大气CO_2浓度升高对香蕉光合作用及光合碳循环过程中叶氮分配的影响

Influence of elevated atmospheric CO_2 concentration on photosynthesis and leaf nitrogen partition in process of photosynthetic carbon cycle in Musa paradisiaca.

生长在高CO2 浓度 (70 0± 5 6 μl·L-1) 1周的香蕉叶片 ,其光合速率 (Pn ,μmol·m-2 ·s-1)为 5 .14± 0 .32 ,较生长在大气CO2 浓度 (35 6± 30lμl·L-1)的高 2 2 .1% ,而生长在较高CO2 浓度下 8周 ,叶片Pn较生长在大气CO2 浓度的低 18.1% ,表现香蕉叶片对较长期高CO2 浓度的驯化和光合作用抑制 .生长在高CO2 浓度的香蕉叶片有较低光下呼吸速率 (Rd) ,而不包括光下呼吸的CO2 补偿点则变幅较小 .最大羧化速率 (Vcmax)和电子传递速率 (J)分别较生长在大气CO2 浓度的低 30 .5 %和 14 .8% ,根据气体交换速率计算的表观量子产率 (α ,molCO2·mol-1光量子 ) ,生长在较高CO2 浓度下 8周的叶片为 0 .0 14± 0 .0 1,而生长在大气CO2 浓度下的为 0 .0 2 5±0 .0 0 5 .较高CO2 浓度下叶片的表观量子产率降低 44% .光能转换效率 (electrons·quanta-1)亦从 0 .2 0 3降低至0 .136 .生长在较高CO2 浓度下香蕉叶片的叶氮在Rubicos分配系数 (PR)、叶氮在生物力能学组分分配系数(PB)和叶氮在光捕组分的分配系数 (PL)均较生长在大气CO2 浓度低 ,表明在高CO2 浓度下较长期生长 (8周 )的香蕉叶片多个光合过程受抑制 ,光合活性明显降低 .

The photosynthetic rate (Pn) in leaves of Musa paradisiaca grown under elevated CO 2 concentration (700±56μl·L -1 ) for one week was 5.14±0 32μmol·m -2 ·s -1 ,22.1% higher than that under ambient CO 2 concentration,while under elevated CO 2 concentration for 8 week,the Pn decreased by 18.1%.It can be inferred that the photosynthetic acclimation to elevated CO 2 concentration and the Pn inhibition occurred in leaves of M.paradisiaca.The respiration rate in light (Rd) was lower in leaves under higher CO 2 concentration,compared with that under ambient CO 2 concentration.If the respiration in light was not included,the difference in CO 2 compensation point for the leaves of both plants was not significant.Under higher CO 2 concentration for 8 weeks,the maximum carboxylation rate(Vcmax)and electron transportation rate (J) in leaves decreased respectively by 30.5% and 14.8%,compared with that under ambient CO 2 concentration.The calculated apparent quantum yield (α) in leaves under elevated CO 2 concentration according to the initial slope of Pn/PAR was reduced to 0.014±0.010 molCO 2·mol -1 quanta,compared with the value of 0.025±0.005molCO 2·mol -1 quanta in the control.The efficiency of light energy conversion also decreased from 0.203 to 0.136 electrons·quanta -1 in plants under elevated CO 2 concentration.A lower partitioning coefficient for leaf nitrogen in Rubisco,bioenergetics and thylakoid light harvesting components was observed in plants under higher CO 2 concentration.The results indicated that the multi process of photosynthesis was suppressed significantly by a long term(8 weeks) higher CO 2 concentration incubation.