noun, plural: proplastids
A proplastid is an organelle found in the meristematic regions of the plant. It is colourless and small. It is from where plastids are derived. It is still undeveloped and may divide to produce more proplastids. As the cell containing proplastids mature, the proplastids transform and develop into plastids with specialized functions.
Plastids are organelles that come in different forms depending on their function. Plastids with chlorophyll (green pigment) are called chloroplasts. They give the plant parts the green colour. These plastids are involved in photosynthesis. Those that have other pigments are called chromoplasts. They are involved in producing and storing pigments, e.g. carotene, xanthophylls, etc. They abound in fruits, flowers, and roots. A plastid that lacks pigments is called leucoplast, and is involved mainly for storing food. A leucoplast may be an amyloplast that stores starch, an elaioplast that stores fat, or a proteinoplast that stores proteins. Tannosomes are also leucoplasts and are involved in the synthesis of tannins and polyphenols. Like mitochondria, plastids have their own DNA and ribosomes. Hence, they may be used in phylogenetic studies.