Abstract: In accordance with the present invention, there are provided methods to modulate plant lignification. For example, the level of the enzyme phenylalanine ammonia-lyase (PAL), a key enzyme in the production of lignin precursors, can be increased or decreased, as desired, to increase or decrease lignification levels. Alternatively, the level of lignin precursors in the plant can be modulated either by enhancing the plant's ability to produce such precursors, or by causing the compounds which are required for the production of lignin precursors to undergo alternative chemical conversions (which prevent the incorporation of such compounds into lignin by diverting the lignin precursors to other chemical pathways). In addition, there is provided a method for producing plants having modified lignin composition and content, by converting a portion of the cinnamic acid in said plant to styrene.