Exogenous melatonin affects photosynthesis in characeae Chara australis

Area of Science:

• Plant Physiology
• Biochemistry
• Photosynthesis Research

Background:

• Melatonin is a known antioxidant and signaling molecule in animals.
• Its presence and function in freshwater plants like Characeae are less understood.
• Characeae algae are ecologically important and sensitive to environmental changes.

Purpose of the Study:

• To investigate the presence and concentration of melatonin in Chara australis.
• To determine the effect of exogenous melatonin on the photosynthetic efficiency of Chara australis.
• To elucidate the mechanism behind melatonin's impact on photosystem II.

Main Methods:

• Quantification of endogenous melatonin in different tissues of Chara australis.
• Measurement of chlorophyll fluorescence parameters, specifically the quantum yield of photochemistry of photosystem II (PSII).
• Analysis of changes in the proportion of open reaction centers of PSII upon exogenous melatonin application.

Main Results:

• Melatonin was identified in Chara australis tissues, including photosynthesizing cells and non-photosynthesizing rhizoids, at concentrations around 4 μg/g.
• Application of 10 μM exogenous melatonin significantly increased the quantum yield of PSII photochemistry by 34%.
• This enhancement was attributed to an increase in the number of open PSII reaction centers, indicating improved overall photosynthetic electron transport.

Conclusions:

• Melatonin is an endogenous compound in freshwater algae Chara australis.
• Exogenous melatonin enhances photosynthetic efficiency in Chara australis by improving the functionality of the entire photosynthetic transport chain.
• Melatonin likely provides protection against reactive oxygen species for both chlorophyll and photosynthetic proteins.