Effect of zinc application on tryptophan synthesis, total amino acids and total soluble proteins of leaves of coffee seedlings

Avaliou-se, neste trabalho, o efeito da aplicação de Zn via foliar na síntese de triptofano, aminoácidos totais e proteínas solúveis totais em mudas de cafeeiro (Coffea arabica L.). Cultivaram-se as mudas em solução nutritiva sem Zn durante quatro meses e após esse período, pulverizaram-se as plantas com ZnSO4.7H2O a 0,6 %, definindo-se os tratamentos segundo a posição de aplicação (basal: 6 pares de folhas inferiores, ou apical: 6 pares de folhas superiores, além dos ramos plagiotrópicos). As plantas foram coletadas nos tempos: 0 (testemunha), 12, 24, 48 ou 72 h após aplicação de Zn, separando-se as folhas da região apical, basal e dos ramos plagiotrópicos. Determinaram-se as concentrações foliares de triptofano, aminoácidos totais e proteínas solúveis totais. Pelos resultados, observou-se redução na concentração de triptofano e aumento na concentração de aminoácidos totais e proteínas solúveis totais após a pulverização com Zn.An experiment was conducted aiming to evaluate the effect of the application of Zn on tryptophan synthesis, total amino acids and total soluble proteins of leaves of coffee seedlings (Coffea arabica L.). The seedlings were grown in nutrient solution without Zn for a four-month period. After that time treatments were applied. The plants were sprayed with 0.6 % ZnSO4.7H2O in three different regions (basal: 6 pairs of lower leaves; apical: 6 pairs of upper leaves; and plagiotropic branches). The plants were harvested at times: 0 (control), 12, 24, 48 or 72 h after application of Zn. The leaves were then separated into lots taken from the basal as well as from the plagiotropic branches. These were analysed for tryptophan, concentration, total amino acids and total soluble proteins. From the results obtained a reduction in the tryptophan concentration was observed following Zn application together with an increase in the concentration of total amino acids and total soluble protein