Plant TissueDiscussant:Ms. Janette D. Japones

Plant Organs The 3 primary organs found in plants are:

• Leaves• Stems• Roots

Since flowers are thought to have evolved from leaves, they are called “reproductive structures”.

Leaves, stems, roots, and flowers are all made up of various tissues.

What is plant tissue?

Is an organization of mature cells of one or more types that have common origin to perform a particular function.

Develops by means of differentiation.

Tissue

a group of similar cells organized into a structural and functional unit.

Tissue system

a tissue or group of tissues organized into a structural and functional unit, larger units of the plant body.

Meristematic Tissues

Meristems are places in plants where cell division is occurring.

During cell division, one cell becomes two cells. Each new cell can also divide.

Meristematic Tissues

In this class we will discuss three kinds of meristems:

• Apical Meristems• Lateral Meristems• Intercalary Meristems

Apical Meristems In plants belonging to

the DICOT class, apical meristems are located in BOTH the shoot tips and root tips. A shoot is simply a young, leaf-bearing stem.

In plants belonging to the MONOCOT class, apical meristems are located ONLY in the root tips.

Microscopic View of an Apical Meristem

Apical Meristems

Apical meristems cause PRIMARY GROWTH.

As cells in apical meristems divide and elongate, shoot tips and root tips grow longer. This increase in length is called primary growth.

Apical Meristem in a Root Tip

Apical Meristems• Primary growth of shoots

and roots occurs as the cells of the apical meristem divide and elongate.

Apical Meristems

A bud is a dormant apical meristem.

When conditions are favorable for growth, buds “break” and begin pushing out new growth.

Bud Break

Buds

Buds come in 3 basic types:• Vegetative-produce stems and leaves.• Flower-produce only flowers.• Mixed-produce stems/leaves and flowers.

Mixed Buds

Mixed buds of Amelanchier x grandiflora

Mixed Buds of Cornus alternifolia

1 2

3 4

Pussy WillowPussy Willow is a plant which bears separate vegetative and flower buds. In the image to the left you can see vegetative buds producing green leaves and flower buds producing male flowers (the species is dioecious). Also, note that the two different types of buds are indistinguishable from one another.

vegetative bud

flower bud

Lantanaphyllum Viburnum

Viburnum x rhytidophylloides, Lantanaphyllum Viburnum, also bears separate vegetative and flower buds. However, the two types of buds are distinctly different from one another in appearance.

flower bud vegetative bud

Lateral Meristems In addition to the

apical meristems located in the shoot and root tips, plants in the DICOT class have lateral meristems.

Lateral meristems cause SECONDARY GROWTH.

Secondary growth causes stems and roots to grow larger in diameter.

Lateral Meristems cause an increase in stem diameter

Lateral Meristems

Think of a lateral meristem as being a cylinder, several cell layers thick, of actively dividing cells.

Lateral Meristems MONOCOTS do not have lateral

meristems. Lateral meristems come in two basic types: Vascular cambium; meristematic tissue

located between the xylem and phloem. The vascular cambium makes new xylem and phloem cells.

Cork cambium; meristematic tissue located just below the bark in woody dicot stems. The cork cambium makes new bark cells.

Lateral Meristems

Phloem

Vascular Cambium

Xylem (Wood)Cross Section of a Woody Dicot Stem

Lateral Meristems

Cork (Bark)

Cork Cambium

Vascular Cambium

Woody Dicot Stem

Intercalary Meristems

In addition to the apical meristems located in their root tips, plants in the MONOCOT class have special meristems called intercalary meristems.

Intercalary meristems are located on monocots where the leaf bases connect to the stem of the plant.

Intercalary Meristems

Monocots, like grasses, have intercalary meristems which allow the leaves to grow

back after mowing.

Group 1.Make a short essay.

Why do we need to study the plant tissue?

Group 2.Make a short poem showing the importance of plant tissue.

Thank you!!

Discussant:Ms. Janette D. Japones BEED 4A