Effects of Sample Storage on Spectral Reflectance Changes in Corn Leaves Excised From the Field

Characterization of leaf spectra is useful for estimating spectra at the canopy level when viewed from airborne or space-borne sensors. When excising and transporting leaves to the laboratory, care must be taken so that degradation does not take place and alter the spectral signature. We compared the effect of elapsed time on leaf reflectance when excised corn leaves were stored inside and outside a cooler. Hyperspectral measurements were obtained 15 minutes after excision, then again 1, 2, 3, 4, 5, 6, and 24 hours after excision. Each hyperspectral band was modeled independently using a piecewise function with a linear portion for the first hour after plant excision and exponential portion after the first hour. Results showed that for the first hour, storage technique did not influence the signature. After the first hour, the leaves stored outside the cooler showed less change than leaves stored in the cooler. Furthermore, after approximately 30 minutes a large percentage of hyperspectral bands drifted beyond the level of significance (as determined by the mean plus or minus two standard deviations). These findings are valuable for developing methods for storage and analysis to support field studies and collection of ground-truth data to support remote sensing.