Chapter 31, pages 668-691
Plant Anatomy-1 9:59-19:05
I. Development of the Young Stem from the Seed
A. Seed Structure
3. Cotyledons
4. Seed Coat
B. Seed hydrates, which begins the process of seed germination
1. Absorbs water
2. Metabolism begins in the seed
3. Radicle breaks through seed coat and pushes down into the soil
4. Shoot and cotyledons push up through the soil to the sunlight
5. Plumule fans out
6. Cotyledons shrivel as they release their food stores
7. Photosynthesis begins
8. Plant is on its own
C. Stem begins to differentiate
II. Morphology of the Stem
A. Definition of Terms
1. Anatomy - internal structure of the stem
2. Morphology - external structure and form of the stem
B. Functions of the Stem
1. Support
2. Conduction
3. Storage
C. General Structure of the Stem
1. Node
2. Internode
3. Leaf Scars
4. Bundle Scars
5. Lenticels
6. Buds
a. Type
(1) Apical or Terminal buds
(2) Lateral buds
(3) Leaf buds
(4) Flower buds
b. Arrangement on the stem
(1) Alternate
(2) Opposite
(3) Whorled
(1) Bud scales - structures that cover the terminal buds during winter dormancy
(2) The bud scales fall off in the spring when the terminal buds begins to grow
(3) The bud scales leave scars on the stem where they fall off
(4) The
bud
scale scars on the stem tell when the stem begins to grow each
spring. Thus the bud scale scars can be
used to determine the age of the
stem.
III. Monocots, Dicots, and Gymnosperms
A. Monocots ------ one seed leaf per seed
B. Dicots ---------- two seed leaves per seed
C. Gymnosperms -- many seed leaves per seed
IV. Differentiation in Stems
A. Two types of growth in stems
a. Is growth in length of the stem
b. Caused by the activity of the apical meristem in the terminal bud
c. Produces herbaceous stems
a. Is growth in girth of the stem
b. Caused by the activity of the vascular cambium
c. Produces woody stems
B. Regions of the growing shoot tip
(1) Produces leaf primordia on its flanks
(2) Produces lateral buds on its flanks
(3) Produces flower buds on its flanks
(4) Produces cells that will differentiate into stem tissues in the center
b. Stems cells are laid down like a brick-layer lays bricks, on top of another
c. Cells that differentiate into stem tissues do so as they get older
C. Differentiation of Apical Meristem cells into Mature Stem cells
1. Apical Meristem cells differentiate into Primary Meristem Tissues
2. Primary Meristem Tissues are:
a. Protoderm - differentiates into the epidermis of the stem
b. Ground Meristem - differentiates into the cortex, pith rays, and pith
c. Procambium - differentiates into the vascular tissue of the stem
3. Each Primary Meristem Tissue differentiates into a Primary Tissue
4. THUS: Apical Meristem -> Primary Meristem Tissues -> Primary Tissues
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