EFFECTS OF PHOSPHATE UPTAKE ON ROOT ARCHITECTURE OF APPLE SEEDLINGS IN WATER CULTURE

Phosphate uptake and root architecture of apple (Malus hupehensis Rehd.) seedlings at the 25 leaf stage were studied under five phosphate concentrations (0 to 10 mM phosphate) in hydroponic culture for 30 days. The length of the first order lateral roots, the number of lateral roots and phosphate absorption decreased consistently with increasing phosphate concentration. Under phosphate starvation, the number of lateral roots and the length of the first order lateral roots increased, while the proportion of thin roots was 73%. Roots of apple stock quickly reached their greatest phosphate uptake rates in 30 min. The total number of lateral roots was similar, and lower than that in P deficiency of 0.01 mM and 1.0 mM phosphate. But the length of the first order lateral roots were closer than that in phosphorus deficiency, and the portion of thin roots also increased (63%) in 0.01 mM phosphate. The length of the first order lateral root was reduced, but the proportion of thin roots also increased (64%). Apple roots reached their greatest phosphate uptake rates in 1h in 0.01 mM and 0.1 mM P. First order lateral roots became shorter and thicker in 1 mM and 10 mM P, and the roots reached their greatest phosphate uptake rates in 2h, but their overall phosphate uptake rates were lower. The results demonstrate that the capacity of phosphate uptake is improved by forming the root architecture in P-deficiency, and reached its greatest phosphate uptake rates in 30 min. While the phosphate avail¬ability changes, root architectures are altered and caused relative changes of P-uptake rates in apple seedlings. This is an adaptation to the changes of rhizosphere phosphate availability in apple trees.