Download Anatomy of Plants

Section #2
Plant Structure and Anatomy
Most plants that people deal with daily are in the subdivision angiospermae
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Angiospermae – plant that produces seed that are enclosed in a
fruit
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Angiospermae is divided into two classes
o Dicotyledonae – 2 embryonic seed leaves (includes
legumes)
o Monocotyledonae – 1 embryonic leaf (includes grasses)
Plants are divided into three basic parts
1. Roots
2. Stems
3. Leaves
Hierarchy of Human Structure
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Cells ⇒ tissues ⇒ organs ⇒ Organ systems ⇒ Human body
Hierarchy of Plant Structure
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Cells ⇒
tissues
A plant is an organ system
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Roots
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Stems
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Leaves
⇒ organs ⇒
Plant
Roots
Functions
1. anchoring the plant
2. absorb water and minerals from soil and transporting them
3. storing food produced by above ground portion of plant
4. propagation of new growth (tubers bulbs, rhizomes)
Parts of a root system
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primary root – originates from the embryo (main stem)
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secondary roots (fibrous)- branches of primary root
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root hairs – specialized cell extensions that enter spaces between soil
particles
Dicotyledonae root system
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large primary root with fine branching laterals
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fineness increases with each branching order
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primary or secondary may swell (carrot, radish)
Monocotyledonae root system
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often called fibrous root system
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lack ability to thicken
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has two phases
1. seminal roots (seed roots)
o emerge from first node of seed embryo
2. adventitious roots (nodal or coronal)
o emerge from basal nodes of grasses just below
soil surface
o become dominant root system for monocots
Stems
Functions
1. above ground structural component
2. attachment for leaves, flowers and fruit
3. water and food distribution (vascular system)
Stem
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develops from bud to bear leaves
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contain nodes – point where leaf is attached (# leaves = # of
nodes)
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contain internodes – spaces between nodes, point of growth
for plants (internode elongation)
Leaves
Function
1. conduct photosynthesis
2. intercept light
3. gaseous exchange
4. cool plant
Parts
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blade – broad thin part of leaf
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petiole – attaches blade to stem (some plants have no apparent
petiole)
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stipules – leaf like appendages at bases or petioles (not on all
leaves)
Arrangement of veins
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parallel
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netted venation
Anatomy of Plants
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The Cell = basics structural unit and physiological unit of crop plants, where
chemical reactions of life occur providing metabolites for plant life and for human
use.
Two types of cells exist:
1. Prokaryotes
• Cells without nucleus
• Have genetic material not enclosed by membrane
• Examples – bacteria and cyanophytes
• no internal organelles
2. Eukaryotes
• Cells with nucleus (genetic material surrounded by membrane)
• Found in humans, plants animals, algae and protozoa
• Cellular and nuclear membrane
• Plants differ having
o Cell wall
o Large vacuoles
o Chloroplasts
Eukaryotes
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90% fluid ie. Cytoplasm
o free amino acids
o proteins
o gluclose
Structures of the Cell
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Cell walls
Non living
Surrounds the protoplast
Extend during cell enlargement
Thickens during maturation
Can maintain 70 psi
Gives plant turgor
Secondary cell walls made of cellulose, lignin
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Plasma membrane
Regulates flow of dissolved substances and water in and out of
the cell
Contains lipid bilayer
hydrophilic (water loving) facing outward
hydrophobic (fat loving) facing inward
Contains proteins embedded in lipid bylayer
Regulate flow in and out of cells
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Cytoplasm
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Liquid matrix
Suspends cytoplasmic organelles
Water solutes and proteins
Cellular Organelles
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Chloroplasts
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Double membrane plastids
Contain chlorophyll
Conducts Pn (autorophs)
Have DNA (once separate organism???)
Vacuole
Occupies major volume of the cell
Enables plant to separate from cytoplasm
Contains sugars, water, salts
Helps maintain turgidity of cell
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Mitochondria
Site of aerobic respiration ie. Release of energy
Allow plants to metabolize reduced carbon
Converts stored food into ATP
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Nucleus
Contain cellular DNA
Governing body of cell
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Endoplasmic Reticulum (ER
Site of protein synthesis
Rough ER has ribosomes
Transport for molecules with specific functions
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Ribosomes
Protein synthesis
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Golgi Apparatus
Collects packages and delivers proteins made by ER
Helps in creation of membranes (tonoplast surrounding
vacuole)
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Peroxiomes
Function in photoresiration
Use oxygen to carry out catabolic reactions
Types of Cells Found in Simple Tissues
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Parenchyma cells
Most abundant and occur in all plant organs, thin cell walls,
large vacuole, contain chloroplast if found in leaves,
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Collenchyma cells
Thick cell walls, function as supporting tissue, flexible and
living at maturity
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Sclerenchyma cells
Thick rigid walls, heavily lignified, dead at maturity
Tissues
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Tissues = large group of organized cells of similar structure to perform specific
functions in the plant
Two general types
1.
meristematic
2.
permanent
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Meristematic
Contain actively dividing cells forming new tissues
Found in
1.
root tips
2.
shoot tips
3.
nodes
4.
cambium parts
Four types of meristematic tissues are
1.
apical – shoot or root (at apex or tip)
add height or length
can appear at axillary buds in leaf axils (can give rise to
apical meristem if original is damaged)
produce buds, leaves, flowers and new root extensions
in roots
2. lateral – gives rise to thickening or increased girth
located near outer edge stems and leaves
form vascular cambium and give rise to new vascular
tissue (xylem and phloem)
cambium is responsible for bark production
3. intercalary – found between two previously differentiated
tissues
found just above the nodes or base of leaves
found in grasses between node and internode or
between the leak blade and sheath
increase length of stems and leaves in grasses
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Permanent Tissues – generally do not become meristematic
• Simple permanent – one type of structure
• Epidermis – single layer found on exterior of stems ,
leaves flowers and fruits, usually have no pigment,
protective covering, excrete waxy substance, allow for
gaseous movement into plant
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Complex permanent – conductive tissues (contain one or more simple cells)
• Xylem – vertical transport of water and dissolved minerals
and aerial support, water moves with transpiration stream
due to differences in water potential, includes several types
of cells tracheids, fibers and parenchyma cells
• Phloem- movement any direction of OM like carbohydrates
and amino acids, contains parenchyma and sclerenchyma
fibers
Anatomy of Primary Organs
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Roots
Penetrate into soil due to cell divisions and elongation
Root tip protected by root cap
Root hairs found just behind region of elongation
• Small projections of epidermal cells
• Increase total surface area
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Stems
Support provided by thick celled cells and turgor
Water and mineral transported in xylem
Food is transported in phloem
Monocot vs dicot arrangement
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Leaves
Flat broad thin structure increasing surface area
Can reduce light impact by adjusting angle, by thickening
and reflective surface
Contain stomata, controlled by guard cells
Two layers of cells palisade (thick) and spongy (loose)
Pn occurs in palisade cells