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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.

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High-light induced photoinhibition of GL assessed by several parameters. Shade-leaves were exposed to high-light (2300 μmol m-2 s-1) at zero time after preexposure to medium-light (1000 μmol m-2 s-1) for 30 min. A schematic illustration shows the outline of photosynthesis including the electron transport process in thylakoid membranes. Letters (A-D) in filled circles, which correspond to those of the panels A-D, represent the sites where the photo synthetic parameters can be measured. A, Immuno blotting of the D1 protein contained in leaf-extract. B, Degradation of the in vivo D1 protein induced by high-light. Each point was plotted using a relative density of band on the gel as shown in A. C, Decline of Fv/Fm induced by high-light. Note that the time indicated represents total illumination time. D, High-light induced inhibition of the activity of O2 evolution from intact detached leaves. E, High-light induced inhibition of the activity of CO2 assimilation in intact detached leaves. Points are taken by a separate measurement in different leaves (A, B, D) or a leaf (C, E). (•, blue), WT; (Δ, red), GL.
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Figure 4: High-light induced photoinhibition of GL assessed by several parameters. Shade-leaves were exposed to high-light (2300 μmol m-2 s-1) at zero time after preexposure to medium-light (1000 μmol m-2 s-1) for 30 min. A schematic illustration shows the outline of photosynthesis including the electron transport process in thylakoid membranes. Letters (A-D) in filled circles, which correspond to those of the panels A-D, represent the sites where the photo synthetic parameters can be measured. A, Immuno blotting of the D1 protein contained in leaf-extract. B, Degradation of the in vivo D1 protein induced by high-light. Each point was plotted using a relative density of band on the gel as shown in A. C, Decline of Fv/Fm induced by high-light. Note that the time indicated represents total illumination time. D, High-light induced inhibition of the activity of O2 evolution from intact detached leaves. E, High-light induced inhibition of the activity of CO2 assimilation in intact detached leaves. Points are taken by a separate measurement in different leaves (A, B, D) or a leaf (C, E). (•, blue), WT; (Δ, red), GL.

Mentions: Figure 4 shows effects of high-light on several indicators of photoinhibition: D1 protein content, Fv/Fm value, O2 evolution rate and CO2 assimilation rate. Before high-light exposure, there was no substantial difference between WT and GL shade-leaves in D1 protein content on protein basis (Fig. 4A) and Fv/Fm value (Fig. 4C). GL showed a significant decrease in the D1 protein content and Fv/Fm value upon high-light illumination (Fig. 4A,4B,4C). Similar to the indicators specific for PSII activity, those for net photosynthetic activity (i.e. O2 evolution and CO2 assimilation rates) also decreased upon high-light illumination (Fig. 4D,4E). In contrast to these responses observed in GL, WT showed only a small decrease in D1 protein content and Fv/Fm value (Fig. 4A,4B,4C). The O2 evolution and CO2 assimilation rates in WT did not change even under high-light condition (Fig. 4D,4E).


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)

High-light induced photoinhibition of GL assessed by several parameters. Shade-leaves were exposed to high-light (2300 μmol m-2 s-1) at zero time after preexposure to medium-light (1000 μmol m-2 s-1) for 30 min. A schematic illustration shows the outline of photosynthesis including the electron transport process in thylakoid membranes. Letters (A-D) in filled circles, which correspond to those of the panels A-D, represent the sites where the photo synthetic parameters can be measured. A, Immuno blotting of the D1 protein contained in leaf-extract. B, Degradation of the in vivo D1 protein induced by high-light. Each point was plotted using a relative density of band on the gel as shown in A. C, Decline of Fv/Fm induced by high-light. Note that the time indicated represents total illumination time. D, High-light induced inhibition of the activity of O2 evolution from intact detached leaves. E, High-light induced inhibition of the activity of CO2 assimilation in intact detached leaves. Points are taken by a separate measurement in different leaves (A, B, D) or a leaf (C, E). (•, blue), WT; (Δ, red), GL.
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Related In: Results  -  Collection

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Figure 4: High-light induced photoinhibition of GL assessed by several parameters. Shade-leaves were exposed to high-light (2300 μmol m-2 s-1) at zero time after preexposure to medium-light (1000 μmol m-2 s-1) for 30 min. A schematic illustration shows the outline of photosynthesis including the electron transport process in thylakoid membranes. Letters (A-D) in filled circles, which correspond to those of the panels A-D, represent the sites where the photo synthetic parameters can be measured. A, Immuno blotting of the D1 protein contained in leaf-extract. B, Degradation of the in vivo D1 protein induced by high-light. Each point was plotted using a relative density of band on the gel as shown in A. C, Decline of Fv/Fm induced by high-light. Note that the time indicated represents total illumination time. D, High-light induced inhibition of the activity of O2 evolution from intact detached leaves. E, High-light induced inhibition of the activity of CO2 assimilation in intact detached leaves. Points are taken by a separate measurement in different leaves (A, B, D) or a leaf (C, E). (•, blue), WT; (Δ, red), GL.
Mentions: Figure 4 shows effects of high-light on several indicators of photoinhibition: D1 protein content, Fv/Fm value, O2 evolution rate and CO2 assimilation rate. Before high-light exposure, there was no substantial difference between WT and GL shade-leaves in D1 protein content on protein basis (Fig. 4A) and Fv/Fm value (Fig. 4C). GL showed a significant decrease in the D1 protein content and Fv/Fm value upon high-light illumination (Fig. 4A,4B,4C). Similar to the indicators specific for PSII activity, those for net photosynthetic activity (i.e. O2 evolution and CO2 assimilation rates) also decreased upon high-light illumination (Fig. 4D,4E). In contrast to these responses observed in GL, WT showed only a small decrease in D1 protein content and Fv/Fm value (Fig. 4A,4B,4C). The O2 evolution and CO2 assimilation rates in WT did not change even under high-light condition (Fig. 4D,4E).

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.

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