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PLANT HISTOLOGY

Meristems:
1) Apical- (at the tip for vertical growth) protoderm, ground meristem, procambium
2) Lateral- (at the sides for increase in width) vascular cambium and cork cambium
3) Intercalary- (base of young leaves and internodes) for lengthening/growth stem and leaves far from the tip

Simple Permanent Tissues (1 type of cell only):
1) Epidermis- outermost tissue (young:uniseriated, old:multiseriated) of all monocots and herbaceous dicots
- has a cuticle which is made up of cutin to lessen water loss
- has out gowths called TRICHOMES (root hairs in roots which protect and lessen H2O loss as well as increase surface area)
Functions: protection from predators and reduce evaporation of water
Types:
a) Glandular- has secretions and alive at maturity
Muntigia calobura
b) Non-glandular- no secretions and dead at matuirty
1-Simple hairs: Theobroma cacao (uni)
2-Bristle: Mucuna pruriens (multi)

3-Stellates: Urena lobata (multi)
4-Branching: Vervascum thapsus (multi)
5-Scale (multi)
2) Parenchyma- uniformly thin cell wall and alive at maturity
- for food storage
3) Collenchyma- non-uniform cell wall thickness and alive at maturity
- for structural support and protection and sometimes for food storage too
4) Sclerenchyma- thick cell wall (contain lignin) and dead at functional maturity
- for structural support and protection

5) Cork- outermost tissue of leaves and roots as well as stem of woody, dicot plants
- for protection

Complex Permanent Tissues (More than 1 type of cell):
1) Phloem- for transport of dissolved food material/nutrients
a) Sieve tubes- no nucleus, arranged end-to-end
b) Companion cells- has nucleus, narrower and vertical elongation

2) Xylem- for H2O transport
a) Vessel elements- perforated ends
b) Tracheids- not perforated
Tracheary elements- with lignin in their cell walls (the two above)
Types:
1-Annular: Zea mays mancerated (ring)
2-Helical: Tilia mancerated (spiral)
3-Reticulated (net-like)
4-Pitted: Cucurbita mancerated (many, non-lignified pits)
5-Bordered pits: Pine mancerated
6-Scalarifom: Cucurbita mancerated
*Stomata: for cellular respiration
a) guard cells (2) flexible anticlinical walls
b) accessory/subsidiary cells- participate in osmotic changes involved in movements of guard cells (variable #)
c) stoma

ROOTS

Root Systems:
1) Tap root- has primary root; mostly for dicots
2) Fibrous root- no primary root/ diffuse; mostly for monocots
*adventitious root: arises from stem/ leaves (e
...
prop roots of zea mays or pandan)

Longitudinal Regions:
1) Root cap- group of cells at the root tip which protect meristematic part
2) Embryonic region- zone of cell division; actively dividing region
3) Region of cell elongation- increase in length of the root
4) Region of cellular maturation/differentiation- root hairs are here, differentiated for specific functions
*youngest root hair near meristem; older farther

Monocot vs
...
bamboo)
*differentiated tissues on lowermost internode
*ENDARCHY- centrifugal xylem differentiation; prtoxylem in
MONOCOT
-scattered vascular bundles
-outercovering: epidermis only

DICOT
-in a ring/ circular arrangement
-can be epidermis; (woody) periderm

-no secondary growth (no vascular cambium)

-has secondary growth (has vascualr cambium)

-no cork cambium

-may have cork cambium

WOODY DICOT
-seondary xylem is bulk of stem

PINE (GYMNOSPERM)
-primary xylem

-w/ companion cells and vessels

-no companion cells and veseels

-no secretory cells and resin ducts

-with resin ducts and secretory cells

-isodiametric cells

-cubical cells

LEAVES

Important Terms:
1) Phyllotaxy- arrangement of leaves
a) Alternate/ spiral- 1 leaf per node can be distichous (180 degrees separation)
b) Opposite- 2 leaves per node (decussate (90 deg) or distichous)
c) whorled- 3 or more leaves per node
2) Blade/lamina- thin, flat structure (usually green)
3) Leaf Stalk/Petiole
*sesille- without petiole (most monocots)
4) Stipules- outgrowths of some dicot leaves at base
5) Petiolule- stalk of leaflet
6) Stipels- secondary stipule in pairs at base of petiolule
7) Rachis- extension of petiole

8) Nature of Leaf blade:
simple- one piece
compound- separate segments called leaflets or pinnae
9) Venation
parallel- most monocots, no network (dicot: plantain and Nerium oleander- adelfa)
reticulated/netted- most dicots, network (monocot: Diffenbachia-dumb cane and Colocasia esculenta-taro)

Internal Structure of Leaves:
1) Epidermis- outermost
-covered by cuticle on both sides
-more stomata on abaxial side than adaxial side
2) Mesophyll- photosynthetic, parenchymatous region
a) pallisade- collumnar and closely arranged
b) spongy- iregular shape, loosely arranged for gas exchange
3) Vascular tissues
a) border parenchyma- thin cell wall
b) bundle sheath- thick cell wall
*Bulliform cells- large and thinly walled for rolling of leaves

Anatomical Features:
Feature

Dicot

Monocot

Gymnosperm

Epidermis

P (1 layer)

P (1 layer)

P (1 layer)

Stomata

A

P (in line)

P (suken stomata)

Mesophyll

P both

P (spongy)

P (lobed mesophyll)

Vascular tissue

P (scattered)

P (arranged)

P (tracheids)

Blade

P

P

P (scale like)

Midrib

P

P

P

bundle sheath and

resin ducts and secretory cells

bulliform cells

transfusion tissue

(pallisade and spongy)

Others

hypodermis

Leaf Forms: linear, elliptical, lanceolate, oblanceolate, ovate, obovate
Leaf Margins: entire, sinuate, crenate, serrate, cleft
Leaf Apex: rounded, acute, acuminate, obcordate (emarginate)
Leaf Base: rounded, cordate, peltate, sagittate, auricled, acute

GUTTATION AND TRANSPIRATION

Guttation
-occurs in the hydathode which secretes the water
-modified stomata: epithem (parencymatous) and H2O pore
-happens at night and the dews are observed in the morning
-relieve of pressure due to the huge uptake of water at night
-observed along leaf margin

Transpiration
-evaporation of H2O from plant leaves
Factors affecting:
1) Atmospheric humidity- dry air increases transpiration (occurs as long as H2O potential of atmosphere is less than water

potential of the leaf); humid air slows it down
2) Internal CO2 concentration- reduce in supply for photosynthesis opens up the stomata, increasing transpiration
3) Wind- *'boundary layer' [thin, moist air adjacent to transpiring leaf]
- Thick boundary decreases diffusion gradient, decreasing transpiration

-WIND replaces boundary layer wuth drier air, increasing transpiration
4) Air Temperature- high temp increases H2O vapor pressure, increasing water potential, ergo faster transpiration
5) Soil- absorb water from soil as long as water potential is less than the soil
6) Light intensity- causes stomata to open, increasing transpiration



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