Abstract: To determine photosynthetic dynamics of pepino leaves in growth stages and photosynthetic responses to light densities and CO₂ concentrations under different fertilizations, gas exchange parameters and their diurnal changes at different growth stages, photosynthetic responses to PAR and CO₂ were measured in a greenhouse experiment employing pepino cv. Ascar as the materials. The results showed that the chlorophyll contents of the pepino leaves increased initially and then decreased during plant growth, and reached the peak at fruit developmental stage. Chlorophyll contents with organic fertilizer application were significantly higher than those without fertilizer; the chla/chlb ratio was lower than species in the same family and at mid-winter implying low light adaptability to some degree. Leaf stomatal conductance (G_s) and evaporation (Tr) increased from seedling to fruit developmental stage and then decreased, with those from fertilized plants significantly higher than those without fertilization. Leaf G_s was very significantly positively correlated with Tr(r=0.816), and significantly correlated with net photosynthetic rate (P_n, r=0.555), while Tr and P_n was not significantly correlated (r=0.415). Gas exchange parameters of pepino leaves demonstrated a sigle peak type from flowring till fruit ripening, with the peaks at around noon, no midday depression of photosynthesis was found under greenhouse condition. Leaf G_s and Pn under fertilization was higher than those from no fertilization but no significant difference was found in EVAP between two treatemnts. Photosynthetic responese to photosynthtic avaible radiation could be fitted with the modified rectangular hyperbola model, and to the CO₂ concentration with the rectangular hyperbola model. The initial quantum efficiency at fruit ripening stage was significantly higher than but the carboxylation efficiency was significantly lower than those at flowering or fruit developmental stage. The initial quantum efficiency under fertilization was significantly lower than but the carboxylation efficiency was significantly higher than those without fertilization. Light compensation point, CO₂ compensation point and CO₂ saturation point of leaves from fertilized plants were significantly lower than those from no fertilized plants, but no difference in light saturation point, maximum net photosynthetic rate, respiration rates under dark or light were found between the two treatments. The results suggest that pepino leaves have better ability to utilize high light intensity but poor capacity for low light, though they showed some weak light adaptability, and fertilization may have potential to increased low light utilization and carbon assimilation of pepino under greenhouse production.

Key words: Solanum murcatum, fertilization, photosynthesis, light response, CO₂ response