Transport in Plants Important Questions

Transportation in plants is a vital process. Trees transport all of the nutrients and water they require to survive from their roots to the tips of their leaves. Plants have pipe-like vessels that allow water and minerals to enter the plant. These vessels are constructed of elongated cells with thick walls. A tissue is a collection of cells that performs a specific function inside an organism. These are conductive tissues. These conducting tissues are classified into two types: xylem and phloem.

---

Very Short Answer Questions [1 Marks Question]

Ques: What exactly are porins?

Ans: Porins are proteins that generate massive holes in the outer membranes of plastids, mitochondria, and some bacteria, allowing molecules as tiny as small proteins to pass through.

Ques: What is the Casparian strip?

Ans: The inner margin of the cortex, the endodermis, is resistant to water due to a suberized matrix link known as the Casparian strip.

Ques: When does wilting take place?

Ans: When the rate of evaporation of water exceeds the rate of water intake by roots.

Ques: What is the potential for water?

Ans: Water potential refers to a solution's ability to contain the most quantity of water.

Ques: The direction and rate of osmosis are determined by_________

Ans: It is affected by both the concentration and pressure gradients.

Ques: Water absorption by dry seeds from soil raises the ______, assisting seedlings in emerging from the soil.

Ans: The seed components absorb water, which drives the seedlings out of the soil, causing the seed to enlarge and the imbibition pressure within the seeds to rise, allowing seed germination.

Ques: What is the reasoning behind the increased salt content of the pickles?

Ans: High salt concentrations keep pickles from spoiling by inhibiting the development of bacteria.

Ques: What determines the direction of water flow from one cell to the next?

Ans: The direction of water flow from one cell to another is determined by the cell's water potential.

---

Short Answer Questions [2 Marks Question]

Ques: What exactly is osmosis?

Ans: It is the migration of water molecules through the plasma membrane from an area of high concentration to a region of low concentration. It is a critical procedure. Various physiological processes in plants are carried out by osmosis.

Ques: What exactly is active water transport?

Ans: It is the movement of water molecules against a concentration gradient while utilizing energy (ATP). The molecules travel from low to high concentrations via active water transport.

Ques: Why is the photosynthetic mechanism of C4 plants more useful than that of C3 plants?

Ans: The C4 photosynthetic system was designed to maximize carbon dioxide availability while reducing water loss. In terms of carbon fixation, C4 plants are two times more effective than C3 types. To repair one gram of CO₂ molecule, C4 plants lose just 300 g of water through evaporation, but C3 plants lose 600 g of water to fix the same gram of carbon dioxide.

Ques: How does exudate analysis allow one to discover minerals and the manner in which they are built in the plant?

Ans: Chemical examination of exudate (plant sap) can aid in understanding the form and identity of mineral nutrients conveyed in plants since exudate is a mixture of inorganic and organic substances such as ions, amino acids, sugars, and so on. Sulphur, for example, is absorbed and carried as sulphate ions, whereas nitrogen is absorbed and transported as NO₂ and NO₃.

Ques: Differentiate between diffusion and imbibition.

Ans:

Ques: What is the process for regulating stomatal pore opening and closing?

Ans: The stomata's opening and closure are controlled by the following factors:

1. Light: The intensity of light must be modest for the stomatal pore to open. When exposed to light, the stomatal hole opens and closes. In the case of CAM plants, the stomatal pore remains closed in the day and opens in the nighttime.
2. Temperature: As the temperature is low, the stomatal pore closes, but when the temperature rises, it opens.
3. Water Availability: Stomata stays closed under water-stressed and water-deficient conditions.
4. Carbon Dioxide Concentration: Even when there is enough light, the stomatal pore stays closed in high concentrations of carbon dioxide. When the plant uses up the carbon dioxide and its concentration falls, the pore opens up.

Ques: What is the element influencing the rate of transpiration?

Ans: There are two aspects to consider, Internal and External Factors.

1. External factors that influence:

Light: Causes stomatal opening

Temperature: A high temperature reduces relative humidity, which increases transpiration.

Humidity: It has a direct impact on the rate of transpiration, which is proportional to the vapor pressure of the atmosphere.

2. Internal factors that influence

Root Shoot Ratio: Because roots absorb water and should release water, their ratio influences transpiration.

Leaf area: Smaller plants transpire at a faster rate per unit area than bigger ones.

Leaf Anatomy: Leaf modification impacts transpiration.

---

Long Answer Questions [3 Marks Question]

Ques: What is the water potential?

Ans: Water potential is the chemical energy or chemical potential of water measured in pressure terms and influenced by pressure and concentration gradients. It is a term that refers to the free energy of water molecules. It is symbolized by the psi sign (Ψ). Pure water has no water potential. This water potential is the sum of the solute potential, the matric potential, and the pressure potential = Ψ m+ Ψ s+ Ψ p. Water moves from a high water potential to a low water potential.

Ques: How do halophytes have such a high precell pressure in comparison to air pressure?

Ans: To grow, halophytes require soil with a high salt content. There is a buildup of salts in the cytoplasm, which causes the osmotic concentration in the cytoplasm to rise, allowing water to enter the cells. As a result, the turgor pressure in halophytes cells is greater than in other cells. Halophytes have adopted two ways to limit it:

They collect salts away from the cytoplasm in vacuoles.

Excess salts are eliminated by the presence of salt-secreting glands.

Ques: Describe the plant cell in terms of an osmotic system.

Ans: The plasma membrane of plant cells, either alone or in conjunction with the vacuolar membrane and cytoplasmic film, is semi-permeable in nature. This membrane enables water molecules to move freely but prohibits specific molecules from entering. The cytoplasm in plant cells is enclosed by a cell wall that is more concentrated than the fluid that enters plant cells via osmosis. As a result, plant cells behave similarly to the osmotic system if the following two requirements are met:

If a semipermeable membrane exists.

Plant cells behave as an osmotic system because they contain a significantly larger concentration of a liquid component.

Ques: Explain facilitated diffusion.

Ans: Facilitated diffusion is also known as carrier protein transport or career-mediated diffusion. This happens as a result of a concentration gradient sustained by the carrier protein, such as glucose diffusion in Red Blood Cells (RBCs). Some chemicals can penetrate the cell membrane via the cell membrane. It doesn't create a concentration gradient. Even though the protein-membrane promotes diffusion without spending ATP energy, there is a concentration gradient that allows the molecules to diffuse. It is possible that the net transfer of molecules from low to high concentrations will occur as a result of the energy input. When all protein transporters are employed, the maximum transport rate is achieved. It is very particular, allowing the cell to choose the strand on the protein side. Because permeases are present as carrier proteins, the enhanced diffusion is stereospecific.

---

Very Long Answer Questions [5 Marks Question]

Ques: Which sorts of forces are involved in water absorption from the soil via root hairs?

Ans: (a) As a result of transpiration pushed by aerial plant parts, a negative pressure is forced down the roots, lowering the water potential of the roots and favoring soil water absorption.

(b) Water absorption from the soil is favored by a reduction in water potential in the root cell.

(c)The cohesive force between water molecules and the adhesive force between water and xylem cells maintain the pillar of water intact in the xylem vessel's capillary. In the xylem vessel, there is a gradient of water potential that likes to absorb water from the soil from the roots to the leaf.

(d) Soil water penetrates the root hairs and travels to the xylem vessel, which has a low water potential. As a result, root pressure develops. Water is pushed to the aerial plant parts by this root pressure.

Ques: Describe the cohesive force hypothesis of sap ascent in plants.

Ans: Dixon and Jolly proposed the cohesive force idea, sometimes known as the transpiration pull theory. The following are the theory's primary points:

1. Water's Strong Cohesive Force or Tensile Strength: Water molecules have a mutual force of attraction that is known as 'cohesive force.' Adhesion is the force of attraction between the xylem element's wall and water molecules. The cohesive force is the force that aids in the tensioning of a long column of water.
2. Water column continuity in plants: Air blockage can preserve the overall cohesive system. Trees sustain the quick flow of tree sap without disrupting the complete flocculation mechanism. With transpiration ability, water or sap may be drawn.
3. Tension or tensile stress caused by transpiration in an unbroken water column: Water is continually infiltrated from neighboring cells as a result of the transpiration process, which draws water from mesophyll cells to the intercellular space. Water is drawn in and distributed, and no pressure or suction power was created. Adjacent cells suck up water from the leaf's barrels. Because these barrels are linked to the root barrels through stem barrels, tension is created in the barrel's water column, which physically lifts the whole column.

Ques: Is there a universal mechanism that explains stomatal opening and closing? Justify your response.

Ans: There is no universal mechanism that explains stomatal opening and shutting. Because the concentration of solute in the guard cells regulates the opening and shutting of stomata. Solutes are taken up by the guard cells, lowering their osmotic potential and water potential. As a result, the guard cells become turgid and increase in size, culminating in the stomatal opening. Water goes out when guard cell solutes decrease, resulting in the stomatal opening.

There are two ideas that describe the process of stomatal opening and shutting.

1) The shift in osmotic concentration is caused by the conversion of starch into glucose and vice versa, according to the classic starch sugar conversion theory.

2) Theory of K+ Influx and Efflux: When the leaf is exposed to light, the pH of the guard cells rises owing to the active transfer of H+ ions from the cytoplasm into the chloroplast's consumption of CO in photosynthesis, according to this idea. Stomata in the majority of plants remain open throughout the day and close at night.

As a result, there is no generic mechanism that can explain stomatal opening and closure.

Also check: