The rapid chlorophyll a fluorescence characteristics of different cotton genotypes reflect differences in leaf senescence*

XUE Huiyun, WANG Sufang, ZHANG Xin, ZHANG Zhiyong

The rapid chlorophyll a fluorescence characteristics of different cotton genotypes reflect differences in leaf senescence*

XUE Huiyun, WANG Sufang, ZHANG Xin, ZHANG Zhiyong**

(Henan Institute of Science and Technology / Henan Collaborative Innovation Center of Modern Biological Breeding / Henan Key Laboratory for Molecular Ecology and Germplasm Innovation of Cotton and Wheat, Xinxiang 453003, China)

Cotton; Leaf senescence; Chlorophyll a fluorescence; Photosystem Ⅱ; Rapid chlorophyll a fluorescence parameter

Cotton (spp.) has infinite reproductive properties, and is an important cash crop. Appropriate senescence can improve ?ber yield and quality of cotton by withstanding adverse weather conditions, efficiently utilizing material resources and energy during the growing season (Chen et al., 2018). Premature senescence generally leads to yield loss of about 10%, even more than 20% (Dong et al., 2005; Wright, 1999), and has been commonly in many cotton-growing countries (Dong et al., 2006; Dong et al., 2005) due to imbalance of source and sink (Wright, 1999) or poor ability to take up nutrients from soil in late season (Brouder and Cassman, 1990) and so on.

Leaf senescence can dramatically affect crop production by reducing photosynthetic capacity and influencing dry matter transfer from senescing leaves to harvestable organs (Gregersen et al., 2008; Rajcan et al., 1999; Rajcan and Tollenaar, 1999a; Rajcan and Tollenaar, 1999b). Research shows that the disassembly of the photosynthetic apparatus (PSA) within chloroplasts of plants and the electron flow that through the light reactions of photosystem Ⅱ (PSⅡ) and photosystem Ⅰ (PSⅠ) are greatly associated with the photosynthetic capacity decline (Grover, 1993; Smart, 1994; Weng et al., 2005; Wingler et al., 2004). Furthermore, it has been proved that PSⅡ is more susceptible to senescence than PSⅠ in senescent leaves (Grover et al., 1986). Kautsky and Hirsch (1931) firstly proposed the possibility using fluorescence methods for PSA analysis, because they founded there was a close relationship between chlorophyll fluorescence and primary reaction of photosynthesis.

Chlorophyll a ?uorescence (Chl F) analysis is noninvasive, fast and precise, and has been widely used for assessment of the physiological state of PSA of different species under different environment conditions (Baker and Rosenqvist, 2004; DeEll et al., 1999; Wang et al., 2016). The most commonly and widely used Chl F analyses are performed by the saturation pulse method, which uses the darkness adapted leaf samples to obtain different parameters characterizing the steady-state status of the PSA (Baker, 2008; Lazár, 2015). In the last two decades, because fast Chl F rise kinetics OJIP which showed a typical O-J-I-P phase and OJIP test analysis can capture more detailed information on the structure and function of the PSA, primarily PSⅡplant, it was developed to rapidly evaluate the physiological state of PSA in a high number of field grown plants (Goltsev et al., 2016) based on the energy flux theory in photosynthetic membranes (Strasser and Strasser, 1995). The OJIP test reflects the behavior of PSⅡ function, which includes the energy ?ow in PSⅡ and electron transport from H2O to the ?nal electron acceptors of PSⅠ (Ivanov et al., 2008; Papageorgiou, 2013). Wang et al (2016) examined the PSⅡ photochemistry by Chl F analysis in high-yield rice () ‘LYPJ’ flag leaves during senescence and found that natural senescence inhibited oxygen-evolving complex (OEC)-PSⅡ electron transport, also significantly limited the PSⅡ-PSⅠ electron flow. Paunov et al. (2018) analyzed the effect of cadmium and zinc on Chl F in durum wheat (var.) and found that both metals disturbed photosynthetic electron transport processes, which led to a 4- to 5-fold suppression of the ef?ciency of energy transformation in PSⅡ. Urbano Bron et al. (2004) used Chl F as a tool to evaluate the ripening of ‘Golden’ papaya fruit (), finding that maximal chlorophyll ?uorescence (M) and minimal chlorophyll ?uorescence (O) showed strong correlation with changes in skin color and fruit ?rmness, which suggested a relationship between the ?uorescence and the level of papaya fruit senescence. Although many researches about the Chl F parameters in senescence leaves have been reported, more detailed information describing the status of PSⅡ by the fast induced ?uorescence during leaf senescence is still unclear (Lu et al., 2002; Tang et al., 2015). And there is no report about Chl F in different cotton genotypes. In order to capture more detailed information describing the status of PSⅡ during leaf senescence and rapidly screen cotton genotypes with different duration of photosynthetic capacity, we observed the change of PSⅡ status using fast induced Chl F analysis during leaf senescence of different cotton genotypes under the same weather condition.

1 Materials and Methods

1.1 Cotton materials

Three insect-resistant transgenic cotton genotypes were used for this study. They are ‘Baimian1’, bred by Henan Institute of Science and Technology with a performance of early-maturing but slow leaf senescence (Hu et al., 2014; Wang et al., 2020); ‘DP99B’ bred by the Monsanto Company and officially registered in Hebei Province in 2000 with a performance of early-maturing and fast leaf senescence(Zhang et al., 2007; Wang et al., 2020); ‘Baimian5’ bred by Henan Institute of Science and Technology with a performance of early-maturing but middle leaf senescence.

1.2 Experimental design

A ?eld experiment was conducted at the experimental station of Henan Institute of Science and Technology in Xinxiang, Henan Province, China (35°18′N, 113°55′E). A randomized experiment was designed with three cotton genotypes and three replicates in sandy soil with pH 8.5, 6.0 g?kg?1organic matter, 18.6 mg?kg?1available nitrogen, 16.2 mg?kg?1available phosphorus, 158.5 mg?kg?1available potassium in 2012. The cotton population was 4.5×104plants?hm?2for three genotypes. Before planting the land was plowed and irrigated. The three different cotton genotypes had a conventional field management, planted in 20 April and topped in 15 July. The weather conditions of the study area were provided in Table 1.

Table 1 The weather conditions of Xinxiang, Henan, China in 2012 and from 1961 to 2011

1.3 Chlorophyll fluorescence measurements

From 20 July (after topping) to 11 October (harvest time), polyphasic Chl F transient (OJIP) of the first leaves counted from the stem top of each cotton genotypes were measured with a portable fluorometer (Handy PEA, Hansatech, UK) by according to methods of Strasser et al. (1995) in the afternoon (16:00–17:00) at approximately 20 days intervals. Each cotton genotypes contained six leaves with the similar growth condition. Before measurements, leaves were dark-adapted for 30 min. Then OJIP transient was induced by 1 second pulses of red light (650 nm, 3500 μmol?m–2?s–1). The OJIP test (Strasser et al., 2004) was used to analyze each OJIP transient. The formulae and explanation of the technical data of the OJIP curves, as well as the selected OJIP test parameters used in this study was list blow (Table 2).

1.4 Statistical analysis

Duncan test was used to determine the differences among genotypes at<0.05 with SPSS (version 22.0; IBM). Charts were generated using Excel 2003 and Origin 9.0 software (OriginLab Inc., USA). Data presented in the figures and tables are means of six biological replicates.

2 Results

2.1 Identification of photosynthetic function duration of three cotton genotypes

When the main stem nodes above the uppermost white flower at the first node of fruit branch was equal to 5, it indicates the growth and development of cotton has entered the physiological decline stage. In present study, the physiological decline periods of three cotton genotypes were basically the same between 19 July and 26 July (Table 3). ‘DP99B’ has a significantly less main stem nodes above the uppermost white flower at the first node of fruit branch than that of ‘Baimian1’ between 28 June and 19 July, indicated that the reproductive growth process of ‘DP99B’ was faster than Baimian1 in this stage.

Table 2 De?nitions of measured and calculated chlorophyll a ?uorescence parameters used in the experiment

Table 3 Main stem nodes number above the uppermost white flower at the first node of fruit branch of different cotton genotypes in 2012

Different lowercase letters in the same column indicated significant differences among different cotton genotypes at<0.05.

The performance index based on light energy absorption (PIABS) is a photosynthesis performance index that reflects the overall photosynthetic activity of PSⅡ. Therefore, the variations of PIABSinthree cotton genotypes were observed every 20 days from 21 July based on the results of the main stem nodes above the uppermost white flower at the first node of fruit branch (Table 4). There was no obvious difference in the value of PIABSin three genotypes of cotton on 21 July. With the duration of leaf senescence, PIABSdeclined gradually inthree cotton genotypes. On 10 August, obvious difference of PIABSappeared in ‘DP99B’ compared with the other cotton genotypes. Then, obvious difference of PIABScontinued in ‘DP99B’ compared with the other cotton genotypes. At last, ‘Baimian1’ decreased 57.13%, ‘DP99B’ decreased 89.66%, ‘Baimian5’ decreased 76.17% compared with the PIABSon 21 July. And obvious difference of PIABSappeared between those cotton genotypes on 11 October. These results indicated that the process of leaf senescence in three cotton genotypes were different. The senescence of leaves in ‘DP99B’ was faster than that in the other cotton genotypes. And the rate of leaf senescence in ‘DP99B’ was the fastest, then was ‘Baimian5’, ‘Baimian1’ was the slowest. Taken together, the functional period of leaf in ‘Baimian1’ was longest, ‘DP99B’ was shortest, ‘Baimian5’ was middle.

Table 4 Trends of the performance index based on light energy absorption (PIABS) with time for different cotton genotypes in 2012

Different lowercase letters in the same line at the same date indicated significant differences among genotypes at0.05.

2.2 Chlorophyll a fluorescence OJIP transient in cotton leaves of three genotypes

The state of the light-dependent photosynthetic processes in three cotton genotypes were analyzed with OJIP transient during the leaf senescence (Fig. 1). Characteristic difference existed at each phase (O?J, J?I, and I?P phase) of the OJIP fluorescence. The O?J phase denotes gradual reduction of QAwhich is the primary electron acceptor in PSⅡ. The K-phase will appear before J point when the donor site of PSⅡ is injured. The J?I phase mainly reflect the reduction of the intersystem electron carriers. The I?P phase reflects the reduction of PSⅠ electron acceptor (Strasser et al., 2004; Yusuf et al., 2010).

Compared with the fluorescence intensity on 21 July,Oincreased by 2.84%, 22.91%, 26.29% andPreduced by 4.98%, 7.15%, 23.86% respectively in ‘Baimian1’, ‘Baimian5’ and ‘DP99B’ on 11 October. These results probably indicated that the components of photosynthetic apparatus of three cotton genotypes were differently injured during the leaf senescence. And this result was accord with the above result of PIABS(Table 4).

2.3 Changes of reaction center, donor and acceptor side of PSⅡ in leaves of three cotton genotypes

More parameters involved the reaction center, electron transport at donor and acceptor sides of PSⅡ were analyzed. The variation of RC/CSOandKdemonstrate the changes in the reaction center and donor side of PSⅡ, respectively, were shown in Fig. 2. Parameters such asO,m,I,J,ando primarily re?ect changes in the acceptor site of PSⅡ were shown as a spider plot (Fig. 3).

With the duration of leaf senescence, the RC/CSOof the three cotton genotypes declined greatly before 30 August, then it increased on 20 September, which may be caused by the weather condition during late August. On the whole, the RC/CSOof the three cotton genotypes showed descending trend. It can be seen that those active reaction centers were susceptible to disruption reversibly, but the overall trends of RC/CSOwere decline with the duration of leave senescence. Compared with the highest values of RC/CSO, the RC/CSOvalues of ‘Baimian1’ ‘Baimian5’ and ‘DP99B’ on 11 October decreased by 10.37%, 7.77% and 16.75%, respectively. And different cotton genotypes had similar change on the active reaction centers during leaf senescence. The reduction of active reaction centers number of those cotton genotypes indicated that less energy was used to drive electron transport. With the duration of the leaf senescence, the trends ofKof three cotton genotypes were increasing, the values ofKchanged greatly after 10 August. At last, theKof ‘DP99B’ was significantly greater than that of ‘Baimian1’. And there were evident differences between ‘DP99B’ and ‘Baimian1’, but ‘Baimian5’ had no significantly difference with ‘DP99B’ and ‘Baimian1’ on 11 October. Compared with the value ofKon 21 July, theKon 11 October in ‘Baimian1’ ‘Baimian5’ and ‘DP99B’ increased by 18.40%, 26.95% and 38.53%, respectively. This indicated that the oxygen-evolving complex (OEC) was damaged greatly at the late growth stage, while the damaged extents of the OEC were different in three cotton genotypes even at the same growing environment.

TheJof three cotton genotypes increased during the leaf senescence. TheIof ‘Baimian1’ always increased, while theIof ‘Baimian5’ and ‘DP99B’ first increased then declined during the leaf senescence. TheJof ‘Baimian1’ ‘Baimian5’ and ‘DP99B’ increased by 27.28%, 46.57% and 45.80%, respectively; and theIof ‘Baimian1’, ‘Baimian5’ and ‘DP99B’ increased by 28.74%, 25.78% and 22.18%, respectively, on 11 October, compared with those on 21 July. It indicated that the electron transport had stronger inhibition in ‘Baimian5’ and ‘DP99B’ than that in ‘Baimian1’ at J phase. While the strength of inhibition was ‘Baimian1’ > ‘Baimian5’ > ‘DP99B’ at Ⅰ phase.

2.4 Variations of PSⅡ and PSⅠ efficiency and excitation energy dissipation in cotton leaves of three genotypes

With the duration of the leaf senescence, theΦO, ΦOand ΦOdecreased, while ΦOincreased. On 11 October, there were evident differences among those cotton genotypes in PSⅡ and PSⅠ efficiency. Among those genotypes, the range of change in energy efficiency was ‘DP99B’ > ‘Baimian5’ > ‘Baimian1’ from 20 July to 11 October. This indicated that with the cotton leaf senescence, the functional activity of PSⅡ and PSⅠ could be maintained until 11 October, accompanied the increase of the thermal dissipation quantum yield (Table 5).

Table 5 Mean values of PSⅡ reaction center numbers and energy allocation of three cotton genotypes in different days

Different lowercase letters in the same line at the same date indicated significant differences among genotypes at0.05.

3 Discussion

3.1 Senescence being reflected by PIABS and differences exist among three genotypes

Leaf senescence is an integrated response of leaf cells to age information and other internal and environmental signals, early leaf senescence may decrease yield in crop plants by limiting the growth phase (Lim et al., 2007). Senescence may differ between genotypes because the internal factors, especially the senescence related genes, and the external factors including light, temperature, water availability, carbon dioxide, nutrients and so on (Chen et al., 2018). In this paper, the three cotton genotypes enter into the senescence periods at the time between 19 July and 26 July which were proved by the main stem nodes above the uppermost white flower at the first node of fruit branch under the same environment (Table 3).

The disassembly of the photosynthetic apparatus within chloroplast and the concomitant decrease in photosynthetic activity of PSⅠ and PSⅡ, especially PSⅡ, are the most remarkable events in leaf senescence (Grover and Mohanty, 1992; Grover et al., 1986; Woolhouse, 1987). PIABSis shown to be well correlated with photosynthetic capacity which can be measured as CO2assimilation (Heerden et al., 2003; Ripley et al., 2004). PIABSis more sensitive than commonly used parameter maximum quantum yield of photosystem Ⅱ (V/M) (?iv?ák et al., 2008), very susceptible to environmental stress, so it has been used to differentiate genotypes by their responses to different abiotic stresses including natural senescence (Boureima et al., 2012; Holland et al., 2014; Kalaji et al., 2014). Chen and Dong (2016) proposed that there were three senescence performance categories including normal, premature and late senility in cotton. In this research, three genotypes showed distinctly leaf senescence differences being expressed by PIABS(Table 4), which could classify ‘Baimian1’ ‘Baimian5’ and ‘DP99B’ into late, middle and early senescence types. Furthermore, the senescence of leaves in ‘DP99B’ not only began earlier, but also expanded faster than that in ‘Baimian1’ and ‘Baimian5’ (Table 4), which was identical to the phenomenon observed at the yield level, and also explained why ‘DP99B’ usually had lower fiber yield than ‘Baimian1’ (Wang et al., 2020).

3.2 Different electron transport exist in different senescence performance

The senescence pattern which affects photosynthesis is variable and differences among cultivars with different genotypes (Falqueto et al., 2009). Anything affecting photosynthesis can affect the intensity of Chl F, so Chl F can be used as a versatile tool to sense environmental and physiological changes of plants (Guo and Tan, 2015). The shape of the fluorescence rise kinetics (OJIP) is highly dependent on the physiological conditions. In the present study, the major difference during natural senescence for different cotton genotypes occurred in the J?P phase, indicating major difference existed at the intersystem electron carriers and PS Ⅰ electron acceptors among different genotypes. Furthermore, during the leaf senescence the PSⅡ?PSⅠ electron flow was also significantly limited. Among those cotton genotypes, the variation of fluorescence intensity about ‘DP99B’ was the biggest, ‘Baimian1’ was the least, ‘Baimian5’ was the middle at the J?P phase on 11 October compared with 21 July (Fig. 1).

In order to further identify the damage site and sensitive functions during the photosynthetic electron transport within senescent leaf, we calculated several OJIP parameters. The OJIP parameters are quantitative analysis of the OJIP transient (Chen et al., 2016), helping account the different steps and phases of the OJIP transient with the redox states of PSⅡ and realize the efficiencies of electron transfer through the intersystem chain to the end electron acceptors at the PSⅠ acceptor side, concomitantly (Pollastrini et al., 2014; Tsimilli-Michael and Strasser, 2008).Kis a relative measure of inactivation of OEC. With the duration of leaf senescence, the overall trends ofKin three cotton genotypes were increasing (Fig. 2). At the same time, the inhibition of the acceptor side of PSⅡ was greater than that of the donor side, which can be proved by the bigger increase ofJandIthanKin three cotton genotypes. Among those genotypes, ‘DP99B’ had the biggest increase ofK, ‘Baimian5’ had the biggest increase ofJ, ‘Baimian1’ had the biggest increase ofI(Fig. 2 and Fig. 3).

4 Conclusion

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基于快速葉綠素?zé)晒鈪?shù)的不同基因型棉花葉片衰老研究*

薛惠云, 王素芳, 張 新, 張志勇**

(河南科技學(xué)院/河南省現(xiàn)代生物育種協(xié)同創(chuàng)新中心/河南省棉麥分子生態(tài)和種質(zhì)創(chuàng)新重點(diǎn)實(shí)驗(yàn)室 新鄉(xiāng) 453003)

棉花; 葉片衰老; 葉綠素?zé)晒? 光系統(tǒng)Ⅱ(PSⅡ); 快速葉綠素?zé)晒鈪?shù)

10.13930/j.cnki.cjea.200888

XUE H Y, WANG S F, ZHANG X, ZHANG Z Y. The rapid chlorophyll a fluorescence characteristics of different cotton genotypes reflect differences in leaf senescence[J]. Chinese Journal of Eco-Agriculture, 2021, 29(5): 870?879

S562

*This study was supported by the Program for Innovative Research Team (in Science and Technology) in University of Henan Province (21IRTSTHN023) and the National Natural Science Foundation of China (31571600, 31271648).

, E-mail: z_zy123@126.com

Nov. 17, 2020;

Feb. 20, 2021

* 河南省高校科技創(chuàng)新團(tuán)隊(duì)支持計(jì)劃項(xiàng)目(21IRTSTHN023)和國(guó)家自然科學(xué)基金項(xiàng)目(31571600, 31271648)資助

張志勇, 主要研究方向?yàn)樽魑镌耘嗌怼-mail: z_zy123@126.com

薛惠云, 主要研究方向?yàn)樽魑镌耘嗌?。E-mail: xuehy8310@163.com

2020-11-17

2021-02-20