Articles
PREDICTING STORAGE QUALITY FROM PREHARVEST FRUIT MINERAL ANALYSES A REVIEW
It is well known that many physiological disorders such as bitter pit and internal breakdown of apple are associated with too low a calcium concentration in fruit flesh (see Shear, 1975, Bangerth, 1979, Bünemann, 1980, Ferguson, 1984 for reviews). Maintenance of relatively high calcium concentrations associated with relatively low potassium concentrations in fruit tissue results in a slower rate of ripening as seen in reduced rates of respiration (Faust et al, 1972), in reduced ethylene production (Lieberman and Wang, 1982), in slower softening of fruit flesh (Bangerth et al, 1972) and in reduced lipoxygenase activity of fruit tissue (Leshem et al, 1981, Marcelle, 1988). It has also been shown that sugar content and acidity, important factors of the gustative quality of fruit, are positively correlated with the K/Ca ratio of fruit flesh (Marcelle, 1985).
Until now the role of calcium in fruit senescence is not absolutely understood.
The most logical and best documented explanations remain those based on the role of CA2+ in cell wall structure (the cross-linkage of pectic molecules) and on the role of Ca2+ in maintaining membrane integrity, ensuring the maintenance of selective permeability.
Our present knowledge does not permit to affirm that calmodulin (the best known Ca2+-binding protein) plays a role in fruit ageing but some plausible hypotheses have been presented by different authors (see reviews by Ferguson et al., 1988 and Poovaiah, 1988).
However, as in many cases in horticulture, it is not necessary to perfectly understand a phenomenon in order to use it with the aim of helping practicians.
Starting from the fact that fruit mineral content greatly influences storage it was tempting to build a practical service for giving advices on the storage quality of fruit by means of preharvest mineral analyses.
Why not of leaves ? Simply because the mineral content of a fruit is almost never significantly correlated with the mineral content of leaves.
Our practical service of fruit analysis exists since 1975 and was described earlier (Marcelle, 1984).
In this review paper it is intended to show the different systems used for sampling and analyzing fruit in different laboratories as well as the different methods recommended by authors for interpreting the analytical results in terms of storage quality.