levels following a (Ca 2+ ) cyt perturbation (stimulated). Ca 2+ contributes to the structure of cell wall, stability of cell membrane, photosynthetic reaction, photo-protection (D1 protein, PsbS regulated by Ca 2+ ), stomatal movement and pollen tube growth and elongation. Calcium sensors, including calmodulin (CaM), calmodulin-like (CML) proteins, calcineurin B-like proteins (CBL), and calcium-dependent protein kinases (CDPK) helps in Ca 2+ signaling pathway during stress and non-stress condition. Deficiency symptoms occur more often in developing tissue such as young leaves and fruits, due to low remobilization from old to young tissue via the phloem. This leads to a strong dependency of Ca 2+ supply via the xylem. Resulting physiological disorder are tip burn in lettuce or blossom end rot in tomato. Plants deficient in calcium have been shown to be more susceptible to pathogens and exogenous calcium supply in turn has been shown to improve the plant’s resistance. Conserved microbial patterns for example PAMP initiating a signaling cascade leading to induction of downstream responses of defense gene expression. Future research will shed more light on the different functions of this important nutrient and how they are interconnected. Keywords Calcium nutrition, Ca 2+ -ATPases, Apoplastic way Accepted: 07 September 2020 Available Online: 10 October 2020 Article Info