Biology Presentation

BIOLOGY PRESENTATION

The uptake of ions by active transport Plants take up mineral ions by active transport. Active transport is the process by which dissolves molecules moves across a cell membrane from a low to a high concentration. in this process mineral ions are moved against a concentration gradient which requires:  Numerous mitochondrion in root hair cells for ATP production.  Protein channels in the cell membranes for active transport.  Oxygen in the soil that is absorbed by root hair cell respiration. In order for mineral ions to be pumped into the roots the mineral ions must make physical contact with protein pumps on cell membranes of root hair cells. The mineral ions move into contact with root hair proteins in one of two ways: 1. Diffusion 2. Mass flow Diffusion and mass flow are two slow processes because mineral ions are bind to the surface of soil particles.

Role of the endodermis The endodermal layer in a plant, almost always in the root, regulates the water and other substances that get into the plant. The endodermis is a single layer of cells that borders the cortex of a root. The whole system in which the endodermis functions allows the roots to select what gets into the vascular core. So basically the main function of the endodermis is for protection.

The entry of water into plant roots through water potential Water potential is the measure of potential energy in water and drives the movement of water through plants. 

Plants use water potential to transport water to the leaves so that photosynthesis can take place.

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The internal water potential of a plant cell is more negative than pure water; this causes water to move from the soil into plant roots via osmosis.

The ascent of water 1.

Root pressure

Root pressure, in plants force that helps to drive fluids upward into the waterconducting vessels (xylem). It is primarily generated by osmotic pressure in the cells of the roots and can be demonstrated by exudation of fluid when the stem is cut off just aboveground. It is partially responsible for the rise of water in plants. 2. Capillarity action Plants use capillary action to bring water up the roots and stems to the rest of the plant. The molecules of the water (the liquid) are attracted to the molecules of the inside of the stem (the solid). This attraction is used to help force the water up from the ground and disperse it throughout the plant.

3. Cohesion This explains that the upward movement of water is mainly due to the creation of a negative force or tension attributed to the continuous evaporation of water at the surfaces of leaves in the process of transpiration. Water molecules remain attached to one another by a strong mutual force of attraction called cohesion force. 4. Adhesion Adhesion is the process of attaching one thing to another. For plants, adhesion allows for the water to stick to the organic tissues of plants.

4. Transpiration pull

As molecule after molecule of water evaporates through the stomata, it creates a pulling action on the next molecules of water in the transpiration stream. This pulling force, otherwise called transpiration pull, is strong enough to overcome the force of gravity which is responsible for the tendency of water to move downward. The role of the stomata in transpiration is that ; 

It provides the main passage for transpiration of water vapor and assimilation of carbon dioxide by plants.

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It also helps to reduce water loss by closing when conditions are hot or dry. Stomata look like tiny mouths which open and close as they assist in transpiration.

The impact of environmental factors on the rate of transpiration The environmental factors affecting transpiration in plants include light, relative humidity, temperature, availability of water, and wind. Specifically, these are climatic elements which also affect photosynthesis and other plant growth and development processes. 

Relative humidity (RH) is the amount of water vapor in the air compared to the amount of water vapor that air could hold at a given temperature.

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Temperature greatly influences the magnitude of the driving force for water movement out of a plant rather than having a direct effect on stomata. As temperature increases, the water holding capacity of that air increases sharply.

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Light – Stomata are triggered to open in the light so that carbon dioxide is available for the light-dependent process of photosynthesis. Stomata are closed in the dark in most plants. Very low levels of light at dawn can cause stomata to open so they can access carbon dioxide for photosynthesis as soon as the sun hits their leaves.

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Wind – Wind can alter rates of transpiration by removing the boundary layer, that still layer of water vapor hugging the surface of leaves. Wind increases the movement of water from the leaf surface when it reduces the boundary layer, because the path for water to reach the atmosphere is shorter.

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Availability of soil water- greatly affects the rate of transpiration. If there is little water available, the resulting tendency for dehydration of the leaf causes stomatal closure and a consequent fall in transpiration.

Transpiration Transpiration is the loss of water vapor from a plant to its environment, by diffusion down a water potential gradient.

Structure of the xylem vessel and its functions

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Xylem is the tissue of vascular plants that transports water and nutrients from the soil to the stems and leaves.

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Xylem plays an essential ‘supporting’ role providing strength to tissues and organs, to maintain plant architecture and resistance to bending.

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The water‐transporting cells of mature xylem are dead, and therefore the transport of water is mostly a passive process with a very small active root pressure component.

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Are lignified or thickened to prevent collapsing.

Factors Affecting the Rate of Transpiration 

Wind Speed and Temperature

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Very Dry Conditions

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Light Intensity

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Humidity

Types of Pathways 

Symplastic Pathway

Water Moves from cell to cell via the plasmodesmata 

Apoplastic Pathway

Water moves through the cell walls

A Potometer

The Phloem

Sieve Tubes and Companion Cells

Solutes in the Phloem Sap

Translocation The Transport of solute organic substances within a plant

How Translocation Occurs

Loading and Unloading of Sucrose

Evidence for the Mechanism for Phloem Transport 

The Phloem sap always has a relatively high ph,often around 8

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There is a difference in electrical potential across the plasma membrane of companion cells, which is more negative inside that outside.

THE END