Abstract
Phenotypic plasticity, in response to adverse conditions, determines plant productivity and survival. The aim of this study was to test if two highly productive Populus genotypes, characterised by different in vitro etiolation patterns, differ also in their responses to hormones gibberellin (GA) and abscisic acid (ABA), and to a GA biosynthesis inhibitor paclobutrazol (PBZ). The experiments on shoot cultures of ‘Hybrida 275′ (abbr. H275; Populus maximowiczii × P. trichocarpa) and IBL 91/78 (Populus tremula × P. alba) were conducted by either modulating the physical in vitro environment or by adding specific chemicals to the nutrient medium. Our results revealed two main sets of differences between the studied genotypes in environmental and hormonal regulation of growth responses. First, the genotype H275 responded to darkness with PBZ-inhibitable shoot elongation; in contrast, the elongation of IBL 91/78 shoots was not affected either by darkness or PBZ treatment. Secondly, the explants of H275 were unable to recover their growth if it was inhibited with ABA; in contrast, those of IBL 91/78 recovered so well after the temporal inhibition by ABA that, when rooted subsequently, they developed longer shoots and roots than without a previous ABA treatment. Our results indicate that GA catabolism and repressive signalling provide an important pathway to control growth and physiological adaptation in response to immediate or impending adverse conditions. These observations can help breeders define robust criteria for identifying genotypes with high resistance and productivity and highlight where genotypes exhibit susceptibility to stress.
Highlights
Forest trees have tremendous economic and ecological value and possess unique biological properties that are of fundamental scientific interest [1]
The shoots of H275, grown in the dark, were 3.7 times longer than in light. This dark-induced shoot elongation in H275 was suppressed by the PBZ back to the control level
In contrast to H275, the average shoot length of IBL 91/78 was not increased by the dark treatment and, correspondingly, not affected by the PBZ applied in the dark
Summary
Forest trees have tremendous economic and ecological value and possess unique biological properties that are of fundamental scientific interest [1]. Populus is the most widely distributed genus in the Northern Hemisphere and has several advantages as a model system, including rapid growth, prolific sexual reproduction, ease of cloning, a small genome, facile transgenesis, and a tight coupling between physiological traits and biomass productivity [1]. Due to their fast growth and favourable wood properties (fibre parameters) and chemical composition (high cellulose content), poplar genetic resources are widely used as a fibre source for the pulp and paper industry and, more recently, for biomass and biofuel production, carbon sequestration, and phytoremediation [4–7]. The selection of appropriate genotypes in tree plantations should be directed to many traits of economic and adaptive importance
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