Response in chlorophyll a fluorescence of six New Zealand tree species to a step-wise increase in ultraviolet-B irradiance.
A laboratory protocol to quantify damage from a sudden increase in ultraviolet-B irradiance (UV-B, waveband 280-320 nm) to cucumber (cv. Poinsett) seedlings, including saturating photosynthetically active irradiance (400-700 nm, 1200 µmol/m2/s), was determined using leaf chlorophyll a fluorescence measurements to estimate photoinhibition. Seedlings of six native New Zealand tree species (Griselinia littoralis, Coprosma robusta, Corokia cotoneaster, Aristotelia serrata, Nothofagus fusca and Nothofagus solandri var. cliffortioides), grown in a common garden, were irradiated for 4 h, receiving a total biologically-effective UV-B dose of 17 kJ/m2 or about twice that on a clear summer day in New Zealand. There was a wide range of responses to an increase in UV-B irradiance including a 20% increase in photoinhibition for two shade tolerant species and 10% increase for the shade intolerant red beech (Nothofagus fusca). The other species were not affected. Mountain beech (N. solandri var. cliffortioides ) was particularly tolerant of high UV-B doses. Leaf and epidermal thickness, and flavonoid concentration did not correspond well with species response.