Promotion ofin vitro shoot formation from excised roots of silktree (Albizzia julibrissin) by an oxime ether derivative and other ethylene inhibitors.

This report describes the regeneration response of excised seedling roots of silktree (Albizzia julibrissin) to added ethylene precursors/generators (1-amino-cyclopropane-1-carboxylic acid [ACC], 2-chloroethylphosphonic acid [CEPA]), biosynthesis inhibitors (aminoethoxyvinylglycine [AVG], an oxime ether derivative [OED={[(ispropylidene)-amino]oxy}-acetic acid-2-(methoxy)-2-oxoethyl ester], CoCl(2) [Co(++)]), and an ethylene action inhibitor (AgNO3 [Ag(+)]). When placed on B5 medium, about 50% of the control explants formed shoot buds within 15 days. Addition of ACC or CEPA (1-10 µM) to the culture medium decreased both the percentage of cultures forming shoots and the number of shoots formed per culture. In contrast, AVG and OED (1-10 µM) increased shoot formation to almost 100% and increased the number of shoots formed per culture. Likewise, both Co(++) and Ag(+) (1-10 µM) increased shoot regeneration, but the number of shoots produced after 30 days was less than with AVG or OED. The inhibitors of ethylene biosynthesis were partially effective in counteracting the inhibitory effect of ACC on shoot formation. These results suggest that modulation of ethylene biosynthesis and/or action can strongly influence the formation of adventitious shoots from excised roots of silktree.