LARS Tech Report Number
A leaf begins to senesce as soon as it is removed from the plant and changes in metabolic processes and spectral properties are inevitable. If senescence can be delayed for several days without significant changes in spectral properties, then samples of leaves at remote test sites could be prepared and shipped to laboratories which have the equipment to measure spectral properties. The objective of this study was to determine the changes in spectral properties of detached leaves. Leaves from red birch (Betula nigra L.) and red pine (Pinus resinosa Ait.) were immersed for 5 minutes in water or 0.001 M benzylaminopurine (BAP) and stored in plastic bags in the dark at either 5° or 25° C. Total directional-hemispherical reflectance and transmittance of the adaxial surface of birch leaves were measured over the 400 to 1100 nm wavelength region with a spectroradiometer and integrating sphere (LICOR LI-1800). Pine needles were taped together and reflectance of the mat of needles was measured. Spectral properties changed less than 5% of initial values during the first week when leaves were stored at 5° C. Storage at 25° C promoted rapid senescence and large changes in spectral properties. BAP delayed, but did not stop, senescence at 25° C. Low temperature was more effective than BAP in delaying senescence. It appears possible to store leaves at low temperatures in plastic bags in the dark for several days without significantly altering the spectral properties in the 400 to 1100 nm wavelength region.
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