Causes Of Calcium Uptake From Foliar Application

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Calcium Uptake from Foliar Application
Foliar Ca2+ application has been suggested to increase the fruit-Ca2+ supply that may, in turn, reduce fruit-Ca2+ deficiency disorders. Spraying with Ca2+- solution reduces Ca2+-deficiency injury in plants (Kleemann 2000b) e.g. foliar Ca2+-spray reduces BER incidence of tomato (Schmitz-Eiberger, Haefs, and Noga 2002) ; spraying of 0.5% solution of ‘Calciogreen’ in glasshouse completely prevents BER incidence of bell pepper variety ‘Cecil’ though the fruit mass was reduced(Parađiković et al. 2004) ; spraying of young tomato with CaCl2 limits the development BER (Schmitz-Eiberger, Haefs, and Noga 2002); spraying of celery with CaCl2 or Ca(NO3)2 completely control blackheart (Geraldson 1952, 1954).
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However, direct application of Ca2+ can reduce the symptoms of Ca2+-deficiency disorder but does not remove them completely (Ferguson and Watkins 1989) and exogenous Ca2+ may not bound with the cell structure tightly that leads to easy leakage of it (Ferguson and Watkins 1983).

Calcium Translocation within Plant
Soil solution Ca2+ enters the root apoplast with mass flow of water (Barber 1995) and is transported to the xylem via apoplastic or symplastic pathways (White and Broadley 2003). Apoplastic pathway consists of cell wall and intercellular spaces where Ca2+ moves with water passively across the gradient of water potential (Karley and White 2009; White 2001). Symplastic pathway consists of cytoplasm where Ca2+ moves from cell to cell through plasmodesmata (Karley and White 2009; White 2001). Tight regulation of cytosolic Ca2+ at a very low concentration (0.1-0.2 μM) implies that apoplastic pathway is the main route of Ca2+ translocation across the root cortex (White and Broadley 2003; Taylor and Locascio 2004; Karley and White 2009). However, presence of Casparian strip at the root endodermal cells prevents further movement of Ca2+ towards the xylem. The Casparian strip prevents apoplastic movement of solutes (Clarkson 1993; White 2001) and suberization restricts the movement of Ca2+ into the endodermal cells(Moore et
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