Sugarcane micropropagation and phenolic excretion

Sugarcane shoot formation was followed using a temporary immersion system. Plant fresh weight, plant dry weight, shoot number and phenolic excretion t o the culture medium were recorded during shoot formation. Shoot number inc reased for 30 days of culture but formation of new shoots was greatly reduc ed from 31 to 40 days. Phenolic excretion also increased during the first 2 0 days of culture (gallic acid represented 82% total phenolics) and decreas ed during the last 10 days (31-40 days of culture). The most intensive peri od of phenolic excretion (11-20 days) preceded the most intensive period of shoot formation (21-30 days). The same relationship does not seem to exist between the accumulation of fresh and dry weights. Subculture onto fresh m edium at the beginning of proliferation (10 days after culture initiation) was detrimental to shoot formation in the subsequent period (11-20 days). H owever, such a detrimental effect could be avoided if gallic acid was added to the medium. Addition of cysteine to the culture medium reduced both exc retion of phenolics and shoot formation but not fresh weight. The use of te mporary immersion systems, the increase of culture medium volume per initia l explant and the addition of paclobutrazol promoted both phenolic excretio n and sugarcane shoot formation. Results presented here indicate a relation ship between phenolic excretion and shoot formation but not with accumulati on of plant weight.