In which plants does photosynthesis occur? Ans
Answers
Photosynthesis is a process by which plants & certain organisms convert the light energy to chemical energy.This process is basically divided into 2 reactions - light dependent reaction & light independent reaction. For the whole process of photosynthesis to occur, 3 important things are required : water, carbon dioxide & light. Water & other nutrients are absorbed by the plant from the soil into the root system via the root hairs and then to the shoot system via the xylem vessels which play a major role in conducting water & ions in the plant. Water then reaches the leaves. Carbon dioxide is absorbed by plants from the atmosphere through pores present in the leaf which is called as stomata. In order to understand how & where does photosynthesis occur, we need to know about the structure of the leaf in detail (Since leaves are the organ of photosynthesis).
STRUCTURE OF A LEAF & THEIR ROLE IN DIFFERENT STAGES OF PHOTOSYNTHESIS:
The outermost layer of the leaf is called cuticle which protects the leaf & also prevents water loss. Next to cuticle is the upper epidermis which consist of single layer of cells which regulates transpiration. Upper epidermis contain no or very few chloroplasts. It is the cells present in epidermis which allow the light which strikes them to the inside structures. Below epidermis is palisade layer which consist of few layers of cylindrical cells and this layer has many chloroplasts. Chloroplast is one of the plastids present within plant cells. It has different layers - outer & inner membrane, thylakoid, stroma & granum. Thylakoid system consists of numerous thylakoids which are suspended in the stroma and thylakoid are sacks which contain many chlorophyll. Chlorophyll is a green pigment which absorbs light energy. Various electron transfer reactions takes place in the thylakoid membrane by means of chlorophyll which eventually leads to production of ATP & NADPH. So, light dependent reactions takes place within the thylakoid membrane of chloroplast. After this, light independent reactions (Dark reaction) take place in the stroma of the chloroplast. In stroma, calvin cycle takes place where ATP & NADPH ( formed during light reaction) combines with CO2 & water to give glucose.Next layer of leaf is spongy layer which is meant for temporary storage of sugars synthesized in palisade layer. They also contain chloroplasts. There are interconnecting air spaces present in the mesophyll and also in the lower epidermis which also aids in the exchange of gases whose activity is regulated by guard cells present in lower epidermis.
So to summarize, photosynthesis ( light & dark reactions) occur in chloroplasts of parenchyma cells present in the mesophyll ( palisade & spongy layer) of a leaf.
Light reaction - thylakoid of chloroplast.
Dark reaction - stroma of chloroplast.
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Answer:
chloroplasts
In plants, the process of photosynthesis takes place in the mesophyll of the leaves, inside the chloroplasts. Chloroplasts contain disc-shaped structures called thylakoids, which contain the pigment chlorophyll. Chlorophyll absorbs certain portions of the visible spectrum and captures energy from sunlight.