02179naa a2200181 a 450000100080000000500110000800800410001910000190006024500950007926000090017452016420018365000140182565000100183965000200184965300190186970000190188877300900190712140792022-05-14       2005    bl uuuu     u00u1 u    #d1 aBALIGAR, V. C.  aAluminum influence on growth and uptake of micronutrients by cacao.h[electronic resource]  c2005  aCacao (Theobroma cacao L) productivity in tropical soils is largely determined by aluminum toxicity and inadequate supply of essential availablenutrient. However, information on micronutrient requirements by cacao in acid soils is scarce. A growth chamber experiment was conducted toevaluate soil Al saturation (0.2, 19 and 26% of CEC) effects on root and shoot growth and micronutrient uptake parameters (concentration, uptakeefficiency ratios, influx and transport) by cacao. Root and shoot growth were significantly reduced by higher soil Al saturations, however, rootgrowth was more sensitive to Al toxicity than shoot growth. Critical soil Al saturation (soil Al saturation at which 10% reduction of optimal growthis achieved) for root growth was 2% and for shoot growth it was 15%. Uptake of Cu, Fe, Mn and Zn decreased quadratically with increasing soilAl saturation in the range of 0.2 to 26% but uptake for B increased with increasing soil Al saturation. Among the micronutrients, maximum uptakewas for Mn and minimum uptake was for Cu. Micronutrient use efficiency ratio (ER, mg shoot dry wt produced/mg of element in shoot) was inthe order of Cu &gtB &gt Zn &gt Fe &gt Mn. The ER for B, Mn and Zn increased quadratically and significantly with increasing soil Al saturation. Positivequadratic relations were observed for soil Al saturation and influx of micronutrients with the exception of Fe. The transport of Cu, Fe, Mn and Znto shoots decreased quadratically with increasing soil Al saturation. Applications of micronutrients are generally required for improving yieldpotential of cacao in highly weathered tropical soils.  aAlumínio  aCacau  aTheobroma Cacao  aMicronutriente1 aFAGERIA, N. K.  tJournal of Food, Agriculture & Environmentgv. 3, n. 3/4, p. 173-177, July/Oct. 2005.