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Growth and defence of aspen (Populus tremula) after three seasons under elevated temperature and ultraviolet-B radiation

Sivadasan, Unnikrishnan, Chenhao, Cao, Nissinen, Katri, Randriamanana, Tendry, Nybakken, Line, Julkunen-Tiitto, Riitta
Canadian journal of forest research 2018 v.48 no.6 pp. 629-641
Populus tremula, adults, biomass, buds, chlorophyll, climate change, females, field experimentation, genotype, herbivores, leaf area, leaf rust, leaves, males, molecular weight, phenolic compounds, photosynthesis, salicylates, stems, temperature, ultraviolet radiation
The predicted climate change will affect the growth and secondary chemistry of plants, but most studies only include leaves and leave out the effects on the secondary chemistry of other plant parts. In a field experiment, we studied the stem phenolic chemistry, as well as the growth of male and female genotypes, of aspen (Populus tremula L.) after three years under single (T, UVA, UVB) and combined (UVA + T, UVB + T) treatments at elevated temperature (T, +2 °C) and ultraviolet-B radiation (+30% UVB). In addition, bud mass and photosynthesis, as well as leaf rust attack and leaf herbivory, were measured. We found that elevated temperature markedly reduced concentrations of salicylates, which were the most abundant compounds among the low relative molecular mass phenolics in the stem. Elevated temperature also increased the biomass, height, and diameter of both males and females, as well as leaf area and herbivory damage in leaves. In combination with UVB, elevated temperature decreased the height of both males and females. Moreover, male buds were bigger than female buds, and females had higher chlorophyll content than males. To conclude, warming promoted growth and reduced phenolic concentration in stems of P. tremula with little difference between the sexes during the adult vegetative phase. UVB had no individual effects on any of the studied variables, implying that the plants were fairly tolerant to increased UVB levels.