Studies on mineral nutrition of the coffee plant (Coffea arabica L. cv. Catuaí Vermelho): LXIV. Remobilization and re-utilization of nitrogen and potassium by normal and deficient plants

RESUMO

Remobilization and re-utilization of 15N and 85Rb labelled nitrogen and potassium reserves for new growth and fruit formation was studied under greenhouse conditions using both normal and deficient young coffee plants. It was found that K reserves are used in higher proportion than is stored N by fruits and other organs. The export of N by organs of residence in the normal plants obeyed the following proportions of the total leaves 47 percent-58 percent, branches and flower buds 21 percent-27 percent, roots 21 percent-32 percent. The corresponding figures in the case of deficient plants were leaves 49 percent-65 percent, branches and flower buds 21 percent-27 percent, roots 14 percent-25 percent. Re-utilization of K took place in the following proportions in the normal plants leaves 54 percent-64 percent, branches and flower buds 20 percent-21 percent, roots 30 percent-41 percent. In K deficient plants the figures were leaves 62 percent-79 percent, branches and flower buds 1.2 percent-4.4 percent, roots 20 percent-33 percent. In tissues formed after the initiation of flowering buds, the demand for N is met by reserves as follows normal plants fruits 20.6 percent-24.8 percent, leaves 15.6 percent-19.4 percent, twigs 19 percent-20.5 percent; deficient plants fruits 43.5 percent-48.5 percent, leaves 48.1 percent-51.9 percent, twigs 46 percent-53 percent. The K needs for new tissues are met in the order normal plants fruits 40 percent-45.8 percent, leaves 27 percent-37.6 percent, twigs 26 percent-33.1 percent; deficient plants fruits 65.7 percent-81.5 percent, leaves 52.6 percent-68.4 percent, twigs 62 percent-86.1 percent. Fruits represent the main sink for both N and K. Re-utilization of both elements is higher in the case of deficient plants.