The isogram of the PCGA was drawn out with 0.2 contours which showed the geographical model of northeast-southwest variation trends of phenotypial characteristics of M. azedarach.

• 采用内插法在苦楝自然分布区内按0.；2表型性状梯度差值绘出等值线图，揭示出苦楝表型性状东北-西南梯度变异的地理模式。