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

ABSTRACT

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%-58%, branches and flower buds 21%-27%, roots 21%-32%. The corresponding figures in the case of deficient plants were leaves 49%-65%, branches and flower buds 21%-27%, roots 14%-25%. Re-utilization of K took place in the following proportions in the normal plants leaves 54%-64%, branches and flower buds 20%-21%, roots 30%-41%. In K deficient plants the figures were leaves 62%-79%, branches and flower buds 1.2%-4.4%, roots 20%-33%. In tissues formed after the initiation of flowering buds, the demand for N is met by reserves as follows normal plants fruits 20.6%-24.8%, leaves 15.6%-19.4%, twigs 19%-20.5%; deficient plants fruits 43.5%-48.5%, leaves 48.1%-51.9%, twigs 46%-53%. The K needs for new tissues are met in the order normal plants fruits 40%-45.8%, leaves 27%-37.6%, twigs 26%-33.1%; deficient plants fruits 65.7%-81.5%, leaves 52.6%-68.4%, twigs 62%-86.1%. Fruits represent the main sink for both N and K. Re-utilization of both elements is higher in the case of deficient plants.

RESUMO

A remobilização do N (15N) e do K (85Rb) de reserva e seu uso pelas diferentes partes do cafeeiro (Coffea arabica cv. Catuaí Vermelho) no período reprodutivo, particularmente pelos frutos, foram estudados sob condições normais e de carência de N ou K. O K de reserva, comparado ao N de reserva, é utilizado em maior proporção pelos frutos e demais órgãos do cafeeiro. A exportação do N pelos órgãos de reserva foi a seguinte plantas normais - folhas (47%-58%); ramos + gemas florais (20%-21%); raízes (21%-32%). Plantas deficientes - folhas (49%-65%); ramos + gemas florais (21%-27%); raízes (14%-25%). A remobilização do K de reserva ocorreu na seguinte proporção plantas normais - folhas (54%-64%); ramos + gemas florais (20%-21%); raízes (30%-41%). Plantas deficientes - folhas (62%-79%); ramos + gemas florais (1,2%-4,4%); raízes (20%-33%). Em tecidos lançados após a iniciação da gema floral, a demanda por N é coberta pelas reservas do cafeeiro com o seguinte porcentual plantas normais - frutos (20,6%-24,8%), folhas (15,6%-19,4%), ramos (19,0%-20,5%); plantas deficientes frutos (43,5%-48,5%); folhas (48,1%-51,9%); ramos (46,0%-53,0%). Para o K em plantas normais frutos (40,0%-45,8%), folhas (27,0%-37,6%), ramos (26%-33,1%); plantas deficientes frutos (65,7%-81,5%); folhas (52,6%-68,4%); ramos (62,0%-86,1%).