Abstract: To understand the morphological and physiological regulation effects of exogenous spermine (Spm) on Toona ciliata Roem. seedlings under drought stress, twoyearold potted seedlings of T. cilliate were adopted as experimental materials, and a drought stress and exogenous Spm regulation experiment was carried out under rain shelter by combining persistent drought stress with soil moisture measurement. The experiment contained 4 drought stress treatments: control (relative soil water content 45%-50%, watering  to saturation state of soil moisture every day, CK), mild (relative soil water content 30%-38%, persistent drought for 7 days), moderate (relative soil water content 25%-30%, persistent drought for 14 days), and severe (relative soil water content 20%-25%, persistent drought for 21 days). Afterwards, spraying Spm (1 mmol·L^-1) was applied to the seedlings after the mild, moderate, and severe drought treatments for 3 consecutive days, then the seedlings were normally managed for 5 days. The repair effect of exogenous Spm on morphological damage in plants under severe drought stress was much lower than those under mild and moderate drought stress. There were extremely significant differences in leaf relative water content and leaf chlorophyll content among CK, droughtstress treatment (either mild, moderate or severe) and Spm regulation treatment (P<0.01). There was extremely significant difference in leaf relative conductance among CK, moderatedroughtstress treatment (or severedroughtstress treatment) and Spm regulation treatment (P<0.01). Differences in leaf MDA content and POD content were significant (P<0.05) among CK, milddroughtstress treatment and Spm regulation treatment and they were extremely significant among CK, severedroughtstress treatment and Spm regulation treatment (P<0.01). The proline content was extremely significantly different among CK, severedroughtstress treatment and Spm regulation treatment (P<0.01). Therefore, we could conclude that 1 mmol·L^-1 exogenous Spm treatment could repair the morphological and physiological damages of T. ciliata seedlings under drought stress and promote the drought resistance ability, and such effects were more obvious in plants under mild and moderate drought stress.

Key words: EM compost, community composition, biodiversity., micro- and medium-sized soil fauna, black soil, farmland ecosystem