to become wood or like wood as a result of the depositing of lignin in the cell walls
verblig·ni·fied, lig·ni·fy·ing, lig·ni·fies
To turn into wood or become woody through the formation and deposit of lignin in cell walls.
To make woody or woodlike by the deposit of lignin.
(third-person singular simple present lignifies, present participle lignifying, simple past and past participle lignified)