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BIOL 117 Plant Growth
Turner
PLANT STRUCTURE AND GROWTH
I. Plant Body
A. Vascular Tissue
1. Xylem -
2. Phloem -
B. Root System
1. Functions
a. Anchors plant in soil
b. absorbs minerals and water
c. conduct water and nutrients
d. stores food
2. Structural Adaptations
a. Taproot
b. Fibrous root system
c. Root Hairs
d. Adventitious Roots
C. Shoot System
{Vegetative Shoots - bear leaves & Floral shoots - terminate in flowers}
1. Stems
a. Nodes are the point of attachment for leaves
b. Internodes are segments between nodes
c. Axillary bud
d. Terminal bud
e. Apical Dominance
i. Adaptation that increases the plant's exposure to light, in areas of dense vegetation
ii. Concentrates resources in growing taller
iii. Pruning trees can trigger axillary buds to grow
f. Underground Stems
i. Rhizomes -
ii. Stolons (runners) -
iii. Tubers -
iv. Bulbs -
2. Leaves
a. Main photosynthetic organ, but stems are also involved
b. Consists of blade and petiole (stalk)
i. Some monocots lack petioles like grasses
ii. Other monocots have petioles like palm trees
c. Vein Variation in Monocots and Dicots
i. Monocots have parallel major veins
ii. Dicots generally have a network of major veins
d. Variations other than Venation
i. Arrangement on Stem
1. Opposite
2. Alternate
3. Whorled
ii. Simple vs Compound
iii. Shape
iv. Margin
II. Plant Cells & Tissues
A. Plant Cells
1. Parenchyma Cells
a. Least specialized ; "typical plant cell"
b. Primary cell wall relatively thin & flexible
2. Collenchyma Cells
a. Thicker primary walls; unevenly thick
b. Help support young growing parts
3. Sclerenchyma Cells
a. Function in supporting the plant
b. Very thick secondary cell walls; impregnated with Lignin
c. Very rigid; cannot elongate
d. Lost ability to grow; infact they are dead at maturity
e. Two forms
i. Sclerids (stone cells)
ii. Fibers (tapered, spear-like)
4. Tracheids & Vessel Elements
a. water-conducting elements of xylem
b. Dead at functional maturity
c. Tracheids are long, thin cells with tapered ends
i. Water moves from cell to cell mainly through pits
ii. Function in support as well as water movement
d. Vessel elements - are wider, shorter, thinner walled
i. aligned end to end forming long micropipes
ii. Xylem vessels
iii. End walls are perforated, enabling water to flow freely through xylem vessels
5. Sieve-Tube Members
a. Phloem conducts food materials throughout the plant and provides
support
b. Phloem is a complex tissue in flowering plants
c. Sieve tube members conduct food materials in solution
i.
6. Companion Cells are adjacent to sieve tube members
a. They are living cells, complete with a nucleus
b. Nucleus is thought to direct the activity of both Companion cells and
Sieve Tube Members
B. The Three Tissue System of a Plant
1. Dermal Tissue system {epidermis and periderm}
a. In herbaceous plants, dermal tissue is a single layer of cells called the
epidermis.
b. Woody plants initially produce an epidermis, but is splits apart as the plant increases in girth.
i. Periderm, tissue several cell layers thick, forms
under the epidermis to provide protection
i. Composes the outer bark {replaces
epidermis in the stem and roots of older woody plants}
2. Epidermis is a complex tissue composed mostly of
a. parenchyma
b. scattered guard cells
c. trichomes (outgrowths or hairs)
d. Epidermal cells consist of a single layer of flattened cells.
e. Epidermal Cells of aerial parts secrete a waxy layer termed a cuticle over the surface of their exterior walls
i. prevents water loss, but restricts carbon dioxide diffusion from atmosphere into the leaf
ii. Stomata facilitate CO2 diffusion
iii. generally open during the day
iv. water loss while open provides some evaporative cooling --Transpiration
v. Close during the night.
f. Guard Cells
3. Vascular Tissue System
a. functions in transport & support
b. consists of xylem and phloem
4. Ground Tissue System
a. makes up the bulk of a young plant; fills in between Vascular and
Dermal Tissue
b. Predominantly Parenchyma but also collenchyma and sclerenchyma
are present.
C Growth at Meristems
1. Meristems
a. retain the ability to divide by mitosis
b. retain the capability for growth throughout their entire life span
c. 2 kinds of Meristematic growth
i. Primary growth ý increase in stem and root length
ii. Secondary growth - increase in the girth of a plant; generally only gymnosperms and woody dicots experience secondary growth
2. Apical Meristems
a. located at the tip of roots and within the buds of
stems
b. result in primary growth activity
c. Root tip is covered by a protective layer of cells called a root cap
d. The Primary Meristems form 3 cylinders above the root apical
meristem
i. Protoderm - dermal
ii. Procambium - vascular
iii. Ground Meristem - ground tissue
3. Lateral Meristems
a. two lateral meristems are responsible for secondary growth
i. Vascular Cambium
ii. Cork Cambium
b. Vascular Cambium
c. Cork Cambium
d. Bark ý outermost covering over woody stems and roots
i. consists of all plant tissues located outside the vascular cambium
ii. has 2 regions ý living inner bark composed of secondary phloem and mostly dead outer bark composed of periderm
D. Primary Tissues of Roots
1. Three Primary Meristems give rise to three Primary tissues of roots.
a. Protoderm
b. Protoderm
c. Procambium
2. The protoderm is the outermost primary meristem
3. Procambium gives rise to the central vascular cylinder
4. Ground meristem is between Protoderm and Procambium
E. Primary Growth of Shoots
1. Dome shaped mass of meristematic cells at the tip of the terminal bud
2. Gives rise to the 3 primary meristems
3. Leaves arise as leaf primordial on the sides of the apical meristem.
4. Axillary buds develop from islands of meristematic cells left by the apical
meristem at the bases of the leaf primordial
5. Axillary buds have the potential to form branches of the shoot system at a later time
6. Important difference in how roots and shoots form lateral organs
a. Lateral roots originate from deep within the main root as outgrowths
from the pericycle
b. Branches of the shoot system originate from axillary buds, located at
the surface of a main shoot
F. Primary Tissues of Stems
1. Considerable structural variation in stems, but all possess
i. an outer protective covering (epidermis or periderm),
ii. one or more types of ground tissue, and
iii. vascular tissue (xylem & phloem)
2. Young sunflower is representative of herbaceous dicot
3. Pith at the center of the herbaceous dicot stem
a. composed of large, thin-walled parenchyma cells
b. function primarily in storage
c. NO Distinct separation of cortex and pith between the vascular bundle
4. Monocot stems, example corn, are covered by an epidermis with a waxy
cuticle
a. Contrast to dicots, monocots DO NOT have vascular bundles arranged in circles; they are scattered throughout the stem.
i. each vascular bundle is enclosed in a bundle sheath of supporting sclerenchyma.
ii. Does not have distinct areas of cortex and pith.
b. Ground Tissue in which vascular tissue is embedded performs the
same functions as cortex and pith in herbaceous dicot stems.
c. Lateral Meristems, Vascular Cambium and Cork
Cambium, that give rise to secondary growth are absent in MONOCOTS
i. Monocots have primary growth ONLY
ii. | 
