Non-pigmented part of chloroplast is called Stroma.

Stroma is the aqueous matrix present in chloroplasts. It is the non-pigmented part of chloroplasts and fills the space between the thylakoid membranes and the inner membrane of the chloroplast. It is a gel-like fluid that contains several enzymes, DNA, ribosomes, and other soluble proteins. The stroma is enclosed by a double membrane, which separates the chloroplast from the cytoplasm.

Functions of Stromal Enzymes:

1. Calvin Cycle: The stromal enzymes play a crucial role in the carbon fixation process (Calvin cycle) of photosynthesis. The enzymes present in the stroma are responsible for converting CO2 into carbohydrates.

2. Fatty Acid Synthesis: Stromal enzymes also play a role in the synthesis of fatty acids from acetyl-CoA, which is generated during the light-dependent reactions of photosynthesis.

3. Amino Acid Synthesis: The stromal enzymes are involved in the synthesis of amino acids, which are the building blocks of proteins.

4. Nitrogen Assimilation: The stromal enzymes are responsible for the assimilation of nitrogen from the atmosphere into the chloroplast.

Conclusion:

Thus, stroma is an important part of chloroplasts that contains several enzymes and other soluble proteins which are important for the functioning of the chloroplast. The stromal enzymes play a crucial role in the carbon fixation process, fatty acid synthesis, amino acid synthesis, and nitrogen assimilation. Therefore, stroma is an essential component of the photosynthetic machinery of plants.

In chloroplast. chloroplast structureThe internal (thylakoid) membrane vesicles are organized into stacks, which reside in a matrix known as the stroma.in chloroplast. All the chlorophyll in the chloroplast is contained in the membranes of the thylakoid vesicles.