Introductory Crop Physiology (1+1)

Photosynthetic apparatus

• The chloroplast in green plants constitutes the photosynthetic apparatus.
• In higher plants, the chloroplast is discoid in shape, 4-6 µ in length and 1-2µ thick.
• The chloroplast is bounded by two unit membranes of approximately 50°A thickness and consists of lipids and proteins.
• The thickness of the two membranes including the space enclosed by them is approximately 300°A (1 Angstrom: 0.1 cm).
• Internally, the chloroplast is filled with a hydrophilic matrix called as stroma embedded with grana.
• Each grana consists of 5-25 disk shaped grana lamellae (thylakoids) placed one above the other like the stack of coins.
• Each grana lamella of thylakoid encloses a space called loculus and the thylakoid membrane consists of alternating layer of lipids and proteins.
• Some of the grana lamella of thylakoids of grana are connected with thylakoids of other grana by somewhat thinner stroma lamella or fret membrane.
• Chlorophyll and other photosynthetic pigments are confined to grana.
• The chlorophylls are the site of photochemical reactions.

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