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| Home > Publications database > The influence of spatially heterogeneous soil temperatures on plant structure and function |
| Dissertation / PhD Thesis/Book | PreJuSER-46950 |
2007
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-507-4
Please use a persistent id in citations: http://hdl.handle.net/2128/3102
Abstract: In nature, vertical gradients in soil temperature are ubiquitous, but research on the influence of spatially heterogeneous soil temperatures on plant structure and function is scarce. Most experiments with plants even ignore the gradient in soil temperature found under natural conditions. For this reason, in this study it was examined for the first time, whether a vertical gradient in soil temperature influences plant growth and development in a different way than uniform root temperatures usually examined in the literature. Furthermore, it was analyzed whether functional and/or structural traits of the plant might be responsible for these potential effects. Data of barley plants ($\textit{Hordeum vulgare}$ cv. Barke) grown at a vertical root temperature gradient (RTG) of 20-10°C from the top to the bottom of a plant pot were compared with data obtained for barley plants grown at uniform root temperatures (RT) of 10°C, 15°C and 20°C, respectively. Plants grown at the RTG developed faster and produced more biomass compared to plants grown at uniform root temperatures. The root system was characterized by shallow rooting with most roots present in 0-10 cm depth and a quite high fraction of thick roots ($\geq$ 1.0 mm in diameter) in the entire root system. In this way, the root system of plants grown at the RTG was similar to plants grown at 15°C RT. However in contrast to 15°C RT, plants grown at 20-10°C RTG did not reach highest fraction of total root length in 0-5 cm but in 5-10 cm depth, although less root dry weight was present in 5-10 cm compared to 0-5 cm depth at both temperature treatments. This was explained by differences in fractions of individual root diameters within the respective depths. Additionally, experiments on N metabolism in plants revealed higher concentrations of most free amino acids in shoots at 20-10°C RTG and varying protein concentrations in roots between plants grown at RTG and 15°C uniform root temperature. Therefore, it was demonstrated that a vertical gradient in root temperature influences plant structure and function in a different way than the respective uniform root temperature representing the average temperature of this gradient. No significant differences between 20-10°C RTG and 15°C RT occurred, when nutrient uptake and translocation were analyzed with stable isotopes as tracers ($^{15}$N, $^{25}$Mg). However, in general it has to be stated that at active nutrient uptake processes direct root temperature effects, e.g. lower N uptake at 10°C RT compared to higher root temperatures were overridden by the adaptation of plant structure to the respective root temperature. This underlines the importance of structural traits (e.g. biomass allocation to the shoot, fractions of individual root diameters) to nutrient demand and supply. In contrast, direct temperature effects remained detectable at passive uptake processes (e.g. Mg). Therefore, it was hypothesized, that plants grown at a vertical root temperature gradient grow faster compared to plants at uniform root temperatures due to a combination of structural and functional components making nutrient uptake, translocation and use more effective. Furthermore, it was shown, that root temperature effects on plant structure change in amplitude with plant age and development stage. Consequently, effects found in this study represent a snapshot of plant responses to root temperature.
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