Plant Tissues and Organs

Fig. 38.6

REMEMBER: “STEM CELLS IS TO ANIMAL CELLS MERISTEMS IS TO PLANT CELLS”

MERISTEM

MERISTEM a. Terminal meristems- ends of stems, branches and roots Tissues of most plants consisting of undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place (tips of the roots and stems). The meristematic cells give rise to various organs of the plant: a. Terminal meristems- ends of stems, branches and roots b. Axillary meristems- base of leaves, branches c. Lateral meristems are parallel to sides of plant parts and increase girth.

TYPES OF MERISTEM Primary Growth Secondary Growth Apical Meristems Vascular cambium Cork Cambium

PRIMARY GROWTH The apical meristems give rise to three types of embryonic tissue system, called primary meristems. Protoderm (forms the epidermis) Procambium (produces the primary vascular tissues) Ground Meristem (forms the ground tissues)

SECONDARY GROWTH The secondary growth are most dramatic in woody plants, which have two lateral meristems. Cork Cambium (produces the cork cells of the outer bark) Vascular Cambium (produces secondary vascular tissues)

PLANT TISSUES

FLOWERING PLANTS HAVE 3 BASIC TISSUE TYPES Dermal (from the Protoderm) Cover surface of plant and for Protection The guard cells, trichomes and root hairs are specialized cells that occurs in the epidermis Vascular (from the Procambium) Conducting tissue (Xylem and Phloem) Ground (from the Ground Meristem) Consists of the Parenchyma, Collenchyma and Sclerenchyma cells

VASCULAR TISSUE Xylem Phloem Mostly to conduct water and nutrients E.g., roots to shoots Phloem Mostly to conduct sugars, amino acids, etc. E.g., leaves to roots or flowers

THE GROUND TISSUES

PARENCHYMA CELLS The most abundant cells of primary tissues, which have large vacuoles and thin walls. They have functional nuclei and are capable of dividing, commonly also store food and water.

COLLENCHYMA CELLS They are relatively flexible, provide support for plant organ, allowing them to bend without breaking. The part of celery that we eat have “strings” that consists mainly of collenhyma and vascular bundles.

SCLERENCHYMA CELLS They are tough and with thick walls their secondary cell walls are often impregnated with LIGNIN, a highly branched polymer that makes cell walls more rigid. They have two types the Fibers and Sclerids. Both of these tough, thick-walled cell types serve to strengthen the tissue in which they occur.

Vegetative Organs Roots Stems Leaves

ROOTS and ROOT SYSTEMS

Root Structure and Function Penetration of Soil Gravitropism Downward Growth Water and Mineral Intake (Absorption) Storage of Materials Anchor the plant Nitrogen Fixation Conduction (Xylem and Phloem)

STRUCTURE OF ROOTS: Longitudinal Section of Roots (Length) Root cap Zone of cell division (meristematic region) Zone of cell elongation Zone of maturation

ROOT CAP It covers and protects the delicate growing tip of the root from injury and damage It continuously shed cells that facilitate the growth of the root through the soil. It gives CO2 to the soil (CO2 + H2O = Carbonic Acid) which dissolves mineral in the soil.

MERISTEMATIC REGION Adds new cells to the root cap and the region of elongation

ZONE OF ELONGATION 1 to 3 millimeters above the meristem. The cell stops to divide, but the cell walls expand and vacuoles increases in size, making the cells longer Increase in the length of the roots

ZONE OF MATURATION Cells are uniform in structure Cells begin to differentiate and develop into many tissues. The outermost tissue becomes Epidermis with root hairs

Radish seedlings have roots with long root hairs that increase the surface area for water and mineral uptake ©1996 Norton Presentation Maker, W. W. Norton & Company

Zone of Maturation - cell differentiation Zone of Cell Elongation - cell expansion Zone of Cell Division - new cells by mitosis Root Cap - penetration, padding

STRUCTURE OF ROOTS: Cross Section of Root (Primary Roots) Root hairs Cortex Endodermis (Casparian Strip) Pericycle

STRUCTURE OF ROOTS: Cross Section of Root (Secondary Growth) Cambium – Growth Tissues The inner edge of Phloem tissue in the roots is the cambium The widening in diameter of a root is called secondary growth

Types of Roots Fibrous Root System Taproot System Deep-penetrating Fibrous Root Fleshy Taproots Adventitious Roots Brace or Prop Roots Climbing Roots Propagation Roots ……………...

THE STEM

Function of Stems support leaves to maximize light absorption part of conduit for transport of water, minerals, and organic solutes storage

TWO TYPES OF STEM Herbaceous Stems Woody Stems

HERBACEOUS STEM WOODY STEM

Fig. 38.23

Fig. 38.28a

Fig. 38.28b

Fig. 38.28c