A1 Refereed original research article in a scientific journal
Flavonols do not affect aphid load in green or senescing birch leaves but coincide with a decrease in Photosystem II functionality
Authors: Mattila, Heta; Khorobrykh, Sergey; Tyystjärvi, Esa
Publisher: Company of Biologists
Publication year: 2024
Journal: Biology Open
Journal name in source: Biology open
Journal acronym: Biol Open
Article number: bio060325
Volume: 13
Issue: 7
eISSN: 2046-6390
DOI: https://doi.org/10.1242/bio.060325
Web address : https://doi.org/10.1242/bio.060325
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/456992058
Instead of red anthocyanins, birches synthesize colourless (to human eye), UV-absorbing flavonols during autumn senescence. To test if flavonols protect against insects, and if leaves with high or low amounts of flavonols differ in their photosynthetic functions, aphid-free and aphid-infested green and senescing birch leaves were collected from outdoors-grown trees and analysed. Photosynthetic parameters were greatly affected by the leaf chlorophyll content (i.e. the phase of senescence). Photochemical quenching and the amount of functional Photosystem I decreased linearly with chlorophyll content while FV/FM (Photosystem II functionality) decreased strongly only at the end of senescence. Non-photochemical quenching of excitation energy (NPQ) increased towards the end of senescence. However, no significant differences in the total flavonol amounts, nor in individual flavonol species, were found between aphid-free and aphid-infested leaves, suggesting that flavonols play no role in defence against aphid herbivory. Interestingly, both green and senescing leaves with a high flavonol content showed low FV/FM values. High flavonol content slowed down PSII photoinhibition and improved recovery, but only in green leaves. Previously, we proposed that anthocyanins provide an additional sink for photosynthates at the nitrogen resorption phase during autumn senescence, and the present data may suggest that flavonol synthesis plays a similar role.
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Funding information in the publication:
We thank Research Council of Finland (project 333421), the Ella and Georg Ehrnrooth Foundation and the Osk. Huttunen Foundation for financial support.
