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Transport in Plants

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Explain pressure flow hypothesis of translocation of sugars in plants.

The pressure flow hypothesis states that food is prepared in the plant leaves in the form of glucose. For translocation to the other parts the glucose is converted to sucrose a disaccharide. The sucrose is moved into the companion cells and then into the living sieve tube cells by active transport. This process is called loading and creates a hypertonic condition in the phloem. Water from the adjacent xylem moves into the phloem by osmosis. Increasing osmotic pressure results in the movement of phloem sap to areas of lower pressure. To reduce the osmotic pressure at the sink the sucrose is moved out of the phloem by active transport. The sucrose is converted to energy, starch or cellulose. The removal of the sugars lowers the osmotic pressure resulting in the movement of water out of the phloem. 



Who introduced the apoplast—symplast concept ?

E. Munch (1930).

Why the water is forced to move through cell membrane beyond endodermis ?

Water is forced to move through cell membranes beyond endodermis because of the suberin (waxy substance) present on radial walls of endodermal cells blocks water and solute movement through cell walls of endodermis. 

Why the cortex produces no resistance to movement of water ?

The cortical cells are loosely packed and produce no resistance to movement of water via cell walls or apoplast.

What is transmembrane pathway ?

The movement of water through cell membranes is called trans membrane pathway.

Give the term for the ability to resist a pulling force.

Tensile strength