21.

Mention the most significant role of each of the following :

Bulliform cells    

Mention the most significant role of each of the following :

Quiescent centre

State the best known contribution of :

Earnest Hackel  

State the best known contribution of :

Carl Landsteiner

State the best known contribution of :

Robert Koch    

State the best known contribution of :

Hensen

(a) What are guard cells? Explain their role in regulating transpiration.

(b) Explain tunica corpus theory of origin of shoot apex.

(c) Give one function and one deficiency symptom of each of the following in plants:

(i) Magnesium

(ii) Calcium

(iii) Molybdenum

Explain the mass flow hypothesis of transport of food.

Differentiate between cyclic and non-cyclic photophosphorylation.