Bill Shoemaker wshoemak at
Wed Aug 8 09:31:38 EDT 2001

>Marcie and Bill, if we REALLY want to get technical I believe that BER
>is caused by a lack of calcium UPTAKE, not a lack of calcium.  There
>may be adequate calcium in the soil or in the case of hydroponics,
>which is how I grow, in the nutrient solution. BUT, if the pH is off
>or the ratios among critical nutrients is out of balance, the plants
>will not be able to absorb the available calcium.

That's true. And while pH and nutrient balance are especially critical in
hydroponics, most soils have adequate nutrients and buffering capacity to
discount those issues in field production, especially when managed
organically. The reason water plays such an important role in the calcium
disorder called BER is that calcium is a large element that moves passively
through the transpiration stream in the plant. Because Ca movement is
passive, the calcium is essentially going with the flow of water. During
warm summer days crops like tomato grow rapidly and so have high need for
calcium, which is essential in all plant tissue as it plays a key role in
cell wall development (strange that we use it as morter in wall development
too). The transpiration stream goes from the roots through the plant and out
the leaf surfaces. When fruit begin growing rapidly, the demand for calcium
in the growing fruit (the leading edge is the blossom end) siphons off water
(becoming a "sink") and, by default, the calcium in the water. If water is
plentyful there is no problem. But if water is lacking, the calcium begins
to fall short. The rapidly developing tissue in the tomato fruit begins to
fall short of calcium and the cell walls begin crumbling. In other words,
the tissue just doesn't have all the ingredients and simply fails. Fungal
organisms move in for the feast and a blackened patch develops at the base
of the fruit. That's why I say that, while all the other practices might
help load the transpiration stream with calcium, the plant must have
adequate water to be able to move the calcium passively to the fruit. And in
hot temperatures, the plant cannot afford to wait. It just keeps pushing
itself to produce.

    I know this is more than two cents worth but I thought it might be
worthwhile to share this.

Bill Shoemaker
Sr Research Specialist, Food Crops
Univ of Illinois - St Charles Hort Research Center

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