Question

What is stroma in a plant cell? State its function and location in a plant cell.

Answer 1

Hint: Green plants are the only producers on our Earth. The green color of these plants is due to the presence of a specific green-colored pigment called Chlorophyll. There is a specific organelle that functions as a site for photosynthesis, i.e. chloroplasts.
Complete step-by-step answer:
Inside the chloroplasts, there is the presence of a colorless fluid called the stroma. The stroma surrounds the grana within the chloroplasts. The grana(sing. granum), are groups of thylakoids stacked over one another and it is the cell organelles where photosynthesis is commenced.

Image – Location of grana in chloroplast
Photosynthesis is a biochemical process that occurs in two steps over the span of the day and night time. Those two steps are:-
i) Light-dependent step- All the reactions in photosynthesis that require the presence of sunlight take place in this step. It is done in the daytime.
ii) Light-independent step- All the reactions which occur without the presence of light take place in this step. It is done at nighttime.
All of these redox reactions take place inside the stroma. This biochemical redox reaction is collectively called the Calvin cycle. The grana are connected to each other with the help of a layer of thin tissue called the stroma lamellae. It joins two separate grana's thylakoids.



The function of stroma lamellae is:
1) The stroma lamellae act as a skeleton of the chloroplast.
2) The stroma lamellae assist in absorbing as much sunlight as possible in order to boost photosynthesis rates.
3) The stroma lamellae also help in increasing the efficiency of photosynthesis by keeping the grana at a particular distance. This prevents the grana from becoming cluttered.

Note: The chloroplast is surrounded by a double membrane, which consists of an outer membrane and an inner membrane. This is an exact similar structure to that of the double membrane of mitochondria. Inside the chloroplast's inner membrane and surrounding the thylakoids is the fluid matrix called the stroma.