[Effects of shading on squash seedlings' morphological and photosynthetic physiological characteristics]

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 (Pn), stomatal conductance (Gs), 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 (Ci) 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 micromol x m(-2) x s(-1)) but a lower light compensation point (15.2 micromol x 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.