Abstract: In order to explore the different tolerance to copper toxicity among different citrus rootstocks，and analyze the physiological responses of the citrus rootstocks seedlings under copper excess stress，180-day-old seedlings of four citrus rootstocks including trifoliate orange[Poncirus trifoliata（L.）Raf]，Ziyang Xiangcheng[Citrus junos（Sieb.）Tanaka]，red tangerine[Citrus tangerina Hort.ex Tanaka] and Shatian pomelo[Citrus grandis（L.）Osb.‘Shatianyou’] were used as materials. The plants were treated with CuSO4 solution of 1.5（control），7.5，37.5，187.5 and 937.5 mol • L-1. The results showed that the content of chlorophyll and photosynthetic capacity decreased under high concentration treatment，and the relative conductivity and MDA content of leaf cells increased significantly. The activities of SOD， POD increased. Under high concentration，the effect of rootstock on uptake and transport of K，P，Ca，Mg，Fe，Mn and Zn decreased. The high copper concentration caused the leaves to turn yellow and fall off，the roots to turn brown and short，the growth of rootstocks was blocked，and even died. The tolerance of different rootstocks to excessive copper stress was significantly different. Trifoliate orange was the first rootstock to show the decline of physiological indexes such as new leaf chlorosis，old leaf abscission，growth and photosynthetic capacity. Then，the Shatian pomelo，red tangerine，and Ziyang Xiangcheng seedlings appeared toxic symptoms in turn. The principal component analysis and subordinate function analysis were performed to evaluate the stress tolerance. The results showed that Ziyang Xiangcheng exhibited the strongest tolerance to excessive copper stress，followed by red tangerine and Shatian pomelo，and trifoliate orange was the most sensitive to excessive copper stress.

Key words: citrus, rootstock, copper toxicity, stress tolerance, physiological and biochemical indexes, mineral element