Current Trends in Forest Research (ISSN: 2638-0013)

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Effect of High CO2 Concentration on FourPopulusby the Fast Fluorescence Rise OJIP

RuyuXie, Mu Peng, Tao Wang, Tie Li, FanjuanMeng*

College of Life Science, Northeast Forestry University, Harbin, China

*Corresponding author:Fanjuan Meng, College of Life Science, Northeast Forestry University, Harbin 150040, China. Tel: +8618845897145; Email:

Received Date: 15 September, 2018; Accepted Date: 26 September, 2018; Published Date: 04 October, 2018

Citation: Xie R, Peng M, Wang T, Li T, Meng F (2018) Effect of High CO2 Concentration on Four Populus by the Fast Fluorescence Rise OJIP. Curr Trends Forest Res: CTFR-124. DOI: 10.29011/ 2638-0013. 100024

1.                  Abstract

Increased atmospheric carbon dioxide (CO2) concentration affects plant physiological and ecosystem processes. The aim of this study was finding out the main reasons why PSII were affected by CO2 in four different kinds ofPopulus(PopulusL.) (PopulusX, Populusdeltoides ×cathayana, Poplus alba ‘Berdinensis’ L., Populuseuramerican‘N3016’×Populusussuriensis) and the differences of responses in these four kinds of Populus. The chlorophyll fluorescence technique was considered as an effective tool in the context of non-destructive leaf photosynthetic apparatus of the degree of thermal, and has been widely used in relevant studies of CO2 stress. The JIP-test is a method for analyze the fluorescence transient which transformed the measured value to a serials biological parameters, and also detect the energy strength generated by PSII. The results show that the PSII performance was negatively influenced by CO2stress. CO2stress resulted in down-regulation of Fm, φPo(=Fv/Fm), ψEo, φEoandPItotalin all four kinds of Populus. And a significant decrease in the P-step level of the fluorescence transients OJIP curves of four Populusspecies after 7 days of treatment with high CO2. So a fast decrease of the P-step level indicated there was main change to fluorescence transients. Generally speaking, these results indicated that the main reasons why PSII were affected by CO2 were degradation of antenna pigment and inhibition of the electron transport at the acceptor side of PSII.

2.                  Keywords: Atmospheric Carbon Dioxide (CO2); Photosynthetic Performance; PopulusL.; OJIP

1.                  Introduction

Environmental changes caused by increased emissions of greenhouse gasses have influenced the stability of ecosystems worldwide[1]. The increase of atmospheric carbon dioxide (CO2) is one of the most important environmental changes in the world in the past and the future. Especially, human activities also increased the concentration of CO2 in the atmosphere, which is expected to reach 700 μL/L by the middle of the next century [2-5]. Current evidence showed the increase of CO2 concentration will influence on plant growth, development biological yield. In general, high CO2 concentrations increase photosynthetic rates, which promoted the growth

of plants. 

However, there are most reports on the response of crop plant species to elevatedatmospheric CO2, but few of them have given account of the response of woody species to high CO2 levels. In this study, we compared the effect of elevated CO2 on the growth and photosynthetic characteristics of four Populus (PopulusL.) species.

Populus spp., as poplar hybrids, belongs to a fastest-growing tree. For their rapid growth, their wood can be used for construction, pulp, paper, and as a renewable, cost-effective alternative to fossil fuels. Previous reports showed that poplars are sensitive to environmental stress compared with other tree specise[6,7]. To date, the effects of high CO2 levels on Populusphysiology and growth have been studied in numerous researches. For example, in birch, elevated CO2 treatments had no major impacts on wood anatomy or wood density [8]. Lee et al., (2014) found that the cuttings of Populus alba × glandulosaunder the elevated CO2treatment showed reduced tree height and photosynthetic pigment contents such as chlorophyll and carotenoid. In particular, the elevated treatment resulted in a marked reduction in the chlorophyll a. However, some works also showed that increased CO2 delayed leaf fall, but this effect is species-specific. However, there are few tests of whether differences in photosynthetic abilityexist between different Populusspecies in response to elevated CO2. Generally, the photosynthetic ability was reported to a reliable indirect indicator of tree performances under different environmental stress [9,10].

As a rapid and non-destructive technique, this technology is very useful to investigate the photosynthetic function, and has been used to study the effects of drought, high temperature, salt stress on plant species. Additionally, this technology has also provided valuable information on the functional and structural attributes of components involved in photosynthetic electron transport and especially to study photosystem II (PSII) behavior[11- 21]. In general, a sequence of phases (labelled as O, K, J, I, P) can be obtained in the fluorescence rise during the first second of illumination from the initial (Fo) to the maximal (Fm) fluorescence value. This mathematical model was named as JIP-test, which can provide quantum yields, biophysical parameters and probabilities characterizing structure and function of PSII [22,23]. PS is very sensitive to environmental stresses [9,10]. However, a complex study comparing influences of high CO2 levels on PSII behaviors of woody species is still lack. Therefore, a detailed comparison of high CO2-induced changes in PSII photochemistry in different Populus spp. species was carried out by using the fast Chl fluorescence records.

In our study, we have examined photosynthetic responses of fourPopulus spp. species to high CO2 levels using fast Chlorophyll (Chl) a fluorescence transient (O-J-I-P) technology. In this study, we analyzed the transient fluorescence using JIP-test in four Populusspecies (PopulusX, Populusdeltoides ×cathayana, Poplus alba Berdinensis ′ L,Populuseuramericana′N3016′ ×Populusussuriensis) under atmospheric CO2 (1500 ± 50 μmol/mol). Our objectives were to determine that whether differentPopulusspeciesvary in their PS traits under elevated atmospheric CO2.

2.                  Materials and Methods

2.1.              Plant Material and Stress Treatment

Experiments were performed at College of Life Science, Northeast Forestry University, which is located in Harbin, Heilongjiang Province. Four Populus species including PopulusX,Populusdeltoides × cathayana,Populus alba ′Berdinensis′ Land Populuseuramericana′N3016′ × Populusussuriensiswere used in the experiments.

The cuttings were planted in plastic pots (60 cm in length, 25 cm in breadth and 15 cm in depth) filled with 1.5 kg of soil and sand (2: 1). The experiments were carried out in the close gas-exchange system consisting of chambers of 300 L volume (71cm in length, 73cm in breadth and 175 cm in height). There are 10 cuttings in each pot. Potted plants were grown in the conditions: day/night air temperature, 28/22°C; photoperiod, 12h; relative humidity, 65-85%. One Chamber was kept at a CO2 concentration (average ± SD) of 370 ± 15 μmol/mol (control), while another chamber was treated with an elevated CO2 concentration of 1500 ± 50 μmol/mol (hereafter denoted as treatment). In order to study the effect of CO2 for every variety of poplar, we choose the seventh day after treatment to JIP-test in this study.We repeated the experiment three times with 10 plants in total, 10 for controls and 10 for elevated treatment.

2.2.              Chlorophyll a Fluorescence Transient Measurement and the JIP-Test

JIP - test is a method to analyze the transient fluorescence, also known as fluorescence fast dynamic research method. Measuring the curve of rising fluorspar light (FLR) (rapid fluorescence kinetics) needed very strict about equipment, and the light source for high strength of saturated excitation light (strong degrees in 3000 ~ 10000 μmol photons/(m-2 s)), starting fast, and can quickly capture the fluorescence signal.

JIP - test is an important method of analysis of fluorescence kinetics curve, the purpose of this method is to turn the parameters of the measured values into a biological significance that can direct energy intensity produced by PSII. In general, there are four important inflection point on the fluorescence fast dynamic curve, namely the O - J - I - P turning point, respectively is: 1) O point shows that the system (PSI) release amount of the fluorescent light, which can be understood as the light of the PSI and efficiency, the fluorescence intensity is at 0.02 ms (F0). 2) Fluorescence intensity at 2ms, called Fj, J inflection point reflect the reaction in the accumulation of the electron acceptor QA- to QB-, the oxidation of the Q. 3) Fluorescence intensity at 30ms calledFi.4Maximum fluorescence intensity is Fm.

Leaves were dark adapted for 30 min to ensure that all PSII RCs were in the dark adapted state with open RCs. Then chlorophyll-a fluorescence transients were recorded and digitized with the portable Handy PEA (Hansatech Instruments, Ltd., King’s Lynn Norfolk, UK) with a 12-bit resolution from 10 s to 1 s and a time resolution of 10 s for the rst 200 data points (Strasser et al., 1995). All measured and derived parameters (Table 1) are based on Strasser et al. [24,25] and Tsimilli-Michael[26].

Poplar leaves can completely cover the fluorescent clip test hole, it can measure directly. The excitation light was red light whose intensity was 3000 µmol/m2s saturated light intensity with peak wavelength of 650 nm. Fluorescent signal recording time of 10s, each group of plant test repeat 5 times.

2.3.              Date Analysis

Each experiment was conducted at least five times independently. All data presented were mean values of each treatment. Standard Errors (SE) for the values obtained were calculated. All the above data analyses were processed using SPSS17.0 Software.

3.                  Results

3.1.              Changes in Photosystem II (PS II) Under CO2 Stress

In Figure 1, four typical O-J-I-P chlorophyll fluorescence transient in leaves of untreated and treated seedlings of four Populus species are shown. To analyze changes in the shape of the transients among all Populus genotypes, All O-J-I-P transients were normalized at the O- and P-step. In four genotypes the response of treated seedlings was not similar.

In PopulusX, at the 7th day, relative fluorescence intensity was decreased (Figure 1A). Thus high CO2 conditions after long time inhibited the fluorescence intensity, especially from I- to P- step of Populus X. In Populusdeltoides×cathayana, at 7th day, relative fluorescence intensity was increased. While, relative fluorescence intensity was increased from J- to I- step (Figure 1B), which showed different changes from these genotypes in relative fluorescence intensity. In Populus alba ‘Berdinensis’ L, relative fluorescence intensity was similar between control and treatment from J- to I- step (Figure 1C). InPopuluseuramericana′N3016′ ×Populusussuriensis, an increase in relative fluorescence intensity was observed from I- to P- step (Figure 1D).

3.2.              Changes of Fluorescence Parameters Under CO2Stress

In Table 2, no significant high CO2-induced changes were observed in the minimum fluorescence (Fo), fluorescence at the J-step (Fj) and fluorescence at the I-step (Fi). In contrast, drastic decreases inF maximum fluorescence (Fm)values of fourPopulusspecies were recorded after 7 days of CO2 treatment (Table 2). In parallel, all Populus species showed significant decrease in maximum quantum yield of PSII primary photochemistry (φPo), the efficiency with which the energy of a trapped exciton is converted into electron transport beyond QA- (ψEo), the quantum yield of electron transport beyond QA(φEo) and total performance index per absorption basis (PItotal) after high CO2 treatment. Especially, PItotal value sharply decreased after treatment. On the other hand, the values of relative variable fluorescence at the J-step (Vj) and relative variable fluorescence at the I-step (Vi) of treated-plants were higher than those of controls. There is higher value in ABS/RC (measure of the average total absorbance per active PSII RC) of treated plants compared to those of control plants. However, an exception for the Populusdeltoides × cathayanaafter treatment had no difference between CO2-treated and control plants (Table 2).

4.                  Discussion

In this study, the shapes of chlorophyll a fluorescence transient (O-J-I-P) were markedly different in the four high CO2-treated leaves, however the values of Fv/Fm showed similar decreasing tendency (Table 2). Thus, there is the heterogeneous behavior of PSII in Populusleaves as similar Fv/Fm. Generally, the level of photochemical reaction can be evaluated according to the chlorophyll fluorescence intensity. And Fv/Fm was used to describe the trapping efficiency of the absorbed light, which can reduce primary quinone electron acceptor of PSII (QA) [27]. Therefore, the different fluorescence transients of leaves under high CO2 levels indicated that the photochemical reactions were different in differ Populusspecies, although there were similar decreasing Fv/Fm(reflecting trapping efficiencies of the absorbed light). In contrast, previous studies showed the Fv/Fmratio reflects the photochemical efficiency of PSII [28]. Various environmental stress can lead to inhibition of photosynthetic efficiency, accordingly, affecting state of the photosynthetic apparatus.

For O-J-I-P, point O represents the fluorescence of PS action center when all of the electron acceptor (QA, AB, PQ, etc.) are fully open in the maximum oxidation state. The fluorescence intensity of point O is connected with the content of the antenna pigment and the activity of action center. Point J reflects the rate of reduction of QA, which is connected with reaction centre pigments, light-harvesting pigment and the state of QA and QB. If the electrons transfer from QA to QB is restricted, the value of point J will rise [29]. Here, higher J value in the leaves. In addition, point I reflects the heterogeneity of PQ, the electron acceptor state in point I mainly is related to QA- and QB2-. Furthermore, the structure and function of PS complexes and the size of the PQ library is attributed to appearing time of point P. In this study, high CO2 level caused a significant decrease in the P-step level of the fluorescence transients OJIP curves of four Populus species after 7 days of treatment with high CO2. So a fast decrease of the P-step level indicated there was main change to fluorescence transients. Generally, the “P” level was connected with the process of the electron transportation from QBto PQ, and it can mark concentrations of both QAQB2− and PQH[30, 31].

No significant changes in Fo, Fj and Fiof different Populusspecies were observed when   subjected to high CO2 stress. However, high CO2stress result Fm in decrease. Fm reflects maximum fluorescence intensity at the P-step[32]. Therefore, this result suggested that the Fmmay be a good marker of PSII vitality under CO2 stress.

The PSII switches from the process of converting light energy into biochemical energy storage to the energy conversion process that transforms absorbed light energy into heat dissipation[33].One of parameters used to analyze the response of the plant’s PSII is PItotal. PItotalis sensitive to changes in either antenna properties, trapping efciency or electron transport beyond QA[34]. In this study, we found that PSII performance was represented using this index (PItotal). In general, the observed PItotalis influenced by changes in antenna, RC, electron transport and end-acceptor reduction dependent parameters. Thus, PItotalintegrates the response of RC/ABS, TRo/ABS(=Fv/Fm), ETo/TRo(= [1 −Vj]) and REo/ETo(=[1 − Vi]/[1 −Vj]).

In summary, inhibition of PSII under CO2stress involved in changes of Fm and PItotal. In other words, these two parameters can be used in indicate the changes of PSII. These results indicated that the main reasons why PSII were affected by CO2were degradation of antenna pigment and inhibition of the electron transport at the acceptor side of PSII.

5.                  Acknowledgement

This study was supported by the Fundamental Research Funds for the Central Universities (No. 2572015DA03 and No. 2572016EAJ4).

6.                  Conflict of Interest

The authors declare that there are no conflicts of interest.

Figures 1(A-D):The relative fluorescence transients in fully dark-adapted PopulusX leaves (A), Populusdeltoides×cathayanaleaves (B), Populus alba Berdinensis′ L leaves (C) and Populuseuramericana′N3016′× Populusussuriensisleaves (D) under CO2stress and the control condition at 7 days. 


Measured parameters from the chlorophyll-α fluorescence transient





Fluorescence intensity at time measured after onset of actinic



Fo= F20μs



Minimum reliable fluorescence intensity at 20μs





Fluorescence intensity at the L-step (100 μs)





Fluorescence at the K-step (300 μs)





Fluorescence at the J-step (2 ms)






Fluorescence at the I-step (30 ms)



Fp= Fm





Maximum fluorescence intensity at the P-step



Derived parameters




Selected OJIP-test parameters




Vj= (F2msFo)/ (FmFo)



Relative variable fluorescence at the J-step


Vi= (F30msFo)/(FmFo)



Relative variable fluorescence at the I-step


Mo= 4 × (F300 sFo)/ (FmFo)



Approximated initial slope per ms of the fluorescence transient



ABS/RC = [Mo/Vj] × [1/(Fv/Fm)]



Measure of the average total absorbance per active PSII RC



Quantum yields



φPo= TRo/ABS = (FmFo)/Fm= Fv/Fm


Maximum quantum yield of primary photochemistry, equal to the efficiency by which an absorbed photon trapped by the PSII RC will result in reduction of QA to QA


ψEo= ETo/TRo= (1 − Vj)


The efficiency by which a trapped exciton, having triggered the reduction of QA to QAcan move an electron further than QA into the intersystem electron transport chain


δRo= REo/ETo= (1 − Vi)/(1 − Vj)


The efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end acceptors


Performance index



PIabs= [RC/ABS] × [φPo/(1 −φPo)] × [ψEo/(1 −ψEo)]


Performance index on absorption basis, incorporating the steps from antenna, reaction center and electron transport parameters


PItotal= [RC/ABS] × [φPo/ (1 −φPo)] × [ψEo/ (1 −ψEo)] × [δRo/ (1 −δRo)]


Total performance index per absorption basis, integrates into the sum of changes in quantum yields and absorption

Table1: Formulae and explanation the technical data of the OJIP curves and the selected JIP-test parameters used in this study.



Populusdeltoides × cathayana

Poplus alba Berdinensis’ L.

Populuseuramericana“N3016”× Populusussuriensis


Measured parameters



















































Derived parameters

















































































Values of the mean ± standard error for the un-manipulated control are given. The parameters are, minimum fluorescence at 20 s, Fo; fluorescence intensity at 2 ms, Fj; fluorescence intensity at 30 ms,Fi; maximum fluorescence, Fm; relative variable fluorescence at the J-step, Vj; relative variable fluorescence at the I-step, Vi; measure of the average total absorbance per active PSII RC, ABS/RC; maximum quantum yield of primary photochemistry, φPo(=TRo/ABS); probability that a trapped exciton moves an electron into the electron transport chain beyond QA-, ETo/TRo; total performance index per absorption basis, PItotal (see also Table 1). Results are presented as mean of five individual measurements.


Table 2: The fluorescence parameters on four Populusspecies under CO2 stress.

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