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| Gollan, T; Schurr, U; Schulze, ED: Stomatal response to drying soil in relation to changes in the xylem sap composition of Helianthus annuus. I. The concentration of cations, anions, amino acids in, and pH of, the xylem sap, Plant, Cell and Environment, 15, 551-559 (1992) | |
Abstract:
Sunflower plants (Helianthus annuus L.) were subjected to soil drying with their shoots either kept fully turgid using a Passioura-type pressure chamber or allowed to decrease in water potential. Whether the shoots were kept turgid or not, leaf conductance decreased below a certain soil water content. During the soil drying, xylem sap samples were taken from individual intact and transpiring plants. Xylem sap concentrations of nitrate and phosphate decreased with soil water content, whereas the concentrations of the other anions remained unaltered. Ca concentrations also decreased. K, Mg, Mn and Na concentrations stayed constant during soil drying. In contrast, the pH, the buffering capacity at a pH below 5 and the cation/anion ratio increased after soil water content was lowered below a certain threshold. Amino acid concentrations of the xylem sap increased with decreasing soil water content. The effect of changes in ion centrations in the xylem sap on leaf conductance is discussed.
Keywords: Helianthus annuus, Sunflower, water stress, root-to-shoot-communication, xylem sap, ionic composition, aminod aicd, pH, buffering capacity |
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