chlorophyll-a and methyl-bensulfuron

A potted soil experiment was conducted to investigate the effects of bensulfuron-methyl (BSM) residue on the growth and photosynthesis of seedlings of a local cucumber variety (Xia Feng No.1). When the residue of bensulfuron-methyl in soil exceeded 50μg kg-1, it significantly inhibited the growth of cucumber, chlorophyll content and photosynthetic capacity of cucumber. BSM treatment caused significant decreases in the biomass, chlorophyll content, net photosynthesis rate, stomatal conductance, and transpiration rate, photosystem II (PSII) maximum quantum yield, actual quantum yield, photochemical quenching coefficient, and electron transport rate in cucumber seedlings, but increased the minimal fluorescence yield and dark respiration rate. Moreover, comparisons of the patterns of absorbed light energy partitioning revealed that the fractions of excess and thermally dissipated energy increased with rising concentrations of the BSM residue, but the fraction of PSII photochemistry declined. The BSM residues caused reversible destruction in the PSII reaction centers and decreased the proportion of available excitation energy used in PSII photochemistry. The results suggested that rice or wheat fields sprayed with BSM will not be suitable for planting cucumbers in succession or rotation.

Topics: Chlorophyll; Crop Production; Cucumis sativus; Fluorescence; Herbicides; Photosynthesis; Plant Leaves; Seedlings; Soil; Sulfonylurea Compounds

The physiological effects of 4 herbicides (butachlor, quinclorac, bensulfuron-methyl and atrazine) on 3 submerged macrophytes (Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii) were tested in laboratory. The variables of the relative growth rate and the photosynthetic pigment content showed that all of the tested herbicides affected the growth of the plants obviously, even at the lowest concentration (0.0001 mg/L). Except for the C. demersum treated with quinclorac at 0.005 and 0.01 mg/L, the relative growth rates of the plants were inhibited significantly (p < 0.01). Statistical analysis of chlorophyll a (Chl-a) contents was carried out with both the t-test and one-way ANOVA to determine the difference between the treatment and control. The results showed that Chl-a contents of the plants in all treatment groups were affected by herbicides significantly, except for the C. demersum treated with bensulfuron-methyl at 0.0005 mg/L. The decrease in Chl-a content was positively correlated to the dosage of the herbicides in most treatment groups. It was suggested that herbicides in water bodies might potentially affect the growth of aquatic macrophytes. Since the Chl-a content of submerged macrophytes responded to the stress of herbicides sensitively and directly, it could be used as a biomaker in environmental monitoring or in the ecological risk assessment of herbicide contamination.

Topics: Acetanilides; Alismatales; Anthocerotophyta; Atrazine; Chlorophyll; Chlorophyll A; Herbicides; Hydrocharitaceae; Sulfonylurea Compounds

Effects of butachlor, bensulfuron-methyl, and dimethoate on the growth, photosynthesis, and photoinhibition of the edible cyanobacterium Ge-Xian-Mi were examined in order to gain insight into the relationship between its productivity reduction and the abusive use of pesticides in the field. Severe inhibition of growth was found in the presence of four- to six-fold field concentration of butachlor and very high concentrations of bensulfuron-methyl and dimethoate. Mild stimulation of photosynthesis was observed over a limited range of low concentrations of these three pesticides. We found that PSII and PSI were, respectively, the inhibitory sites of 150microM butachlor and 150microM bensulfuron-methyl. However, the inhibitory site of 2000microM dimethoate seems to be situated at the terminal of the whole chain or dark reaction. The colonies exposed to 150microM butachlor were more sensitive to high light than control cells and those exposed to bensulfuron-methyl, dimethoate, or low butachlor concentration. Dim light-induced rapid recovery of photoinhibited colonies was observed for the control, 10microM butachlor, bensulfuron-methyl, and dimethoate treatments. However, the maximal PSII photochemical efficiency of photoinhibited colonies treated with 150microM butachlor was maintained at a relatively stable value in low light. Our findings suggest that the abusive utilization of butachlor might be an important factor limiting the productivity of Ge-Xian-Mi in the field.

Topics: Acetanilides; Acetone; Cell Respiration; Chlorophyll; Chlorophyll A; Dimethoate; Electron Transport; Nostoc; Oxygen; Pesticides; Photosynthesis; Photosystem I Protein Complex; Sulfonylurea Compounds; Time Factors