Abstract: The aerial roots of Chlorophytum comosum were planted in water to grow hydroponic roots to study the negative phototropism performance and mechanism and its regulation.（1）All the adventitious roots and their branch roots bent away from light，the maximum curvature maybe 88.5°.（2）Photo perception site was root cap. The curvature was increasing when light intensity ranged from 0 to 110 μmol ? m-2 ? s-1. Blue-violet light induced the negative phototropism prominently while red light had no effect.（3）The negative phototropism curvature could be promoted by exogenous CaCl2，but inhibited by exogenous LaCl3，meanwhile，exogenous CaCl2 could relieve the inhibiting effect of LaCl3.（4）Unilateral light induced horizontal transport of IAA from the irradiated side to the shaded side which resulting in the unequal distribution of IAA in the both sides that led to the formation of negative phototropism. The horizontal transporting of IAA was promoted exogenous Ca2+ but inhibited by exogenous La3+.

Key words: Chlorophytum comosum, root, hydroponics, negative phototropism, mechanism；regulation