Rumex crispus and R. obtusifolius are known to be nitrophilous but it is not known whether either or both species require a high N supply at all developmental stages. Furthermore, it is not clear whether both species require a high P supply, attain flowering in the seeding year, or have similar levels of winter resistance. The effect of nutrient availability on the emergence, growth and over-wintering of both Rumex species was investigated in a pot experiment (ten N, P and K fertilizer treatments) in Prague, Czech Republic. In both species, emergence of seedlings was negatively affected by very high N, but positively affected by increased P availability in the soil. No effect of K supply on the emergence, or subsequent growth, was recorded. High flowering in the seeding season and high winter mortality of R. obtusifolius contrasted with no flowering and no mortality of R. crispus. Over-wintering was not markedly affected by N, P or K supply. Both Rumex species are sensitive to a very high N supply in early developmental stages but tend to require a high N supply from the fully developed rosette-stage onwards. In addition to high N requirements during stem growth, flowering and seed ripening, both species also require a high P supply. At least some Central European populations of R. crispus, in contrast to R. obtusifolius, do not flower in the seeding year. In Central Europe, the frequently reported high field winter mortality of R. obtusifolius can be caused by its low frost resistance.

Rumex crispus is believed to be a highly nutrientdemanding weedy species that spreads mainly by seeds. However, the effects of nutrient availability on its performance and seed production have never been fully investigated. In this study, we investigated how plant size, seed production and germination were affected by the supply of N, P and K. In May 2008, a pot N, P and K fertiliser experiment was established in Prague (Czech Republic). During 2009, plant growth data were collected, and fully ripe seeds were tested for germination and N, P and K concentrations. Rumex crispus showed high phenotypic plasticity in plant height, number of leaves, leaf length and number of stems per plant in relation to N, P and K supply. Seed production per plant ranged from <2000 in the control and low P treatment up to almost 25 000 in the high NPK treatment. More than 16 000 seeds were produced per plant in all treatments where N and P were applied together. To produce a high quantity of rapidly germinating seeds, R. crispus requires a balanced N, P and K supply, as a deficiency of P and K together with a high N supply can result in the production of P-and K-deficient seeds (P and K <3 g kg )1 ) with lower germination ability. In central Europe, at least some populations of R. crispus do not flower in the seeding year and are strictly monocarpic. Given the short lifespan and monocarpic character of the species, control is probably most effective if applied at the rosette stage, prior to the production of viable seeds.

Rumex obtusifolius is a troublesome weed widely spread in temperate grasslands and can be potentially used for detection of soils contaminated by trace elements. We asked how emergence and survival of its seedlings are affected by application of quick lime (Ca) and superphosphate (P) additives in soils contaminated by trace elements. We performed the pot seeding experiment with slightly acid Litavka soil contaminated by arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) and alkaline Mal&iacute;n soil contaminated by As, Cd, and Zn. We used a control without any additives, Ca and P treatments in both soils. Higher and quicker emergence, together with substantially higher mortality of seedlings, was recorded in Litavka than in Mal&iacute;n. A positive effect of the Ca treatment on seedlings was recorded in Litavka, but a negative in Mal&iacute;n. Small seedlings with narrow and long leaves of reddish colour were recorded in Litavka in the control and in the P treatment both with high availability of Zn, Cd, and Pb. In the Ca treatment, leaves of seedlings were more elliptic and less reddish. In Mal&iacute;n, seedlings were green and substantially more vital in the control and in the P treatment than in Litavka. In the Ca treatment, small and unviable seedlings were recorded. Seedlings of R. obtusifolius are sensitive on high availability of Ca, Zn, Cd, and Pb in the soil. &nbsp; &nbsp;

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