Abstract
The effect of two different mechanisms of phosphorus ion transport from the nutrient solution volume to the surface areas of excised maize roots was studied under concentrations ranging from 0.01 mM to 50.0 mM KH2PO4. A modified technique of study of kinetic ion absorption was used. In the control series, the roots were placed in absorption solution without flow (the dominant mechanism of ion transport to the roots being diffusion), while in the experimental series the absorption solution was flowing round the roots at a rate of 0.162 cm s−1 (the dominant mechanism of ion transport to the roots being mass flow). The rate of phosphorus absorption by the roots from flowing solutions was highly significantly increased at all concentrations of absorption solution except for the 50.0 mM KH2PO4 concentration. The increase in phosphorus absorption in the case of 50.0 mM KH2PO4 concentration was non-significant due to the fact that the high concentration of phosphorus together with the diffusion of phosphorus ions ensured a sufficient supply of phosphorus to the roots, covering the requirement for their uptake.
The results point to the need for an analysis of environmental factors to be carried out in studying ion absorption kinetics, and reveal the inadequacy of methods usually employed in such investigations, in particular with respect to the homogeneity of the nutrient solution in the whole of its volume and especially round the roots.
Abstract
Byl sledován efekt dvou rozdílných mechanismů transportu iontů fosforu z objemu živného roztoku k povrchům odřezaných kořenů kukuřice v koncentračním rozpětí 0,01 mM až 50,0 mM KH2PO4. Byla použita modifikovaná metodika studia kinetiky absorpce iontů. V kontrolní sérii byly kořeny umístěny v absorpčním roztoku bez pohybu (dominantním mechanismem transportu iontů ke kořenům je difuse), v pokusné sérii proudil absorpční roztok kolem kořenů rychlostí 0,162 cm s−1 (dominantním mechanismem transportu iontů ke kořenům je mass flow). Míra absorpce fosforu kořeny z proudícího roztoku byla vysoce průkazně zvýšena při všech koncentracích absorpčních roztoků mimo koncentraci 50,0 mM KH2PO4. Zvýšení absorpce fosforu pří koncentraci 50,0 mM KH2PO4 bylo neprůkazné proto, poněvadž vysoká koncentrace fosforu spolu s difusí fosforečných iontů zabezpečovala dostateěnou dodávku fosforu ke kořenům, pokrývající požadavek jejich příjmu.
Výsledky ukazují na nutnost analýzy faktorů vnějšího prostředí při studiu kinetik absorpce iontů a na neadekvátnost obvykle používaných metodik při těchto studiích, především z hlediska homogenity živného roztoku v celém objemu a zvláště kolem kořenů.
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Dedicated to Academician S. Prát on the occasion of his 80th birthday
Address: Kotlářská 2, 611 37 Brno, Czechoslovakia.
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Čížková-Macůrková, R., Laštůvka, Z. A kinetic study of phosphorus absorption by excised maize roots from flowing solutions with different phosphorus concentrations. Biol Plant 17, 385–391 (1975). https://doi.org/10.1007/BF02921046
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DOI: https://doi.org/10.1007/BF02921046