The impact of Cu treatment on phenolic and polyamine levels in plant material regenerated from embryos obtained in anther culture of carrot

The influence of copper sulphate on the regeneration of carrot (Daucus carota L.) androgenic embryos and changes in the levels of phenolic substances and polyamines that might be indicative of the response to oxidative stress were investigated. The cultivation on the regeneration medium supplemented with Cu2+ at the concentrations 1 and 10 mu M for 15 weeks resulted in significant dose-dependent inhibition of the growth and organogenic ability of carrot embryos. The total content of phenolic acids (represented by the sum of all soluble and insoluble fractions) in the Cu2+-treated carrot cultures did not change in comparison with the control (0.1 mu M Cu2+). However, the levels of phenolic acids in the individual fractions showed significant differences. The cultivation in the presence of increased Cu2+ evoked first of all the rise of free chlorogenic and caffeic acids, and the increase in soluble ester-bound ferulic acid. Marked dose-dependent decline in the amount of ferulic acid incorporated into the cell walls of the Cu2+-treated carrot cultures was partly compensated by the increase in the content of p-hydroxybenzoic acid. Decline in the total polyamine contents in the carrot tissues cultivated in the presence of increased Cu2+ concentrations was observed. The most abundant polyamine, both in a free and PCA-soluble conjugated forms, was putrescine, the least abundant was spermine, which occurred in free form only. While the levels of free polyamines, slightly decreased in a dose-dependent manner in the Cu2+-treated cultures, those of PCA-soluble conjugates markedly rose (enhancement to 135 and 170% in 1 and 10 mu M Cu2+, respectively, compared with the control). The decline in the total polyamine contents was caused mainly by the decline in the levels of PCA-insoluble conjugates. The decrease observed in this fraction was approximately to 70 and 50% in 1 and 10 mu M Cu2+-treated cultures, respectively, when compared with the control. The role of phenolic acids and polyamines in preventing Cu2+ stress in the carrot tissues is discussed. (c) 2006 Elsevier Masson SAS. All rights reserved.