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24 Cards in this Set
- Front
- Back
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Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant
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Outline three differences between the structures of dicotyledonous and monocotyledonous plants
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Feature: Monocotyledonous plants: Dicotyledonous plants
Pattern of veins in leaves: Parallel: Net-like Floral organs: Multiples of 3: Multiples of 4 or 5 Cotyledons: 1: 2 Vascular bundles: Scattered throughout the cortex but concentrated around the edge: Arranged in a single ring close to the epidermis |
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Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues
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Epidermis - Exchange of matter between plant and environment
• Above ground organs (leaves and stems) – gas exchange • Below ground organs (roots) – water and ion uptake Vascular tissues - Transport of water and dissolved substances within the plant • Xylem – carries water and dissolved ions from the roots to stems and leaves • Phloem – carries dissolved sugars from leaves to other areas Ground tissues - Metabolism, support and storage • Leaf – uses energy in sunlight to synthesize sugars (photosynthesis) • Stem – develops support cells, to hold the young plant upright • Root – stores energy-rich carbohydrates |
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Identify modifications of roots, stems and leaves for different functions: bulbs, stem tubers, storage roots and tendrils
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Bulbs:
• Layers of leaf bases that have swollen • Cells are packed with starch, grains and other nutrients • Only a small amount of clorophyll • E.g Onion Stem Tubers: • Modified, swollen stems • Cortex cells are packed with starch, grains and other nutrients • E.g Carrots Storage roots: • Modified, swollen root • Cortex cells are packed with starch, grains and other nutrients • E.g Carrots Tendrils: • Tendrils are modified leaves • When a tendril touches something, the other side will grow faster, making it wrap, and support the plant • E.g Sweet pea |
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State that dicotyledonous plants have apical and lateral meristems
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Dicotyledonous plants have apical and lateral meristems
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Compare growth due to apical and lateral meristems in dicotyledonous plants
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Merisistematic tissue contains small unspecialised cells that can undergo mitosis. After cytokineses one cell differentiates and the other remains in the meristem They result in plant growth.
- Apical meristems are found at the shoot and root tips, they result in growth in the length of the shoot or root. - Lateral meristems are the strips of cambium in the vascular bundles. They result in the growth of diameter of the root or shoot. |
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Explain the role of auxin in phototropism as an example of the control of plant growth
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- Phototropism is the growth of the plant either towards or away from a light source.
- Roots (if they show are response) are generally negatively phototropic. - Shoots generally show a positive phototropic response. The value of this is that it brings the leaves into a better position for photosynthesis. - Phototropism is controlled by a plant growth regulator called auxin. - Auxin stimulates growth by increasing the length of the cells behind the apical meristem. - Auxin may either accumulate on the shaded side, stimulating growth on the illuminated side or light may stimulate the synthesis of auxin inhibitors, so the illuminated side grows more slowly (The exact mechanism is unclear). |
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Outline how the root system provides a large surface area for mineral ion and water uptake by means of branching and root hairs
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• The root have many branches
• Root tips are covered with thousands of tiny root hairs, which are extensions of a single cell from the epidermis • These elements provide a large surface area which comes in contact with the soil for • Mineral ions and water are taken up through these root hairs |
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List ways in which mineral ions in the soil move to the root
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There are three processes:
Diffusion of mineral ions: - Some minerals are more concentrated in the soil than the roots, and will move via diffusion to an area of lower concentration. Fungal hyphae (mutualism): - Many plant species work together with a fungus - The threads of fungus (hyphae) grow through the soil and absorb minerals - They grow in the roots and absorb the minerals in the soil too - The fungus receives sugar from the plant, so both benefit Mass flow of water in the soil carrying ions: - The plant takes in water which contains some minerals |
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Explain the process of mineral ion absorption from the soil into roots by active transport
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- If the plant contains higher concentrations of ions than the surrounding soil, it uses active transport to move mineral ions against the concentration gradient
- Active transport takes place across the cell surface membrane of the root hairs - Carrier proteins use ATP to carry out active transport - Roots pump out H+, causing an electrochemical gradient - It is more negative inside than in soil, therefore positively charged mineral ions enter the roots - Negatively charged ions also move with the H+ as it diffuses back |
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State that terrestrial plants support themselves by means of thickened cellulose, cell turgor and lignified xylem
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Terrestrial plants support themselves by means of thickened cellulose, cell turgor and lignified xylem
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Define transpiration
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Transpiration is the loss of water vapour from the leaves and stems of plants
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Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion and evaporation
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State that guard cells can regulate transpiration by opening and closing stomata
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Guard cells can regulate transpiration by opening and closing stomata
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State that the plant hormone abscisic acid causes the closing of stomata
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The plant hormone abscisic acid causes the closing of stomata
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Explain how the abiotic factors light, temperature, wind and humidity, affect the rate of transpiration in a typical terrestrial plant
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Factor: Effect on transpiration: Mechanism
Increasing light: Increases: guard cells gain water, enlarging stoma. Increasing temperature: Increases: More water evaporates from spongy mesophyll cells, humidity is decreased, rate of diffusion through stomata increased. Increasing wind: Increased: regions of air around stomata saturated with water vapour are blown away, blows away layers of humid air and increase the rate of evaporation, diffusion gradient increased. Increasing humidity: decreases: water vapour will be lost more slowly through the stomata, diffusion gradient decreased. |
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Outline four adaptations of xerophytes that help to reduce transpiration
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Lowered number of stomata - Cuts down the amount of water lost from the leaves
Thickened waxy cuticle - The thicker the cuticle, the less water will escape. Spines - Less surface area for evaporation, also deters animals from consuming water Reduced leaves - Reduces surface area exposed to the sun, and lowers the number of stomata |
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Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots)
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Phloem cells form long sieve tubes. Nuclei and most other organelles are lost, modified cytoplasm remains, plasma membrane remains, end wall partially dissolved forming sieve plate.
1. Solutes such as sucrose and amino acid from the source cell are actively transported into the sieve tube 2. Creates an osmotic gradient, so water enters the sieve tube, decreasing pressure 3. Solutes from the sieve tube are actively transported out into the sink cell and converted 4. Creates an osmotic gradient so water leaves the sieve tube, increasing pressure 5. The pressure gradient courses a flow from source to sink |
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Draw and label a diagram showing the structure of a dicotyledonous animal-pollinated flower
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Distinguish between pollination, fertilization and seed dispersal
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Pollination: the transfer of pollen grains from the anther to the stigma
Fertilisation: the fusing of the male and female gametes Seed dispersal: the spreading of the seeds away from the parent plant |
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Draw and label a diagram showing the external and internal structure of a named dicotyledonous seed
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Explain the conditions needed for the germination of a typical seed
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1. Moisture - seeds dry out for dispersal. At germination the cells need to rehydrate so that metabolic reactions can take place.
2. Warmth - Many of the metabolic events of germination use enzymes. These are sensitive to temperature. Temperature is often a triggger for germination. 3. Oxygen - Many of the events of germination use energy. This is produced by aerobic respiraiton. 4. Light – necessary for the normal growth and development of the seedling containing chloroplasts and no etiolated growth |
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Outline the metabolic processes during germination of a starchy seed
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1. The seed absorbs water through micropyle ad this causes secretion from the cotyledon of plant growth regulators called gibberellins.
2. The gibberellins diffuse into the aleurone layer where they stimulate the synthesis f amylase and protease enzymes. 3. These enzymes digest the stored protein and starch in the endosperm releasing small nutrient molecules such as amino acids and maltose. 4. These nutrient molecules then diffuse into the embryo and are used by the embryo for energy and growth. |
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Explain how flowering is controlled in long-day and short-day plants, including the role of phytochrome
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• Conversion of Pr to Pfr in light
•Pfr gradually converts to Pr in darkness • Pfr is the promoter of flowering in long-day plants, and the inhibitor of flowering in short day plants |
