Frequency and length of stomata of 21 Populus clones

Frequency and length of stomata of field-grown plants of 21 Populus clones were studied. All clones except one were amphistomatous, and all clones had the greatest number of stomata per unit of leaf area on the abaxial surface. Variation in stomatal frequency, length, and relative distribution of stomata between abaxial and adaxial leaf surfaces among clones was found. Although differences in stomatal frequency and length were observed in some cases between early and late leaves of a clone, pore area differences were small because of the tendency for leaves with fewer stomata to have larger stomata. Cluster analysis utilizing abaxial and adaxial stomatal frequency and length as independent variables indicated that stomatal characteristics were related to parentage. Relationships between clonal stomatal characteristics and preliminary shoot dry weight data were not significant.