A new
family of bio-based herbicidal ionic liquids (HILs) has been
synthesized starting from the renewable resource glycine betaine (a
derivative of natural amino acids). After esterification, the obtained
alkyl betainate bromides containing straight alkyl chains varying
from ethyl to octadecyl were combined with a herbicidal anion from
the sulfonylurea group (iodosulfuron-methyl). The melting points of
the iodosulfuron-methyl-based salts were in a range from 51 to 99
°C, which allows their classification as ionic liquids (ILs).
In addition, the new HILs exhibited good affinity for polar and semipolar
organic solvents, such as DMSO, methanol, acetonitrile, acetone, and
chloroform, while the presence of bulky organic cations reduced their
solubility in water. The synthesized products turned out to be stable
during storage at 25 °C for over 6 months; however, at 75 °C
they underwent fast, progressive degradation and released volatile
byproducts. The values of the logarithm of the octanol–water
partition coefficient of ILs with alkyls longer than hexyl occurred
in the “safe zone” (between 0 and 3); hence, the risk
of their migration into groundwater after application or the possibility
of their bioaccumulation in the environment is lower in comparison
with the currently available commercial form (iodosulfuron-methyl
sodium salt). Greenhouse studies confirmed a very high herbicidal
efficacy for the obtained salts toward tested plants of oilseed rape,
indicating that they may become an attractive replacement for the
currently available sulfonylurea-based formulations.
MCPA (4-chloro-2-methylphenoxy) acetic acid is a common synthetic auxin used as a herbicide. The purpose of this study was to determine the effects of four new forms of MCPA being the herbicidal ionic liquids (HILs) with MCPA as an anion and two previously known formulations (potassium-sodium salt and 2-ethylhexyl ester) on seed germination and seedling development of winter oilseed rape (Brassica napus). Rape plants are susceptible to MCPA and volunteers can be a big problem in crop rotation. Seedling fresh weight and root length were quantified, mitotic activity, as well as lipid, starch, hydrogen peroxide and polyphenol contents were assessed by light and fluorescence microscopy and the computer-aided cytophotometer. In primary roots mitotic activity was almost completely inhibited under the influence of herbicides, cell elongation zones and root hair zones were significantly reduced, and a characteristic bolded root segment formed just above a meristem. In contrast to the traditional salt formulation the new HILs were weak inducers of hydrogen peroxide synthesis, but were potent stimulators of the synthesis of phenolic compounds and storage as well as emergency substances such as lipids and starch. All tested forms of MCPA caused strong phytotoxic effect on winter rape seedlings, but the tested HILs were more effective.
Camelina is an oil plant classified as a minor crop. The small acreage is the main cause of the small amount of plant protection products that are registered for use on camelina plantations. This contributes to difficulties in the protection of this plant. In the conducted experiment, the genetic similarity of genotypes of camelina was compared. The effect of selected herbicides (propaquizafop at rate 70 g a.i. ha−1, quizalofop-p-ethyl at rate 50 g a.i. ha−1, clopyralid at rate 90 g a.i. ha−1, and picloram at rate 24 g a.i. ha−1 applied in the three-four-leaves growth stage of camelina) on six individual genotypes of the plant and plant chlorophyll fluorescence after the use of these substances was also determined. The Przybrodzka variety showed the lowest level of damage in the assessment carried out 42 days after herbicide application and the damages of plants after quizalofop-p-ethyl and propaquizafop was completely gone. The variety Przybrodzka had the lowest genetic similarity to all analyzed genotypes. In other cases, genetic similarity of analyzed genotypes could not be linked to herbicide-related damage. Picloram contributed to the greatest damage to test plants and had the greatest impact on the operation of photosystem II (PSII). However, the level of plant chlorophyll fluorescence parameter values indicates small PSII damage for all substances and the possibility of subsequent plant regeneration. The results of the presented research indicate that it is worth referring to several plant varieties in phytotoxicity studies of herbicides towards arable crops.
The evaluation of the effects of grass and broadleaf weed control with different mixture rates of mesotrione plus nicosulfuron with methylated rapeseed oil and urea-ammonium nitrate liquid fertilizer (UAN) applied postemergence in maize was conducted in field experiments during the agricultural seasons of 2006, 2007 and 2008. Contact angle and surface tension were measured for all tank-mix solutions. There was no phytotoxicity observed on maize following the application of the herbicide-plus-additives treatment. Reduced rates of herbicide with additives provided similar control levels of Echinochloa crus-galli (L.) Beauv. as mesotrione used alone. The tank-mix of herbicides and adjuvants gave no antagonistic effect and it increased weed control. Plots treated with a reduced rate of tank-mix with additives, were always among the highest yielding as compared to untreated plots. Any reductions in cob and grain yield were associated with high weed fresh matter yields, indicating that it was the competition with weeds that led to a reduction in the maize grain yield and not the herbicide phytotoxicity.
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