Abstract: Calculation and analysis system were established for crop gross photosynthesis measurement in climate chambers and effects of climate factor on muskmelon (Cucumis melo var. reticulatus Naud. ) canopy photosynthesiswere studied. It indicated that elevated CO₂ obviously increased gross photosynthesis ( P_gc ) ,especially under high radiation conditions. P_gc increased 30.1% and 44.6% when CO₂ concentration rose from 400 to 700 and 1 000 μmol·mol^{- 1} respectively. Elevated CO₂ also enhanced photochemical efficiency (α_c ) and maximum gross photosynthesis rate ( P_{gc, m ax} ). Temperature had high influence on P_gc also, higher temperature reduced α_c and P_{gc, max} increased under low CO₂ condition, whereas it's different when CO₂ concentration was heightened to a relative high level because of CO₂—emperature interactions effect. Temperature that maximized P_gc at different CO₂ and light conditions were calculated and determined as well in the experiment.

Key words: Muskmelon, Cucumis melo var. reticulatus Naud., Gross photosynthesis, CO₂ , Temperature