A modified leaf is an adaptation of plant meant for its own survival due to its environmental stress. When a leaf performs functions other than photosynthesis and transpiration, structural changes may occur. Plants may change either the structure of the leaves, the color (to attract insects), or may add spines or thorns to protect itself.
Examples of plants with modified leaves are: Nepenthes, Drossera, Tendrils, Venus fly-trap, sundew, poinsettias, and pitcher plants.
The plant pictured is an Aloe Vera plant. The plant’s leaves are covered in thorns to protect itself from potential predators and to preserve water.