Anatomical and Physiological peculiarities of C-4 plants

Anatomical and Physiological peculiarities of C-4 plants  are as under:-

(A)  Anatomical Peculiarities

(i)                The leaves of C-4 plants have Kranz type of anatomy.

(ii)             The leaves have dimorphic chloroplasts.

(iii)           Chloroplasts in mesophyll cells are normal i.e. With grana and stroma.

(iv)           Chloroplasts  in bundle sheath cells are comparatively larger and are wihout grana and PS-II.

(B)   Physiological Peculiarities.

(i)                Dark reaction of photosynthesis consists of C-4 cycle and C-3 cycle reactions.

(ii)             C-4 cycle reactions occur in stroma of mesophyll chloroplasts.

(iii)           C-3 cycle reactions occur  in stroma of bundle sheath chloroplasts.

(iv)           Initial CO2 acceptor is 3-C PEPA in mesophyll chloroplast and first stable product is 4-c oxalo acetic acid.(OAA).

(v)             C-4 plants grow well in hot and dry climate of tropical and sub-tropical regions (optimum temperature for their growth varies between 30-45oC).

(vi)           This is because these plants are physiologically adapted to high temperature and high light intensities.

(vii)        C-4 plants are described as physiologically (and photo synthetically) “efficient plants” because they have the following:

(a)  Negligible photo respiration.

(b) Higher water use efficiency

(c)  Higher nitrogen use efficiency.’

(d) higher solar energy harvest efficiency.

(e)  Temperature independent quantum yield.

(viii)      In C-4 plants, O2 conc.has no inhibitory effect on photosynthesis.