光强和氮素对芒萁光响应及叶绿素荧光参数的影响

Light response and chlorophyll fluorescence parameters in Dicranopteris dichotoma with light intensity and nitrogen treatments

以亚热带森林退化植被“标志种”之一的芒萁Dicranopteris dichotoma为研究材料,采取盆栽控制实验,设置不同光强[透光率35.96%(L1)、13.00%(L2)和4.75%(L3)]和氮素水平[施氮(N1)和不施氮(N0)],探究盆栽芒萁对光强和氮素的光响应,分析叶绿素荧光参数变化。结果表明:光强对光响应特征参数有显著影响(P<0.05)。未施氮组,L2处理下盆栽芒萁最大净光合速率(Pnmax)、光饱和点(PLS)最大,光补偿点(PLC)、暗呼吸速率(Rd)和表观量子效率(AQY)最小;施氮提高了3种光强下盆栽芒萁的Pnmax,但差异不显著(P>0.05)。未施氮组,净光合速率(Pn)和蒸腾速率(Tr)大小变化顺序为L2>L1>对照>L3,气孔导度(GS)为L1>对照>L3>L2,施氮组均为L1>L2>L3;2种氮素水平下,胞间二氧化碳浓度(Ci)大小顺序均为对照>L1>L2>L3。未施氮组,叶绿素a、叶绿素b、总叶绿素及类胡萝卜素随光强减弱而增加,叶绿素a/b随光强减弱而降低,且差异显著(P<0.05)。L1光强下光合色素质量分数施氮组显著高于未施氮组(P<0.05),其他光强下施氮组均降低。未施氮组盆栽芒萁叶绿素荧光参数随光强增加而下降;施氮组盆栽芒萁的初始荧光(F0)显著低于同等光强未施氮组,最大荧光(Fm)L1和L3光强低于未施氮组,L2则高于未施氮组;PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/F0)和以吸收光能为基础的性能指数(Piabs)L1和L2光强高于未施氮组,但差异不显著。由此认为:施氮一定程度上提高各光强盆栽芒萁的净光合速率,有利于缓解强光光抑制作用,但不利于L2和L3光强下光合色素的提高。

This study was conducted to determine the photo-response and chlorophyll fluorescence parameters of potted Dicranopteris dichotoma for different light intensities and nitrogen application.Using one of the“marker species”of degraded vegetation in subtropical forests as the research material.Pot experiment were conducted to design with six treatments of different light intensities,including transmittance 35.96%(L1),13.00%(L2)and 4.75%(L3),and nitrogen level,including nitrogen(N1)and without nitrogen(N0).All-light was used as control.The photosynthetic-light curve,photosynthetic characteristic parameters,gas-exchange,chlorophyll a fluorescence parameters and photosynthetic pigments were measured three times for each treatment.Results showed that:(1)Without nitrogen application,for L2,Pnmax and PLS were highest;PLC,Rd,and AQY were least.(2)For N0 application,the order of Pn and AQY was L2>L1>ck>L3,Gs was L1>ck>L3>L2;for N1 application the order of Pn,AQY and Gs was L1>L2>L3.For N1 and N0,the order of Ci was ck>L1>L2>L3.(3)For N0,under L2 and L3 light intensity,chlorophyll a,chlorophyll b,total chlorophyll content and carotenoids were significantly higher than those under L1 and ck(P<0.05),and the overall performance increased with the decrease of light intensity.Chlorophyll a/b significantly decreased with a decrease in light intensity(P<0.05).For the same light intensity,the content of photosynthetic pigments in the N application group was significantly higher than that in the non-N application group under L1 light intensity(P<0.05),and significantly higher than that in other treatments(P<0.05).(4)Except for L1 in N0 group,Fo and Fm under other light intensities were significantly different and increased with the decrease of light intensity(P<0.05),the Fv/Fm of ck was significantly lower than that of other light intensities(P<0.05).Compared with the N0 group,Fo decreased significantly,Fm of L3 decreased significantly,Fv/Fo and Piabs of L2 increased significantly(P<0.05).In a word,under full light,the photos-inhibition of potted D.dichotoma is the most serious.N can improved the net photosynthetic rate of potted D.dichotoma to a certain extent,increased heat dissipation and alleviated the photo-inhibition,but it is not conducive to the improvement of photosynthetic pigments of L2 and L3.