Ethylene-brassinolide

Transverse geotropism in stems is a characteristic response to ethylene. It has been reported that treatments with epibrassinolide at concentrations of 1-10 ppm accelerated ethylene production in etiolated mung bean hypocotyl segments by increasing ACC (1-aminocyclopropane-l-carboxylic acid) (7). Thus it is possible that the transverse geotropism and even the twining growth response evoked by brassinolide at 10 1-10° ppm were related to the production of ethylene. 

The three experiments with brassinolide showed that the physiological effect of brassinolide seems to be that of both an auxin and cytokinin. The twining growth effect, however, is the characteristic response evoked by brassi-nosteroids, and it was thought that the twining movement of the tendril and the twiner (climber) reported for auxin, or abscisic acid (ABA), or ethylene earlier is doubtful. In other words, brassinolide as a steroid may act on membrane systems. 

Table III. Effect of Brassinolide on Ethylene Evolution from Panicles under Greenhouse Conditions...

Until the discovery of brassinolide by USDA scientists in 1979, it was thought that only five groups (indole auxins, gibberellins, cytokinins, abscisic acid, and ethylene) of hormones were responsible for regulating plant growth and development. Following this discovery, a number of compounds similar to brassinolide both in structure and physiological activity were isolated from different parts of plants. On the basis of published... 

The mimetic of brassinolide 81 was prepared in high yield by the coupling of fran5 -bis(tri-n-butylstaimyl)ethylene (79) with the enol triflate 80 [37]. 

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