Solar UV Upregulates Photoprotection but Slows Photosynthesis in Subalpine Australian Plants

Abstract

ABSTRCTRecent literature suggests a shifting paradigm in relation to photobiology associated with ultraviolet (UV) radiation. UV has been repeatedly shown to be less detrimental to plant performance than previously thought. Nonetheless, relatively few plant species have been studied; too few to make definitive statements about effects of UV on plants at the ecosystem scale. We present findings of a field-based study using natural solar radiation, coupled with UV screening films, to determine physiological costs and benefits of exposure to solar UV for three species representative of subalpine Australian flora: a tree (Eucalyptus pauciflora), a forb (Geranium antrorsum), and a grass (Poa hiemata). Photochemical and photosynthetic responses to UV exclusion varied among species; exposure to UV was of no consequence to the structure, chemistry, or incidence of photoinhibition for E. pauciflora. UV was effectively screened at the leaf surface of P. hiemata. The response of G. anstrorsum to UV exclusion suggests greater susceptibility to photodamage; less successful in screening against UV and exposure reduced rates of photosynthesis, despite increased capacity to scavenge reactive oxygen species (via accumulating ascorbate). This study clarifies that responses to UV are highly species-specific, and that the endemic native flora is seemingly well-adapted to mitigate negative effects.