Variações sazonais na composição mineral de fôlhas de videira e efeitos do porta-enxêrto e da presença de frutos

No presente trabalho estuda-se a influência da época de amostragem, do porta-enxêrto e da presença de cacho nos ramos, sôbre a concentração dos principais nutrientes nas fôlhas de videira. As amostras de fôlhas procederam de plantas da variedade Angélica (Híbrido IAC 344-2) enxertada sôbre dois diferentes porta-enxertos, em algumas das quais havia sido notada incidência de clorose foliar. Os resultados foram obtidos para fôlhas de mesma idade fisiológica, nas diversas épocas distribuídas durante o ciclo vegetative. Os dados reafirmaram para a videira a necessidade de conhecimento da época de amostragem e do porta-enxêrto nos estudos de diagnose foliar. Não houve interferência da presença de frutos na composição das fôlhas, através do ciclo A study has been made on the changes taking place in the dry-weight composition (nitrogen, phosphorus, potassium, calcium, and magnesium) of grape leaves thoroughout the growing season. Vines of the variety Seibel 10 076 x Pirovano 54 (Angélica) budded on two different stocks were used in order to obtain additional information of rootstock influence on the inorganic composition of the scion. Leaves of a definite age were obtained for analysis. The youngest fully matured leaf was collected separately from fruiting branches and non-fruiting shoots. The levels of N and P in the leaves were maximum at blooming time and decreased fast at the fruit setting time, after which there was little change. The percentage of K was also highest at blooming time and decreased as the season progressed. The influence of rootstock on the concentration of N, P, and Mg in the leaves, has been evident only at the flowering time and on K and Ca contents during the season as a whole. Leaves from fruiting and non-fruiting branches showed about the same mineral composition all trough the season.