Limits...
High-susceptibility of photosynthesis to photoinhibition in the tropical plant Ficus microcarpa L. f. cv. Golden Leaves.

Takahashi S, Tamashiro A, Sakihama Y, Yamamoto Y, Kawamitsu Y, Yamasaki H - BMC Plant Biol. (2002)

Bottom Line: We compared the response of photosynthetic activities to strong light between GL and its wild-type (WT, Ficus microcarpa L. f.).In contrast, WT did not show any substantial changes of Fv/Fm values throughout the day (between 0.82 and 0.78).We conclude that the photosynthetic apparatus of GL is more highly susceptible to photoinhibition than that of WT.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, Okinawa, Japan. takahashishunichi@hotmail.com

ABSTRACT

Background: The tropical plant Ficus microcarpa L. f. cv. Golden Leaves (GL) is a high-light sensitive tropical fig tree in which sun-leaves are yellow and shade-leaves are green. We compared the response of photosynthetic activities to strong light between GL and its wild-type (WT, Ficus microcarpa L. f.).

Results: Field measurements of maximum photosystem II (PSII) efficiency (Fv/Fm) of intact sun-leaves in GL showed that photo synthetic activity was severely photoinhibited during the daytime (Fv/Fm = 0.46) and subsequently recovered in the evening (Fv/Fm = 0.76). In contrast, WT did not show any substantial changes of Fv/Fm values throughout the day (between 0.82 and 0.78). Light dependency of the CO2 assimilation rate in detached shade-leaves of GL showed a response similar to that in WT, suggesting no substantial difference in photosynthetic performance between them. Several indicators of photoinhibition, including declines in PSII reaction center protein (D1) content, Fv/Fm value, and O2 evolution and CO2 assimilation rates, all indicated that GL is much more susceptible to photoinhibition than WT. Kinetics of PAM chlorophyll a fluorescence revealed that nonphotochemical quenching (NPQ) capacity of GL was lower than that of WT.

Conclusion: We conclude that the photosynthetic apparatus of GL is more highly susceptible to photoinhibition than that of WT.

Show MeSH

Related in: MedlinePlus

Yield of PSII (A, D), 1-qp reflecting the reduction state of the qa pool (B, E), NPQ (C, F) in shade-leaves of WT (•, blue) and GL (Δ, red). Each measurement was made after the exposure of leaves to actinic light for 3 min at different intensities (A-C). In D, E and F, high light (2300 μmol m-2 s-1) was used as actinic light to record time courses of Yield (D), 1-qP (E), and NPQ (F). Points are presented as the means of 5 (A-C) or 3 (D-F) separate measurements ± SEM.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC102767&req=5

Figure 5: Yield of PSII (A, D), 1-qp reflecting the reduction state of the qa pool (B, E), NPQ (C, F) in shade-leaves of WT (•, blue) and GL (Δ, red). Each measurement was made after the exposure of leaves to actinic light for 3 min at different intensities (A-C). In D, E and F, high light (2300 μmol m-2 s-1) was used as actinic light to record time courses of Yield (D), 1-qP (E), and NPQ (F). Points are presented as the means of 5 (A-C) or 3 (D-F) separate measurements ± SEM.

Mentions: When plants are exposed to high-light that exceeds the capacity of photosynthesis, excess absorbed light energy can be safely dissipated as heat [22]. This energy dissipation can be measured as the NPQ of PAM chlorophyll a fluorescence analysis. NPQ includes the quantum yield of PSII as an index of heat energy dissipation, photoinactivation of PSII and distribution of photon acceptance between PSII and PSI due to the state transition. It is known that the sate transition can be controlled by the redox state of QA[23], which can be measured as 1-qP. Figure 5 shows that there is no significant difference between GL and WT in yield and 1-qP values. Furthermore, measurements of the electron transport rate (ETR) showed essentially no difference in the sensitivity of PSII photoinactivation between GL and WT (data not shown). However, GL showed a much lower level of NPQ compared to WT (Fig. 5C,5F). These results suggest that low NPQ in GL can be attributed to dysfunction of the heat dissipation mechanism.


High-susceptibility of photosynthesis to photoinhibition in the tropical plant Ficus microcarpa L. f. cv. Golden Leaves.

Takahashi S, Tamashiro A, Sakihama Y, Yamamoto Y, Kawamitsu Y, Yamasaki H - BMC Plant Biol. (2002)

Yield of PSII (A, D), 1-qp reflecting the reduction state of the qa pool (B, E), NPQ (C, F) in shade-leaves of WT (•, blue) and GL (Δ, red). Each measurement was made after the exposure of leaves to actinic light for 3 min at different intensities (A-C). In D, E and F, high light (2300 μmol m-2 s-1) was used as actinic light to record time courses of Yield (D), 1-qP (E), and NPQ (F). Points are presented as the means of 5 (A-C) or 3 (D-F) separate measurements ± SEM.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC102767&req=5

Figure 5: Yield of PSII (A, D), 1-qp reflecting the reduction state of the qa pool (B, E), NPQ (C, F) in shade-leaves of WT (•, blue) and GL (Δ, red). Each measurement was made after the exposure of leaves to actinic light for 3 min at different intensities (A-C). In D, E and F, high light (2300 μmol m-2 s-1) was used as actinic light to record time courses of Yield (D), 1-qP (E), and NPQ (F). Points are presented as the means of 5 (A-C) or 3 (D-F) separate measurements ± SEM.
Mentions: When plants are exposed to high-light that exceeds the capacity of photosynthesis, excess absorbed light energy can be safely dissipated as heat [22]. This energy dissipation can be measured as the NPQ of PAM chlorophyll a fluorescence analysis. NPQ includes the quantum yield of PSII as an index of heat energy dissipation, photoinactivation of PSII and distribution of photon acceptance between PSII and PSI due to the state transition. It is known that the sate transition can be controlled by the redox state of QA[23], which can be measured as 1-qP. Figure 5 shows that there is no significant difference between GL and WT in yield and 1-qP values. Furthermore, measurements of the electron transport rate (ETR) showed essentially no difference in the sensitivity of PSII photoinactivation between GL and WT (data not shown). However, GL showed a much lower level of NPQ compared to WT (Fig. 5C,5F). These results suggest that low NPQ in GL can be attributed to dysfunction of the heat dissipation mechanism.

Bottom Line: We compared the response of photosynthetic activities to strong light between GL and its wild-type (WT, Ficus microcarpa L. f.).In contrast, WT did not show any substantial changes of Fv/Fm values throughout the day (between 0.82 and 0.78).We conclude that the photosynthetic apparatus of GL is more highly susceptible to photoinhibition than that of WT.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, Okinawa, Japan. takahashishunichi@hotmail.com

ABSTRACT

Background: The tropical plant Ficus microcarpa L. f. cv. Golden Leaves (GL) is a high-light sensitive tropical fig tree in which sun-leaves are yellow and shade-leaves are green. We compared the response of photosynthetic activities to strong light between GL and its wild-type (WT, Ficus microcarpa L. f.).

Results: Field measurements of maximum photosystem II (PSII) efficiency (Fv/Fm) of intact sun-leaves in GL showed that photo synthetic activity was severely photoinhibited during the daytime (Fv/Fm = 0.46) and subsequently recovered in the evening (Fv/Fm = 0.76). In contrast, WT did not show any substantial changes of Fv/Fm values throughout the day (between 0.82 and 0.78). Light dependency of the CO2 assimilation rate in detached shade-leaves of GL showed a response similar to that in WT, suggesting no substantial difference in photosynthetic performance between them. Several indicators of photoinhibition, including declines in PSII reaction center protein (D1) content, Fv/Fm value, and O2 evolution and CO2 assimilation rates, all indicated that GL is much more susceptible to photoinhibition than WT. Kinetics of PAM chlorophyll a fluorescence revealed that nonphotochemical quenching (NPQ) capacity of GL was lower than that of WT.

Conclusion: We conclude that the photosynthetic apparatus of GL is more highly susceptible to photoinhibition than that of WT.

Show MeSH
Related in: MedlinePlus