Resumo
Two water-culture experiments were carried out to study the absorption and the translocation of radiozinc in young coffee plants as influenced by two factors, namely, concentration of heavy metals (iron, manganese, copper and molybdenum) and method of application. Inert zinc was furnished at a uniform rate of 0.05 p.p.m.; the levels of iron supply were 0, 1.0 and 10 p.p.m.; manganese was supplied in three doses 0, 0.5, and 5 p.p.m.; copper - 0, 0.02, and 0.2 p.p.m.; molybdenum - 0, 0.01 and 0.1 p.p.m. When applied to the nutrient solution the activity of the radiozinc was 0.15 microcuries per plant. In the study of the leaf absorption, the radiozinc was supplied at the level of 0.10 microcuries per plant; in this case the material was brushed either on the lower or in the upper surface or both of two pairs of mature leaves. In both experiments the absorption period was 8 weeks. The following conclusions can be drawn: 1. Among the heavy metals herein investigated the iron concentration did not affecc the uptake of the radiozinc; by raising the level of Mn, Cu and Mo ten times, the absorption dropped to 50 per cent and even more whe compared with the control plant; however, when these micronutrients were omitted from the nutrient solution an increase in the uptake of zinc was registered only in the minus - Cu treatment. The effects of high leveds of Mn, Cu and Mo probably indicate an interionic competition for a same site on a common binding substance in the cell surface. 2. The absorption of the radiozinc directly applied to the leaf surface reached levels as high as 8 times that registered when the root uptake took place. Among the three methods of application which have been tried, brushing the lower surface of the leaves proved to be the most effective; this result is easily understood since the stomatal openings of the coffee leaves are preferentially located in the lower surface. In this treatment, about 40 per cent of the activity was absorbed and around 12 per cent were translocated either to the old or to the newer organs. 3. Data herein presented suggest that leaf sprays should be preferred - rather than soil applications - to control zinc deficiency in coffee plants when growing in field conditions.
Nota preliminar sôbre a absorção e a translocação do radiozinco no cafeeiro [Coffea arabica] cultivado em solução nutritiva* * Trabalho feito com ajuda da Fundação Rockefeller. Aprovado no 5.° Congresso Brasileiro de Ciência do Solo (Pelotas, Julho de 1955). Entregue para publicação em 30.7.1955.
J. Dal Pozzo Arzolla; H. P. Haag; E. Malavolta
Cadeira de Química Orgânica e Biológica Escola Superior de Agricultura "Luiz de Queiroz" Universidade de S. Paulo - Piracicaba
SUMMARY
Two water-culture experiments were carried out to study the absorption and the translocation of radiozinc in young coffee plants as influenced by two factors, namely, concentration of heavy metals (iron, manganese, copper and molybdenum) and method of application. Inert zinc was furnished at a uniform rate of 0.05 p.p.m.; the levels of iron supply were 0, 1.0 and 10 p.p.m.; manganese was supplied in three doses 0, 0.5, and 5 p.p.m.; copper - 0, 0.02, and 0.2 p.p.m.; molybdenum - 0, 0.01 and 0.1 p.p.m. When applied to the nutrient solution the activity of the radiozinc was 0.15 microcuries per plant. In the study of the leaf absorption, the radiozinc was supplied at the level of 0.10 microcuries per plant; in this case the material was brushed either on the lower or in the upper surface or both of two pairs of mature leaves. In both experiments the absorption period was 8 weeks.
The following conclusions can be drawn:
1. Among the heavy metals herein investigated the iron concentration did not affecc the uptake of the radiozinc; by raising the level of Mn, Cu and Mo ten times, the absorption dropped to 50 per cent and even more whe compared with the control plant; however, when these micronutrients were omitted from the nutrient solution an increase in the uptake of zinc was registered only in the minus - Cu treatment. The effects of high leveds of Mn, Cu and Mo probably indicate an interionic competition for a same site on a common binding substance in the cell surface.
2. The absorption of the radiozinc directly applied to the leaf surface reached levels as high as 8 times that registered when the root uptake took place. Among the three methods of application which have been tried, brushing the lower surface of the leaves proved to be the most effective; this result is easily understood since the stomatal openings of the coffee leaves are preferentially located in the lower surface. In this treatment, about 40 per cent of the activity was absorbed and around 12 per cent were translocated either to the old or to the newer organs.
3. Data herein presented suggest that leaf sprays should be preferred - rather than soil applications - to control zinc deficiency in coffee plants when growing in field conditions.
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AGRADECIMENTOS
Os autores agradecem: 1) ao Laboratório de Isótopos da Universidade de S. Paulo pelo fornecimento do radiozinco; 2) ao Prof. E. A. Graner da Secção de Agricultura Especial e Genética Aplicada da "Luiz de Queiroz" pelo fornecimento das mudas usadas no presente trabalho; 3) ao Sr. Vinicius Ferraz pela ajuda prestada no decorrer dos experimentos.
LITERATURA CITADA
- BIDDULPH, O., 1953 - Translocation of radioactive mineral nutrients in plants. A conference on the Use of isotopes in plant and animal research, TID-5098: 48-58.
- EPSTEIN, E. and C. E. HAGEN, 1952 - A kinetic study of the absorption of alkali cations by barley roots. Plant Physiol. 27 (3): 457-474.
- FRANCO, C. M. e H. C. MENDES, 1953 - Deficiência de microelementos em cafeeiro (Nota preliminar). Bol. Super. Serv. Café 28 (318): 19-22.
- HOAGLAND, D. R. and D. I. ARNON, 1950 - The water-culture method for growing plants without soil. California Agr. Exp. Sta., Berkeley, Calif., Circ. 347: 31.
- MALAVOLTA, E. e D. PELLEGRINO, 1954 - Estudos sôbre a distribuição do radiozinco no tomateiro (Lycopersicum esculentum) Anais E. S. A. "Luiz de Queiroz", U. S. P. (Piracicaba, E, de S. Paulo, Brasil) 11: 78-84.
- OVERSTREET, R. and L. JACOBSON, 1952 - Mechanisms of ion absorption by roots. Ann. Rev. Plant Physiol. 3: 198-206.
Datas de Publicação
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Publicação nesta coleção
28 Set 2012 -
Data do Fascículo
1956
