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 to the culture medium were recorded during shoot formation. Shoot number increased for 30 days of culture but formation of new shoots was greatly reduced from 31 to 40 days. Phenolic excretion also increased during the first 20 days of culture (gallic acid represented 82% total phenolics) and decreased during the last 10 days (31–40 days of culture). The most intensive period 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 medium at the beginning of proliferation (10 days after culture initiation) was detrimental to shoot formation in the subsequent period (11–20 days). However, such a detrimental effect could be avoided if gallic acid was added to the medium. Addition of cysteine to the culture medium reduced both excretion of phenolics and shoot formation but not fresh weight. The use of temporary immersion systems, the increase of culture medium volume per initial explant and the addition of paclobutrazol promoted both phenolic excretion and sugarcane shoot formation. Results presented here indicate a relationship between phenolic excretion and shoot formation but not with accumulation of plant weight. This revised version was published online in June 2006 with corrections to the Cover Date.