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BIOL 225 FORM AND FUNCTION OF ORGANISMS MIDTERM 2 NOTES Concordia University
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BIOL 225 FORM AND FUNCTION OF ORGANISMS MIDTERM 2 NOTES Concordia University
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BIOL 225 FORM AND FUNCTION OFORGANISMS MIDTERM 2 NOTES Concordia
University
Plant Lecture 1
- The structure of plant body is dynamic, because most plants exhibit indeterminate growth!
Plants are:
- Multicellular: single celled organisms that photosynthesize are not considered plants
- Eukaryotic: all plants have compartmentalized organelles
- Photosynthetic Autotrophs: plants feed themselves using fuel from light to make sugars that
are used for energy and substrate to build their bodies
- Built with cellulosic cell walls
Plants gather their nutrients from extremely dilute sources:
- SOIL
water present in films around soil particles, nutrients are present in 1 mM or less
concentration in soil solution, but generally are in much higher concentration in the plant body
- AIR
Oxygen and nitrogen make up most of the air’ carbon dioxide is at ~400 ppm
- LIGHT
Sunlight is more than sufficiently bright for photosynthesis, but within canopies and in shade,
light is much less available
Their cells and bodies are built to maximize surface-to-volume ratio.
Why are most leaves thin and broad? To maximize their ability to collect
light. Plant Structure
Hierarchy of organization in a plant body:
Whole organism Plant
Organ system Root, shoot
Organs Leaves, stems, roots
Tissue system Epidermal, ground, vascular
Tissues Ground (e.g. parenchyma, mesophyll, cortex)
xylem, phloem, meristem, cambium
1
,Cell types Epidermal cells, sclerenchyma, vessels, sieve
tubes, guard cells, collenchyma, tracheids,
companion cells, parenchyma, fibers
The three basic plant organs: Roots, Stems and Leaves
- Basic morphology of vascular plants reflects their evolution as
organism that draws nutrients from below and above the ground
- Plants take up water and minerals from below the ground (root system)
- Plants take up CO2 and light from above the found (shoot system)
2
, Plant structure (morphology)
- The shoot system is aboveground and acquires Carbon dioxide and light from the atmosphere
- The root system is belowground and acquires water and dissolved nutrients from the
soil Root and Shoot
- Roots rely on sugar produced by photosynthesis in the shoot system, and
- shoots rely on water and minerals absorbed by the root system
- Monocots and Eudicots are the two major groups of
angiosperms MONOCOT:
EUDICOT:
ANGIOSPERM:
Roots
root is an organ with important functions:
A
1. Anchoring the plant
2. Absorbing minerals and water
3. Storing carbohydrates
Roots in Monocots and Eudicots
- Most eudicots and gymnosperms have a taproot system, which consists of:
□ A taproot; the main vertical root
□ Lateral roots or branch roots; that arise from the taproot
- Most monocots have a fibrous root system that consists of:
□ Adventitious roots that arise from stems or leaves
□ Lateral roots that arise from adventitious roots
Roots can also be modified for functions other than anchoring and absorbing water and ions from the
soil. Roots that are part of the root system can also have specialized functions
Modified Roots
- Adventitious roots are roots that develop from the shoot system instead of the root system:
□ Corn plants have adventitious roots called prop roots that help brace individuals
in windy weather
- pneumatophores of mangrove trees allow gas exchange to occur between root tissues and the
atmosphere
Stems
3
, A stem is an organ consisting of:
- Nodes, the points at which leaves are attached
- Internodes, the stem segments between
nodes Modified Stems
Not all stems grow vertically, and not all stems acquire carbon
dioxide and photons. In fact, modified stems are common.
- An axillary bud is a structure that lies at the junction
of the stem and petiole of a plant and has the potential
to form a lateral shoot or branch
- An apical bud, or terminal bud, is located near the shoot tip
and causes elongation of a young shoot
Apical dominance helps to maintain dormancy in most axillary
buds. The Leaves
- In most plant species, the vast majority of
photosynthesis occurs in leaves.
□ The leaf’s relatively large surface area is available for absorbing photons.
- The external anatomy of a typical leaf consists of the expanded portion called the blade and
the stalk, or petiole.
- Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves
□ Most monocots have parallel veins
Most eudicots have branching veins
- In classifying angiosperms, taxonomists may use leaf morphology as a
criterion Leaves: Simple & Compound
Modified Leaves
4
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