Browsing by Person "Belz, Regina"

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Enhancing weed suppression in plants by artificial stress induction
(2025) Merkle, Michael; Petschenka, Georg; Belz, Regina; Gerhards, Roland
Various plant species from the Poaceae, Cannabaceae, and Brassicaceae families are used as cover crops to suppress weeds and volunteer crops through competition and allelopathy. This study examined the effects of artificially induced stress on the physiological processes, total phenolic content (TPC), and allelopathic potential of the plant species Avena strigosa, Cannabis sativa , and Sinapis alba at an early growth stage with the aim to increase their weed suppression abilities. Stress was induced at the 3–4 leaf stage in greenhouse-grown plants via harrowing, methyl jasmonate (MeJA) application, insect stress simulation, or a combination of insect stress and harrowing. Maximum quantum yield of photosystem II and shoot dry matter in the three plant species were only minimally or not affected a few days after treatment (DAT). Insect stress caused visible symptoms on treated leaves in all plants. The TPC in the shoot extracts of combined stress-treated C. sativa and insect-stressed S. alba was significantly higher by 1.7 and 1.9 times, respectively, five DAT compared to the shoot extracts from untreated control plants. Additionally, laboratory bioassays with aqueous shoot extracts from the untreated and treated plants were conducted to identify changes in allelopathic potential within the shoot tissues. The application of shoot extracts from MeJA-treated C. sativa and S. alba resulted in the lowest seed germination rates for the two weed species Alopecurus myosuroides and Stellaria media , as well as for the volunteer wheat Triticum aestivum , which were up to 65% lower 10 DAT compared to seeds treated with shoot extracts from non-stressed plants. However, the root-suppressing effect of the shoot extracts on weeds was not influenced by the stress treatments. This study reveals that artificial stress induction can be a suitable management strategy to enhance weed and volunteer cereal suppression in plants in an early growth stage but may vary between stress types and plant species, and requires further optimization and field testing.
Low glyphosate doses change reproduction and produce tolerant offspring in dense populations of Hordeum vulgare
(2021) Belz, Regina ; Sinkkonen, Aki
BACKGROUND: Low toxin doses that do not affect mean responses in plant populations can still change the growth of subpopulations. Studies covering vegetative stages ascribed fast-growing plants higher thresholds for growth stimulation and inhibition, compared with the rest of the population. We hypothesized that such selective effects also play a role after reproduction; that is, the offspring of glyphosate-treated tolerant, fast-growing phenotypes is more tolerant than the offspring of untreated plants. An experimental, high-density barley population was exposed to a range of glyphosate concentrations in the greenhouse, and reproduction and final growth were analyzed for selective effects. Therefore, F0, F1 treated and F1 non-treated offspring were re-exposed to glyphosate. RESULTS: Low doses of glyphosate inhibited the growth and reproduction of slow-growing plants at concentrations that did not change the population mean. Concentrations that inhibited average-sized plants hormetically increased the biomass and seed yield of fast-growing plants. Compared with F0 and F1 non-treated offspring, F1-treated offspring from hormetically stimulated fast-growing plants were more glyphosate tolerant. Hence, a pesticide can shape the reproductive pattern of a plant population and alter offspring tolerance at concentrations that have no effect on average yield. CONCLUSIONS: Toxin levels that do not change the population mean still alter the reproductive output of individuals. Sensitive phenotypes suffer, whereas the reproduction of tolerant phenotypes is boosted compared with toxin-free conditions. Because glyphosate is one of the leading herbicides in the world, tolerant phenotypes may benefit from current agricultural practices. If these results apply to other toxicants, low toxin doses may increase the fitness of tolerant phenotypes in a way not previously anticipated.