Lignification response for rolled leaves of Ctenanthe setosa under long-term drought stress

Leaf rolling is a dehydration avoidance mechanism for plants under drought stress. To understand how it affects the lignification process in response to long-term drought stress in Ctenanthe setosa plants that have the leaf-rolling mechanism, the enzymes in lignification were studied in unrolled leaves as a control and at 2 different leaf rolling indices at days 35 and 47 of the drought period. The results indicated that the activities of phenylalanine ammonia lyase, indole-3-acetic acid oxidase, soluble peroxidase, ionically wall-bound peroxidase, covalently wall-bound peroxidase, and polyphenol oxidase were increased during long-term drought stress. However, nitrate reductase activity was decreased while lignin content was increasing during the period of drought. Lignin content was positively correlated to activities of phenylalanine ammonia lyase, indole-3-acetic acid oxidase, soluble peroxidase, ionically wall-bound peroxidase, and polyphenol oxidase, but it was negatively correlated to activity of nitrate reductase. Furthermore, there was a positive correlation between leaf rolling and lignin content. The results indicate that the leaf-rolling process may be related to the lignification mechanism in alleviating damage from stress in Ctenanthe setosa under long-term drought stress.