Abstract:

【Objective】 The objective of the experimentis to investigate the effect of rhizosphere CO2 concentration on growth and development of muskmelon. 【Method】 By the aeroponics culture system, the effects of rhizosphere different CO2 concentration on plant growth and root nitrogen metabolism of muskmelon were studied during anthesis and fruiting periods. 【Result】 The results showed that in treatments with CO2 concentrations at 2 500 and 5 000 μL?L-1, plant growth was significantly inhibited, the content of NO3--N and NH4+-N and the activity of nitrate reductase (NR) and glutamate dehydrogenase (GDH) in root were higher than that the 350 μL?L -1 (control) at the initial stage of treatment. Moreover, the increment in treatments with 5 000 μL?L-1 CO2 was larger than that with 2 500 μL?L-1 CO2. The activity of NR decreased rapidly and then reached that in the control, NO3--N content, NH4+-N content and the activity of GDH were decreased with treatment time progressed. The soluble protein content, the activity of glutamine synthetase (GS), glutamic acid oxaloacetate transa-minase (GOT), glutamic acid-pyruvic acid transaminase (GPT),the content of total amino acid and the major part amino acid in xylem sap were decreased with the increasing rhizosphere CO2 concentration over the treatment time. 【Conclusion】 It was concluded that the uptake of nitrogen, assimilation, amino acid synthesis and transporation were inhibited in root when the rhizosphere CO2 concentration reached 2 500 μL?L-1 in fruit development period of muskmelon, which resulted the decrease of the ability of nitrogen metabolism and the level of plant nitrogen cycle.

Key words: muskmelon, rhizosphere CO2 concentration, plant growth, nitrogen metabolism