光照强度和氮素形态对棉花-丛枝菌根真菌共生体碳氮代谢的影响

Effects of Light Intensity and Nitrogen Forms on Carbon and Nitrogen Metabolism in Cotton Arbuscular Mycorrhizal Fungi Symbionts

接种丛枝菌根(Arbuscular mycorrhiza,AM)真菌可以提高棉花对氮(N)的吸收,但光照强度和N素形态对棉花-AM真菌共生体生长及碳氮(C-N)代谢的影响鲜有报道。本研究以陆地棉(Gossypium hirsutum L.)和AM真菌异形根孢囊霉(Rhizophagus irregularis)为研究对象,以不同光照强度(20%2390 lux、60%7170 lux、80%9598 lux)和总N浓度为4 mmol/L不同形态N素(硫酸铵、硝酸钾、尿素、谷氨酰胺)为试验因子,采用三室培养法和同位素示踪技术探究不同光照强度和N素处理对棉花-AM真菌共生体生长及C-N代谢的影响。研究发现硫酸铵或尿素处理下,菌根^(15)N丰度随光照强度增强而升高,说明当光照强度增强时,寄主植物可能传递更多的C给AM真菌,从而使AM真菌根外菌丝同化和转运更多的外源N(特别是含NH_(4)^(+)的N源)给寄主植物。60%与80%光照处理下,各N素处理AM真菌侵染强度均显著高于20%光照处理,但60%与80%光照处理相比,各N素处理AM真菌侵染强度无显著差异。20%和60%光照处理下,施加尿素或硫酸铵更有利于菌根化棉花N、磷(P)、可溶性糖及叶绿素的积累,80%光照处理下,施加硫酸铵对共生体N、P积累最有利,施加硝酸钾对共生体可溶性糖和叶绿素积累最有利,但与各N素组内20%光照处理对比,80%光照下,共生体N、P及叶绿素积累均有所下降。综上所述,60%光照强度,施加4 mmol/L铵态氮(NH_(4)^(+)-N)更有利于棉花-AM真菌共生体的生长发育及C-N代谢。

Inoculating arbuscular mycorrhiza(AM)fungi can improve the absorption of nitrogen(N)by cotton,but the effects of light intensity and N form on the growth and carbon and nitrogen(C-N)metabolism of cotton-AM fungal symbionts are rarely reported.In this experiment,upland cotton(Gossypium hirsutum L.)and AM fungi(Rhizophagus irregularis)were used as the research objects.Different light intensities(20% 2390 lux,60% 7170 lux,80% 9598 lux)and different forms of N(ammonium sulfate,potassium nitrate,urea,glutamine)with total N concentration of 4 mmol/L were used as the test factors,the effects of different light intensities and nitrogen treatments on the growth and C-N metabolism of cotton-AM fungal symbionts were investigated by three-chamber culture and isotope tracing techniques.The study found that under the treatment of ammonium sulfate or urea,the abundance of mycorrhizal 15 N increased with the increase of light intensity,indicating that when the light intensity increased,the host plant might transmit more C to AM fungi,thus enabling AM fungi to assimilate and transport more exogenous N(especially N source containing NH_(4)^(+))to the host plant.Under 60% and 80% light treatment,the AM fungal infection intensity of each N treatment was significantly higher than that of 20% light treatment,but there was no significant difference between 60% and 80% light treatment.Under 20% and 60% light treatment,applying urea or ammonium sulfate is more beneficial to the accumulation of N,P,and soluble sugar and chlorophyll in mycorrhizal cotton.Under 80% light treatment,applying ammonium sulfate is the most beneficial to the accumulation of symbiotic N,P and potassium nitrate is the most beneficial to the accumulation of symbiotic soluble sugar and chlorophyll.However,as compared with 20% light treatment in each N element group,the accumulation of symbiotic N,P and chlorophyll has decreased under 80% light.To sum up,applying 4 mmol/L ammonium nitrogen(NH_(4)^(+)-N)at 60% light intensity is more conducive to the growth and development of cotton-AM fungal symbionts and C-N metabolism.