對(duì)OJIP曲線和MR820曲線影響的比較深入解析五種光合抑制劑的生理作用機(jī)制
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DOI:https://doi.org/10.1016/j.plaphy.2020.08.044
文章亮點(diǎn)：
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文章結(jié)論：
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本研究同時(shí)比較了TeA、DCMU、Bentazone、DBMIB和MV五種光合抑制劑(除草劑)對(duì)紫莖澤蘭(Ageratina adenophora)瞬時(shí)熒光和MR820信號(hào)的影響，以期闡明它們對(duì)紫莖澤蘭光系統(tǒng)的精確影響。
1. 五種抑制劑對(duì)葉綠素?zé)晒釵JIP曲線的影響
眾所周知，DCMU是一種優(yōu)秀的經(jīng)典PSII除草劑，而TeA與DCMU相比是一種弱PSII抑制劑(Chen et al., 2007)。TeA、DCMU和Bentazone通過(guò)與D1蛋白相互作用影響初級(jí)光化學(xué)并阻斷從QA 到次級(jí)醌受體QB 的電子傳輸(Nimbal et al., 1996; Bagchi et al., 2003; Strasser et al., 2004; Chen et al., 2007)。如上圖，此三種抑制劑均增加了OJIP曲線的J-相，DCMU和Bentazone導(dǎo)致J-相快速增加接近于對(duì)照組P-相高度，并且導(dǎo)致I-P相消失；而TeA處理后J-相也明顯增加，但仍存在I-P相。
Bentazone抑制光合電子傳遞的機(jī)制尚未明確，僅提出假說(shuō)可與PSII的還原位點(diǎn)結(jié)合(Bagchi et al., 2003)。本研究結(jié)果表明Bentazone處理后J-相快速升高至P-相，表明其主要抑制QA以外的電子傳遞鏈，PSII活性反應(yīng)中心RCs閉合速率快速上升，QA被迅速還原，QA-快速積累。
L-band is known as an indicator of the grouping of the PSII units or energetic connectivity between antenna and PSII RCs (Srivastava et al., 1997; Strasser et al., 2004). |
L-峰可指示PSII不同組分間的聚集性或天線色素與PSII活性反應(yīng)中心RCs的能量傳遞連通性。
查看L-brand情況，如下圖A中上部所示，對(duì)O點(diǎn)(20μs)和K點(diǎn)(300μs)之間進(jìn)行標(biāo)準(zhǔn)化處理Wok = (Ft − Fo)/(Fk − Fo) 即可。同時(shí)以線性時(shí)間軸分析L-brand差分動(dòng)力學(xué)(下圖A底部)，即 ：
An increase of the K-step indicates the inactivation of OEC centers at the PSII donor side(Srivastava and Strasser, 1995; Srivastava et al., 1997; Strasser et al., 2004) |
| The occurrence of K-step has been observed in plants that suffer from heat or drought stress and is an indicator of the destruction of OEC(Strasser et al., 2004; Tόth et al., 2011; Chen et al., 2016). |
The maximal amplitude of WOI≥ 1 reflects the size of the pool of the end electron acceptors at the PSI acceptor side and the WIP represents the reduction rate of the end electron acceptor in PSI(Oukarroum et al., 2009; Yusuf et al., 2010). |
如上圖A\B及下圖C所示，DCMU和Bentazone處理使I~P相振幅完全消失、曲線上升半程時(shí)間升高，表明此兩種抑制劑可抑制PSI受體側(cè)末端電子受體庫(kù)，且降低其還原速率。而TeA僅降低了受體側(cè)末端電子受體庫(kù)，對(duì)其還原速率不產(chǎn)生影響。
5. 820nm調(diào)制反射動(dòng)力學(xué)曲線模型&參數(shù)
典型的820nm調(diào)制反射瞬態(tài)動(dòng)力學(xué)曲線包括從MR0(約0.7ms)到MRmin(約7ms)的快速下降階段(快相)，然后是從MRmin到MRmax(約300ms)的緩慢增加相位(慢相)。
快相反映了PC和P700的氧化狀態(tài)，可以量化為∆MRfast/MR0。慢相代表PC+和P700+的再還原狀態(tài)，表示為∆MRslow/MR0。
(Strasser et al., 2004)。MV直接從電子傳輸鏈捕獲電子，速度幾乎與PSII將其泵入鏈中的速率相同(Schansker et al., 2005)。在DCMU和MV處理的葉片中，沒(méi)有電子參與P700+和PC+的再還原，而B(niǎo)entazone和TeA不能完全阻斷通過(guò)QA到PC+和P700+的PSII電子流。
可見(jiàn)，葉綠素快速熒光動(dòng)力學(xué)OJIP曲線和MR820動(dòng)力學(xué)曲線為評(píng)價(jià)和監(jiān)測(cè)PSII和PSI活性的變化提供了方便的方法和新的思路。這兩種測(cè)量方法都清楚地顯示了植物遭受不同光合抑制劑脅迫時(shí)的敏感性和優(yōu)勢(shì)。
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