| Summary: Photochemical efficiency of photosystem II of Ctenanthe setosa which is used as a model plant in this study was investigated to understand photosynthetic adaptation mechanism under drought stress causing leaf rolling. Stomatal conductance (gs), the levels of photosynthetic pigments and photosynthetic parameters were determined in leaves that had four different degree of leaf rolling (control (0 %), 20-30 %, 50-60 %, 70 % and more), opened after irrigation and mechanically opened by clamping with plastic wires at 70 % and more degree of leaf rolling. gs value, gradually decreased in adaxial and abaxial surfaces in relation to degree of leaf rolling. In addition, pigment contents decreased to 50- 60 % degree of leaf rolling but reached control with further the rolling. No significant variations in quantum yield of PS II, electron transport rate (ETR) and photochemical quenching (qP) were found up to 50-60 % degree of leaf rolling while they significantly decreased at 70 % and more degree of leaf rolling. Non-photochemical quenching ( NPQ ) increased at 20-30 % degree of leaf rolling and then decreased. Steady state chlorophyll fluorescence was enhanced during all degree of leaf rolling. After irrigation, the chlorophyll fluorescence and other physiological parameters reached to approximately control (0 %), again. As for mechanically opened leaves by clamping, gs continued to decrease during drought period. The decrease in adaxial surface was lower in the rolled leaves than those of the clamped leaves during 5 days of drought. NPQ was high in the clamped leaves compared to the rolled leaves. ETR did not change in the rolled leaves but decreased in the clamped leaves. Quantum yield significantly declined on the 5th day of drought after 70 % and more degree of leaf rolling in the rolled leaves while decrease in the clamped leaves was observed on the 2nd day. qP also decreased more in the clamped leaves than in rolled leaves. In conclusion, the results indicate that leaf rolling protects PS II functionality from damage induced by drought stress.
Key Words: Chlorophyll Fluorescence, Ctenanthe setosa, Drought, Leaf Rolling, Protection, PS II Functionality.
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