Studies on the mineral nutrition of the rice plant: XII. effects of the deficiencies of macronutrients on the varieties IAC-25 and IAC-47

Plantas de arroz, variedades IAC-25 e IAC-47, foram cultivadas em solução nutritiva completa e com deficiência de macronutrientes. Foram obtidos dados sobre a influência dos tratamentos na área foliar, produção de matéria seca e na composição mineral e observados os sintomas de carência. O estado nutricional das plantas deficientes em N foi também avaliado pela determinação da atividade da redútase de nitrato na folha.Rice plants, varieties IAC-25 and IAC-47 were grown in nutrient solution both in the presence and in the absence of macronutrients. Symptons of deficiency were observed in general agreement with description found in the literature. The deficiency of N affected most dry matter yield among the three major macronutrients. although the effect on grain production was greater when K was omitted. The following levels could be taken as indication of adequate nutrition when leaf samples are analysed at the boot stage (respectively) for var. IAC-25 and IAC-47): N - 4.18% and 3.54%; P - 0.36 and 0.27; K - 2.30 and 2.09; Ca - 1.22 and 1.00; Mg - 0.80 and 0.77; S - 0.24 and 0.18. Leaf nitrate reductase activity at the same physiological period correlated well both with N supply and dry matter production

Estudos sobre a nutrição mineral do arroz: X. marcha de absorção de micronutrientes pela variedade IAC-25

The uptake of micronutrients (B, Cu, Fe, Mn and Zn) by the variety IAC-25 in various phases of its development was studied, the plants being grown in nutrient solution, Main conclusions were the following: (a) only two variables, namely dry matter production an Fe accumulation, showed a tendency to level off as the plants complete their life cycle; (b) indication of internal redistribution was observed in the case of Fe and Mn; (c) maximum rate of uptake, was well as of dry matter production took place in the period which goes from tillering to grain filling.Em condições controladas estudaram-se: acumulação de micronutrientes e produção de materia seca pela variedade de arroz IAC-25. A curva que descreve a produção de matéria seca total em função do tempo apresentou a tendência a sigmóide. Com respeito a acumulação global de micronutrientes, entretanto, o mesmo foi observado somente no caso do ferro