Takashi Ohnuki

MOLECULAR MECHANISM OF THE CONTROL OF NYCTINASTIC LEAF-MOVEMENT IN LESPEDEZA CUNEATA G. DON

Abstract The nyctinastic leaf-movement of plants is controlled by an endogenous biological clock. In a nyctinastic plant, Lespedeza cuneata G. Don, this movement is controlled by the balance of the concentration between the leaf-closing and -opening substances. Quantitative HPLC analysis revealed that the change in the concentration of this leaf-opening substance is inversed through a day, and the deactivation of this substance is performed by a glucosidase whose activity is controlled by a biological clock. The leaf-movement of nyctinastic plants is caused by the balance of two leaf-movement factors, which is controlled by the enzymatic transformation.

THE CHEMICAL CONTROL OF LEAF-MOVEMENT IN A NYCTINASTIC PLANT, LESPEDEZA CUNEATA G. Don.

Abstract Potassium d -idarate ( 1 ) was isolated from Lespedeza cuneata G. Don as a bioactive substance for nyctinasty. The compound was quite effective for leaf-closing of the plant at 1 × 10 −6 M in the daytime and caused leaf-closing movement on the leaf of Cassia mimosoides L. Inversely effective two leaf-movement factors, 1 and potassium lespedezate ( 2 ), were isolated from the same plant.

Leaf-opening substance of a nyctinastic plant, Cassia mimosoides

Abstract Calcium 4- O -β- d -glucopyranosyl-(Z)- p -coumarate, isolated from Cassia mimosoides , was effective for leaf-opening of the plant 4 × 10 −6 M at night. This leaf opening substance and potassium chelidonate, which is a leaf-closing factor isolated previously, were inversely effective for the leaf of Cassia mimosoides .

Leaf-opening Substance in the Nyctinastic Plant, Albizzia julibrissin Durazz

cis-p-Coumaroylagmatine (1) was isolated from Albizzia julibrissin Durazz, a nyctinastic plant, as a leaf-opening substance. The compound was quite effective for opening the plant leaves at 5×10(-6) M at night, but was not effective for other nyctinastic plants. The bioactive fraction with leaf-closing activity was also separated from the plant extract. Although the leaf-opening activity of the plant extract changed between the day and night, the content of 1 was almost constant through a 24-h day. These results suggest that the change in content of an unknown leaf-closing factor induced balance between the two leaf-movement factors through a 24-h day.

Chemical studies on plant leaf movement controlled by a biological clock

Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning according to the circadian rhythm controlled by a biological clock. Extensive studies on nyctinastic plants led to the isolation of a variety of leaf-closing and -opening substances. And we found that the biological clock regulates the balance of concentration between leaf-opening and -closing substances in the plant body during the day.

The structure of a novel inhibitor of dextransucrase

Abstract The structure of ribocitrin ( I ), a novel dextransucrase inhibitor produced by a Streptomyces was elucidated to be 2-(S)-[O-α(-D-ribofuranosyl-(l→2)- O-α-D-ribofuranosyl- (1→3)-α-D-ribofuranosyloxyl -1,2,4-butanetricarboxylic acid.