Hitoshi Kuramochi

Improving salt tolerance of cotton seedlings with 5-aminolevulinic acid

Of 12 different plant growth regulators (PGRs) tested,5-aminolevulinic acid (ALA) was found to improve the salttolerance of cotton seedlings. Cotton seedlings treated with ALAcould grow in soil containing levels as high as 1.5% (wt/wt)NaCl. The analyses of mineral compositions of plant parts revealed that the Naplus concentrations in the roots of the plantstreated with ALA were suppressed to low concentrations. Fromthese results, it can be presumed that the presence of ALA maycause a reduction of Naplus uptake.

Enantioselective Herbicidal Activity of Chiral α-Methylbenzylphenylureas against Cyperaceae and Echinochloa Paddy Weeds.

Optically active α-methylbenzylphenylureas were synthesized and tested for their herbicidal activities against barnyardgrass and Cyperaceae paddy weeds in a greenhouse to evaluate the cross intergenus phytotoxicity between rice and barnyardgrass and the enantioselective phytotoxicity to the weeds. Several compounds controlled the growth of the weeds, and a suitable enantiomer for successful weed control was dependent on the type of weed and on the substituent at the aniline moiety. The (R)-2-isoPr and (R)-2-tert-Bu derivatives significantly controlled barnyardgrass and both annual and perennial Cyperaceae paddy weeds. The (R)-2-Et and (R)-2-CF3 derivatives showed the strong herbicidal activity against perennial Cyperaceae paddy weeds, while the (S)-enantiomers of the unsubstituted and fluoro derivatives were active against barnyardgrass. The enantioselectivity of the most potent compounds was high.

Promotion of Flowering in Sagittaria pygmaea Miq. by 2, 6-Diisopropylphenoxyacetic Acid

The flowering of Sagittaria pygmaea Miq. was promoted by 2,6-diisopropylphenoxyacetic acid, as well as by gibberellic acid (GA3). Uniconazole canceled the promotive effect of the phenoxy-acetic acid, while prohexadione shortened the period required for flowering. Endogenous GAs seem to play an important role in the flowering of S. pygmaea, and 2,6-diisopropylphenoxyacetic acid might affect GA biosynthesis or metabolism.

Effects of Plant Growth Regulators on Shoot Growth and Flowering of a Perennial Paddy Weed, Sagittaria Rygmaea Miq.

Plant growth regulators (PGRs) including gibberellins (GAs) were examined for their effects on shoot growth and flowering of a perennial paddy weed, Sagittaria pygmaea Miq. Among PGRs tested, only GAs (A1 A3, A4, and A5), AC-94377 [1-(4-chloro-1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)cyclohexanecarbox-amide] and 2,6-diisopropylphenoxyacetic acid (DIPA) promoted both shoot growth and flowering. Structural requirements of GAs for promotion of flowering seemed to be different from those for shoot growth of the weed. In addition, since the course of flowering induced by DIPA was clearly different from that observed in plots treated with GA3 or AC-94377, different mechanisms may be involved in promotion of flowering.

Restoration of gibberellin biosynthesis by 2,6-diisopropylphenoxyacetic acid in uniconazole-treated rice plants

Abstract2,6-Diisopropylphenoxyacetic acid (DIPA), a promoter of growth and flowering of Sagittaria species, was found to improve the shoot growth of rice plants treated with uniconazole, an inhibitor of gibberellin (GA) biosynthesis. In a modified micro-drop bioassay using semi-dwarf rice, Oryza sativa L. cv. Tan-ginbozu, in which uniconazole had been incorporated into the agar medium, a significant recovery from growth inhibition was observed for both the 3rd and the 4th leaf sheaths but not for the 2nd sheath. In greenhouse experiments, uniconazole-treated rice plants partially recovered from growth inhibition when DIPA was applied after uniconazole treatment, whereas DIPA applied with, or before, uniconazole treatment did not improve growth. The levels of GA1 and GA20 in the rice plants treated with uniconazole plus DIPA were almost equal to those of the untreated controls, indicating that the observed growth recovery is attributable to the restoration of GA biosynthesis by DIPA.

Photosystem II inhibition by pyran-enamine derivatives

Abstract Through the studies on structure-activity relationships of 5-acyl-3-(1-aminoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity of the molecule was found to be a major determinant for the activity. In the substituted N -benzyl derivatives, not only the lipophilicity but also the electronic and steric characters of the substituents greatly affected the activity. Their mode of PS II inhibition seemed to be similar to that of DCMU , whereas pyran-enamine derivatives needed to be highly lipophilic to block the electron transport in thylakoid membranes, which in turn diminished the permeability through biomembranes.