Plastids

Plastids are organelle characteristics of plants lying greenly in cytoplasm. These are also present in photosynthesis protists (algae).

Types

• ·         Chloroplasts        Chromoplasts      and    Leucoplasts.
• 1.       Chloroplasts:

These are present in the green parts of the plant particularly in leaves.

Structure of Chloroplasts

Each chloroplast is bounded by a double membrane. The outer membrane is smooth. Inner membrane gives rise to stacked membrane system composed of sacs which are called thylakoids. Stacks of thylakoids are called Grana. Chloroplasts are filled with semi fluid matrix called stoma. Thylakoids contain green pigments (chlorophyll)

Function of Chloroplast

Due to the chlorophyll, photosynthesis takes place in them.

• 2.       Chromoplasts

These give various colours to the plant and plant parts (other than green). These are present in the cells of flowers petals and fruits. Their function is to give colours so that insects attract towards them and so help in pollination and dispersal of fruits.

• 3.       Leucoplasts

These are present in the cells or those parts of the plants where food is stored because their function is to store starch, proteins and lipids. These are colourless.