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Two objections to starch – sugar inter conversion theory:

1. In monocots, guard cell does not have starch. 

2. There is no evidence to show the presence of sugar at a time when starch disappears and stomata open.

Correct Answer is: (d) Von Mohl

The non photosynthetic parts of a plant that need a supply of sucrose: 

1. Roots 

2. Tubers 

3. Developing fruits and 

4. Immature leaves.

The water is lost in the form of vapour from leaves to the atmosphere.

When lateral translocation of food occurs in root or stem, transport from phloem to pith is radial translocation while that from phloem to cortex is tangential translocation.

1. The loss of water in the form of water vapour is called transpiration. 

2. About 90 – 93% of transpiration occurs through stomata, small apertures located in the epidermis of leaves.

3. For this process stomata must remain open and then only gaseous exchange by diffusion takes places. 

4. Gaseous exchange is necessary for respiration and photosynthesis. If stomata remain closed then it will affect productivity of plant. 

5. The process is necessary evil because water which is important for plant is lost in the process. 

6. At the same time it helps in absorption of water and its translocation. Hence it cannot be avoided. So Curtis has rightly called it as necessary evil.

Correct answer is (a) xylem

1. Root pressure theory is proposed by J. Pristley. 

2. For translocation of water, activity of living cells of root is responsible. 

3. Absorption of water by root hair is a constant and continuous process and due to this a hydrostatic pressure is developed in cortical cells

4. Owing to this hydrostatic pressure i.e. root pressure, water is forced into xylem and further conducted upwards. 

5. Root pressure is an osmotic phenomenon.

Limitation of this theory:

1. Not applicable to tall plants above 20 metres. 

2. Even in absence of root pressure ascent of sap is noticed. 

3. In actively transpiring plants, root pressure is not developed. 

4. In taller gymnosperms, root pressure is zero. 

5. Xylem sap is under tension and shows negative hydrostatic pressure.

The discovery of enzyme phosphorylase in guard cells by Hanes (1940) greatly supports the starch – sugar interconversion theory. The enzyme phosphorylase hydrolyses starch into sugar and high pH followed by endosmosis and the opening of stomata during light. The vice versa takes place during the night.

Land plants absorb water and mineral salts from soil with the help of their roots.

In turgid cell, due to increased turgor pressure of photosynthetic cell, sugar is forced into the sieve tube of the vein, which is known as loading of vein.

The transport of food from one part of plant to the other part, i.e. source to sink is called translocation of food.

Food is translocated in downward direction from leaves (source) to root, while during germination of seed, bulbil, corm it is in upward direction.

1. Capillarity theory of water translocation is proposed by Bohem. 

2. Capillarity is because of surface tension and cohesive forces and adhesive forces of water molecules. 

3. Xylem vessels and tracheids are tubular elements having their lumen. 

4. In these elements water column exists due to combined action of cohesive and adhesive forces of water and lignified wall. 

5. As a result of this capillarity water is raised upwards.

1. Cohesion tension theory is widely accepted theory for translocation of water proposed by Dixon and Joly. 

2. It is based on principles cohesion and adhesion of water molecules along with transpiration pull. 

3. Strong attractive force between water molecules is cohesive force and the strong force of attraction between water molecules and wall of lumen of xylem vessels is called adhesive force. 

4. Owing to these cohesive and adhesive forces a continuous column of water is maintained in xylem elements from root to aerial parts, tips of leaves. 

5. Transpiration pull is developed in the xylem vessel in leaves. 

6. This pull is transmitted downwards and due to suction pressure, water is pulled passively against gravity, i.e. ascent of sap.

Limitations of theory-

1. For activity of transpiration pull, water column should be maintained constantly and continuously. Owing to changes in temperature during day and night, gas bubbles may be formed in the water channel. This will break the continuity. 

2. According to this theory, tracheids are more efficient than vessels because of their tapering end walls which support water column. Vessels are tubular structure with open ends.

1. The absorption of water takes place by two modes, i.e. active absorption and passive absorption. 

2. Passive absorption is the chief method of absorption (98%). 

3. There is no expenditure of energy in passive absorption. 

4. Transpiration pull is a driving force and water moves depending upon concentration gradient. Water is pulled upwards. 

5. It occurs during daytime when there is active transpiration. 

6. Active absorption occurs usually during night time as due to closure of stomata transpiration stops. 

7. Water absorption is against D.ED. gradient, A.T.R energy is required which is available from respiration.

8. Active absorption may be osmotic or non- osmotic type. 

9. For osmotic absorption root pressure has a role.

1. Keeps cells and cell organelles stretched 

2. Provides support 

3. During growth essential for cell enlargement 

4. Maintains shape of cell 

5. Facilitates opening and closing of stomata

Correct answer is (c) +1 to +2 bars

Correct answer is (c) stomata

Correct answer is (b) B to A

At the sink end, turgor pressure is lowered and hence turgor pressure gradient is developed from sieve-tube which translocates food passively along concentration gradient, this is vein unloading.

Correct option is (b) capillary water

1. Water is absorbed by unicellular root hairs from soil. 

2. Presence of capillary water in soil is needed as this water from soil is absorbed by root hairs.

3. Soil temperature of 20-30°C favours water absorption. 

4. Rate of absorption is decreased by high concentration of solutes in soil. 

5. Soil should be properly aerated, poorly aerated soil shows poor absorption rate. 

6. Increased transpiration accelerates rate of absorption of water.

Correct answer is (b) Become flaccid

Correct answer is (d) night-time

1. This is very widely accepted theory of ascent of sap proposed by Dixon and Joly. 

2. It is based on principles of adhesion and cohesion of water molecules and transpiration by plants. 

3. A strong force of attraction existing between water molecules is cohesion and the force of attraction between water molecules and lignified walls of xylem elements is adhesion. 

4. Ascent of sap occurs through lumen of xylem elements. 

5. Owing to cohesive and adhesive forces a continuous water column is maintained in xylem from root to aerial parts i.e. leaves. 

6. Transpiration occurs through stomata and transpiration pull is developed in leaf vessels. 

7. This tension or pull is transmitted downwards through vein to roots which triggers ascent of sap.

8. In transpiration, water is lost in vapour form and this increases D.PD. of mesophyll cells that are near guard cells. 

9. Mesophyll cells absorb water from xylem in leaf and a gradient of D.PD. or suction pressure (S. E) is set. 

10. Owing to this gradient from guard cell to xylem in leaf, a transpiration pull or tension is created in xylem. 

11. Hence water column is pulled upward passively against gravity

The inner wall of guard cell that faces opening is thick and inelastic while its outer wall or lateral wall is thin and elastic.

Secondary roots that originate from pericycle that is outer layer of vascular cylinder, bypass endodermis with Casparian strip allow direct apoplast pathway to enter xylem and phloem.

Root hairs are the extensions of epiblema or epidermal cells in the region of absorption.

This zone has unicellular root hairs which absorb water available in rhizosphere.

1. Unicellular root hairs which are tubular extensions of epiblema cells absorb readily available capillary water from soil. 

2. The three physical processes imbibition, diffusion and osmosis are concerned with absorption of water. 

3. Water molecules get adsorbed on cell wall of root hair (imbibition). 

4. They enter the root hair cell by diffusion through cell wall which is freely permeable. 

5. By process of osmosis they enter through plasma membrane which is semipermeable. 

6. The root hair cell becomes turgid and hence its turgor pressure increases and D.ED. value decreases. 

7. The adjacent cell of cortex has more D.ED. value as its osmotic potential is more. 

8. The cortical cell thus takes water from epidermal cell which is turgid. This process goes on due to gradient of suction pressure developed from cell to cell till thin walled passage cells of endodermis. 

9. From endodermis it will enter pericycle and then due to hydrostatic pressure it is forced in protoxylem cell. 

10. The pathway of water is by apoplast and symplast. 

11. When water passes through cell wall and intercellular spaces of cortex it is apoplast pathway. 

12. When water passes across living cells through their plasmodesmatal connections it is symplast pathway.

Correct answer is (c) pericycle

Correct answer is (c) accessory cells

A root hair is a cytoplasmic extension of epiblema cell which is colourless, unbranched, ephemeral, very delicate tubular structure of about 1 to 10 mm long.

Correct answer is (c) zone of absorption

Correct answer is (a) apoplast

Correct answer is (c) imbibition

Correct answer is (b) pectin

Correct answer is (a) epiderinal

Correct answer is (c) Microenvironment around root

Kari pushed his friend into the stream because a boy was lying flat on the bottom of the river. Kari wanted his friend to save the life of that boy, so he pushed his friend into the stream.

Kari stole the bananas from the table near the window in the dining room. He put his trunk through the window very much like a snake and disappeared with all the bananas without any one noticing it.

The correct answer is B) Bitter gourd.

1. It is simply a science trick. 

2. Magician prepares a knife by applying an indicator like methyl orange or hibiscus solution on it. 

3. Then he cut the lemon before us. 

4. Due to the reaction the lemon juice (acid) turns red and we are made to believe that blood is coming out of the lemon.

Correct option is (c) Downward legitimate power

Correct option is (c) Legality

Correct option is (d) Technical conference method