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Questions and Answers
What is the primary function of the epidermis in plant stems?
Which structure mentioned is responsible for the storage and support functions in plant stems?
What do terminal buds primarily produce?
What occurs to the cells outside the ring of vascular cambium?
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Which structure is characterized by developing above the leaf scars?
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What is the primary function of plant hormones produced in roots?
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Which part of the root system is characterized by a large main root that penetrates deep into the soil?
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What is the role of the Casparian strips found in the endodermis?
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Which hormone affects seed germination and stem elongation?
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Which of the following structures contributes to the growth of lateral roots?
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Which statement accurately describes the fibrous root system?
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Which specialized root structure is used by parasitic plants to absorb nutrients from their hosts?
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What is a function of ethylene in plants?
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What is the primary function of heart wood in trees?
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Which part of the periderm replaces the epidermis as the plant matures?
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What role do cork cells play in the plant?
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What type of stem is characterized by its thickened underground structure specialized for food storage and reproduction?
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Which of the following describes a pinnately compound leaf?
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Where are stomata replaced in cork cells?
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What type of leaf arrangement has two leaves growing at each node?
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Which of the following stems is specifically an enlarged, fleshy structure that serves as a food storage organ?
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Which term refers to a leaf that has a single blade?
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What is the main function of leaves in plants?
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Which characteristic describes eudicot leaves?
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What is the primary function of spongy mesophyll in a leaf?
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What process occurs in the abscission zone as autumn approaches?
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Which of the following features is NOT associated with monocot leaves?
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How does the dermal tissue system contribute to a plant's survival?
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Which tissue type is primarily responsible for conducting water in plants?
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In eudicot plants, what is the shape of guard cells typically like?
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What role does leaf abscission play in the survival of trees in temperate forests?
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Study Notes
Plant Structure
- Plants consist of three basic parts: roots, stems, and leaves.
- Roots absorb water and nutrients from the soil.
- Roots act as storage for plant food.
- Roots hold the plant in its place.
- Stems transport water and nutrients from the roots.
- Stems act as storage for plant food and nutrients.
- Stems hold leaves, flowers, and buds.
- Stems contain apical meristem, which produces new tissue.
- Leaves are the primary site of photosynthesis in the plant.
Plant Hormones
- Auxin promotes elongation in response to stimuli and apical dominance.
- Gibberellin promotes seed germination and stem elongation.
- Cytokinin promotes cell division, ensures equal growth of roots and shoots, promotes fruit growth, and drives secondary (lateral) growth.
- Ethylene regulates maturation, aging, and ripening of fruits.
- Abscisic acid inhibits cell division, initiates leaf death (abscission), controls seed dormancy and stress response, and closes stomata.
Root Systems
- Taproots grow from dicots and gymnosperms.
- Taproots have a large central root that penetrates deep into the soil.
- Taproots store food.
- Fibrous roots grow from monocots and seedless vascular plants.
- Fibrous roots do not have a large main root and penetrate shallow in soil.
- Fibrous roots do not store food.
Root Structures
- The root cap protects the root from damage during growth.
- The apical meristem is the region of cell division in the root.
- Cells become longer and larger in the region of elongation.
- The root hair zone is the site of cell maturation.
- The endodermis surrounds the vascular cylinder, and its walls are impregnated with suberin.
- The Casparian strip restricts water movement through the cell walls, forcing it to move through the cell membrane.
- Passage cells allow for the movement of substances between the cortex and the vascular bundle.
- The vascular cylinder conducts water and food in solution.
- The pericycle is the site of lateral root development.
Specialized Roots
- Prop roots arise from the stem to provide support for the plant.
- Haustoria roots penetrate the host plant's tissues to absorb water and minerals.
- Buttress roots support trees in shallow, wet soil.
- Aerial roots may be photosynthetic, and anchor climbing plants.
- Epiphyte roots hang from the plant and anchor it to the soil.
- Contractile roots adjust the depth of bulbs and corms in the soil.
- Pneumatophores (breathing roots) help facilitate gas exchange in submerged environments.
- Suckers are above-ground stems that develop into independent plants.
Stem Structures
- Terminal buds grow stems that bear leaves and flowers at the stem's tip.
- Bud scales protect dormant terminal buds.
- Bud scars form after the bud scales fall off.
- Axillary buds (lateral buds) grow stems that bear leaves and flowers found in the stem's axis.
- Axillary buds develop above leaf scars.
- Leaf scars show where leaves were attached to the stem.
Stem Internal Structures
- The epidermis, the outer covering of the stem, protects the plant.
- The epidermis produces a fatty substance called cutin.
- The cortex, the thick cylinder of ground tissue, functions in storage, support, and photosynthesis.
- The stele is the central cylinder of the stem, composed of the vascular bundle.
- The vascular bundle contains primary phloem and xylem.
- The pith is composed of large parenchyma cells functioning in storage.
- The vascular cambium divides to produce secondary xylem (wood) inwards and secondary phloem (inner bark) outwards.
- Secondary xylem that is still functioning is known as sapwood.
- Non-functioning wood is called heartwood.
- The cork cambium divides to produce cork cells, creating the periderm (outer bark), which replaces the epidermis as the stem matures.
- Cork cells are dead at maturity and are water-proof, and they protect the stem from injuries, fire, pests and diseases, temperature extremes, and water loss.
- Cork parenchyma stores water and food.
- The bark consists of periderm (outer bark), secondary phloem (inner bark), and any tissues outside the vascular cambium.
Specialized Stems
- A corm is a short, underground stem used for food storage and reproduction.
- A bulb is a rounded, underground bud used for food storage and reproduction.
- A rhizome is a horizontal, underground stem that functions in storage and reproduction.
- A tuber is a thickened, fleshy end of a rhizome used for food storage.
- A stolon/runner is an aerial, horizontal stem with long internodes that can produce new plants.
Leaf Functions
- Leaves give the plant its identity through their shapes and colors.
- Leaves are the primary site of photosynthesis in the plant.
Leaf Parts
- The lamina/blade is the flat, broad part of the leaf.
- The petiole is the stalk that attaches the leaf to the stem.
- Stipules are leaf-like outgrowths at the base of the petiole.
Leaf Types
- Simple leaves have a single blade.
- Compound leaves have two or more leaflets.
Compound Leaf Types
- Pinnately compound leaves have leaflets borne on an axis that is a continuation of the petiole.
- Palmately compound leaves have leaflets arising from a common point at the end of the petiole.
Leaf Arrangement
- Alternate leaf arrangement has one leaf at each node.
- Opposite leaf arrangement has two leaves at each node.
- Whorled leaf arrangement has three or more leaves at each node.
Leaf Venation
- Parallel venation has primary veins running parallel with smaller veins connecting them.
- Reticulated (netted) venation has smaller veins branching off larger veins, forming a network.
- Pinnately netted venation has major veins branching off along the length of the midvein.
- Palmately netted venation has several major veins radiating from a point.
Leaf Structures
- The dermal tissue system (epidermis) provides protection, prevents water loss, facilitates gas exchange, and regulates temperature.
- The palisade mesophyll is the main site of photosynthesis in the leaf.
- The spongy mesophyll helps in gas diffusion, particularly carbon dioxide.
- Xylem conducts water through the leaf.
- Phloem conducts sugars produced by photosynthesis.
Eudicots Versus Monocots
- Eudicots have blades and petioles, netted venation, distinct palisade and spongy mesophylls, and kidney-bean-shaped guard cells.
- Monocots have blades but lack petioles, parallel venation, no distinct palisade and spongy mesophylls, and dumbbell-shaped guard cells.
Leaf Abscission
- Abscission is the normal shedding of leaves or other plant parts.
- Abscission is important for the survival of trees in temperate forests during cold winters.
- The abscission zone is the area where the leaf petiole detaches from the stem.
- A protective layer of cork cells forms in the abscission zone, helping facilitate leaf detachment.
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Description
Test your knowledge on the basic structure of plants, including roots, stems, and leaves, and their various functions. Explore the roles of different plant hormones and how they affect growth and development. This quiz combines essential concepts from plant biology.
