Biology Chapter 35 and 39 Notes

Topics: Plant stem, Plant physiology, Root Pages: 14 (2121 words) Published: April 20, 2011
Chapter 39

Plant Responses to Internal and External Signals

No groups of plants is more important to human survival than seed plants plants are key sources of food fuel wood products and medicine our reliance of plants

Products from Seed Plants

Most of our food comes from angiosperms
Six crops yield 80% of the calories consumed by humans

sweet potatoes

Other Products from Seed Plants

Secondary compounds of seed plants are used in medicines
Know table 30.1

Threats to plant Diversity

Destruction of habitat
In causing extinction of many plant speciesCHapter 35
Plant structure, Growth, and Development.

Overview no two plants are alike

To some people the fanwort is an intrusive weed but to others it is an attractive aquarium plant

Fanwort exhibits plasticity, the ability to alter itself in response to its environment.

Plant Anatomical Organization

Plants like animals, have systems composed of organs

The two plant systems are:


The organs found in both systems are:

roots, stems, and leaves


Functions of roots:

Anchoring the plant
absorbing minerals and water
storing organic nutrients and other functions

Absorption of water and minerals occurs near the root tips, where root hairs increase the surface area. Many plants have modified roots:
Prop roots in mangrove
Tubers in sweet potato and cassava
Tubers are enlarge root or stem that acts as nutrient storage Aerial roots of the strangler fig tree
Strangler fig use their roots to strangle their host to death Buttress roots
large above ground roots surrounding the tree
help to stabilize tall and large trees
tropical trees generally have shallow roots due to poor nutrient soil. Pneumatophore roots of mangroves and bald cypress
Help in gas exchange in habitats where roots are often submerge under water. Toxic roots
roots of the common reed P australis secretes


A stem is the above ground plant structure
It consist of:
nodes, the points at which leaves are attached
internodes, the segments between nodes.
An axillary bud is a structure that has the potential to form a branch (lateral shoot), flower, or leaves A terminal bud is located near the shoot tip and causes elongation of a young shoot. Many plants have modified stems:

horizontal stems that grow on soil surface or below
underground shoot with thickened leaf base which act as nutrient storage Potato tuber is an enlarged underground stolon
Underground horizontal stem which sends out roots and shoots Found in ginger and galangal.


The lead id the main photosynthetic organ of most vascular plants Leaves generally consist of
A blade and a stalk (petriole)
Some plants have modified leaves that serve various functions Tendril
Use by climbing plants for support and attachment
function as anti-herbivory
water conservation?
Water storage i.e. onion, succulents
Function as petals to attract pollinators
Reproductive leaves i.e. Kalanchoe

The Three Tissue Systems: Dermal, Vascular, and Ground

Each plant organ has three types of tissues
In non-woody plants, the dermal tissue system is compose of mainly the epidermis In woody plants, the stem and root epidermis is eventually replace by protective tissues called the periderm (bark). The vascular tissue of a stem or root is collectively called the stele In angiosperm

The stele of roots is a solid central vascular cylinder
The stele of stems and leaves is divided into vascular bundles. Tissues that are neither dermal nor vascular are the ground tissue system Ground tissue cells are specialized for storage, photosynthesis, and support. Some major types of plant cells:

a. Parenchyma
b. Collenchyma
c. Sclerenchyma
d. Water-conducting cells of the xylem
e. sugar-conducting cells of the phloem

A. Functions of Parenchyma...
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