Growth of different Aspen genotypes in Vitro under water deficit stress

Abstract

Six aspen genotypes – R-38 (Populus tremula L.), 117-3 (Populus tremuloides × P. tremula), 64-3 (Populus tremuloides × P. tremula), Hb8 (Populus tremuloides Michx. × P. tremula), 64-15(15B) (new hybrid aspen) and Gig-27 (new hybrid aspen) – were compared in order to assess their behaviour under water deficit stress. Aspen explants (10 – 12 mm apical shoot segments) were cultured in 150 × 20 mm glass tubes sealed with parafilm. Woody Plant Medium was used as a basal culture medium and water deficit was induced with addition of polyethylene glycol (PEG-6000) to the medium. PEG-6000 was added at the concentrations of 50, 100, and 150 g/l. The result analysis included such parameters as plant height, leaf, shoot and root number per plant, root length, green and dry plant mass, cellulose, chlorophyll content and leaf stomata number. Some of the studied aspen genotypes were found to be more resistant to the inhibitory effect of water deficit on shoot growth than others. At 50 g/l PEG, hybrid aspen 117-3 explants showed the least shoot height difference from the control group (although this same genotype had the most reduced shoots at 150 g/l PEG). Meanwhile, at 100 g/l PEG, the shoot height of aspen R-38 explants was least different from the control group. Interestingly, R-38 was one of the two genotypes (another one – hybrid aspen 64-3) that developed more adventitious shoots at 100 g/l PEG than under control conditions. Root number was most reduced by PEG in the genotypes 117-3 and 64-3, while the genotypes Gig-27 and R-38 were least affected (at 100 g/l PEG). The highest plant dry mass under water deficit stress accumulated, at 50 g/l PEG, in the genotype 117-3 and, at 100 g/l PEG, in the genotypes 64-15 and Hb8. Higher leaf stomata numbers in stressed, in comparison to control, explants were found in the genotypes 117-3 (at 50 g/l PEG) and R-38 (at 100 g/l PEG).[...]