Question

Stroma is ground substance of
A. Nucleus
B. Chloroplast
C. Mitochondria
D. Endoplasmic reticulum

Answer 1

Hint: Chloroplast is a cell organelle present in all the green plant cells. Each chloroplast is enclosed by a unit or double membranes. The ground substance is present within the inner membrane.

Complete answer:
Chloroplast is a green colour plastid due to the presence of chlorophyll. Chloroplasts are found in the cells of all the green plants. They are generally biconvex but in different plants, chloroplasts have different shapes such as discoid, spheroid, filamentous.
Each chloroplast is surrounded by the two membranes, outer and inner membranes. Within the inner membrane, matrix or ground substance is present which is called stroma.
Stroma is an alkaline aqueous fluid, rich in protein. It contains enzymes that are the site for dark reaction or Calvin cycle of the photosynthesis. In the stroma reduction of the carbon dioxide with use of assimilatory power which produced during light reaction of photosynthesis. During dark reactions carbon dioxide is fixed into sugar (carbohydrate).
Within the stroma, a collection of membranous sacs are present which is called thylakoids on which the chlorophyll is found in the thylakoids and is the site for the photochemical reactions or light reactions of photosynthesis.

Thus, option B is the correct answer.

Note: Chloroplast and mitochondria are semi-autonomous cell organelles as they contain DNA and ribosomes. Besides nucleus, only these two cell organelles have DNA. They can form their own protein. Therefore, they are semi-autonomous.