Seasonal Patterns in Spectral Irradiance and Leaf UV-A Absorbance Under Forest Canopies

Copyright © 2020 Hartikainen, Pieristè, Lassila and Robson..

Plants commonly respond to UV radiation through the accumulation of flavonoids and related phenolic compounds which potentially ameliorate UV-damage to crucial internal structures. However, the seasonal dynamics of leaf flavonoids corresponding to epidermal UV absorbance is highly variable in nature, and it remains uncertain how environmental factors combine to govern flavonoid accumulation and degradation. We studied leaf UV-A absorbance of species composing the understorey plant community throughout two growing seasons under five adjacent tree canopies in southern Finland. We compared the relationship between leaf flavonol index (Iflav-repeatedly measured with an optical leaf clip Dualex) and measured spectral irradiance, understorey and canopy phenology, air temperature and snowpack variables, whole leaf flavonoid extracts, and leaf age. Strong seasonal patterns and stand-related differences were apparent in Iflav of both understorey plant communities and individual species, including divergent trends in Iflav during spring and autumn. Comparing the heterogeneity of the understorey light environment and its spectral composition in looking for potential drivers of seasonal changes in Iflav, we found that unweighted UV-A irradiance, or the effective UV dose calculated according to the biological spectral weighting function (BSWF) for plant growth (PG action spectrum), in understorey shade had a strong relationship with Iflav. Furthermore, understorey species seemed to adjust Iflav to low background diffuse irradiance rather than infrequent high direct-beam irradiance in sunflecks during summer, since leaves produced during or after canopy closure had low Iflav. In conclusion, we found the level of epidermal flavonoids in forest understorey species to be plastic, adjusting to climatic conditions, and differing according to species' leaf retention strategy and new leaf production, all of which contribute to the seasonal trends in leaf flavonoids found within forest stands.

Medienart:

E-Artikel

Erscheinungsjahr:

2019

Erschienen:

2019

Enthalten in:

Zur Gesamtaufnahme - volume:10

Enthalten in:

Frontiers in plant science - 10(2019) vom: 02., Seite 1762

Sprache:

Englisch

Beteiligte Personen:

Hartikainen, Saara Maria [VerfasserIn]
Pieristè, Marta [VerfasserIn]
Lassila, Joose [VerfasserIn]
Robson, Thomas Matthew [VerfasserIn]

Links:

Volltext

Themen:

Flavonoids
Flavonol index
Journal Article
Phenology
Secondary metabolism
Spectral irradiance
UV radiation

Anmerkungen:

Date Revised 28.03.2024

published: Electronic-eCollection

Citation Status PubMed-not-MEDLINE

doi:

10.3389/fpls.2019.01762

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM307240665