根际CO_2浓度对网纹甜瓜生长和根系氮代谢的影响

【目的】探讨根际CO2浓度对网纹甜瓜生育的影响。【方法】采用雾培植株根际通CO2处理方式,在开花结果期对网纹甜瓜进行不同浓度的根际CO2处理,研究根际CO2浓度对网纹甜瓜植株生长和根系氮代谢的影响。【结果】在网纹甜瓜果实发育期间,根际2500μL·L-1和5000μL·L-1CO2浓度处理同350μL·L-1(对照)处理相比,植株生长受到明显抑制。根系硝态氮(NO3--N)含量、氨态氮(NH4+-N)含量、ATP酶活性、硝酸还原酶(NR)活性和谷氨酸脱氢酶(GDH)活性均表现出先增后降的变化趋势,且5000μL·L-1处理变化的幅度大于2500μL·L-1处理。根系中可溶性蛋白质含量、谷氨酰胺合成酶(GS)活性、谷草转氨酶(GOT)活性和谷丙转氨酶(GPT)活性在整个处理期间,均随着根际CO2浓度的升高而降低。根际高浓度CO2使根系伤流液中氨基酸的总量和大部分氨基酸的含量下降。【结论】在网纹甜瓜果实发育期间根际CO2浓度长期达到2500μL·L-1以上时,植株生长和果实发育受到抑制,根系对氮的吸收、代谢能力下降,植株氮循环水平降低。

Effects of Rhizosphere CO2 Concentration on Plant Growth and Root Nitrogen Metabolism of Muskmelon

【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.