Pattern of berry Ca accumulation

Calcium is considered to have low phloem mobility (Welch 1986) and therefore most likely enters the berry through the xylem. The accumulation of Ca++ principally takes place during herbaceous growth of the fruit (before verai-son). During ripening, the accumulation of this cation is low to absent and depends on plant water status. Several studies have shown that Ca++ is accumulated in the berry throughout its development (Schaller et al. 1992, Ollat and Gaudillere 1996, Rogiers et al. 2000, Cabanne and Doneche 2003). However, others indicate that the accumulation of Ca++ ceases after veraison (Hrazdina et al. 1984, Possner and Kliewer 1985, Creasy et al. 1993). It appears that in grapes, as in apple fruit (Saure 2005), Ca++ accumulation patterns are variable. This may be due to seasonal differences in vapour pressure gradients and thus transpiration (Marschner 1995). Since Ca++ is carried along the transpirational stream, any environmental factor which influences the flow rate of this stream would also influence the accumulation of Ca++ into the transpiring organ. Our results suggests that the Ca++ content per berry may have a steady upward trend during post-veraison enlargement under certain conditions, e.g. non-restrictive water supply to the plant (Fig. 3b). Climatic conditions as well as soil characteristics (including moisture levels and mineral content), may also play significant role in determining nutrient translocation to the berry.

On the other hand, Ca++ concentration expressed per unit of dry matter (mg.g-1 DW) showed a quite different trend in comparison to plots of the total amounts per berry (data not shown). Between veraison and maturity, the concentration of Ca++ decreased significantly (around 35%). This decline occurred due to post-veraison accumulation rates not exceeding pre-veraison rates. In all cases, the differences between the irrigated and non-irrigated vines were not statistically significant (data not shown).

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