The influence of enhanced UV-B radiation on the spring geophyte Pulmonaria officinalis

Abstract

Pulmonaria officinalis is an understorey spring geophyte, which starts its vegetative period before full foliation of the tree storey. During its early growth phase it is exposed to full solar radiation, therefore the enhanced UVB radiation could present a threat to this species. An outdoor experiment in which potted plants were exposed to below ambient, ambient, and above ambient (corresponding to 17% ozone reduction) UV-B radiation, was conducted in order to evaluate the radiation effects. The amount of photosynthetic pigments and photochemical efficiency of PSII were not affected, but the amount of UV-B absorbing compounds was lower in plants grown under reduced UV-B. This change was measurable after only fourteen days in reproductive shoots, while in the vegetative shoots, it was not detectable until after three months. The leaves of P. officinalis are variegated and the light green spots became less transparent to PAR under enhanced UV-B. The results reveal that under simulated 17% ozone depletion the harmful effects of UV-B on the measured parameters were negligible.

Photoprotective implications of leaf variegation in E. dens-canis L. and P. officinalis L.

“…In P. officinalis, light green variegation occurred due to the presence of loosely packed cells, not affecting the thickness of the leaves ( Figure 2C), while green tissues showed a typical layer of densely packed palisade parenchyma cells ( Figure 2B). As a consequence, Chl content in light green parts of P. officinalis was 30% lower than in green tissues (Table 1), as has also been shown by Gaberscik et al (2001). This pattern of variegation significantly reduced photoprotective molecules (a-Toc, b-carotene and VAZ pigments) by unit area in light green tissues, but ratios to Chl remained unchanged.…”

“…Gaberscik et al (2001) concluded that, under UV-B, light green spots of P. officinalis became less transparent to PAR, likely due to a structural change in the mesophyll. The case of E. dens-canis is, to a certain extent, different because the reddish variegation was due to the presence of a single layer of red cells in the upper parenchyma, which accumulated anthocyanins in the vacuole (Figure 2A).…”

“…Variegated leaves could confer a drawback for photosynthetic efficiency; however, the presence of variegation in nature suggests an adaptive role. The use of variegated leaves in comparative studies is not new and has been previously employed to characterise physiological processes under controlled assays, such as stomatal function (Zeiger et al, 1980;Aphalo and Sánchez, 1986), antioxidant metabolism (Peltzer et al, 1999), air pollution (Niewiadomska and Miszalski, 1997), carbohydrate metabolism (Madore, 1990), anthocyanin function (Burger and Edwards, 1996), oxidative stress (Niewiadomska and Miszalski, 1997;Peltzer et al, 1999) and enhanced UV-B radiation (Gaberscik et al, 2001). Studies of an anatomical basis for variegation (Tsukaya et al, 2004) have also been conducted.…”

Biological Flora of the British Isles: Pulmonaria officinalis

“…Despite the higher reflectance of the blotches for all wavelengths, the light green leaf areas are not more photo-protected than the other leaf portions (Esteban et al 2008). In both leaf areas, the same amount of UV-B absorbing compounds was stored under elevated UV-B radiation (Gaber s cik et al 2001).…”

The response of Ceratophyllum demersum L. and Myriophyllum spicatum L. to reduced, ambient, and enhanced ultraviolet-B radiation

“…The majority of research into UV-B and higher plants was conducted in the terrestrial environments. The potential of terrestrial plants to cope with UV-B radiation depends on growth form, life span, radiation environment and position in the phylogenetic tree (Les, 1988;Les et al, 1991;Rozema et al, 1997;Bj} orn, 1999;Gabersˇcˇik et al, 2001;Gabersˇcˇik et al, 2002). Aquatic plants are flexible and continuously change their position in the water column.…”