Abstract:Response of pepper (Capsicum annum) seedlings growing at different N concentrations to varying low temperature was investigated. The seedlings of three pepper varieties grown in pot-culture at three N concentrations including 0.00, 2.00, and 3.00g?L-1 urea at 22.0-28.0℃ were transferred to climate chambers (12h light/12 h dark with light intensity of 350 μ mol?m-2?s-1 ) respectively. These seedlings were grown with 3 low temperature grades in chambers until the 4 leaves with one bud stage. Subsequently, there were significant difference in damage responded low temperature among three pepper varieties seedlings, which were grown at a same low temperature grade. Honglong showed the highest damage degree, followed by Shiqiang 206, and Zhongjiao No.4. In particular, the pepper seedlings at varying N levels were injured severely after 3 days at low temperature stress of 11.0/5.0℃. Significant differences in all of physiological index tested were observed between treatment and control seedlings. It appeared from the results that damage degree of the seedlings under low temperature stress varied with varieties and N concentrations. The lower N concentration was, the more severely injured. However, after 3 days at low temperature stress of 15.0/9.0℃ (Ⅰ) or 13/7℃（Ⅱ）the pepper seedlings injured differently depending on varieties and N concentrations as well, differences with CK of all tested physiological index were reduced significantly, and could recover at 22.0-28.0℃ for the following 6 days, the higher N concentration, the better recovered. It could be concluded that N concentrations impacted the responses of pepper seedlings to low temperature. The higher concentration (3.00g?L-1 urea) should enhanced pepper seedlings anti-low-temperature ability. Though the higher N concentration could mitigate the low temperature injuries on pepper seedlings, it couldn′t entirely offset the low temperature effects.