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Abstract

Currently more and more research is being done on integrated weed management to reduce or avoid herbicide use. Some growers are already using isotherapic dilutions to control weeds in organic farming. Isotherapy is different from homeopathy because it uses diluted and potentized (succussed) solutions of alcoholic macerate of the very pest causing health troubles. We set up a germination experiment to test if isotherapic dilutions of leaf macerate of annual ryegrass affect the dynamics of its seed germination in Petri dishes. Our results were diverse, from no effect to 10% more growing degree days necessary to reach 50% germination. It is doubtful that so low an effect will contribute to integrated weed management unless the slightly delayed germination triggers secondary effects at other life stages. This is in accordance with the scientific literature on that topic: two-fifths of the reports showed no effect, two-fifths resulted in positive responses and one-fifth had diverse responses for the criteria tested.
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Abstract

The major aim of the study was to identify the relationships of photosynthetic pigments with elemental contents of plants exposed to various ambient air conditions. Lolium multiflorum L. plants were exposed at five sites varying in environmental characteristics, including potential air pollution levels. The effect of air pollution by trace elements on plants was examined. Selected trace elements (Pb, Cd, As, Ni, Cr), some macro-elements as well as chlorophyll content were measured after each of four series. The graphical visualization revealed groups of sites with similar response of elements and chlorophyll contents. Sites located outside the city were grouped into one, and two urban sites were grouped into another. The trace element contents were relatively low and, excluding Ni and As, did not reach toxic levels in dry mass of leaves. However, some relations could be noted, which indicates the sensitivity of the photosynthetic process even at low levels of trace elements in ambient air. Chlorophyll b was found to be more sensitive to most of the analyzed trace elements than chlorophyll a. The results revealed chlorophylls, K and Na as indicators of plant stress caused by trace elements present in ambient air, even at relatively low levels.
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