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We propose a max-plus equation which reproduces evolutional patterns often observed in reaction-diffusion systems of excitable media. The equation gives a travelling wave, a target pattern and a spiral pattern from appropriate initial data. Moreover, using the advantages of max-plus equations, we obtain the solutions exactly by a reduction from the high-dimensional equation to a lower one. In the reduction, we use coordinate curves according to a pattern shape. It is interesting that all patterns satisfy the same reduced equation. We also propose two other models similar to the previous one and discuss the behaviour of solutions.

Effects of epibrassinolide (EBR), one of the brassinosteroids (BRs), on culture of Chinese cabbage mesophyll protoplasts were researched. The addition of EBR to the liquid culture medium increased the cell division rate and the amount of soluble protein of the protoplasts during culture. These results showed that EBR enhanced cell reproduction of Chinese cabbage mesophyll protoplasts. EBR 10-1 mg/L was especially effective. After 3 weeks of culture, there were more cell clusters in the petri dishes containing EBR than in those not containing EBR. The number of clusters increased in direct proportion to the EBR concentration. The clusters in liquid medium were transferred to agarose solidified medium which contained the same concentration of EBR as liquid culture, and after that colony formation was observed. As the result, the addition of 10-1 mg/L EBR obviously enhanced colony formation of the protoplasts. It was shown that EBR was effective in multiplication of the protoplasts.

The metabolism of exogenously applied14C-24-epibrassinolide (14C-EBR) in seedlings of cucumber and wheat was examined. Total lipids were extracted with isopropanol and chloroform, and then partitioned with water. More than 80% of radioactivity was distributed to chloroform-phase. Concentrated chloroform-phase was applied to silica gel plate and was developed with chloroform-ethanol (5:1 v/v). Rf value of original14C-EBR was about 0.6. In cucumber leaves harvested after 2 day-culture, three peaks were detected at Rf 0.11, 0.47 and 0.84. In cucumber petioles of 2 day-culture, however, a major peak was detected at Rf 0.90. But14C-EBR was hardly metabolized in hypocotyls and roots after 2 days.

Summary When 14 C-24epibrasinolide ( 24 C-EBR) was applied to the roots of cucumber seedlings, 14 C-EBR was metabolized to les polar and polar metabolites. Chemical characterization of these metabolites was investigated by acid and alkali hydrolysis. The sterol obtained from these hydrolysates was a unique sterol (EBR*) having higher polarity than the original EBR. These results indicate that EBR was metabolized to EBR*, and then EBR* was conjugated with fatty acid and/or sugar in cucumber seedlings. The chemical structure of EBR* was determined to be 2,24-diepibrasinolide, which was a 2-epimer of EBR, by liquid chromatography-mas spectrometry (LC-MS)and gas chromatography-mas spectrometry (GC-MS). It is suggested that 2,24-diepibrasinolide was an important intermediate to form conjugates.

The uptake and the transport of exogenously applied epibrassinolide (EBR) in seedlings of cucumber and wheat were examined by autoradiography using14C-EBR.14C-EBR was applied to roots, young and mature leaves, and the shoot apex. When applied to roots,14C-EBR was readily taken up and was swiftly transported throughout both plant species. When14C-EBR was applied to the adaxial surface of a young cucumber leaf, it was readily taken up, but was very slowly transported. In cucumber leaves,14C-EBR was transported throughout the treated leaf after 3 days of treatment, and then it was transported to upper leaves from the treated leaf after 7 days. Some 6.3% of applied14C-EBR was transported to the newly expanded leaves. In wheat leaves,14C-EBR was transported only in the apical direction from the treated spot after 3 days of treatment, but it was not transported from the treated leaf to the other leaves or organs even after 7 days. Some 1.3% of applied14C-EBR was transported to the tip area of the treated leaf. These results indicate that exogenous EBR applied to intact plants is acropetally transported.

Spray treatment with 22R, 23R epibrassinolide (EBR, 0.1 ppm) increased the length and dry weight of both the top and root of sorghum plants under various soil water conditions, although the extent of growth promotion was small. Under well-watered conditions, abscisic acid treatment (ABA, 50 ppm) inhibited top growth but promoted root growth. However, under water-stressed conditions, ABA-treated plants grew at a higher rate than control and EBR-treated plants. The accelerated growth of ABA-treated plants was apparent both in the top and the root. Treatment with 0.1 ppm EBR + 50 ppm ABA inhibited growth even more than ABA treatment under well-watered conditions, but it increased the growth rate more than ABA alone under water stressed conditions. Treatment with EBR + ABA promoted root growth to a larger extent even than ABA treatment. From the above results, it was concluded that EBR increased the effects of ABA both under well-watered and water stressed conditions. Treatment with EBR and ABA increased the survival ability of plant and leaf under severe drought. This effect of ABA was also enhanced by EBR. Thus, synergistic interaction between ABA and EBR was observed in almost all aspects examined.

2-Mono- and 2, 3-diacetate derivatives of (22R, 23R)- and (22S, 23S)-24-epibrassinolides, and (22R, 23R)- and (22S, 23S)-2-deoxy-24-epibrassinolides were synthesized. They were found to possess weak biological activity in a rice-lamina inclination test.