Articles
ANTAGONISM BETWEEN CALCIUM AND OTHER ELEMENTS
With intensive Ca-treatments of fruits on the tree Mr.
Cooper in our laboratory could prevent bitter pit completely.
The antagonizing influence of other ions on bitter pit development is therefore restricted to low Ca contents in the fruits and never occurs when the Ca content exceeds a certain threshold.
Considering how ions may antagonize Ca in the fruit there seem to be two possibilities.
One way how this can be achieved is the influence of different cations on Ca-uptake and -translocation in the tree thus influencing the Ca content in the fruit.
This topic will be discussed in the next chapter.
Another possibility is the antagonizing effect of these ions or organic compounds in the fruit itself and this is the subject with which I would like to deal.
The existence of such antagonizing effects was already noticed by Garman and Mathis in their classical paper, where they pointed to the fact, that the relation of Ca to Mg and possibly to potassium was more important than the Ca content alone.
The importance of this relation was emphasized many times in later reports.
Mg and K are the only ions mentioned in the literature to antagonize the function of Ca in bitter pit development.
This is certainly because they are the only ones with a concentration high enough to compete with Ca.
It is surprising that such Ca antagonizing effects do occur normally only in fruits and in a few other storage organs.
In other plant organs they can be observed only after an artificially low Ca supply in the nutrient solution.
In this case a number of cations (Na, K, Mg, H+) can antagonize the function of Ca.
The reason why this naturally happens only in fruits, is the extremely high Mg+K/Ca ratio in fruits compared to other plant organs.
This ratio is about 1–2:1 in leaves compared to 20–50:1 in fruits.
Now, where and how can antagonism between Ca and other ions occur during the development of bitter pit? This of course depends on where we see the main function