Blue‐green fluorescence excited by UV laser on leaves of different species originates from cutin and is sensitive to leaf temperature

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Abstract
Under ultra‐violet excitation, intact leaves generate a strong blue‐green fluorescence emission with several bands. Their integrated energy is 6 to 11 times the energy released by chlorophyll a bands (Chappelle et al. 1984, Applied Optics 23, 134–138). This paper provides evidence that the blue‐green fluorescence emission comes mainly from outer epidermal layers of the leaves and can be transferred on a quartz lamina by quickly dipping the leaves in organic solvents with subsequent solvent evaporation. Blue‐green fluorescence displays a diffusion‐controlled quenching of fluorescence intensity between 4°C (high fluorescence) and 37°C (low fluorescence). The blue‐green fluorescence emissivity is not linked to short‐term metabolic effects other than leaf temperature, but epidermis adaptations both to drought and to excessive radiation increase emissivity.