The leaves were divided into four classes according to their positions: stem leaves, top sympodial leaves, middle sympodial leaves, lower sympodial leaves.

• 2）氮素营养缺乏会引起整体叶片的叶绿素、可溶性蛋白质含量大幅度下降，丙二醛含量升高，加速了叶处的衰老进程。