Waterproof

• Waterproof layer of cellsleaf image by Andrey Rakhmatullin from Fotolia.com
  
  The outer layer of cells in plant skin have a waxy feel, and make the plant waterproof.
  
  

Gas Exchange

• Plants don't have lungs, but they do breathe. The integumentary system regulates the intake of carbon dioxide and the output of oxygen.
  
  

Protection

• Though the outer skin of a plant is generally just one cell thick, it protects the inner workings of the stem and leaves from accidental injury.
  
  

Water Retention

• Keeping moisture insmall potted cactus plant image by Wimbledon from Fotolia.com
  
  Just as the integumentary system keeps moisture rolling off the exterior of the plant, it also keeps water that has been drawn in through the root system from leaving. In essence, it keeps the plant from drying out.
  
  

Appendages

• Appendages such as thorns, hairs, and scales form from the tissue of the epidermis, which is part of the integumentary system. These various appendages often provide additional protection for a plant.
  
  

Secretion

• Plants secrete various fluids, including stinging or bad-tasting oils to aid in self-defense, as well as gummy or sticky fluids that serve to immobilize harmful insects and seal any wounds in the plant's skin.