Effects of 24-Epibrassinolide on the Chlorophyll Fluorescence Transient in Leaves of Pepper under Drought Stress

doi:10.7525/j.issn.1673-5102.2021.01.007

Abstract

Abstract:

In order to investigate the role of exogenous 24-epibrassinolide（EBR） in improving drought tolerance in pepper （Capsicum annuum L. cv.Chaola 9）， the chlorophyll fluorescence transient curve（OJIP） was examined in plants under drought stress（15% PEG6000）. Drought reduced the photochemical efficiency and photosynthetic performance of pepper leaves， and induced photoinhibition. Drought not only disrupted the oxygen-evolving complex（OEC）， but also impaired the PSⅡ reaction and acceptor side of PSⅡ， which inhibited the photosynthetic electron transportation. Drought decreased the number of active PSⅡ reaction centers per unit area. Drought also decreased the specific energy fluxes per unit area for absorption（ABS/CS）， trapping（TR_o/CS）， electron transport（ET_o/RC）， but increased dissipation energy fluxes per unit area（DI_o/CS）. These results indicated that drought initiated defense mechanism by decreasing the absorption and transportation of light energy by reversible deactiveation of PSⅡ， and reducing the accumulation of excess excitation energy by promoting heat dissipation. EBR treatment improved the electron transport of PSⅡ acceptor side， alleviated the drought-induced decrease of active reaction center per unit area， optimized the process of photosynthetic electron transport， maintained high heat dissipation capacity in pepper leaves under drought， and alleviated drought-induced photoinhibition. In conclusion， EBR could optimize photochemical efficiency and photosynthetic performance， and protect the photosynthetic electron transport chain and PSⅡ reaction center in pepper leaves under drought stress.

Key words: pepper（Capsicum annuum L.）, drought stress, 24-epibrassinolide, chlorophyll fluorescence transient

CLC Number:

S641.3

Wen-Hai HU, Xiao-Hong YAN, Xiao-Hong LI, Zao-Gui CAO. Effects of 24-Epibrassinolide on the Chlorophyll Fluorescence Transient in Leaves of Pepper under Drought Stress[J]. Bulletin of Botanical Research, 2021, 41(1): 53-59.

Figures/Tables 6

Table 1

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Fig. 1

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参数和公式 Parameters and formulas	参数含义 Explanation of the parameters
F_o	暗适应后的最小荧光强度
F_J	J点处（2 ms）的荧光强度
F_I	I点处（30 ms）的荧光强度
F_m	暗适应后的最大荧光强度
F_v/F_m=(F_m-F_o)/F_m	最大光化学效率
F_v/F_o=(F_m-F_o)/F_o	潜在光化学效率
V_I≡(F_I-F_o)/(F_m-F_o)	I点时的相对可变荧光强度
V_J≡(F_J-F_o)/(F_m-F_o)	J点时的相对可变荧光强度
M_o≡(F_300μs-F_o)/(F_m-F_o)	OJIP荧光诱导曲线的初始斜率
S_m≡(Area)/(F_m-F_o)	标准化后的OJIP荧光诱导曲线及y轴围成的面积
ψ_o≡ET_o/TR_o=(1-V_J)	反应中心捕获的激子中用来推动电子传递到电子传递链中超过Q_A的其它电子受体的激子占用来推动Q_A还原激子的比率
φ_Eo≡ET_o/ABS=[1-(F_o/F_m)]·ψ_o	用于电子传递的量子产额
φ_Ro=(TR_o/ABS)·(1-V_I)	用于还原PSⅡ受体侧末端电子受体的量子产额
ABS/CS≈F_m	单位面积吸收的光能
TR_o/CS=φ_Po·(ABS/CS)	单位面积捕获的光能
ET_o/CS=φ_Eo·(ABS/CS)	单位面积电子传递的量子产额
DI_o/CS=(ABS/CS)-(TR_o/CS)	单位面积的热耗散
RC/CS=φ_Po·(V_J/M_o)·(ABS/CS)	单位面积内反应中心的数量
ABS/RC=Mo·(1/V_J)·(1/φ_Po)	单位反应中心吸收的光能
TR_o/RC=Mo·(1/V_J)	单位反应中心捕获的用于还原Q_A的能量
ET_o/RC=Mo·(1/V_J)·ψ_o	单位反应中心捕获的用于电子传递的能量
DI_o/RC=(ABS/RC)-(TR_o/RC)	单位反应中心耗散掉的能量
PI_ABS=(RC/ABS)·[φ_Po/(1-φ_Po)]· [ψ_o/(1-ψ_o)]	以吸收光能为基础的性能指数

参数 Parameters	CK	EBR	D	D+EBR
LRWC（%）	91.75±0.74a	91.91±0.67a	43.04±2.22b	44.64±1.98b
F_v/F_m	0.775±0.005a	0.776±0.006a	0.698±0.008c	0.730±0.005b
F_v/F_o	3.443±0.107a	3.474±0.122a	2.327±0.091c	2.703±0.080b
PI_ABS	3.01±0.135a	2.97±0.138a	1.296±0.103c	1.975±0.109b

参数 Parameters	CK	EBR	D	D + EBR
M_o	0.592±0.031b	0.613±0.031b	0.799±0.015a	0.788±0.009a
V_J	0.337±0.010b	0.327±0.026b	0.412±0.014a	0.408±0.033a
V_I	0.742±0.014a	0.746±0.039a	0.750±0.024a	0.752±0.018a
S_m	26.1±1.3a	27.8±1.6a	23.5±1.5b	22.9±1.8b
ψ_o	0.663±0.010a	0.673±0.026a	0.588±0.054b	0.592±0.018b
φ_Eo	0.513±0.013a	0.522±0.016a	0.412±0.023b	0.433±0.027b
φ_Ro	0.200±0.006a	0.212±0.004a	0.169±0.004b	0.175±0.003b

参数 Parameters	CK	BR	D	D+BR
RC/CS	1 724±82a	1 595±79a	1 142±40c	1 364±95b
ABS/CS	3 897±70a	3 864±42a	3 158±50c	3 548±32b
TR_o/CS	3 015±73a	3 001±43a	2 208±61c	2 589±41b
ET_o/CS	1 999±76a	2 019±66a	1 304±50c	1 535±46b
DI_o/CS	876±10b	865±25b	950±11a	959±16a
ABS/RC	2.26±0.07bc	2.43±0.09b	2.76±0.05a	2.63±0.07ab
TR_o/RC	1.75±0.04b	1.89±0.07ab	1.93±0.02a	1.91±0.05a
ET_o/RC	1.16±0.01a	1.27±0.08a	1.13±0.09a	1.12±0.04a
DI_o/RC	0.51±0.02c	0.54±0.04c	0.83±0.03a	0.71±0.04b

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