Chapter 23: Roots, Stems, and Leaves

Chapter 23: Roots, Stems, and Leaves
The three principle organs of seed plants
• absorb water and dissolved nutrients
• anchor plants in the ground
• hold plants upright through wind and rain
• support the plant
• transports nutrients to the rest of the plant
• compete for sunlight by holding leaves higher
• are the principle organ for photosynthesis
• have broad, flat surfaces, inc S.A. for sunlight
• pores conserve water and allow gas exchange
Meristem Tissue
The only plant tissue
that produces new
cells by mitosis
Apical meristem is
found at the tips
of stems and roots.
Tissue Systems
Plants consist of 3 tissue systems:
• Dermal tissue – outermost layer; forms the “skin” of the plant
• Vascular tissue – transports water & nutrients; “bloodstream”
• Ground tissue – tissue between the dermal and vascular tissues
Dermal tissue – generally consists of a single layer of
epidermal cells.
The outer layer is often covered with a thick, waxy layer
called the cuticle, which protects against water loss and
Vascular tissue – contains
several different cell types;
transporting water and nutrients
around the plant.
Ground tissue – cells that lie
between the dermal and vascular
Roots absorb water and dissolved nutrients from
the soil. Plants have a one-way system to generate
enough pressure to move water out of the soil and
into the body of the plant.
The water has no where else to go, but
Root hairs increase surface area!
Fibrous roots
Tap roots
Stems have 3 important functions:
Produce leaves, branches and flowers
hold leaves up in the sunlight
transport substances between roots and leaves
Leaves are attached to a
stem at structures called
Some stems can also
carry out photosynthesis
Formation of Wood
The most important “stem” is the stem of the tree.
Wood is actually layers of xylem!
Read p.
Transpiration –
The loss of water from a
plant through its leaves
Maple tree leaves
Black Walnut tree leaves
Study collections