除草剤の酸素電極法による光合成阻害力の検定

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Photosynthesis inhibition was tested with 53 kinds of herbicides or biochemical inhibitors (Table 1.) with the oxygen electrode method, using flag-leaf discs of rice (Oryza sativa L.) plant. Reaction system for measuring photosynthesis with oxygen electrode (Rank Brothers INC. England) consisted of 3 ml of 50 mM HEPES buffer (pH 7.2) plus 0.1 mM CaSO_4 with or without the inhibitors and 20 pieces of 3.0 mm diameter leaf discs. Photosynthetic reaction was started by adding 100 μl of 0.625 M NaHCO_3 (final concentration, 20 mM) under about 60Klux light intensities. Photosynthetic rate was caluclated as μmol O_2/dm^2/hr. Results obtained were as follows: 1. Most of herbicides (DCMU, prometryn, simetryn, metribuzin, linuron, atrazine, propanil, bromacil, simazine, pyrazon, S-52, swep and CMMP) and a biochemical inhibitor (CCCP) belonging to the Hill reaction inhibitors apparently inhibited the photosynthesis of leaf discs (Table 2). Concentrations of 50% inhibition of photosynthesis (pl_<50>) of them were distributed within a range from 10^6M to 10^4M (Table 2). Ioxynil, bromoxynil octanoate and bentazon showed pl_<50> of the dose levels of 10^3M or more. When pl_<50> Of these herbicides were com-pared with the referenced concentrations of 50% inhibition of chloroplast Hill reaction activity (abbreviated as HI_<50>), the ratios of pI_<50> to HI_<50> were about 5 to 200 except ioxynil and S-52 with 1,000〜2,500 (Table 2). 2. Pl_<50> of the inhibitors (dinoseb, PCP, antimycin A, KCN and 2,4-DNP) which are known to disturb the respiration systems was at the dose levels of 10^4M to 10^3M, except 2,4-DNP (Table 3). 3. Herbicides such as auxin-type (2, 4-D, 2, 4, 5-T, and MCPA), protein and nucleic acid synthesis inhibitors (alachlor, thiobencarb, butachlor, diphenamid, molinated and piperophos), mitosis inhibitors (metolachlor, trifluralin, alloxydim and pendimenthalin) and light-required active compounds (amitrol, bifenox, chloronitrofen, nitrofen, oxadiazon and chlomethoxynil) and others (glyphosate, pyrazolate and SL-501) did not disturb photosynthesis of leaf discs in this experimental system (Table 3 and Table 4). 4. Paraquat and diquat, however, which belong to light-required active compounds, inhibited photosynthesis to some extent at more than 10^<g;-3>M concentration. (Table 4). 5. Ioxynil and bromoxynil octanoate, which belong to Hill reaction inhibitors, and CIPC and methazol, which belong to protein and nucleic acid synthesis inhibitors, are known to act also as the uncoupler or inhibitors of oxidative phosphorylation. Pl<50> of these herbicides were approx. 10-3 M or more, which were similar to those of respiration system inhibitors such as PCP and KCN (Table 2 and Table 3). 6. A several kinds of herbicides (chloramben, dicamba, diclofop-methyl, and asulam) inhibited photosynthesis at high concentrations. These inhibitive phenomena might be affected by the surfactant and/or carriers within their commercial formulations (Table 1, Table 3 and Table 4.). 7. There was a positive correlation ( r =0. 697**) between pl_<50> and HI_<50> On the herbicides (except ioxynil) and biochemical inhibitors which inhibited the photosynthesis in this experiment (Fig. 1). From the results obtained here, the different pl_<50>-dependent on herbicide and biochemical inhibitor actions in this experimental system were discussed with reference to the classifications of them by the dose levels of pl_<50> and to the availability of oxygen electrode for an indicator to screen the unknown active compounds.
日本雑草学会の論文
1982-10-26

除草剤の酸素電極法による光合成阻害力の検定

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