ABSTRACT
Calcium is essential for the growth and development of plants. Calcium moves in soil mostly by mass-ow, and its uptake by plants is passive and restricted to the tips of young roots with nonsuberized endodermal cell walls. Calcium is translocated in the xylem mostly through the transpiration stream. Calcium moves upward in the xylem by adsorption onto exchange sites and by chelation with organic acids in the xylem sap. High concentration of calcium in the xylem sap facilitates its movement to the shoot apex (Biddulph et al., 1961; Bell and Biddulph, 1963). Preharvest application of calcium can be applied to the soil or foliage. Application of calcium in the soil will not always increase the concentration of calcium in fruits or vegetables, because of the immobility of calcium inside the plant and competition for calcium among different plant parts. Also, calcium can take up to four years to move from the roots to the leaves or fruits (Jones et al., 1983; Yuen, 1994). Calcium can also be applied as a foliar spray or by postharvest application to the produce. When calcium is applied to fruit, it enters through trichomes, stomata, and lenticels (Scott and Wills, 1975; Glenn et al., 1985). Calcium uptake into leaves also depends on stomata channels. Transportation of calcium to nonvascular esh tissue is by diffusion through the apoplast. Stomata density also can inuence calcium uptake by fruits or leaves (Harker et al., 1989). In the European Union, there are many commercial foliar fertilizers containing various forms of calcium, but their efciency
2.1 Introduction .................................................................................................... 19 2.2 Postharvest Diseases .......................................................................................20 2.3 Physiological Disorders .................................................................................. 21 2.4 Quality and Ripening of Climacteric Fruit ....................................................23 2.5 Quality of Nonclimacteric Fruit .....................................................................26 2.6 Fresh Cuts .......................................................................................................27 2.7 Conclusions .....................................................................................................28 References ................................................................................................................29
