A comparison of three methods for determining the stomatal density of pine needles
Kevin R. Hultine1,2,3 and John D. Marshall1
1 Department of Forest Resources, University of Idaho, Moscow, ID 83843-1133, USA
2 Department of Renewable Natural Resources, University of Arizona, Tucson, AZ 85721, USA
Received 8 September 2000; Accepted 20 September 2000
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, but 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.
Key words: Stomatal density, Pinus ponderosa, Pinus taeda, palaeo-atmospheric reconstructions, environmental change.
Source: Journal of Experimental Botany, Vol. 52, No. 355, pp. 369-373, February 2001.