Effects of localized supply of acid phosphate nitrate sulfate calcium and potassium on the production and distribution of dry matter in young maize zea mays plants

D. Jager A.

The effect of localized supply of H2PO4, NO3, SO4, Ca and K on (net) production and distribution of dry matter was studied in young plants of Z. mays L. with 4 crown roots. Roots of treated plants were divided between 2 compartments, 1 root receiving a complete nutrient solution (supplied root) and the other 3 a solution lacking 1 nutrient (non-supplied roots). In the control plants all roots received either a complete solution (+ control) or a solution lacking one nutrient (-control). Localizing the supply of a nutrient did not significantly affect the rate of dry matter production, nor the shoot/root ratio. The treatment, however, did cause a shift in the distribution of dry matter within the root system, in favor of the supplied root. Except for Ca, this effect was only temporary. The weight ratio supplied root/non-supplied root (+R1/-R1) after the period of adaptation was highest for NO3 and decreased in the order K, H2PO4, SO4, whereas for Ca +R1/-R1 still rose at the end of the experiment. This ratio is mainly determined by growth stimulation of the supplied root, the duration of the period of stimulation being not much different. Possible explanations for the differences in response are discussed in terms of differences in demand of the roots that are dependent in internal supply and differences in phloem mobility of the nutrient concerned.