NCERT Class 11-Biology: Chapter –11 Transport in Plants Part 3

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Question 4:

A flowering plant is planted in an earthen pot and irrigated. Urea is added to make the plant grow faster, but after some time the plant dies. This may be due to _______________ .

Answer:

A flowering plant is planted in an earthen pot and irrigated. Urea is added to make the plant grow faster, but after some time the plant dies. This may be due to exosmosis. Urea is added because it is a fertilizer aiding plant growth but excess of urea causes increase in concentration of solutes in the soil due to which water comes out from the plant’s cytoplasm eventually leading to exosmosis and thus the plant gets Plasmolyzed and dies.

Question 5:

Absorption of water from soil by dry seeds increases the _____________, thus helping seedlings to come out of soil

Answer:

Absorption of water from soil by dry seeds increases the pressure, thus helping seedlings to come out of soil. If not for the pressure by imbibition, dry seeds would not have been able to come out of soil.

Question 6:

Water moves up against gravity and even for a tree of 20m height, the tip receives water within two hours. The most important physiological phenomenon which is responsible for the upward movement of water is _______________________.

Answer:

Transpiration pull

Transpiration pull is the process responsible for the upward movement of water against gravity even for a tree of height up to .

As the plant performs transpiration via stomata, it pulls water molecules upward to the leaf via xylem (adhesion and cohesion of water molecules). This creates a pressure gradient between the atmosphere and sub-stomatal cavity. This is transferred to the intercellular spaces of leaf then to xylem of the leaf vein. This pull is called the transpiration pull.

Transpiration Pull

Transpiration Pull

Transpiration Pull

Question 7:

The plant cell cytoplasm is surrounded by both cell wall and cell membrane. The specificity of transport of substances are mostly across the cell membrane, because _________________.

Answer:

Cell membrane is selectively permeable.

Question 8:

The plants are twice as efficient as plants in terms of fixing but lose only _________ as much water as plants for the same amount of fixed.

Answer:

Half

Question 9:

Movement of substances in xylem is unidirectional while in phloem it is bidirectional. Explain.

Answer:

When the plant is growing, the leaves act as the source of food carrying out photosynthesis. The vascular bundle, phloem is responsible for conducting the food from the source to the sink. But the process is reversed during seasons like spring because during that term the food which is stored in sink is then supplied to the growing parts of the plant. The source and sink relation is hence variable so direction of movement of food via the phloem can be either upwards or downwards i.e. bidirectional.

Question 10:

Identify the process occurring in I, II and III

Chapter 11 - Question 10 Image of Identify the Process Occurring in I, II and III

Identify the Process Occurring

Chapter 11 - Question 10 Image of Identify the Process Occurring in I, II and III

Answer:

(I) Uniport: When a single substance moves in a single direction across a cell membrane, it is called uniport.

(II) Antiport: When two substances move in the opposite direction across a cell membrane, it is called antiport.

(III) Symport: When two substances move in the same direction across a cell membrane, it is called Symport.

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