What is plant senescence, and why is it important?
Senescense, in plants, often refers to the seasonal event of leaves changing colors and dropping in deciduous plants although it also refers to the general shedding of old leaves. Senescence occurs to conserve resources withing a plant. As winter approaches the day gets shorter. Deciduous plants pick up on this and begin to generate hormones such as ethylene which signal that it is time to mobilize some of the more energy-expensive molecules in the leaves. Molecules that take lots of energy to create, such as chlorophyls, are packaged (sometimes in pieces) and moved out of the leaf and into the stems and roots for safe keeping. This process leaves behind the easier-to-manufacture compounds such as carotenoids which give us the brilliant yellows and reds that you see on trees in the fall. Eventually a chemical signal is given to kill off a plane of cells near the base of the leaf causing the leaf to die loosen, and eventually drop to the ground. The process is the same in leaves that ar
