BOTANY LABORATORY
VEGETATIVE PARTS OF PLANT
Roots
- Anchorage
- Absorption of nutrition
2 Types of Root System
1. Taproot
- Primary root is present
- Taps deep sources of water
- Best root system for anchorage
2. Fibrous
- Primary root is lost
- Primary root is replaced by numerous
root arising from the lower part of the
plant
Internal Anatomy
1. Longitudinal Section
Elongation
Region
Root Hair
Protoderm
Merismatic
Region
Ground Meristem
Procambium
Root Cap
a. Root Cap
- Thimble shape
- Forms the apex of the root
- Protects the merismatic region (produce mucigel- a slimy out cell of the root cap are
continually being broken of by their contact with rock particle, as the outer cell are broken,
new root cap cell are being formed in the inner part of the root cap by the cells of the
merismatic region)
- Function: Protection, lubrication, water and nutrient absorption
b. Merismatic Region
- Compress a mass of small nearly cubical cell with thin wall & dense protoplasm
- Region in which new cells are formed by mitosis
- Region where the first phase of growth of a root in length takes place
3 Primary Meristem
Protoderm- develops into epidermis
Ground Meristem- Develops into the Cortex
Procambium- develops into the vascular stele (Pericycle, xylem, phloem)
*Quiescent Zone- Slower or no cell division
c. Elongation Region
- Mass of cells here are recently formed & undergoing enlargement particularly in length
- Cell walls increase in length, new protoplasm is formed and vacuoles increase in size
d. Maturation Region
- Situated above elongation region
- Enlarge cells become differentiated into mature tissue of the root
- All the portions of the root above the elongation region maybe included in the maturation
region
- The younger part of the region of maturation is the root hair zone, in which the epidermal
cells develop protuberance known as root hair
2. Cross Section
Epidermis
Cortex
Stele
a. Epidermis
- Surface layer of the root, uncutinized
- Absorbs water and dissolved material from the soil
- Offers some protection to the inner tissue
b. Cortex
- Region between the stele and epidermis
- irregularly shaped parenchyma cell with many intercellular spaces
- Chiefly a water and food storage region
Endodermis- Innermost cell layer of the cortex
- Composed of:
Casprian strip- Composed of suberin and sometimes lignin, impregnated
cell walls and seal the spaces between the cells
Passage Cell- thin walled cell
- Function as a water dam which prevents the outward passage of water from the tissue
inside the endodermis
c. Stele/Vascular Cylinder
c.1. Pricycle
- Lies interior to the endodermnis
- Gives rise to branch root by cell division
c.2. Xylem
- Composed of vessel, tracheids
- Conducts water, mineral and often food upward
- If the root has four ridges, they appear in cross section as arms of a cross
c.3. Phloem
- Composed mainly of sieve tube and companion cell in groups which alternate with the
radial xylem band
- Function chiefly for downward conduction of food
c.4. Parenchyma
- Surrounds the band of xylem and phloem
- Stores food and gives support to other tissue
*Cambium- Develops between the xylem and phloem area
- Made up of merismatic cell which by preclinical cell division produce secondary
xylem and phloem and thus increase the diameter
Comparison between Monocot and Dicot Stem
Criteria
Type of stele
Presence of cambium
Presence of pith
Type of Vascular Bundle
Monocot (Zea mays)
Siphonostele
Absent
Present
Exarch
Dicot (Aristolochia elegans)
Protostele
Present
Absent
Exarch
Arrangement of Vascular Bundle
Number of Xylem Poles
Specialized Root
Function
Support
Photosynthesis
Protection
Enlarge Root
Alternate
Polyarch
Alternate
Tetrach
Type of Root
Brace Root
Prop Root
Buttress
Green Root
Spine
Food Storage
STEM
- Develop from the epicotyls, a continuation of the hypocotyls, cylindrical structure with a mass of
merismatic cell & often a pair of leaves at the apex.
- Functions for support and conduction of minerals
2 Types of Stem
Herbaceous
Soft and Green
Little growth in diameter
Tissues chiefly primary
Chiefly Annual
Covered with epidermis
Buds mostly naked
Woody
Tough and not green
Considerable growth in diameter
Tissue chiefly secondary
Chiefly perennial
Covered by corky bud
Buds chiefly covered by scale
External Anatomy
1. Buds- Located at the axil of leaves, upper angle between the points of juncture. It is consist of
merismatic cells. (Apical or terminal bud- located at the tip of the stem; Lateral or auxillarylocated at the side of the stem)
2. Node- Point on a stem from which leaves and buds grow
3. Internode- Length of stem between 2 nodes
4. Lenticel- Tiny raised pores for gaseous exchange
5. Lear Scar- Crescent shaped or circular mark left by the fall of leaves
6. Bundle scar- Broken ends of vascular bundle
Comparison of Monocot and Dicot (External Anatomy)
Criteria
Monocot
Nodes
Not Distinct
Internodes
Longer
Leaf Scar
Circular
Lenticel
Absent
Bud
Not Distinct
Dicot
Distinct
Shorter
Present
Present
Present
Internal Anatomy
1. Epidermis
- Cutinized single layer
- Nearly water proof outerwall
- Protective tissue, prevents evaporation of water
2. Cortex
- Contains collenchymas, storage parenchyma usually strengthening fiber and stone cell
- Region of protection, strength and storage
3. Stele
3.1. Pericycle
- Consist of parenchyma cell, often of strengthening fiber
3.2. Phloem
- Found inside the pericycle
- Sieve and companion cell- conducts food downward
- Fiber provides strength, parenchyma stores various substance
3.3. Cambium
- Continuous layer of merismatic cell just inside the phloem
- Forms new xylem and phloem
3.4. Xylem
- Consist of vessel, xylem fiber, tracheids and xylem parenchyma
- Vessel and tracheid- for conduction and support
- Xylem fiber- Thickening walls and strengthening cell
- Parenchyma- stores food
3.5. Ray
- Band of cell (chiefly parenchyma) which extends radially in a stem
- Functions for transverse conduction of material in stem & for food storage
Comparison Monocot vs Dicot (Internal Anatomy)
Criteria
Monocot
Distinctness of region
Not Distinct
Hypodermis
Not Distinct
Bundle Sheath
Present
Vascular Cambium
Absent
Kind of Growth
Endogenous
Arrangement of Bundle Sheath
Scattered
Secondary Growth
- Woody cambium active along the entire stem
- Annual ring- layer of xylem formed by one year of growth
- Tissues formed are secondary xylem and secondary phloem
- Ray- Primary Cells - Outward  Inward
Secondary Cells – Inward  Outward
Dicot
Distinct
Distinct
Distinct
Present
Exogenous
Broken Ring
- Cork cambium – secondary merismatic tissue
- Develop from certain parenchyma cell in the outer and inner face
Cork Cell- Cells formed on the outer face of the cambium
- Walls are suberized
- Annual Ring:
Inner Band- Larger; Formed in spring “Springwood”
Outer Band- Thicker; Formed in summer “Summerwood”
Comparison Sapwood vs Heartwood
Criteria
Sapwood
Location
Outer
Color
Lighter
Nature of Cell
Living
Function
Conduction
Use
Lumber
Heartwood
Inner
Darker
Dead
Support and Strength
Lumber