The effect of benzoic acid derivatives on Nicotiana tabacum growth in relation to PR-b1 production.

Using HPLC quantification, we have shown that benzoic acid derivatives stimulate PR-b1 protein synthesis in the leaf discs of Nicotiana tabacum Xanthi nc. The stimulation of PR-b protein synthesis during treatment with several benzoic acid derivatives is described for the first time in the root system of in vitro grown Nicotiana tabacum plantlets. In healthy in vitro grown plantlets the PR-b1 concentration is similar in roots and leaves (200 ng per gram of fresh material). During chemical treatment, however, the PR-b1 concentration increases to a lesser extent in roots than in leaves (10-fold higher in treated roots and 100-fold higher in treated leaves). Benzoic acid derivatives also have a detrimental effect on the growth of in vitro plantlets, which may be related to the accumulation of PR-b proteins.