Plant Water Relation

Plant obtains variety of substances like water, minerals, nutrients, food and gases like O2 and CO2 , from its surroundings. Productivity in plants is mainly affected by the non-availability of water.

Define and or explain the terms: Osmosis, diffusion, plasmolysis, imbibition, guttation, transpiration, ascent of sap, active absorption, DPD, turgor pressure, water potential, wall pressure, root pressure.

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(i) Osmosis is a specific type of solvent diffusion through a semipermeable membrane. (ii) It involves the movement of ions, atoms, or molecules from areas of higher concentration to regions of lower concentration. (iii) When a living cell undergoes exo-osmosis in a hypertonic solution, it experiences plasmolysis. (iv) The swelling of hydrophilic colloids due to … Read more

Explain movement of water in the root.

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1. Water absorption in root hairs occurs through a process involving imbibition, followed by diffusion and osmosis. 2. As water enters the root hair cell, it undergoes an increase in turgor pressure, resulting in turgidity. 3. The root hair cell possesses lower solute concentration (D.ED.) compared to the adjacent cortical cell with higher solute concentration … Read more

Why is transpiration called ‘a necessary of evil’?

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A ‘necessary evil’ as termed by curtis transpiration because: 1. Stomata, small openings in the leaf epidermis, facilitate 90–93% of transpiration, a vital plant process. 2. To enable gaseous exchange through diffusion, stomata must remain open during this essential biological activity. 3. Gaseous exchange is crucial for both respiration and photosynthesis within plants. 4. The … Read more

Explain capillarity theory of water translocation.

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Capillarity theory of water translocation: 1. Bohem proposed the capillarity theory of water translocation.Capillarity arises from the interplay of surface tension, cohesive forces, and adhesive forces among water molecules. 2. Xylem vessels and tracheids are tubular elements characterized by their luminal structure. 3. Within these elements, a water column is sustained through the synergistic influence … Read more

What is significance of transpiration? Explain root pressure theory and its limitations.

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Significance of transpiration: 1. Facilitating a cooling effect by absorbing plant heat and converting water into vapor during transpiration. 2. Ensuring optimal turgor pressure by absorbing excess water during transpiration, promoting healthy growth. 3. Assisting mineral transport by generating a transpiration pull, aiding the roots in absorbing and distributing soil minerals. 4. Supporting water transport … Read more

What is transpiration? Explain role of transpiration.

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Transpiration is the process wherein water is lost from the plant body in the form of vapor. Role of transpiration: 1. Eliminates excess water. 2. Facilitates passive absorption of water and minerals. 3. Aids in the ascent of sap through transpiration pull. 4. Sustains cell turgor. 5. Provides a cooling effect by reducing temperature. 6. … Read more

What is transpiration? Describe mechanism of opening and closing of stomata.

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Transpiration is the process in which water is lost in the form of vapor. Mechanism of closing and opening of stomata is as follows: Stomatal transpiration primarily involves minute pores. Stomata consist of two guard cells encircled by accessory cells. The opening and closing of stomata are regulated by the turgidity of guard cells. When … Read more

Discuss theories of water translocation.

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Theories of water translocation: The translocation of water is explained by various theories: 1. Vital force theories 2. Root pressure theory 3. Capillary force theory 4. Cohesion force theory Root pressure theory: Root pressure, once believed to drive water up plant stems, faces objections. The force is weak (max 2 atm), insufficient for tall trees. … Read more

Describe mechanism for absorption of water.

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A mechanism of water absorption: Water is absorbed through two mechanisms: active absorption and passive absorption. Active absorption: 1. Osmotic Active Absorption: This process involves water absorption through osmosis, where water moves into the root xylem against the concentration gradient of the root cell. The high concentration of solutes in the cell sap and the … Read more