Luxury consumption and specific utilization rates of three macroelements in two Taraxacum microspecies of contrasting mineral ecology

Plants of Taraxacum sellandii Dahlst., a microspecies adapted to fertile, and Taraxacum nordstedtii Dahlst., adapted to infertile soils, were cultured hydroponically, either on a complete nutrient solution or on one deprived of nitrogen, phosphorus, or potassium ions. For all four treatments, the growth and internal mineral concentration of the plants was monitored. For plants cultured on a complete nutrient solution, the uptake rates of nitrate, phosphate, and potassium ions were determined. Luxury consumption of the three macronutrients was computed as the excess of ion absorption over the ion uptake rates minimally required to sustain maximum growth. In these calculations the critical N, P, or K⁺ concentrations, earlier derived, were used as parameters describing the mineral status minimally required to allow maximum growth. Efficiency in use of the three macroelements at various levels of mineral accumulation was also computed. Finally, the response to phosphate starvation as related to phosphate uptake capacity and the accumulation of P was investigated.
The physiological properies investigated provide a causal background for the superior adaptation of T. nordstedtii as compared to T. sellandii to infertile sites. Taraxacum nordstedtii had a higher relative luxury consumption of NO₃^–, H₂PO^-₄, and K⁺, a higher efficiency in N and P use at N– and (severe) P-deficiency, respectively; and, after phosphate starvation, a relatively high preservation of phosphate uptake capacity and an enlargement of P storage. In combination with the low potential growth, luxury consumption will be particularly effective in T. nordstedtii in preventing or minimizing mineral deficiency. The distribution of minerals between cytoplasm and vacuoles as a factor in mineral use efficiency is discussed.     

Study on nutrient stress tolerance of nine Taraxacum microspecies with a contrasting mineral ecology by cultivation in a low nutrient flowing solution

Growth and mineral status of 9 Taraxacum microspecies were studied under mineral stress conditions, using a flowing solution of low nutrient concentration. Relative growth rate of (whole) plant dry weight, leaf area, and (whole) plant tissue water were used to describe growth. For 4 microspecies, specific uptake rates of NO⁻₃, H₂PO⁻₄, K⁺, Mg²⁺ and Ca²⁺ were investigated.
The applied nutrient condition clearly discriminated between the studied Taraxacum microspecies. With respect to relative growth rate, 3 groups of microspecies could be distinguished: T. nordstedtii > T. lancidens, T. adamii, T. hollandicum, T. taeniatum > T. sellandii, T. eudontum, T. ekmanii, T. ancistrolobum . These categories coincided well with the mineral ecology of the microspecies, going from infertile to fertile sites.
T. nordstedtii , a microspecies of infertile sites, was most efficient in absorbing NO⁻₃, H₂PO⁻₄ and K⁺. T. sellandii and T. eudontum , both occurring in fertile grasslands, showed poor uptake performances for all studied ions. In all Taraxacum microspecies studied, except T. eudontum , internal N concentration appeared to limit growth. Efficiencies in N use, at sub-optimal internal N concentrations, varied with the mineral habitat of the microspecies studied. T. nordstedtii , from infertile sites, and T. sellandii , from fertile sites, were established as high and low extremes, respectively.     

Responses to internal nitrogen and phosphorus concentrations of two Taraxacum microspecies of contrasting mineral ecology: critical N and P concentrations of whole plants

Of the two Taraxacum microspecies used. Taraxacum sellandii Dahlst. usually occurs in grasslands with a high nutrient level; Taraxacum nordstedtii Dahlst. is generally restricted to undisturbed and mineral-poor habitats. Growth response curves for internal N and P were established, based on relative yield of (whole) plant tissue water and (whole plant) internal mineral concentration on a tissue water basis. Critical nutrient concentrations of N and P were determined from the response curves derived. For both macroelements, T. nordstedtii showed lower critical nutrient concentrations. The difference in critical N concentrations coincided with differences in internal NO₃^-₃ concentrations between the microspecies. Finally, we discuss the use of tissue water as a (whole) plant growth parameter and internal mineral concentration on tissue water basis as a parameter describing the mineral status.     

Characterization of the plasmalemma ATPase activity from roots of Plantago major ssp. pleiosperma, purified by the two-phase partitioning method

A purified plasmalemma preparation from roots of Plantago major L. ssp. pleiosperma (Pilger) was obtained by the two-phase partitioning method, using 6.5% (w/w) of Dextran T-500 and polyethylene glycol 3350, respectively. The distribution of murker enzymes proved the purity of the plasmalemma fraction. The ATPase activity was characterized by determining its sensitivity to anions, cations and inhibitors. The Mg²⁺-dependent ATPase activity peaked at pH 7.25, K⁺-stimulation at pH 6.75, and the Cl⁻ -stimulation both at pH 6.75 and 7.5 (all in the presence of 3 m M MgSO₄). The plasmalemma preparations hydrolyzed preferentially ATP (in the presence of Mg²⁺), although they were less specific for ATP at pH 7.5 than at pH 6.75. The Cl⁻ - stimulated ATPase is probably associated with and located on the plasmalemma. The question if the Cl⁻ -stimulated activity is due to an ATPase distinct from the classical K⁺-stimulated ATPase is considered.     

The 1‑year safety and efficacy outcomes of Absorb bioresorbable vascular scaffolds for coronary artery disease treatment in diabetes mellitus patients: the ABSORB DM Benelux study

Background

Diabetes mellitus (DM) patients show higher rates of repeat revascularisation even in the era of modern drug-eluting stents (DES). The concept of bioresorbable scaffolds is becoming captivating, as it might allow for repeat interventions, prolonging the time span during which patients can be treated by percutaneous coronary intervention (PCI).

Aims

We intend to evaluate the short- and long-term safety and efficacy of Absorb bioresorbable vascular scaffolds (Absorb BVS) in the treatment of coronary artery disease (CAD) in DM patients for any indication.

Methods

The ABSORB DM Benelux is an international prospective study in DM patients who have undergone PCI with ≥1 Absorb BVS. Major adverse cardiac events (MACE) at 1 year was the primary endpoint, defined as a composite of all-cause death, any myocardial infarction (MI) and ischaemia-driven target vessel revascularisation (TVR). Secondary endpoints were target lesion failure (TLF) and definite or probable scaffold thrombosis (ScT).

Results

Between April 2015 and March 2017, 150 DM patients and 188 non-complex lesions were treated. Device implantation was successful in 100%. MACE occurred in 14 (9.5%) patients, with all-cause death occurring in 4 (2.7%), any MI in 6 (4.1%) and ischaemia-driven TVR in 7 (4.8%) respectively. TLF was reported in 11 (7.5%). Definite and probable ScT was observed in 2 (1.4%).

Conclusion

Absorb BVS for treatment of anatomically low-risk patients with DM show acceptable safety and efficacy outcomes at 1 year. If these promising results are confirmed after a longer follow-up period, new-generation bioresorbable scaffolds combined with refinement of implantation techniques might open new horizons for CAD treatment in DM patients.

     

Responses to internal potassium ion concentrations of two Taraxacum microspecies of contrasting mineral ecology: The role of inorganic ions in growth

The two microspecies were Taraxacum sellandii Dahlst., which usually occurs in heavily fertilized grasslands, and Taraxacum nordstedtii Dahlst., which on the whole is restricted to undisturbed and mineral-poor habitats. Growth response curves were established, depicting the relative yield of (whole) plant tissue water and the internal K⁺ concentration (on a whole plant basis). The critical K⁺ concentration, i.e. the lowest [K⁺]_i associated with maximal growth, was derived from the response curve. T. nordstedtii , the microspecies with the low maximal growth, showed a distinctly lower critical K⁺ concentration than T. sellandii. A relationship between growth potential and critical K⁺ concentration is proposed. Responses to a declining [K⁺]_i differed between the two microspecies. The roots of T. nordstedtii stopped functioning as a sink for inulin, and mobilized additional carbohydrates for maintaining osmotic potential and growth. The productive strategy of the fast-growing T. sellantlii is lacking such a mechanism to buffer effects of a declining [K⁺]_i.
Various changes were noted as regards the internal concentrations of other inorganic ions, measured as a function of [K⁺]_i, With declining [K⁺]_i, internal NO^-₃ decreased considerably in shoot and roots, especially in T. nordstedtii , while Mg²⁺ accumulated, especially in the roots of T. sellandii. The interactions between growth potential and the accumulation of inorganic ions are discussed.