Mix Examples- Transport in Plants Questions in English

(NONE) Guttation is the exudation of water droplets from the margins of leaves through specialized structures called hydathodes. It occurs due to root pressure,which is generated when the rate of active water absorption by roots is high and the rate of transpiration is low. This creates a positive hydrostatic pressure in the xylem,forcing water and dissolved solutes out of the hydathodes. None of the options $A$,$B$,or $C$ correctly describe this process,as guttation is not regulated by cohesion-tension,is not due to phloem activity,and is not primarily for solute release. Therefore,none of the provided options are correct.

(B) $A.$ The cohesion-tension-transpiration pull model is the most widely accepted theory for water transport in plants, where transpiration creates the negative pressure (pull) required to move water upward.
$B.$ It is a well-established fact that less than $1\%$ of the water absorbed by the plant is utilized in photosynthesis and plant growth; the rest is lost via transpiration.
$C.$ Cobalt chloride paper is a chemical indicator used to detect moisture. It is blue when dry and turns pink upon absorbing water. Therefore, statement $C$ is incorrect.

(D) - Unidirectional,i.e.,from roots to leaves or tips.
$B$ - Multidirectional,because the source and sink are variable in plants.

(A) - Statement $A$ is correct: Nitrogen is primarily taken up by plants as inorganic ions ($NO_3^-$ or $NH_4^+$),but it is transported in the xylem sap largely in organic forms such as amino acids and amides.
- Statement $B$ is incorrect: The movement of nutrients in the phloem is multidirectional,not unidirectional. This is because the source (where sugar is produced) and the sink (where sugar is consumed or stored) can change depending on the plant's needs and developmental stage.

(C) The rate of respiration is directly related to the rate of water and mineral absorption because mineral absorption is an active process that requires $ATP$ produced during respiration.
Increased metabolism leads to higher $ATP$ production,which facilitates active mineral uptake.
Since the Assertion states there is an indirect relationship,it is incorrect.
The Reason is correct as increased metabolism supports active transport of minerals.
Therefore,the correct option is $C$.

(C) The Assertion $(A)$ is correct because from the endodermis onwards,the movement of water occurs through the symplastic pathway,which involves the living parts of the cell (cytoplasm and plasmodesmata).
The Reason $(R)$ is incorrect because the inner boundary of the cortex (endodermis) possesses an impermeable band of suberized matrix,known as the Casparian strip. It is composed of suberin,not lignin.

$(C)$ Cohesion refers to the mutual attraction between water molecules.
$(b)$ Adhesion refers to the attraction of water molecules to polar surfaces.
$(c)$ Surface tension explains why water molecules are more attracted to each other in the liquid phase than in the gaseous phase.
$(d)$ Guttation is the process of water loss in liquid form from the tips of leaves.
Therefore, the correct matching is $(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)$.

(N/A) The movement of water through the root occurs via two distinct pathways:
$1$. Apoplast Pathway: 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 movement occurs exclusively through intercellular spaces and cell walls. It does not involve crossing the cell membrane and is dependent on a gradient. It is a passive process involving mass flow.
$2$. Symplast Pathway: The symplastic system is the system of interconnected protoplasts. Neighbouring cells are connected through cytoplasmic strands that extend through plasmodesmata. Water enters the cells through the cell membrane,making the movement relatively slower. It is also a passive process occurring down a potential gradient,though it may be aided by cytoplasmic streaming.
Regarding active transport: Neither the apoplast nor the symplast pathway of water movement requires active transport. Water movement in both pathways is passive,driven by water potential gradients.

(N/A) Cells swell in hypotonic solutions and shrink in hypertonic solutions. In a hypotonic solution,water enters the cell due to osmosis,causing it to swell. In a hypertonic solution,water leaves the cell,causing it to shrink.
$(b)$ Imbibition is a special type of diffusion where water is absorbed by solids—specifically colloids—causing them to increase in volume. The statement is correct as it describes the physical process of water uptake by substances like seeds or dry wood.
$(c)$ Most of the water flow in the roots occurs via the apoplast pathway. 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.

(B) The apoplastic pathway involves the movement of water through the cell walls and intercellular spaces. In this pathway,water does not cross the cell membrane or cytoplasm. Cytoplasmic streaming is a characteristic feature of the symplastic pathway,where water moves through the cytoplasm and plasmodesmata. Therefore,the statement that the movement is aided by cytoplasmic streaming is not observed during the apoplastic pathway.

(D) In plants,various substances are transported over long distances to support growth and metabolic activities.
$I -$ Water is absorbed by roots and transported to all parts of the plant via xylem.
$II -$ Plant growth regulators (hormones) are synthesized in specific regions and transported to other parts to regulate physiological processes.
$III -$ Mineral nutrients are absorbed from the soil and transported through the xylem to various plant parts.
$IV -$ Organic nutrients (primarily sucrose) are synthesized in leaves and transported to other parts of the plant via phloem.
Therefore,all the listed components $(I, II, III, IV)$ are transported within plants.

(A) In plants,short-distance transport occurs via diffusion $(I)$ and cytoplasmic streaming $(III)$,which helps in the movement of substances within a cell or between adjacent cells.
Long-distance transport occurs through the vascular tissues,specifically xylem and phloem,which is known as translocation $(II)$.
Therefore,short-distance transport involves $I$ and $III$,while long-distance transport involves $II$.

(D) $1$. $A$ mature corn plant absorbs almost three liters of water in a day. This is a standard observation regarding plant water requirements.
$2$. $A$ mustard plant absorbs water equal to its own weight in about five hours. This highlights the high rate of transpiration and water uptake in plants.
$3$. Water is a limiting factor for plant growth and productivity in both agricultural and natural environments. This is a fundamental concept in plant physiology as water availability often dictates the distribution of plants and crop yield.
$4$. Since all the statements provided are scientifically accurate,the correct option is $D$.

(D) Water moves from a region of higher water potential $(\Psi_w)$ to a region of lower water potential $(\Psi_w)$.
Since a dilute solution has more free water molecules, it has higher water potential compared to a concentrated solution.
Osmotic pressure is the pressure required to prevent the movement of water into a solution; water moves towards the region of higher osmotic pressure (where solute concentration is higher).
Therefore, all the given statements correctly describe the direction of water movement.

(C) In plants,transport occurs through two main vascular tissues:
$1$. $Xylem$: It transports water and minerals from roots to leaves. This process is driven by transpiration,which creates a negative pressure (tension) or a negative hydrostatic pressure gradient,similar to sucking water through a straw.
$2$. $Phloem$: It transports food (sucrose) from source to sink. This process is driven by the pressure-flow hypothesis,where high sugar concentration at the source creates a positive hydrostatic pressure gradient,pushing the sap through the sieve tubes,similar to water flowing through a garden hose.

(D) The transport of water in plants occurs through the xylem.
$1$. Plants lose water through stomata in the leaves,a process known as transpiration.
$2$. This creates a negative pressure or tension in the xylem vessels,which pulls the water column upwards from the roots to the leaves.
$3$. The water molecules remain connected due to cohesive and adhesive forces,forming a continuous column.
$4$. This mechanism is widely accepted as the Cohesion-Tension-Transpiration Pull model.
Therefore,all the given statements are correct.

(B) Statement $I$ is incorrect because xylem can also transport some organic nitrogenous compounds.
Statement $II$ is incorrect because phloem can also transport some inorganic ions.
Statement $III$ is correct as there is an exchange of materials between xylem and phloem.
Statement $IV$ is correct because xylem sap contains inorganic nitrogen as well as organic nitrogen in the form of amino acids and related compounds.
Statement $V$ is correct because organic phosphorus and sulfur are also transported through the xylem.
Therefore,the correct statements are $III, IV,$ and $V$.

(B) The correct matches are as follows:
$A$. Cohesion: Mutual attraction among water molecules $(II)$.
$B$. Adhesion: Attraction of water molecules to polar surfaces $(IV)$.
$C$. Surface tension: Water molecules are attracted to each other in the liquid phase more than to water in the gas phase $(I)$.
$D$. Guttation: Loss of water in liquid phase $(III)$.
Therefore, the correct sequence is $A-II, B-IV, C-I, D-III$, which corresponds to option $B$.

(A) Active absorption is an energy-dependent process ($ATP$ is consumed) that occurs when the rate of transpiration is low.
When stomata are open,the rate of transpiration is high,which creates a strong transpiration pull.
This pull facilitates passive absorption of water,which is the primary mechanism for water uptake during the day.
Therefore,active absorption is generally not the dominant process when stomata are open.

(D) Statement $i$ is incorrect because guard cells are kidney-shaped in dicots and dumbbell-shaped in monocots.
Statement $ii$ is correct because the transport of food (sucrose) through phloem is bidirectional (from source to sink,and vice versa depending on the season).
Statement $iii$ is correct because capillary water is the water held in the soil pores by surface tension,which is the primary source of water for plants.
Statement $iv$ is incorrect because lenticels are composed of loosely arranged complementary cells,not compactly arranged cells.
Statement $v$ is incorrect because while stomatal transpiration is primarily a daytime process,it can occur at night in certain conditions,and it is not the only factor affecting absorption.
Therefore,statements $ii$ and $iii$ are correct. However,based on the provided options,the most appropriate choice is $D$ (assuming $v$ is considered correct in the context of standard textbook definitions of stomatal transpiration).

(B) $(i)$ Incorrect: The rate of water absorption is maximum,not minimum,at a soil temperature of $20^{\circ}C$ to $30^{\circ}C$.
(ii) Correct: Capillary water is the form of water available to plants for absorption.
(iii) Correct: Poorly aerated soil lacks oxygen,which is necessary for the metabolic energy required for active water absorption.
(iv) Incorrect: $A$ high transpiration rate,not a low one,creates a pull (transpiration pull) that accelerates water absorption.
$(v)$ Correct: $A$ high concentration of solutes in the soil creates a hypertonic environment,making it difficult for water to enter the root hairs via osmosis.

(D) The capillarity theory suggests that water rises in xylem vessels due to surface tension and adhesion-cohesion forces, similar to a capillary tube.
For this theory to be physically valid, the capillary tube (xylem) must be a continuous, hollow, and open-ended pipe.
Statement-$I$ is incorrect because xylem vessels are hollow and open at the ends to allow continuous water flow, not closed.
Statement-$II$ is correct because xylem is located deep within the root and is separated from the soil water by the epidermis, cortex, and endodermis, meaning it does not have direct contact with soil water as a physical capillary tube would.
Therefore, Statement-$I$ is incorrect and Statement-$II$ is correct.