Early experiments:

1. Joseph Priestley (1733-1804): In 1770 performed a series of experiments that revealed the essential role of air in the growth of green plants. Priestley hypothesised that plants restore the air that is consumed by the breathing animals and burning candles.

2. Jan Ingenhousz (1730-1799): experimentally proved that sunlight is essential for the process of photosynthesis during which carbon dioxide is consumed and oxygen is generated.He showed that it is only the green part of the plants that could release oxygen.

3. Julius von Sachs (1854): He provided evidence for production of glucose durig the photosynthesis process. He found that the green parts in plants is where glucose is made, and that the glucose is usually stored as starch.

4. T.W.Engelmann (1843 – 1909): he was working on green alga, Cladophora that was placed in a suspension of aerobic bacteria. He gave the first action spectrum of photosynthesis.

5. Cornelius van Niel (1897-1985): he showed that photosynthesis is essentially a light-dependent reaction in which oxygen is released from water and not from carbon dioxide. Chemical equation of photosynthesis was introduced by him.

Structure of chloroplast:

These are green plastids that consist of the chlorophyll pigment. Chloroplasts are flat disc shaped structures. It is a double membraned structure. Chloroplast consists of the membranous system consisting of grana, the stroma lamellae, and the matrix stroma. The stacked portion of membrane-bounded, flattened discs of the chloroplasts is known as grana. Each disc-like structure of grana is known as a thylakoid. Grana are made up of disc-like structures known as thylakoids. Stack of thylakoids are placed on each other to form a stack-like structure called Granum. Light reaction takes place in the granum of the chloroplast.. The dark reaction takes place in the stroma of the chloroplast. The colourless fluid of the chloroplast is known as stroma. Stroma lamellae are membranous structure the interconnects the two thylakoids. Photosynthetic pigments: Photosynthetic pigments are substances that have an ability to absorb light, at specific wavelengths. The chromatographic separation of the leaf pigments revealed that four major pigments contribute to the colour of the leaves: Chlorophyll a (bright or blue green) Chlorophyll b (yellow green) Xanthophylls (yellow) Carotenoids (yellow to yellow-orange) Most of the photosynthesis takes place in the blue and the red region of the visible spectrum (VIBGYOR), but some photosynthesis also does take place at the other wavelengths of the visible spectrum. Though chlorophyll a is the major pigment responsible for trapping light, other thylakoid pigments like chlorophyll b, xanthophylls and carotenoids, which are called accessory pigments, also absorb light and transfer the energy to chlorophyll a

Structure of chlorophyll

Chlorophyll is the most widespread pigment in green plants. It is a porphyrin derivative with magnesium ion in the central chemical structure of chlorophyll. Chlorophyll is a tetrapyrrole with four nitrogen and carbons. Tetrapyrrole, along with central magnesium ion, forms a porphyrin ring. Types of complexes present in the thylakoid membrane: Photosystem I: Reaction centre consists of Chlorophyll a with maxim absorption at 700 nm Photosystem II: Reaction centre consists of Chlorophyll a with maxim absorption at 680 nm Cytochrome b6f (cyt b6f) complex: involved in electron transport chain. ATP synthase: involved in ATP synthesis