A comparison of three methods for determining the stomatal density of pine needles
2001
Hultine, K.R. | Marshall, J.D.
Alternative methods were compared for determining the stomatal density of needles from two pine species. Densities estimated from air-dried, whole needles using a binocular dissecting scope were compared to densities estimated from vacuum-dried, intact needles using a scanning electron microscope and expanded peels (or macerated cuticles) using a compound light microscope. Differences among methods were expected from two sources: (1) expansion and shrinkage as a function of water content, and (2) differences in geometry of the measured surface. Estimates from the dissecting scope were similar to those from scanning electron microscopy (t = 0.509, n = 21, P = 0.62), presumably because both used dried, both otherwise intact whole needles. Light microscopy estimates, however, were lower than dissecting scope estimates (t = -2.307, n = 13, P = 0.04). After adjusting for expansion due to hydration and changes in needle geometry, differences disappeared (t = -1.205, n = 13, P = 0.25). These results are an important consideration for researchers reconstructing palaeo-atmospheric conditions and assessing plant response to environmental change.
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