INTERACTION BETWEEN NUTRIENT UPTAKE AND PHOTOSYNTHESIS

Calcium deficiencies are not necessarily alleviated by raising soil calcium levels. Activity of the plant in uptake and translocation of calcium is crucial for accumulating sufficient quantities of this element. Kirkby (1979) reviewed the factors important in maximizing calcium uptake by plants. He reviewed the literature dealing with calcium uptake through the free space pathway (the apoplast) which requires continuously growing roots to always have root segments available for calcium uptake. He pointed to soil factors, such as low temperature, inadequate aeration, poor nutrient status or high hydrogen-ion concentration, which inhibit root growth and also inhibit calcium uptake. Light has also been reported to be a factor in calcium uptake (Kasztori, 1969; Scheidecker and Andropoulos-Remand, 1971). Light may influence the uptake of calcium by influencing photosynthesis.

It is well known that a wide variety of plants, if forced to grow fast, will develop more calcium-related disorders (Shear, 1975; Cox, McKee and Dearman, 1976). Fast-growing plants apparently partition the products of photosynthesis in such a way that the carbohydrate supply received by the root is insufficient for a high rate of calcium uptake. It is immaterial whether the high rate of growth is induced by pruning or by high nitrogen fertilization (Kirkby, 1979). Recent work with photosynthetic inhibitors has indicated that decrease in photosynthetic activity (Sharma, Ferree and Hartman, 1977) may also severely inhibit root growth and calcium uptake (Faust and Korcak, 1979). Thus the role of photosynthesis in calcium uptake is strongly implicated. This work has been undertaken to evaluate the importance of photosynthesis in root growth and/or in calcium uptake.