lecture 8a Flashcards
Describe the 2 basic systems found in vascular plants and explain how these systems are interdependent.
1.Root system . • Belowground; functions in anchoring the plant + acquiring water and dissolved nutrients from the soil. 2. Shoot system • Aboveground; acquires CO2 and light from the atmosphere to carryout photosynthesis. • The shoot system includes the leaves and stems.
List the basic functions of roots.
Root: An organ that anchors a vascular plant in the soil, absorbs minerals and water, and stores carbohydrates.
Compare and contrast the structure and function of taproots vs fibrous roots
Eudicots (and gymnosperms) have a taproot system.
• Consists of one large vertical root (taproot) that produces many small lateral (or branch) roots.
• Taproot systems penetrate deeply.
• Adapted to deep soils, where groundwater is not close to the surface.
Seedless vascular plants and most monocots have a fibrous root system.
• Mat of thin roots that spread out below the soil surface.
• Fibrous root systems generally do not penetrate deeply.
• Are adapted for shallow soils or regions where rainfall is light and does not moisten the soil
much below the surface.
State the function of root hairs
absorption
Describe several root modifications and their functions.
• Prop roots - support tall, top heavy trees where sandy soils are shallow and unstable. Also brace plant in wind.
• Storage roots – e.g., beet, carrot.
• Buttress roots - provide architectural support to tall trees with shallow roots.
• Pneumatophores - enable the root system to obtain oxygen in muddy swamps (act like
snorkels).
• Strangling fig – seeds germinate in the branches of other species; send down numerous roots to the ground, which gradually wrap around the original tree, killing it.
Describe the basic structure and function of plant stems.
Stem: An organ that raises or
separates leaves, exposing them
to sunlight.
Differentiate between an apical bud and an axillary bud.
- Axillary bud
- Located at the angle formed by each leaf and the stem .
- Has the potential to form a lateral shoot or branch.
- Apical (terminal) bud
- At the tip of each stem; where growth that lengthens the stem occurs.
Explain the phenomenon of apical dominance.
Apical buds inhibit the growth of axillary buds = apical dominance.
Why would a young plant do this?
• By concentrating resources on growing taller, apical dominance is an adaptation that exposure of young plant to light.
Describe several modified stems and their functions.
- Stolons - horizontal stems that grow on the surface and enable a plant to colonize large areas asexually.
- Rhizomes - horizontal stems that grow underground.
- Tubers - swollen ends of rhizomes specialized for food storage.
- Bulbs - underground shoots with many layers of modified leaves that store food.
- Thorns – protect plant from herbivores.
- Desert cacti stems are enlarged to store water. Are also main photosynthetic organs (leaves = spines).
Describe the basic structure and function of plant leaves.
• Leaves are the main photosynthetic organs of most plants (although green stems are also photosynthetic).
• Vary extensively in form, but generally
consist of:
1. Flattened blade
2. Petiole - a stalk that joins the leaf to a
stem node.
Distinguish between the leaves of monocots and those of eudicots.
- Monocots have parallel major veins that run the length of the blade.
- Eudicots have a multibranched network of major veins.
Provide examples o f variation in leaf shape and arrangement.
• Simple Single, undivided blade. • Compound Several leaflets attached to the petiole. NOTE: a leaflet has no axillary bud at its base. • Doubly compound Each leaflet is divided into smaller leaflets.
Describe several modified leaves and their functions.
onion leaves- store food
alovera leaves- store water
pitcher plants trap and drown insects
Define phenotypic plasticity in plants and provide an example.
Phenotypic plasticity
• Within species variation in phenotype due to differences in environmental conditions
example: sun leaves verse shade leaves
Describe the 3 tissue systems that make up plant organs
dermal, ground and vascular
Dermal tissue functions
- Dermal tissue (“epidermis”)
- Single-layer of epidermal cells that covers the plant.
- Protects plant against physical damage, water-loss (secretes waxy cuticle), and pathogens.
- Also includes guard cells and trichomes.
- In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots.
Ground tissue Functions
- Bulk of plant body.
- Functions include synthesis, storage, and support.
- Pith: ground tissue that is internal to the vascular tissue.
- Cortex: ground tissue that is external to the vascular tissue.
Vascular tissue Functions
Carries out long distance transport between roots and shoots and also provides support
xylem: transports water and dissolves minerals upward from roots to shoots
phloem: transports food made in the leaves to the roots, to non-photosynthetic parts of the shoot, and to sites of growth
Distinguish between determinate and indeterminate growth.
Plant growth is indeterminate.
• Most plants continue to grow throughout their lives.
• At any given time, a plant has embryonic, developing, and mature organs.
• In contrast, most animals and certain plant organs (e.g., flowers and leaves), undergo determinate growth.
• Cease to grow after they reach a certain size
(not cover the underlying leaves)
Distinguish between the primary and secondary plant body.
grow in length = primary growth.
• Cells derived from apical meristem form the primary plant body.
Contribute to secondary growth in woody plants = progressive thickening of roots and shoots where primary growth has ceased. derived from lateral mertistem
Describe the function of the root cap.
- Group of cells that protect the meristem as the root pushes through the abrasive soil.
- Secretes a polysaccharide slime that lubricates the soil around the growing root tip.
- Senses gravity to determine direction of growth.
Distinguish between the 3 zones of cells in a root undergoing primary growth
- Zone of cell division
• Includes the root apical meristem and its primary
meristems ( protoderm, ground meristem, + procambium).
• New root cells produced, including cells of the root
cap. - Zone of elongation
• Cells elongate by taking up water.
• Elongation of cells is responsible for pushing the
root tip ahead.
• Meristem sustains growth by continuously adding cells to the youngest end of this zone. - Zone of maturation
• Cells differentiate into dermal, ground, and vascular tissue become specialized in structure + function.
• Epidermal cells produce the root hairs.
• Where lateral roots grow.
Describe the process of primary growth of the tissues in roots and shoots
• Apical meristem = dome-shaped mass of dividing cells.
• Just behind apical meristem, primary meristematic cells give rise to dermal, ground, and vascular tissues.
• Elongation of shoot is due to lengthening of internode cells below shoot tip.
• Leaves arise from leaf primordia.
• Finger-like projections along the sides of the apical meristem.
• Axillary buds develop from islands of meristematic
cells left by apical meristems at the bases of the leaf primordia.
Describe in detail the secondary growth of the tissues in roots and shoots.
- Thickens roots and stems by increasing in circumference + forming successive layers of secondary xylem to its interior and secondary phloem to its exterior.
- Produces parenchyma cells that radiate laterally across the xylem and phloem forming vascular rays.
- Allow water and nutrients to be transported laterally across the stem.
