Flavonols do not affect aphid load in green or senescing birch leaves but coincide with a decrease in Photosystem II...

Area of Science:

• Plant Physiology
• Biochemistry
• Ecology

Background:

• Birches synthesize UV-absorbing flavonols during autumn senescence, unlike anthocyanins.
• Flavonols' role in insect defense and photosynthetic function during senescence is unclear.

Purpose of the Study:

• To investigate if flavonols protect birch leaves from aphid herbivory.
• To determine if flavonol content affects photosynthetic functions during autumn senescence.

Main Methods:

• Analysis of aphid-free and aphid-infested green and senescing birch leaves.
• Measurement of photosynthetic parameters including photochemical quenching, Photosystem I and II functionality (FV/FM), and non-photochemical quenching (NPQ).
• Quantification of total and individual flavonol amounts.

Main Results:

• Photosynthetic parameters were primarily influenced by chlorophyll content (senescence stage).
• No significant difference in flavonol content was found between aphid-infested and aphid-free leaves.
• High flavonol content was associated with lower FV/FM values, suggesting slowed photoinhibition and improved recovery in green leaves.

Conclusions:

• Flavonols do not appear to play a role in defending birch leaves against aphid herbivory.
• Flavonol synthesis may serve as an additional sink for photosynthates during autumn senescence, similar to anthocyanins.