Establishment of Ingenhousz’s proposition came after several experiments till the mid 20th century when scientists could also locate the site of photosynthesis and even isolate it.

Around four decades after Ingenhouszs’ proposition scientists could only isolate the green substance to observe its nature and find out whether photosynthesis could be carried out with it.

This had become possible in the year 1817 due to the work of two scientists Pelletier and Caventou who obtained an extract of the green coloured substance and named it ‘chlorophyll’ meaning green leaf.

It was also found that pigments in addition to chlorophyll, carotenoids and phycobilins could also aid in the process of photosynthesis by passing on the energy of sunlight trapped by them to chlorophyll.

Where does Photosynthesis take place?

Where is chlorophyll and other pigments present in the plant?
Try to name some parts where you think photosynthesis occurs.
Do you think the new reddish leaves of plants also carry out photosynthesis? What could be the reason for their colour?

The exact location of the photosynthetic part or a part containing chlorophyll was not known till another six decades after Pelletier and Caventou discovered chlorophyll. It was believed to be spread in the cells of green plant parts.

In 1883, Julius Von Sachs, observed that chlorophyll in plant cells is not spread through out the entire cell.

It is rather found in organelles within the cell. Such organelles were named as ‘chloroplasts’.

These are present in large numbers in the cells (around 40 – 100) of parts like the stomatal guard cells and ground tissues of plants .

You have studied about Chloroplast in Class IX.

Let us observe the figure of TS of leaf showing Chloroplast in Palisade and Spongy Parenchyma.