Please answer all questions 7. Describe how water moves up the stem of a plant f

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Please answer all questions
7. Describe how water moves up the stem of a plant from the roots to the leaves. 8. On St. Patric's Day in many places, florists offer carmations that hav w, petals have not been "dipped" into a green dye carnations are naturally produce these carmie or paint.Use your understanding of water movement in planis als. These aa e green speckled pet Use your 9. Name at least two environmental factors that are likely to cause a high rate of transpiration in plants and explain why they do. 10. Imagine two plants in approximately the same climate conditions. One grows in open meadows and is exposed to full sunlight and brisk winds, while the other grows on the forest floor, beneath the shade of large trees and sheltered from the wind. Which would likely have a greater density of stomata and why?

Explanation / Answer

7) Root is the primary site for absorption of water. Upon seed germination, the embryonic root, called the radicle grows and develops into the first root. A developing root has three zones of development-meristematic zone, elongation zone and maturation zone. The maturation zone is sometimes also called the zone of differentiation or root-hair zone. Root hairs are extensions of the epidermis that serve to increase surface area and of water and aid in the absorption of water and soil nutrients. Absorption of water by roots is a passive, pressure driven process. The actual movement of water through a cell membrane is the result of two processes: diffusion and bulk flow. The size of a water molecule permits it to pass through the bilayer of the plasma membrane. This would be largely a diffusion movement subject to Fick's law. The membrane also possesses transport proteins; the one involved with water transport is called an aquaporin. The aquaporin protein serves as a water-filled channel. The flow through this channel is accomplished by submicroscopic bulk flow. In some cases, aquaporins also allow transport of small neutral solutes across a cellular membrane. Recent data indicate that plant aquaporin activity might be regulated by gating mechanisms. The factors affecting the gating behaviour possibly involve phosphorylation, pH, calcium, pressure and temperature. Regulation of aquaporin trafficking may also represent a way to modulate membrane water permeability. As plants absorb water from the soil, they deplete the soil water near the surface of the roots. This depletion establishes a pressure gradient with respect to neighbouring regions of soil. Water moves through soil predominantly by bulk flow driven by a pressure gradient. The water-filled spaces in the soil are interconnected, water moves to the root surface by bulk flow through these spaces down the pressure gradient.

Once water has been absorbed into the root hairs or epidermal cells, it must transverse the cortex in order to reach the xylem elements. A root in the cross would have an epidermis cortex, endodermis, pericycle, xylem and phloem. Transpiration develops hydrostatic tension in the xylem of the root which draws water from the soil through the intervening tissue of the cortex. intervening tissues of the cortex.The path through which water moves into xylem cells of roots occurs through both apoplast (the continuous system cell wall and intercellular spaces) and symplast (the continuous system of cell protoplast interconnected by the plasmodesmata).

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9) ENVIRONMENTAL FACTORS THAT INFLUENCE THE TRANSPIRATION RATE:

LIGHT: Plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of stomata. Light also increases transpiration rate by warming the leaf.

TEMPERATURE: Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises.

HUMIDITY: increased humidity decreases transpiration as the air is already saturated with water. As the water potential gradient is smaller, less water is lost by transpiration.

WIND: When there is no wind, the air surrounding a leaf becomes increasingly humid thus reducing the rate of transpiration. When the wind is present, the humid air is carried away and replaced by drier air.

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10) the plants that grow on the forest floor, beneath the shade of the large trees and sheltered from the wind have the greater density of stomata than the open meadows and those exposed to full sunlight. because the Plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of stomata. Light also increases transpiration rate by warming the leaf. so, to decrease transpiration rate the open meadow plants have fewer stomata.

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