The key role of cyclic electron flow in the recovery of photosynthesis in the photobiont during rehydration of the lichen Cladonia stellaris
- Author:
- Wang S., Li W., Wufuer R., Duo J., Pei L. & Pan X.
- Year:
- 2023
- Journal:
- Plants
- Pages:
- 12(23): 4011 [14 p.]
- Url:
- https://doi.org/10.3390/plants12234011
Lichens are poikilohydric organisms and an important part of the ecosystem. They show
high desiccation tolerance, but the mechanism of dehydration resistance still needs to be studied.
The photosynthesis recovery of the photobiont in rehydrated lichen Cladonia stellaris after 11-year
desiccation was investigated by simultaneously monitoring both photosystem I and II (PSI and PSII)
activities. The responses of the photochemical efficiency and relative electron transport rate (rETR) of
PSI and PSII, and the quantum yield of the cyclic electron flow (CEF) were measured using a DualPAM-100 system. PSI recovered rapidly, but PSII hardly recovered in C. stellaris during rehydration.
The maximal photochemical efficiency of PSII (Fv/Fm) was generally very low and reached about
just 0.4 during the rehydration. These results indicated that PSII had restored little and was largely
inactivated during rehydration. The quantum yield of PSI recovered quickly to almost 0.9 within 4 h
and remained constant at nearly 1 thereafter. The results showed that the activation of the CEF in the
early stages of rehydration helped the rapid recovery of PSI. The quantum yield of the CEF made up
a considerable fraction of the quantum yield of PSI during rehydration. A regulated excess energy
dissipation mechanism and non-photochemical quenching (NPQ) also recovered. However, the small
extent of the recovery of the NPQ was not enough to dissipate the excess energy during rehydration,
which may be responsible for the weak activity of PSII during rehydration. The results indicated
that both CEF and NPQ were essential during the rehydration of the photobiont in C. stellaris. The
methods used in the measurements of chlorophyll a fluorescence and P700+ absorbance changes
in this study provided a speedy and simple way to detect the physiological characteristics of the
photobionts of lichen during rehydration. This work improves our understanding of the mechanism
behind lichen’s desiccation tolerance.
Keywords: P700+ absorbance; chlorophyll a fluorescence; photosystem I; photosystem II; cyclic
electron flow; non-photochemical quenching; rehydration; lichen.
- Id:
- 35957
- Submitter:
- zpalice
- Post_time:
- Wednesday, 29 November 2023 22:00