NEET Biology Transport in Plants Important Questions Set 02

These Class 11 NEET Biology important questions on Transport in Plants give 23 questions with step-by-step answers, arranged as very short, short and long answer types, taken from a model test paper. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. Give one example of symport.
Answer: Glucose and Na⁺ ions are transported by symport across membrane by symporters (i.e., carrier proteins).

Question 2. Name the process which involves diffusion of water vapour from plants.
Answer: Transpiration.

Question 3. Name the process through which plants maintain their body temperature?
Answer: Transpiration

Question 4. Where are casparian strips located in plants?
Answer: They are found in the endodermis region of roots in plants.

Question 5. Give example of a plant whose seeds cannot germinate without mycorrhizae.
Answer: Pinus.

Question 6. Name the phenomenon involved in water absorption by root hairs.
Answer: Diffusion.

Question 7. In which part or tissue of plants, quantity and types of solutes are selected for transport to all its parts.
Answer: In endodermal cells of root hairs.

Question 8. How are sugars removed at the sink region in plants?
Answer: By active transport, sugars are removed at the sink.

Short Answer Type Questions

Question 9. When does pressure flow of phloem sap begins in plants?
Answer: When hydrostatic pressure in the phloem sieve tube increases, pressure flow begins and the sap moves through the phloem.

Question 10. What happens in sieve tubes of phloem when sugars are removed, at the sink?
Answer: At the sink, when sugars are actively transported out of the phloem sap, osmotic pressure decreases and water moves out of the phloem.

Question 11. What is sink? Give two factors on which source and sink part of the plant is adjusted.

Answer:

Sink is the part of plant which needs or stores the food. This source and sink adjustment depends on-

(a) Season

(b) Plant's requirement

Question 12. (i) Name any two chief sink regions for the mineral elements in plants.
(ii) Name two elements which are transported in small amounts as organic compounds.

Answer:

(i) (a) Apical and lateral meristems

(b) Fruits and seeds

(ii) Phosphorous and sulphur

Question 13. From where are mineral nutrients obtained by plants?
Answer: Plants obtain carbon and oxygen from CO₂ in the atmosphere. Remaining mineral nutrients are absorbed by roots from soil.

Question 14. What changes have to occur inside guard cells to facilitate pore opening?
Answer: Opening and closing of the stomata is brought about by the change in the turgidity of the guard cells. This happens, when guard cells, gain water, they become turgid. Their outer thinner walls are pushed out and this creates tension in inner thicker wall, which moves these wall towards periphery. This leads to the opening of pore i.e., stomatal aperture.

Question 15. What happens when :
(i) A cell is kept in water and then transferred to salt solution.
(ii) External pressure is applied on thistle funnel filled with sucrose solution and is separated by a semipermeable membrane from water kept in a beaker.

Answer:

(i) The cell will first swells up when kept in water and then shrinks when transferred to salt solution.

(ii) When external pressure is applied on a osmotic system comprising thistle funnel and water, the diffusion of water into the funnel stops.

Short Answer Type Questions

Question 16. Give one example to support the fact that the source and sink may be reversed depending on the season. How this relationship helps in food translocation?

Answer:

Source is the region which has high concentration of organic substances while sink region has its low concentration. For example, roots behave as sink in summers and winters while they act as source in early springs because the food stored in them is frequently mobilised to growing buds. Storage organs function both as source and sink.

This source and sink relationship helps in translocation of food through vascular tissue, phloem. As source has higher concentration of organic substances, they tend to flow towards lower concentration areas i.e., sink.

Question 17. Explain with figure, how molecules can be transported passively across the plasma membrane by help of transporters?

Answer:

A well-labelled diagram should show these parts: Transport protein; Transported molecule; Outer side; Inner side of cell of cell of cell; Membrane.

The molecules present in extracellular matrix bind to the transport proteins i.e., porins which rotates and releases it inside the cell. This happens passively as the molecules are transported from their high concentration to their low concentration i.e., along the concentration gradient.

Question 18. How osmotic pressure is related to solute potential?

Answer:

Osmotic pressure is the maximum pressure which can develop in an osmotically active solution when it is separated from its pure solvent by a semipermeable membrane under ideal conditions of osmosis. It is dependent upon the concentration of solutes.

More is the solute concentration, greater will be the pressure required to prevent water from diffusing in. Numerically, osmotic pressure is equivalent to the osmotic potential, but its sign is opposite. Osmotic pressure is the positive pressure applied while osmotic potential (or solute potential) is negative.

Osmotic pressure (O.P.) = – Solute potential (Ψs) or Osmotic potential

The osmotic pressure of a solution can be measured with the help of apparatus called osmometer.

Question 19. (i) When does plasmolysis occur?
(ii) How does a cell become turgid?
(iii) Which phenomenon will occur when grapes are added in 10% salt solution into a petridish?

Answer:

(i) Plasmolysis occurs when cell is placed in hypertonic solution (i.e., in a solution of higher concentration as compared to the cytoplasm)

(ii) When a cell is placed in hypotonic solution, it absorbs water by osmosis and increases its volume to become turgid.

(iii) When grapes or swollen raisins are placed in 10% salt solution, they shrink. Because, they lose water to the salt solution as salt solution is more concentrated than the sap present in grapes. The phenomenon in which water is drawn out of the cell through diffusion into the extracellular fluid, is known as Exosmosis.

Question 20. Why ultimately water moves through the root layers by symplast pathway?
Answer: In the root layers endodermis layers is present in the inner boundary of cortex which is impervious to water. This layer consists of a band of suberised matrix called the casparian strip which is impervious to water. Therefore, water molecules are unable to penetrate this layer, so they get directed to wall regions which are not suberised, into the cells proper through the membranes. Therefore, now water have to enter symplast pathway in the endodermis i.e., water enters into the cells through the cell membrane. In this pathway, water travels through the cell i.e., their cytoplasm and pass from one cell to other through the plasmodesmata. It is aided by cytoplasmic streaming.

Question 21. (i) Do plants utilise the whole amount of water absorbed by them?
(ii) If not then, why?
(iii) Give one example in support of your answer.

Answer:

(i) No, plants cannot utilise the whole amount of water absorbed by them.

(ii) Because it evaporates from stem and leaves i.e., shoot system into the surroundings i.e., air. This loss of water in vapour form, from the aerial parts of plant is called transpiration.

(iii) For example, a plant of maize (corn) absorbs about 3 litres of water per day. A plant of mustard absorbs water equal to its own weight in about 5 hours. But the actual amount of water needed by plant is hardly 1-2% of what is absorbed by them.

Long Answer Type Questions

Question 22. Describe how minerals are absorbed and transported in plants.
Answer: Most minerals enter the root by active absorption into the cytoplasm of epidermal cells. This movement of ions from soil to interior of root is against concentration gradient and require energy. This energy is made available by plants in the form of ATP. The active uptake of ions is partly responsible for water potential gradient in roots and therefore helps in uptake of water by osmosis. Some ions can also be passively absorbed into the epidermal cells of roots by mass flow and diffusion. After the ions, have reached xylem vessels through active or passive absorption or combination of the two, they are further transported upwards, to the stem and all other parts of plant through the transpiration stream. This allows movement of minerals from their conducting tissue towards the area of their sink. The area of sink for the mineral elements are the growing regions of the plants such as the apical and lateral meristems, young leaves, developing flowers, fruits and seeds and the storage organs. Minerals flow towards these areas and are unloaded at fine vein endings through diffusion. They are picked up by cells through active uptake.

Question 23. How is food transported in plants?

Answer:

A well-labelled diagram should show these parts: Sugars leave bysieve tubes; water follows osmosis; Tip of stem; Sugars enter sieve tubes; = High; Sugar solution flows water follows by osmosis turgor to regions of low pressure turgor pressure; Phloem forSugars leave sieveand tube metabolism storage;by water follows osmosis; Root; .

In plants, the most accepted mechanism used for the translocation of sugars from source to sink; is called the pressure flow hypothesis. According to mass flow or pressure flow hypothesis, organic substances (i.e., sucrose) flow in solution form in sieve elements due to development of an osmotically generated pressure gradient between source and sink ends. In plants, the mesophyll cells of leaves synthesize carbohydrates (i.e., glucose) by process of photosynthesis. This glucose is readily converted into sucrose (a disaccharide sugar) Mesophyll cells are only few cells away from sieve tube elements. Therefore, this sucrose moves into the companion cells and then into the living sieve tube elements of phloem, by active transport. This transport requires energy. Now, sieve tubes become loaded with sucrose. This creates hypertonic condition in the phloem. Now these sieve tubes absorb water from the nearby xylem elements by osmosis. This in tern increases osmotic pressure inside sieve tubes and causes flow of phloem sap towards the region where osmotic pressure is low. Usually, a low osmotic pressure is required to be maintained at the sink. Finally, at sink sucrose is moved out of the phloem sap by active transport and these cells use this sugar for obtaining energy or convert in into starch or cellulose. As sugars are removed the osmotic pressure decreases in sieve tube elements and water moves out of the phloem.