Chapter 35

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Chapter 35: Plant Form and Function

A. Cotyledon

i. Seed leaf

ii. Monocots

a. One seed leaf

b. Parallel veins in leaf

c. Scattered vascular bundles in stem

d. Fibrous root systems (usually)

e. Flower parts in 3’s

iii. Eudicots

a. Twos seed leaves

b. Veins usually net-like

c. Vascular bundles arranged in a ring

d. Taproot usually present

e. Flower parts in 4’s and 5’s

B. Root systems

i. Taproot: a long vertical root with smaller lateral roots

ii. Some roots are modified to store food in the form of starch (exp: carrots)

iii. Fibrous root system: an extensive network of roots that do not penetrate very deeply into the ground

iv. The tips of roots care covered with root hairs

a. Root hairs are where most water and minerals are absorbed

v. Adventitious roots

a. Prop roots

b. Extend above ground and give plants additional support

c. Examples: buttress roots and pneumatophores

C. Shoot system

i. Stems are divided up into nodes and internodes

ii. Nodes: the point at which leaves are attached

iii. Internodes: between nodes

iv. Axillary buds: located at the intersection of the stem and leaf

v. Terminal (apical) buds: located at the tip of a growing stem

vi. Vascular bundles: comprised of xylem and phloem

vii. Cortex: the outer layer of the eudicot stem

viii. Pith: the central layer of the eudicot stem

D. Modified stems

i. Stolons: horizontal stems that allow plants to spread over a large area

ii. Rhizomes: horizontal underground stems

iii. Tubers: ends of rhizomes modified for food storage

iv. Bulbs: vertical underground stem s

v. Corms: short, swollen stems

vi. Thorns

E. Leaves

i. Consist of a flattened blade and a petiole: a stalk (the petiole may not be present)

ii. Simples leaves: a single individual leaf

iii. Compound leaves: divided into many leaflets

iv. Modified leaves

a. Tendrils, cactus spines, succulent leaves, brightly colored pastal-like leaves (bracts) and bud scaled, and flower parts

F. Plant tissues

i. Parenchyma

a. Relatively undifferentiated cells

b. Involved in metabolic functions

ii. Collenchyma

a. Provides support for the growing portion of a plant

iii. Sclerenchyma cells

a. Provides support

b. Contains lignin

iv. Xylem: consist of two or more cells, tracheids, and vessel elements

a. These are dead when fully functional

b. Consists of fibers

v. Phloem: consist of living sieve-tube elements (members)

a. Special cells that lack many organelles

G. Plant growth

i. Annuals: plants that live 1 year

ii. Perennials: plants that live more than 1 year

iii. Biennials: live 2 years; growth first year; flower 2nd year

iv. Meristems (growing tissue)

a. Apical (primary) meristem: on tops of roots and shoots

b. Lateral (secondary) meristem: along the sides of roots and shoots

v. Primary growth

a. Primary growth produces the primary plant body consisting of three tissues: dermal, vascular, and ground tissue

1. Allows for extension of the roots and shoots of a plant

b. The root had a root cap to protect the growth meristem

1. The root has 3 zones of growth:

-Meristem and root cap

-Zone of elongation

-Zone of maturation

2. The root has 3 layers:

-Epidermis: an outer layer

-Cortex: middle

-Root core: inner layer

-Xylem and phloem develop in the root core

vi. Secondary growth

a. Secondary growth allows for the increase in the diameter of the plant

1. Produces key constituents of wood and bark

b. Vascular cambium

1. Forms secondary tissue

2. Produces secondary xylem to the inside and secondary phloem to the outside

3. Fully formed secondary xylem is dead and it forms wood

4. Rings are formed by the season growth of vascular cambium

c. Cork cambium

1.A secondary tissue that replaces the epidermis on a stem

2. It forms the outer layer of bark (the cork)