Hint: The third, internal chloroplast membrane in chloroplast, heavily folded and distinguished by the presence of closed discs (or thylakoids), is known as the thylakoid membrane.The thylakoids are arranged in tight stacks called grana (singular granum) in most taller plants.
Complete Answer: - Chloroplasts are a type of plastid — a round, oval, or disk-shaped body involved in the synthesis and storage of foodstuffs. Chloroplasts are distinguished from other types of plastids by their green colour, arising from the presence of two pigments, chlorophyll a and chlorophyll b. The purpose of these pigments is to absorb light energy. - The cylindrical stacks of the pressed membranes correspond to the grana structures defined by A. Meyer. Non-stacked thylakoids are known as stroma thylakoids because they are in close contact with the stroma. - According to this description, the upper and lower membranes of the grana stacks are also stroma thylakoids. Mature chloroplasts contain 40 to 60 grana stacks of 0.3 to 0.6μm in diameter. - The number of thylakoids per stack in mature thylakoids ranges from < 10 in high light chloroplasts to as many as 100 thylakoids in the intense shade of the Alocasia macrorrhiza plant. - Chloroplasts are extremely dynamic — they circulate and pass around inside plant cells, and sometimes pinch into two cells to replicate. Their behaviour is heavily affected by environmental factors such as light colour and strength. Chloroplasts, including mitochondria, produce their own DNA, which is thought to be inherited from their ancestor — photosynthetic cyanobacterium, engulfed by an early eukaryotic cell.
The correct answer is option (D) 40-60.
Note: The first definitive definition of the chloroplast (Chlorophyllkörnen, "chlorophyll grain") was given by Hugo von Mohl in 1837 as discreet bodies inside the green plant cell. In 1883, Andreas Franz Wilhelm Schimper called these bodies "chloroplasts" (Chloroplasts). In 1884, Eduard Strasburger embraced the word "chloroplasts" (chloroplasts)