Absorption of water and Ascent of sap Questions in English

(D) In angiosperms,water and dissolved minerals are transported from the roots to the aerial parts of the plant through the xylem tissue.
Specifically,the translocation of water occurs through the lumen of xylem vessels and tracheids.
The xylem vessel system provides a continuous,low-resistance pathway for the upward movement of sap,driven primarily by transpiration pull.

(B) Root pressure is the positive pressure that develops in the xylem sap of roots due to the active absorption of mineral nutrients from the soil.
When the rate of transpiration is very low (e.g.,at night or during early morning) and the rate of water absorption is high,water accumulates in the xylem vessels.
This accumulation of water creates a positive hydrostatic pressure known as root pressure,which helps in pushing the water column upwards in small herbaceous plants.

(A) When a freshly cut leafy twig (such as a balsam plant) is immersed in a solution of $fuchsin$ (a dye),the dye is transported upward through the stem along with water.
This process demonstrates the ascent of sap.
Upon observing the stem or leaves,the veins become stained or coloured because the dye moves through the $xylem$ tissue.
This experiment confirms that the $xylem$ is the specific tissue responsible for the conduction of water and minerals (ascent of sap) in plants.

(B) The transpiration cohesion pull theory,also known as the Cohesion-Tension theory,explains the ascent of sap in plants.
This theory operates under the mechanism of passive absorption of water.
According to this theory,the forces responsible for the absorption of water do not originate in the root cells but are generated in the transpiring shoot cells due to the loss of water through transpiration.
This creates a negative pressure or tension that pulls the water column upward from the roots to the leaves.

(A) The correct answer is $A$.
In plants,water and dissolved inorganic minerals are absorbed by the roots from the soil.
These materials are transported upward from the roots to the leaves and other parts of the plant through the $Xylem$ tissue.
$Phloem$ is primarily responsible for the translocation of organic food (sugars) synthesized during photosynthesis.

(D) Guttation is the exudation of water droplets from the margins of leaves. It is primarily caused by high $Root \ pressure$. When transpiration is low (usually at night or early morning) and water absorption by roots is high, the positive hydrostatic pressure in the xylem forces water out through specialized pores called $Hydathodes$.

(C) The ascent of sap in plants occurs primarily through the xylem tissue.
When a plant stem is placed in a dye like eosin,the dye is transported upward along with water through the xylem vessels and tracheids.
Since xylem is responsible for the conduction of water and minerals from the roots to the aerial parts,the eosin solution will stain the xylem elements,making them visible under a microscope or even to the naked eye if the dye is concentrated enough.
Therefore,the correct observation is that the xylem elements become stained due to the ascent of sap.

(D) The most widely accepted theory for the ascent of sap in plants is the $Dixon$ and $Jolly's$ $Cohesion-Tension$ and $Transpiration$ $Pull$ $Theory$.
According to this theory,the transpiration pull generated in the leaves creates a negative pressure (tension) in the xylem vessels.
Due to the cohesive and adhesive properties of water molecules,a continuous water column is maintained from the roots to the leaves.
This tension pulls the water column upward against gravity,facilitating the ascent of sap.

(C) The most widely accepted theory for the ascent of sap in plants is the $Transpiration \text{ } Pull \text{ } and \text{ } Cohesion-Tension \text{ } Theory$.
This theory was proposed by $Dixon$ and $Joly$ in $1894$.
According to this theory,the loss of water through transpiration creates a negative pressure (tension) in the xylem vessels,which pulls the water column upward.
The cohesive and adhesive properties of water molecules ensure that the water column remains continuous and does not break under this tension.

(C) The upward movement of water in plants is primarily explained by the $Transpiration \ Pull \ Theory$ (also known as the $Cohesion-Tension-Transpiration \ Pull \ Model$).
While $Root \ Pressure$ contributes to the transport of water in small plants and during the night, it is insufficient to explain the movement of water to the tops of tall trees.
Therefore, the $Transpiration \ Pull \ Theory$ is the most widely accepted mechanism for the long-distance transport of water in plants.

(D) The process of $ascent of sap$ refers to the upward movement of water and dissolved minerals from the roots to the aerial parts of the plant, such as the stem and leaves, against the force of gravity. This transport occurs primarily through the $xylem$ tissue. Therefore, the water and minerals move from the roots towards the stem and leaves.

(B) Root pressure is a positive pressure that develops in the roots of plants due to the active absorption of mineral ions from the soil,followed by the osmotic movement of water into the xylem.
This pressure is responsible for pushing water up to small heights in the stem,which helps in maintaining the continuity of water columns and supports metabolic activities in plants,especially during the night or early morning when transpiration is low.

(C) In angiosperms,water is primarily transported through the xylem vessels. Xylem vessels are long,tube-like structures formed by dead cells that provide a low-resistance pathway for the bulk flow of water and dissolved minerals from the roots to the rest of the plant.

(D) The ascent of sap is the upward movement of water and minerals from the roots to the aerial parts of the plant.
$1$. Root pressure provides a positive pressure that helps in pushing water upwards to small heights.
$2$. Transpiration creates a negative pressure (transpiration pull) which is the primary force for the ascent of sap in tall plants.
$3$. Capillarity (capillary action) due to the narrow diameter of xylem vessels also contributes to the upward movement of water.
Therefore,all these factors contribute to the ascent of sap.

(A) Root pressure is a positive pressure that develops in the xylem of roots due to the active absorption of mineral ions from the soil,followed by water uptake via osmosis.
Root pressure is most observable when transpiration is low (e.g.,at night or early morning) and absorption is high,as this allows water to accumulate in the xylem.
Conversely,when transpiration is high,the water column is pulled upward by the transpiration pull,which often exceeds or masks the effect of root pressure.
Therefore,root pressure is lowest when transpiration is high and absorption is low,as the water is lost rapidly through the leaves and cannot build up the necessary positive pressure in the roots.

(B) The ascent of sap is primarily explained by the Cohesion-Tension-Transpiration Pull model.
Adhesion refers to the attraction of water molecules to polar surfaces,such as the tracheary elements (xylem walls).
Cohesion refers to the mutual attraction between water molecules due to hydrogen bonding.
Therefore,adhesion force is generated between the xylem wall and water molecules,which helps in maintaining the water column against gravity.

(C) During the process of transplantation,the delicate root hairs,which are responsible for the absorption of water and minerals from the soil,are often damaged or destroyed. Since these root hairs are essential for the plant's initial survival and establishment in the new environment,their loss leads to a failure in water uptake,causing the plant to wilt and eventually die.

(A) The transport of water and minerals from the roots to the aerial parts of the plant,including the leaves,is primarily carried out by the $Xylem$ tissue. $Xylem$ forms a continuous vascular system that facilitates the upward movement of water and dissolved mineral nutrients against gravity,driven by transpiration pull and root pressure. In contrast,$Phloem$ is responsible for the translocation of organic nutrients (photosynthates) from the leaves to other parts of the plant.

(C) The ascent of sap in plants is primarily driven by the transpiration pull,which creates a negative pressure (tension) in the xylem vessels.
This tension is transmitted through the water column due to the cohesive and adhesive properties of water molecules.
$1$. Cohesive force: The mutual attraction between water molecules.
$2$. Adhesive force: The attraction of water molecules to the polar surfaces of the xylem vessel walls.
Among the given options,the cohesive force is essential for maintaining the continuity of the water column against gravity,making it a critical factor in the ascent of sap.

(A) The ascent of sap is primarily explained by the Cohesion-Tension-Transpiration Pull Model.
According to this model,water molecules remain connected to each other due to strong cohesive forces (attraction between water molecules).
This cohesion allows water to form a continuous column within the xylem vessels,which can withstand the tension created by transpiration pull.
Therefore,Assertion $A$ is true because water rises as a continuous column,and Reason $R$ is true because the high cohesive force is the scientific basis for this continuity.
Thus,$R$ is the correct explanation of $A$.

(C) The ascent of sap in plants is primarily explained by the Cohesion-Tension-Transpiration Pull model.
Cohesion refers to the mutual attraction between water molecules due to hydrogen bonding.
This property allows water columns to remain intact under the tension created by transpiration pull,enabling water to rise to great heights in tall trees.
Therefore,the ascent of sap is the process that relies on the property of cohesion.

(B) The ascent of sap in plants is primarily driven by the cohesion-tension theory.
$1$. Cohesion refers to the mutual attraction between water molecules due to hydrogen bonding.
$2$. Adhesion refers to the attraction of water molecules to the polar surfaces of the xylem vessel walls.
$3$. Surface tension is the property where water molecules are more attracted to each other than to air.
$4$. Among these,the high cohesive force (Cohesion) allows water to form a continuous column in the xylem,which can withstand the tension created by transpiration pull. Therefore,cohesion is the most critical property for the ascent of sap.

(A) The ascent of sap is primarily explained by the Cohesion-Tension-Transpiration Pull Model.
According to this model,water molecules are held together by strong cohesive forces (attraction between water molecules).
These forces allow water to form a continuous column within the xylem vessels and tracheids,preventing it from breaking under the tension created by transpiration pull.
Therefore,the continuous column of water is maintained due to the high cohesive force between water molecules.
Thus,both $A$ and $R$ are true,and $R$ is the correct explanation of $A$.

(B) $Root$ pressure is a positive pressure that develops in the $xylem$ sap of the roots of certain plants. It is a direct manifestation of active water absorption,where mineral ions are actively transported from the soil into the root hairs,creating a water potential gradient that draws water into the roots.

(D) : Cohesion,adhesion,and surface tension are the forces responsible for the movement of water up the tracheary elements.
Water molecules remain attached to one another by a strong mutual force of attraction called cohesion force.
Due to the cohesion force,the water column can bear a tension or pull of up to $100 \ atm$.
Therefore,the cohesion force is also referred to as tensile strength.
Its theoretical value is about $15,000 \ atm$,but the measured value inside the tracheary elements ranges between $45 \ atm$ to $207 \ atm$.
The water column does not break its connection from the tracheary elements because of another force called adhesion force,which acts between the vessel walls and water molecules.
Additionally,surface tension accounts for high capillarity through tracheids and vessels.

(D) : Various ions from the soil are actively transported into the vascular tissues of roots,water follows its potential gradient and increases the pressure inside the xylem. This positive pressure is called root pressure.
Effect of root pressure is observable at night and early morning when evaporation is low and excess water collects in the form of droplets near the tip of leaves of many herbaceous plants.
Such water loss in its liquid phase is known as guttation.

(D) : Cohesion,adhesion,and surface tension are the forces responsible for the movement of water up the tracheary elements.
Water molecules remain attached to one another by a strong mutual force of attraction called cohesion force.
On account of the cohesion force,the water column can bear a tension or pull of up to $100 \ atm$.
Therefore,the cohesion force is also called tensile strength.
Its theoretical value is about $15,000 \ atm$,but the measured value inside the tracheary elements ranges between $45 \ atm$ to $207 \ atm$.
The water column does not break its connection from the tracheary elements because of another force called adhesion force between their walls and water molecules.
Another force called surface tension accounts for high capillarity through tracheids and vessels.

(C) In plants,the endodermis of the root acts as a control point for water and solute transport.
This is because the endodermal cells contain the Casparian strip,which is composed of suberin.
This strip prevents water from moving through the apoplastic pathway,forcing it to enter the symplastic pathway (crossing the plasma membrane).
This allows the plant to regulate the quantity and types of solutes that reach the xylem.

(B) Root pressure is a positive pressure that develops in the xylem of roots due to the active absorption of mineral nutrients from the soil.
This process leads to water entering the root cells by osmosis,creating a positive hydrostatic pressure.
At night and in the early morning,the rate of transpiration (evaporation from leaves) is very low because the stomata are closed or environmental conditions are humid.
However,the active absorption of ions by the roots continues,resulting in a net influx of water into the xylem.
Since there is little transpiration to pull the water column upward,the accumulated water exerts a positive pressure,which can be observed as guttation (the exudation of water droplets from the tips of leaves).
Therefore,the effect of root pressure is most observable when evaporation is low and absorption is high.

(D) The transport of water from roots to leaves occurs through the xylem vessels.
This process is primarily driven by the $Transpiration \text{ pull}$ theory, also known as the cohesion-tension-transpiration pull model.
$1$. $Cohesion$: The mutual attraction between water molecules due to hydrogen bonding.
$2$. $Adhesion$: The attraction of water molecules to the polar surfaces of the xylem vessel walls.
$3$. $Transpiration \text{ pull}$: The negative pressure (tension) generated by the evaporation of water from the stomata of leaves, which pulls the water column upward.
Since all these factors work together to facilitate the ascent of sap, the correct answer is $All \text{ of the above}$.

(C) In plants,water is absorbed by root hairs from the soil.
From the root hairs,water moves through the root cortex via apoplastic or symplastic pathways.
After passing through the cortex,water reaches the endodermis.
From the endodermis,it moves into the pericycle.
Finally,it enters the xylem vessels to be transported upward to the leaves.
Therefore,the correct sequence is: $\text{Cortex} \rightarrow \text{Endodermis} \rightarrow \text{Pericycle} \rightarrow \text{Xylem}$.

(B) $1$. $Cohesion$ refers to the mutual attraction between water molecules due to hydrogen bonding.
$2$. $Adhesion$ refers to the attraction of water molecules to polar surfaces,such as the walls of tracheary elements (tracheids and vessels).
$3$. Option $A$ is incorrect because cohesion is between water molecules,not water and soil.
$4$. Option $B$ is correct as it describes the attraction between water and the cell wall (adhesion).
$5$. Option $C$ is incorrect because cohesion is not attraction to non-polar surfaces.
$6$. Option $D$ is also technically correct in describing adhesion,but in the context of standard biology curriculum,$B$ is often cited as the primary example of adhesion in tracheids.

(A) Transpiration creates a negative pressure or tension in the xylem vessels,which pulls the water column upward from the roots to the leaves. This is known as the cohesion-tension-transpiration pull model.
Root pressure is a positive pressure that develops in the roots due to the active accumulation of ions,which pushes water upward into the xylem vessels.
Therefore,transpiration acts as a pulling force,and root pressure acts as a pushing force.

(D) The water column in the $xylem$ is maintained by the cohesion-tension theory.
Excessive transpirational pull can sometimes cause cavitation or air bubbles, leading to a break in the water column.
$Root$ $pressure$ is a positive pressure that develops in the roots due to the active absorption of mineral ions, which draws water into the $xylem$.
This positive pressure helps to push the water column upward and can re-establish the continuity of the water column if it has been broken.

(C) The transpiration pull theory (Cohesion-Tension theory) explains water transport in plants.
Statement $(i)$ is correct: There is a continuous column of water from roots to leaves.
Statement $(ii)$ is wrong: The high tensile strength of the water column is due to the cohesive force (attraction between water molecules),not adhesive force.
Statement $(iii)$ is wrong: The attraction between water molecules and the xylem vessel walls is called adhesion,not cohesion.
Statement $(iv)$ is correct: The negative pressure generated by transpiration is sufficient to pull water to great heights.
Therefore,statements $(ii)$ and $(iii)$ are incorrect.

(B) Transpiration is the process of water movement through a plant and its evaporation from aerial parts,such as leaves,stems,and flowers.
Water is absorbed by the roots from the soil and moves through the root tissues to reach the xylem.
The pathway of water absorption and transport in the root is: Root hair $\rightarrow$ Cortex $\rightarrow$ Endodermis $\rightarrow$ Pericycle $\rightarrow$ Xylem.
Once in the xylem,water is transported upward to the leaves to facilitate transpiration.
Therefore,the correct sequence for the movement of water towards the xylem for transpiration is Cortex $\rightarrow$ Endodermis $\rightarrow$ Pericycle $\rightarrow$ Xylem.

(B) The absorption of water by plants occurs primarily through the root hairs.
Root hairs are unicellular extensions of the epidermal cells of the root.
They provide a large surface area for the absorption of water and minerals from the soil.
Once water enters the root hairs,it moves through the epidermis,cortex,endodermis,and pericycle to reach the xylem for upward transport.
Therefore,the first point of entry for water in the root is the root hair.

(B) The destruction of the protoplast is a characteristic feature of the maturation of xylem tracheary elements,specifically vessel elements and tracheids.
These cells lose their protoplasm at maturity to become hollow,dead tubes,which allows them to efficiently transport water and minerals from the roots to the rest of the plant body.
Therefore,the destruction of the protoplast is a primary requirement for the transport of water.

(A) Guttation is the exudation of water droplets from the margins of leaves through specialized structures called hydathodes.
It occurs primarily due to high root pressure when the rate of transpiration is low,typically at night or early morning.
When the soil moisture level is high and the absorption of water by roots is active,the accumulated water creates a positive hydrostatic pressure in the xylem,known as root pressure,which forces the water out through the hydathodes.

(A) Plants absorb water from the soil primarily through their roots.
Soil water exists in various forms:
$1$. Gravitational water: This water drains away deep into the soil due to gravity and is generally unavailable to plants.
$2$. Hygroscopic water: This water is held tightly by soil particles and is not available to plants.
$3$. Chemically bound water: This water is part of the chemical structure of soil minerals and is unavailable.
$4$. Capillary water: This water is held in the capillary spaces between soil particles against the force of gravity. It is the form of water that is readily available for absorption by plant roots.
Therefore,the correct answer is $A$.

(D) The ascent of sap in plants is primarily explained by the Cohesion-Tension-Transpiration Pull model.
Transpiration creates a negative pressure (tension) in the xylem vessels,which pulls the water column upward.
However,if the tension becomes too high,it can cause the water column to break or fracture,a phenomenon known as cavitation or embolism.
This is primarily caused by the excessive transpiration pull that exceeds the cohesive strength of the water column.

(C) The water column in the xylem of tall trees remains intact despite the force of gravity due to the high tensile strength of water. This tensile strength is provided by the cohesive and adhesive properties of water molecules. Cohesion refers to the mutual attraction between water molecules,while adhesion refers to the attraction of water molecules to the polar surfaces of the xylem vessel walls. Together,these forces create a continuous water column that can withstand the tension generated by transpiration.

(B) Root pressure is a positive pressure that develops in the xylem sap of roots. It is primarily a result of active absorption of mineral nutrients from the soil by root hairs. As minerals are actively transported into the root cells,the osmotic potential of the root cells decreases,causing water to move from the soil into the root xylem by osmosis. This accumulation of water creates a positive hydrostatic pressure,known as root pressure,which helps push water upwards in the stem.

(D) Plants absorb water from the soil primarily through their root hairs.
Soil water exists in various forms:
$1$. Gravitational water: This water drains away due to gravity and is not available to plants.
$2$. Hygroscopic water: This water is held tightly by soil particles and is unavailable to plants.
$3$. Capillary water: This water is held in the capillary spaces between soil particles by surface tension. It is the form of water that is readily available for absorption by plant roots.
Therefore,the correct answer is capillary water.

(D) The upward movement of water and dissolved minerals (sap) through the xylem against the force of gravity is known as the ascent of sap.
Root pressure provides a positive push to the water column.
Transpiration creates a negative pressure (transpiration pull) that pulls water upwards.
Capillarity (capillary action) due to the narrow diameter of xylem vessels also assists in the movement of water.
Therefore,all these factors contribute to the ascent of sap.

(D) The $Casparian$ strip is a band of cell wall material deposited in the radial and transverse walls of the endodermis,which is chemically composed of suberin.
It acts as a selective barrier that forces water and dissolved solutes to pass through the plasma membrane of the endodermal cells rather than moving through the apoplastic pathway.
By forcing this movement through the cytoplasm (symplastic pathway),the plant can regulate the uptake of water and minerals into the vascular cylinder (xylem).
If a plant cannot produce $Casparian$ strips,it loses the ability to selectively control the entry of water and solutes into the xylem,leading to an unregulated flow.

(A) The movement of water through the root occurs via two pathways: the apoplast and the symplast. The apoplast is the system of adjacent cell walls that is continuous throughout the plant,except at the casparian strips of the endodermis in the roots. Water and minerals move through the apoplast until they reach the endodermis. The endodermis is impervious to water because of a band of suberized matrix called the casparian strip. Because the apoplastic pathway is blocked at the endodermis by these suberized strips,water is forced to enter the symplast pathway to cross the endodermis. Therefore,both the assertion and the reason are correct,and the reason correctly explains why the apoplastic pathway is interrupted at the endodermis.

(C) Sap is water containing dissolved minerals and organic solutes.
The upward movement of water from the roots towards the tips of stem branches and leaves is known as the ascent of sap.
This process occurs exclusively through the tracheary elements (tracheids and vessels) of the $Xylem$.
$Phloem$ is responsible for the translocation of food (sugars) from leaves to other parts of the plant,not for the upward movement of water.
Therefore,the Assertion is correct,but the Reason is incorrect.

(B) Root pressure is the positive pressure that develops in the roots of plants due to the active absorption of mineral nutrients from the soil.
When nutrients are actively absorbed by root hairs,water follows,increasing the hydrostatic pressure within the xylem.
This pressure provides a gentle push,which is sufficient to transport water up to small heights.
Root pressure is also responsible for guttation,which is the loss of water in the form of liquid droplets from the vein endings of certain herbaceous plants.
While root pressure cannot transport water to the tops of tall trees,it plays a crucial role in re-establishing the continuous chains of water molecules in the xylem that may break under the enormous tensions created by transpiration.