Effects of Aluminum on the Growth of Phosphorus- or Calcium-Deficient Quercus acutissima Seedlings in Hydroponic Culture

Abstract

To determine the effect of Al on the growth of P- or Ca-deficient woody plants, 2-month-old Quercus acutissima Carr. seedlings were preliminarily cultured at pH 5.8 for 9 weeks in one of three hydroponic culture media: (A) 1/5 Hoagland medium containing complete nutrients; (B) 1/5 Hoagland medium without P; or (C) 1/5 Hoagland medium without Ca. Seedlings from each medium were then transplanted to medium containing either 0, 0.27, or 2.7 mM Al with the same nutrient conditions as the preliminary cultivation, and cultured at pH 4.0 for 6 more weeks. The seedlings were then harvested, the dry weights of plant parts were determined, and the Al, Ca and P contents in each plant part were analyzed. In the Ca-deficient medium without Al, the rate of root elongation declined within 9 weeks. However, the dry weight of new roots significantly increased after 6 weeks in the solution without Ca but with 2.7 mM Al. The biomass of both shoots and roots was low in the P-deficient medium containing 2.7 mM Al. With 2.7 mM Al, high levels of Al were detected in roots and leaves. These results indicate that the presence of P is essential for characteristic root development following Al exposure.