The secondary effects of pencycuron on cell membrane of Rhizoctonia solani AG4 were investigated by the observation of giant protoplast formation and lipid per¬oxidaiton. Compared to protoplasts initially produced from the strains, protoplasts of R. solani R-C (sensitive strain) and Rh-131 (non-sensitive strain) increased in their size by 2.0-3.5 times 12 h after incubation in potato-dextrose broth containing novozyme (7 mg/ml) and β-glucuronidase (60 µl/ml) with 0.6 M mannitol (pH 5.2). The increase of protoplast size in R-C was slightly inhibited from 13.8 µm without pencycuron to 10.3 µm with 1.0 µg/ml of pencycuron. However, the size of giant protoplast of Rh-131 was not affected by the pencycuron treatment. Both strains R-C and Rh-131 did not exhibit the lipid peroxidation 12 h after the application of 1.0 µg/ml pencycuron. The remarkable peroxidation of membrane lipid was observed only in R-C 24 h after pencycuron application, but not in Rh¬131. Although the inhibition of giant protoplast forma¬tion and the membrane lipid peroxidation were observed only in the sensitive strain R-C by pencycuron, it is diffi¬cult to conclude that these are the primary mechanism of pencycuron. The mild activity of pencycuron on the inhibition of giant protoplast formation and late mem¬brane lipid peroxidation in the fungicide-sensitive strain did not coincide with the dramatic activity of pencycu¬ron in R. solani. Therefore, our results suggest that inhi¬bition of giant protoplast formation and membrane lipid peroxidation is the secondary effect of pencycuron.
2011年10月8日星期六
Physiology & Metabolism of Dicamba
Mode of Action & Lethality
The mode of action of dicamba is probably similar to that of the phenoxy carboxylic acids. Rapid, abnormal, cell growth then leads to the disruption of the phloem system and normal auxin balance in the plant. As with the phenoxy carboxylic acids, these herbicides act by stimulating abnormal cell growth in meristematic cells. This can result in the blockage of phloem vascular tissue. Extensive destruction of cambial, phloem cells near meristems occurs within days of treatment. The plant is killed by starvation resulting form an inability to translocate needed energy in the phloem.
Uptake and Movement of Dicamba in Plants
Dicamba is rapidly absorbed by plant root and shoot tissue. Dicamba translocates readily in the xylem and phloem. Dicamba taken up by plant roots is translocated mostly in the xylem initially, but over a longer time it moves to areas of high metabolic activity.
Basis of Selective Toxic Action between Susceptible & Resistant Species
Selective dicamba toxicity amongst plant species appears to be a function of uptake, distribution in the plant, and metabolism. In some tolerant species, translocation is limited to the xylem. Tolerant species metabolically degrade dicamba rapidly. The primary degradation pathway is by metabolism of the herbicide (ring hydroxylation followed by very rapid glucoside conjugation).
Yangzhou pioneer chemical CO.,LTD
The mode of action of dicamba is probably similar to that of the phenoxy carboxylic acids. Rapid, abnormal, cell growth then leads to the disruption of the phloem system and normal auxin balance in the plant. As with the phenoxy carboxylic acids, these herbicides act by stimulating abnormal cell growth in meristematic cells. This can result in the blockage of phloem vascular tissue. Extensive destruction of cambial, phloem cells near meristems occurs within days of treatment. The plant is killed by starvation resulting form an inability to translocate needed energy in the phloem.
Uptake and Movement of Dicamba in Plants
Dicamba is rapidly absorbed by plant root and shoot tissue. Dicamba translocates readily in the xylem and phloem. Dicamba taken up by plant roots is translocated mostly in the xylem initially, but over a longer time it moves to areas of high metabolic activity.
Basis of Selective Toxic Action between Susceptible & Resistant Species
Selective dicamba toxicity amongst plant species appears to be a function of uptake, distribution in the plant, and metabolism. In some tolerant species, translocation is limited to the xylem. Tolerant species metabolically degrade dicamba rapidly. The primary degradation pathway is by metabolism of the herbicide (ring hydroxylation followed by very rapid glucoside conjugation).
Yangzhou pioneer chemical CO.,LTD
2011年10月7日星期五
Combination of pencycuron and Pseudomonas fluorescens strain 2-79 for integrated control of rhizoctonia root rot and take-all of spring wheat
Pencycuron (tradename Monceren, a fungicide developed specifically to control Rhizoctonia) was evaluated for in vitro growth inhibition of wheat pathogenic Rhizoctonia spp., Gaeumannomyces graminis var. tritici and Pythium spp., and for control of wheat root diseases in greenhouse trials. In the greenhouse, pencycuron inhibited binucleate Rhizoctonia, R. oryzae, or R. solani in vitro and reduced Rhizoctonia root rot. Pencycuron also inhibited G. graminis var. tritici strains in vitro and slightly reduced take-all disease in the greenhouse. Moreover, pencycuron seed treatment protected plants against a disease mixture of Rhizoctonia root rot and take-all. Pythium spp. were not inhibited by pencycuron in vitro. Pencycuron did not adversely affect seedling emergence, nor did it inhibit rhizosphere colonisation by Pseudomonas fluorescens biocontrol strain 2-79. Combined application of the fungicide and strain 2-79 to seed was more effective than either treatment alone for controlling disease.
Differences in Injury due to Dicamba and 2,4-D
It is hard, if not impossible, to definitely differentiate between injury caused by these two similar herbicides. There are several keys that often can be helpful though.
1. Dicamba translocates more completely throughout a plant and better control of woody and brushy species can help: these species will be injured more by dicamba than 2,4-D.
2. Another difference is the tendency of dicamba to flatten and twist monocot leaves just after treatment, a symptom not encountered as much with 2,4-D.
3. Dicamba can drift in the air to greater distances than does 2,4-D.
4. Dicamba injury often will develop over a longer period than 2,4-D: dicamba is slower acting.
5. 2,4-D often will cause slightly more corn stalk injury under the same conditions than that caused by dicamba.
6. Dicamba has a longer residual effect in the soil than that from 2,4-D.
7. Dicamba costs more than 2,4-D, look for thrifty farmers using 2,4-D.
8. Dicamba may also act so quickly that it doesn"t form the "strap-shaped" leaves, narrow and puckered, that 2,4-D does. Dicamba injured leaves instead are shorter than those with 2,4-D.
Yangzhou pioneer chemical CO.,LTD
1. Dicamba translocates more completely throughout a plant and better control of woody and brushy species can help: these species will be injured more by dicamba than 2,4-D.
2. Another difference is the tendency of dicamba to flatten and twist monocot leaves just after treatment, a symptom not encountered as much with 2,4-D.
3. Dicamba can drift in the air to greater distances than does 2,4-D.
4. Dicamba injury often will develop over a longer period than 2,4-D: dicamba is slower acting.
5. 2,4-D often will cause slightly more corn stalk injury under the same conditions than that caused by dicamba.
6. Dicamba has a longer residual effect in the soil than that from 2,4-D.
7. Dicamba costs more than 2,4-D, look for thrifty farmers using 2,4-D.
8. Dicamba may also act so quickly that it doesn"t form the "strap-shaped" leaves, narrow and puckered, that 2,4-D does. Dicamba injured leaves instead are shorter than those with 2,4-D.
Yangzhou pioneer chemical CO.,LTD
2011年9月30日星期五
The effect of Dicamba on plant regeneration of wheat, barley and triticale
One of the basic components of a medium influencing somatic embryogenesis of cereals from immature embryos is the type of auxin. According to some researchers, phytohormones can also play an important role during Agrobacterium-mediated transformation. In this first part of research, the influence of three types of auxins used alone or in combination of two on somatic embryogenesis and plant regeneration in three cereal species has been tested. Eight cultivars of barley, five cultivars of wheat and three cultivars of triticale have been used. Efficiency of plant development on two regeneration media, with an without growth regulators has been compared. Efficiency of regeneration characterized by frequency of explants that form embryogenic callus ranged from 25% for wheat cultivar Torka to 100% for two barley cultivars. Mean number of plantlets regenerating per explant differed significantly (from 2 to 58) depending on the type of auxin in inducing media, the type of regenerating media as well as cultivar. The biggest differences in regeneration efficiency were observed between barley cultivars, however regeneration of plants occurred in all combinations tested. The best regeneration coefficients for most barley cultivars were obtained after culture on dicamba or dicamba with 2,4-D. However, in the case of highly regenerating cv Scarlett, the most effective culture media contained picloram or 2,4-D alone. The highest values of regeneration coefficients for two triticale cultivars (Wanad and Kargo) were obtained on picloram (26.1 and 21.4, respectively) and for "Gabo" on picloram with dicamba (12.6). The range of mean number of regenerated plantlets was from 12 to 30. 
Dicamba alone or lower concentrations of picloram with 2,4-D were the best media influencing embryogenic callus formation in five wheat cultivars. However, the highest values of regeneration coefficients ranging from 10.6 to 26.8 were obtained at lower concentrations of picloram with 2,4-D or picloram wit.
Dicamba alone or lower concentrations of picloram with 2,4-D were the best media influencing embryogenic callus formation in five wheat cultivars. However, the highest values of regeneration coefficients ranging from 10.6 to 26.8 were obtained at lower concentrations of picloram with 2,4-D or picloram wit. Pencycuron: a new fungicide against black scurf (Rhizoctonia solani) in potatoes
Pencycuron (Monceren) is a new active ingredient from Bayer AG Leverkusen. Pencycuron is a fungicide with contact effect used as seed dressing in potatoes with a specific effect against black scurf (Rhizoctonia solani). A large number of field trials carried out in several countries in western Europe have proven that pencycuron is setting a new standard for the control of black scurf (Rhizoctonia solani) in potatoes achieving a considerable increase in yield and tuber quality of the crop. Pencycuron has also shown its superiority in comparison to other seed dressings in the market. Furthermore the treatment improves the size and shape of the tubers as shown by the number of tubers having size 35-55 mm with lower Sclerotinia darnage in the harvested crop. pencycuron was launched in the Danish market in 1993 as Monceren DS 12,5, a dry powder formulation used with a dosage of 200 g per hkg seed potatoes. In 1994 pencycuron will also be available in Denmark as Monceren FS 250, a liquid formulation used with a dosage of 60 ml per hkg seed potatoes. This formulation is sprayed on the seed tubers while dropping from the potato planter to the soil using special equipment
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