Because of their molecular structure, carotinoid pigments are able to absorb wave lengths of light that are different from those absorbed by chlorophyll pigments. Typical carotinoid pigments are lycopene, alpha carotene,beta carotene, astaxanthin and fucoanthin. These are usually grouped as xanthophylls and carotins. Forms of plastids which exist in plant cells include protoplasts, chloroplasts, leucoplasts, amyloplasts, proteoplasts, chromoplasts and etioplasts. Each are briefly discussed.
Protoplasts are small, undifferentiated, immature plastids in meristematic cells.
They are capable of rapid division and can increase to significant numbers. Upon growth and development, they may differentiate into other specific plastids with specific functions. Chloroplasts have large numbers of thylakoids, containing a myriad of precisely oriented chlorophyll molecules, permitting the generation of minute electrical currents which power the photosynthesis processes. Leucoplasts are chloroplasts which possess only limited numbers of grana comprised of stacks of thylakoids with chlorophyll molecules, thus, cells and tissues in which they exist often appear white or colorless. Amyloplasts are colorless also and usually occur in storage tissues.