Genetic variability in anatomical, physiological and growth characteristics of hybrid poplar (Populus x euramericana Dode (Guinier)) and eastern cottonwood (Populus deltoides Bartr.) clones

Anatomical and physiological parameters of rooted cuttings of eight black p oplar clones (4 Populus x euramericana, and 4 Populus deltoides) were evalu ated in three field experiments on different soil types (humofluvisol, fluv isol f. loamy and fluvisol f. sandy). Measurements were taken on the thickn ess of assimilation tissues (palisade and spongy) on the cross section, and on net photosynthesis, dark respiration and leaf area. At the end of the v egetation period, the main plant growth elements were measured: diameter, h eight and biomass. The results showed a high interclonal variability for mo st parameters. Statistically significant differences among clones, regardle ss of site, indicated that the majority of study characters are controlled by genetic factors, specific to each clone. Most characteristics showed a s tatistically significant genotype x environmental interaction, as clone ran kings at the three locations were not identical. The thickness of spongy ti ssue and plant height exhibited the highest genotype x environmental intera ction, while the number of stomates per mm(2) of the adaxial surface of the leaf, leaf area, and biomass showed the least sensitivity to environmental change. Strong correlations were shown between the number of stomates on l eaf adaxial surface and biomass, thickness of palisade layer and biomass, l eaf area and with height and biomass respectively. Leaf area, also was stro ngly correlated with height. The results indicate that the stomata number a daxial, thickness of palisade tissue, net photosynthesis, and leaf area can be used in the selection of nursery stock for the desired characteristics, that will result in higher biomass production. Construction of high yieldi ng hybrids with desirable anatomical features was considered to be feasible .