LECTURE 4

WHAT ARE THE FUNCTIONS OF PARENCHYMA CELLS

• MANY; OFTEN SPECIALIZED

• MOST METABOLIC PROCESSES (PHOTOSYNTHESIS, STORAGE, SECRETION, FOOD STORAGE)

WHAT ARE THE FEATURES OF PARENCHYMA CELLS

• A TYPE OF GROUND TISSUE (WHEN IN STEMS AND ROOTS)

• USUALLY LACK A SECONDARY WALL

• CAN OFTEN DIVIDE AND DIFFERIENTIATE AT MATURITY

EXAMPLES OF PARENCHYMA CELLS

1. FRUIT FLESH

2. ENDOSPERM

3. PITH & CORTEX OF STEMS AND ROOTS

4. CHLOROPLAST-LADEN CELLS INSIDE LEAVES

WHAT ARE THE FUNCTIONS OF COLLENCHYMA CELLS

• SUPPORT ESPECIALLY YOUNG AND GROWING ORGANS

WHAT ARE THE FEATURES OF COLLENCHYMA CELLS

• A TYPE OF GROUND TISSUE

• THICK, UNEVEN PRIMARY WALL

• NO SECONDARY WALL

• ALWAYS OCCURS JUST BELOW EPIDERMIS

• OFTEN OCCUR IN STRANDS

• ALIVE MAT MATURITY, CAN ELONGATE

WHAT ARE THE EXAMPLES OF COLLENCHYMA CELLS

• CELERY LEAF MIDRIB

• PETIOLE

WHAT ARE THE FUNCTIONS OF SCLERNCHYMA CELLS

• SUPPOT & PROTECTION OF TISSUES NO LONGER ELONGATING

WHAT ARE THE FEATURES OF SCLERNCHYMA CELLS

• A TYPE OF GROUND TISSUE

• THICK SECONDARY WALL WITH LIGNIN (A RIGID POLYMER)

• CANNOT ELONGATE AT MATURITY (MAY BE DEAD)

• 2 FORMS: FIBERS & SCLEREIDS

WHAT ARE THE EXAMPLES OF SCLERNCHYMA CELLS

• BURLAP

• HEMP

WHAT ARE THE FUNCTIONS OF TRACHEIDS AND VESSLE ELEMENTS (WATER-CONDUCTING CELLS)

• SUPPOR AND SUPPLY OF WATER AND MINERALS

WHAT ARE THE FEATURES OF TRACHEIDS AND VESSLE ELEMENTS (WATER-CONDUCTING CELLS)

• TYPES OF VASCULAR TISSUE

• DEAD AT MATURITY (BUT TOTALLY FUNCTIONAL)

• SECONDARY WALL LIGNIFIED, OFTEN SPIRAL

• TRACHEIDS ARE MORE NARROW & TAPERED

• VESSEL ELEMENTS ARE WIDER

XYLEM TISSUE: WHAT ARE PITS

• HIDES IN SECONDARY WALL WHERE ONLY PRIMARY WALL REMAINS.

• ALLOW WATER PASSAGE

• IN BOTH TRACHEIDS AND VESSLE ELEMENTS

WHAT IS LIGNIN?

• CLASS OF COMPLEX ORGANIC POLYMERS

• DEPOSITED IN CELL WALLS; FILLS SPACES AND BINDS CELLULOSE, HEMICELLULOSE AND PECTIN

• GIVES STRENGTH TO WOOD AND BARK

• CAN OCCUR IN CELL WALLS OF NON-WOODY PLANTS (PALM TREES, BAMBOO)

HUMAN USES FOR LIGNIN

• WOOD: LIGNIN IS 20-33% OF IT BY DRY WEIGHT

• ROPE, CLOTHING

• PAPER (LIGNIN REMOVED TO LEAVE CELLULOSE

• ARTIFICAL VANILLA THIS IS AN ARTIFICAL LIGNIN

WHAT ARE THE FUNCTIONS OF SIEVE TUBE ELEMENTS (SUGAR-CONDUCTING CELLS OF THE PHLOEM)

• TRANSPORT SUGARS ESPECIALLY SUCROSE, OTHER ORGAIC COMPOUNDS, SOME MINERALS

WHAT ARE THE FEAUTURES OF SIEVE TUBE ELEMENTS (SUGAR-CONDUCTING CELLS OF THE PHLOEM)

• A TYPE OF VASCULAR TISSUE

• ALIVE AT MATURITY (IN CONTRAST WITH THE TRACHEIDS AND VESSLE ELEMENTS)

• WITH COMPANION CELL (PARENCHYMA)

WHAT ARE MERISTEMS

• ULTIMATE SOURCE OF ALL PARTS OF THE MATURE SPOROPHYTE

• UNDIFFERIENTIATED

• RETAIN “FOREVER” THE ABILITY TO DIVIDE

TYPES AND LOCATIONS OF MERISTEMS

1. APICAL MERISTEMS (AM)

   1. ROOT AM AND SHOOT AM

   2. PRIMARY GROWTH

2. LATERAL MERISTEMS

   1. VASCULAR CAMBIUM & CORK CAMBIUM

   2. SECONDARY GROWTH

APICAL MERISTEM

• SOURCE OF ALL PRIMARY GROWTH OF BOTH ROOT AND SHOOT

• MAKES 3 OTHER MERISTEMS

  • PROTODERM: DERMAL TISSUE

  • PROCAMBIUM: VASCULAR TISSUE

  • GROUND MERISTEM: GROUND TISSUE

WHERE ARE THE YOUNGEST TISSUES LOCATED

AT THE SHOOT TIP

WHAT ARE THE 3 ZONES OF ROOT GROWTH

1. ZONE OD CELL DIFFERIENTIATION (MATURATION)

2. ZONE OF ELONGATION

3. ZONE OF CELL DIVISION

THE POSITION OF THE 3 PRIMARY MERISTEMS MADE BY THE AM FROM THE EPIDERMIS TO THE ROOT CAP

1. PROTODERM

2. GROUND MERISTEM

3. PROCAMBIUM

4. AM

WHAT IS A PERICYCLE

A LAYER OF CELLS IN PLANT ROOTS AND STEMS THAT SURROUNDS VASCULAR TISSUE

• IT GIVES RISE TO ANY BRANCHING ROOT

WHAT IS THE ENDODERMIS

THE INNERMOST LAYER OF CORTEX IN YOUNG ROOTS

WJHAT ARE STELE ORVASCULAR CYLINDAR?

IS ALL CELLS INSIDE ENDODERMIS; ARISE FROM PROCAMBIUM IN YOUNG ROOTS

DESCRIBE LATERAL ROOT

• ORIGINATES IN PERICYCLE (POUTERMOST LAYER OF VASCULAR CYLINDAR)

• GROWS OUT THROUGH CORTEX AND EPIDERMIS

STRUCTURE OF PRIMARY (NON WOODY) ROOTS

1. ROOT CAP - PROTECTS

2. ROOT HAIRS - EPIDERMAL CELLS, INCREASE ABSORPTION RATES

3. ENDODERMIS - INNERMOST LAYER OF CORTEX; SURROUNDS THE VASCULAR CYLINDAR

4. VASCULAR CYLINDAR (STELE) - CENTER OF THE ROOR; CONTAINS VASCULAR TISSUES (XYLEM AND PHLOEM) AND SOME GROUND TISSUE

5. PERICYCLE - BETWEEN VASCULAR CYLINDAR AND ENDODERMIS; ORIGIN OF LATERAL ROOTS.