The growth,flower properties and demography of Anthemis arvensis exposed to enhanced UV-B radiation

The winter annual species Anthemis arvensis L. (Asteraceae) was grown for 3.5 months in the field under ambient or ambient plus supplemental UV-B radiation, simulating a 15% ozone depletion over Patras (38.3° N, 29.1° E). Enhanced UV-B radiation had no effect on the methanol extractable UV-B absorbing capacity of leaves, phenological and morphometric parameters of anthesis (flowering time, anthesis duration, head life span, number of heads per plant, number of tubular and ligulate florets per head, area per ligulate floret). Concerning the optical properties of heads, enhanced UV-B radiation had no significant effect on the extractable absorbance of both floret types nor on the spectral reflectance of the tubular florets. However, under UV-B supplementation the white ligulate florets exhibited a slight, statistically significant decrease of reflectance in the visible region of the spectrum. This may be due to structural changes of the floret surface, since microscopic examination under SEM revealed the papillae of the adaxial epidermal cells to be swollen. The above ground dry mass measured at plant harvest was not affected but a significant increase in root biomass (and accordingly in root/shoot ratio) was observed. We conclude that Anthemis arvensis is resistant against UV-B radiation damage. The possible consequences of UV-B induced structural changes on floret epidermis are discussed.