ORGANS OF PLANTS

The physiology of plants

Roots, Stems and Leaves

Chapter 23: pgs. 579-607 Learning Targets:

I can describe the structure and function of the four major plant organs; roots, stem, leaf and flower.

I can name the three tissue types that comprise these organs.

I can explain the role of the leaf in plant gas exchange by including the role of the stomata.

I can differentiate between primary and secondary growth.

The three principle organs of a plant

Roots: Absorb water and

dissolved nutrients, Store nutrients Anchor the plant

Stems: Support the plant Transport nutrients

Leaves: Photosynthesis Gas exchange Water transportation

Plant Tissue Systems

Dermal Tissue: Coverings Epidermal cells – cuticle

Vascular Tissue: Transportation Xylem – Vessel Elements Phloem – Sieve Tube elements and

companion cells Ground Tissue: Storage and Support

Parenchyma – storage Collenchyma – support Sclerenchyma - support

Meristematic Tissue: Growth Apical meristem - differentiation

Roots:

Taproot – a primary root (Dicots) Fibrous roots – no single root grows larger

than the rest (Monocots) A mature root has an outside layer, the

epidermis, and a central cylinder of vascular tissue. Between these two tissues lies a large area of ground tissue.

The root surface is covered with tiny cellular projections called root hairs. These are able to penetrate spaces between soil particles and produce a large surface area.

Roots:

Roots:

Roots:

Stems:

Stems have three important functions: they produce leaves, branches and flowers, they hold leaves up to the sunlight (support) and they transport substances between roots and leaves.

Stems

Plant Growth and Meristematic Tissue:

Plant Growth and Meristematic Tissue:

Primary and Secondary Growth

Secondary Growth in Woody Plants

Secondary Growth in Woody Plants

Leaves:

The structure of a leaf is optimized for absorbing light and carrying out photosynthesis.

To collect sunlight, most leaves have a thin flattened sections called blades. The blade is attached to the stem by a thin stalk called a petiole.

Leaves:

The leaf has many functions for the plant: Photosynthesis

Mesophyll (ground tissue) is the main site for photosynthesis

Transpiration Stomata – porelike openings in the underside of the leaf

for gas exhange/Guard Cells – specialized cells in the epidermis that control the opening of the stomata.

Gas Exchange Plants keep their stomata open just enough to allow

photosynthesis to take place but not so much that they lose an excess amount of water.

Stomata/Guard Cells

Leaves:

Leaves:

Stomata and Guard Cells

Why do you think Stomata have Guard Cells?

Why are stomata on the underside of the leaves?

Leaves:

Leaves: Quiz!

Homework:

Pg. 605 & 606 questions 1-27