Abstract: The study of squash seedlings’ morphological and photosynthetic physiological characteristics under different shading showed that under 60% light transmittance,their relative growth rate,net photosynthetic rate (P_n),stomatal conductance (G_s),transpiration rate (EVAP),water use efficiency (WUE),saturation steam pressure (MBR),apparent quantum yield of photosynthesis (AQY),and chlorophyll contents were higher,while the intercellular CO₂ concentration (C_i) was lower,compared with those under 20% light transmittance and CK.The seedlings under 60% light transmittance had a higher light saturation point (1 125 μmol·m^-2·s^-1) but a lower light compensation point (15.2 μmol·m^-2·s^-1).Squash seedlings under lower light intensity could endure lower concentration of CO₂,while those under higher light intensity could endure higher concentration of CO₂.Under 60% light transmittance,the malondialdehyde (MDA) and praline (Pro) contents were the lowest,while the peroxidase (POD) and catalase (CAT) activities were the highest.

Key words: economic system, environmental system, coupling coordinated degree, scissors difference, coupling degree model, Shenyang Metropolitan Area