Lesson 1: Introduction Flashcards
Plant Biology
As plants moved from an aquatic environment to land, many adaptations were evolved.
Those include a vascular system, roots and seeds among others.
The dominant type of plants on the planet are flowering plants known as angiosperms. There are 250 000 known species.
Most of our foods come from a few hundred domesticated species.
Two Groups of Angiosperms
Angiosperms are divided into two categories based in several structural features. These two groups are called
monocots and dicots.
These terms derive from the first leaves of the plant embryo which are called cotyledons.
The monocots have one leaf while the dicots have two.
Monocots
A large group of related plants that include orchids, bamboos,
palms, lilies, grasses and grains.
Monocot characteristics
One cotyledon
Parallel leaf venation
Scattered vascular bundles
Flower parts in threes or multiples of threes
Fibrous roots
Dicots
Most dicots are in a related group called the eudicots.
Most flowering shrubs and trees, as well as nearly all the fruits
and vegetables that we eat are eudicots.
Dicot characteristics
Two cotyledons
Branched leaf venation
Ring of vascular bundles
Flower parts in fours or fives or multiples of fours or fives
A taproot system
A Typical Plant:
Angiosperms
A typical plant body contains
three basic organs; roots, stems
and leaves.
Plant organs consist of several
types of tissues that together
carry out particular functions.
Roots
Plants use a root system to
Anchor the plant to the soil
Absorb and transport water and
minerals
Store food
Some plants have modified roots to
grow larger than necessary in order
to store carbohydrates.
Shoot System
The shoot system consists of stems, leaves and adaptations for
reproduction.
The shoot system is used by plants to absorb the sun’s energy and carbon
dioxide from the air.
A stem has nodes and internodes. A node is the point at which leaves are
attached and internodes are the portions of the stem between the nodes.
Stem Buds
Plants typically have two kinds of buds.
Terminal buds are at the apex of stems, with developing leaves and a
compact series of nodes and internodes.
Axillary buds are found in the angles formed by the leaf and the stem.
In many plants, the terminal bud produces hormones that inhibit growth of
the axillary buds in a phenomenon called apical dominance.
Interdependence
Plant root and shoot systems are interdependent.
Plant roots depend on shoots for carbohydrates produced via
photosynthesis.
Plant shoots depend on roots for water and minerals.
Modified Stems
Stems may be modified as
stolons, for asexual reproduction,
tubers, for storage and asexual
reproduction,
rhizomes, for storage and
asexual reproduction, or
cactus stems, for water storage
and photosynthesis.
Modified Leaves
Leaves may be modified for
climbing, such as a pea plant tendril, or
protection, such as a cactus spine.
Plant Tissues
Each plant organ (root, stem, or leaf) has
three types of tissues.
- Dermal tissue provides a protective
outer covering. - Vascular tissue provides support and
long-distance transport. - Ground tissue composes the bulk of
the plant body and is involved in:
food production,
storage, and
support.
Dermal Tissue
Dermal tissues form
a layer of tightly packed cells called the epidermis,
the first line of defense against damage and infection
a waxy layer called the cuticle, which reduces water loss.
In a leaf, the epidermis is interrupted by tiny pores called stomata, which
allow exchange of CO2 and O2 between the surrounding air and the
photosynthetic cells inside the leaf
Each stoma is flanked by two guard cells that regulate the opening and
closing of the stoma.
Vascular Tissue
Vascular tissue is composed of
xylem and phloem and arranged in a
vascular cylinder in a root or
vascular bundles in stems.
Ground Tissue
Ground tissues lie between
dermal and vascular tissue.
Eudicot stem ground tissue is
divided into pith and cortex.
Leaf ground tissue is called
mesophyll.
