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Temporal variation in epidermal flavonoids due to altered solar UV radiation is moderated by the leaf position in Betula pendula
Author(s) -
Morales Luis O.,
Tegelberg Riitta,
Brosché Mikael,
Lindfors Anders,
Siipola Sari,
Aphalo Pedro J.
Publication year - 2011
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2011.01511.x
Subject(s) - betula pendula , epidermis (zoology) , botany , ultraviolet , photoprotection , biology , ultraviolet radiation , chemistry , photosynthesis , horticulture , radiochemistry , anatomy , physics , quantum mechanics
The physiological mechanisms controlling plant responses to dynamic changes in ambient solar ultraviolet (UV) radiation are not fully understood: this information is important to further comprehend plant adaptation to their natural habitats. We used the fluorimeter Dualex to estimate in vivo the epidermal flavonoid contents by measuring epidermal UV absorbance (A 375 ) in Betula pendula Roth (silver birch) leaves of different ages under altered UV. Seedlings were grown in a greenhouse for 15 days without UV and transferred outdoors under three UV treatments (UV‐0, UV‐A and UV‐A+B) created by three types of plastic film. After 7 and 13 days, Dualex measurements were taken at adaxial and abaxial epidermis of the first three leaves (L1, L2 and L3) of the seedlings. After 14 days, some of the seedlings were reciprocally swapped amongst the treatments to study the accumulation of epidermal flavonoids in the youngest unfolded leaves (L3) during leaf expansion under changing solar UV environments. A 375 of the leaves responded differently to the UV treatment depending on their position. UV‐B increased the A 375 in the leaves independently of leaf position. L3 quickly adjusted A 375 in their epidermis according to the UV they received and these adjustments were affected by previous UV exposure. The initial absence of UV‐A+B or UV‐A, followed by exposure to UV‐A+B, particularly enhanced leaf A 375 . Silver birch leaves modulate their protective pigments in response to changes in the UV environment during their expansion, and their previous UV exposure history affects the epidermal‐absorbance achieved during later UV exposure.