New Leaves of Dryopteris intermedia Develop More Slowly When the Petioles of Overwintering Leaves are Broken

Abstract. Wintergreen ferns keep their leaves for an entire year before replacing them with new leaves in the spring. The overwintering leaves of Dryopteris intermedia provide carbon to the new leaves, and if these old leaves cannot become prostrate before winter via the hinge that develops at the base of the petiole, they are frost damaged and broken, which may affect the development of the new leaves in the subsequent year. I compared the vernal development of new leaves in D. intermedia between plants whose old leaves were intact and those whose petioles had been experimentally broken in the fall to determine the importance of the softening of the petiole-base in old leaves to the development of new leaves. Compared to the control, plants whose old leaves had broken petioles had a one-week delay in the development of their new leaves. This delay demonstrates that the evolutionary development of the petiole hinge may have been critical to the functional benefit associated with new leaf development in the wintergreen leaf habit in ferns.