Post-laboratory Discussion

First Departmental Exam

Microscopy

• Review- Parts and function of the microscope- Computation of the CF- Magnification of the drawing- Principles of Microscopy

Some points to remember:

• Plane side- sufficient amount of light• Concave side – artificial light is used

• Cedar oil – oil used in oil immersion objective• Xylol or xylene – to remove the cedar oil

Plant CellCell wall • Composed of cellulose

and hemicellulose, suberin, lignin and proteins

• Functions1.provides shape to the cell2.Contains and protects the

protoplasm Allium cepa

• Layers1. Primary wall2. Secondary wall

• Middle lamella - composed of pectic substances- binds cells; found between 2 adjacent cell- Hydrolyzed by the enzyme pectinase when the

fruit ripens softening

Nucleus• Functions 1.control center of the cell2.cellular reproduction3.Controls and directs protein synthesis

nucleus

Protoplasm cytoplasm & nucleoplasm

Cytoplasmic streaming / CYCLOSIS- Distributes nutrients, gases and wastes all over

the cell- counterclockwise and clockwise direction- Directs chloroplast to the direction of sunlight

Hydrilla verticellata

Plastids- are round, oval and disk-shaped bodies found

in the cells of green plants1.Proplastids - In young cells, from which other plastids may

develop.2. Chloroplasts- with green pigment called chlorophyll- functions in photosynthesis

3. Chromoplasts- plastids responsible for the red, yellow,

brown or orange color of many fruits and veggies

- pigments are called carotenoid such as xanthophyll and carotene lipid-soluble

Capsicum frutescens

4. Leucoplast- colorless plastid that is responsible for food

storage.• Amyloplast – stores starch; stains bluish-

black in iodine in potassium iodide solution (IKI)

• Elaioplast- fats & oils• Aleuroneplast- proteins

Solanum tuberosum

Vacuole- watery compartment surrounded by a

membrane called the TONOPLAST- houses or contains metabolic wastes- stores water, salts, starch, protein bodies and

granules

• Pigmentsanthocyanin - Trandescantia spathacea

- other pigments are betacyanin, anthoxanthin- function :1. coloration/ aesthetic purpose2. defense mechanism of plants against herbivory

• Crystals – metabolic waste product- Functions:1. taxonomic identification2. Anti-herbivory3. Calcium balance

• Types1.Raphide – Sansiviera sp., Diffenbachia sp.2.Styloid - Sansiviera sp., Diffenbachia sp.3.Prismatic – Begonia sp.4.Druse/rosette - Sansiviera sp., Diffenbachia sp. calcium oxalate1.Sandy crystal – Sansiviera sp. silica1.Cystolith – Ficus elastica calcium carbonate

Circle = sandyArrow- styloid

Circle = prismaticArrow- druse

druse raphide cystolith

Plant cells vs Animal cellsParts Plant cell Animal cell

Cell wall present absent

Centrioles absent present

Cleavage furrow absent present

Phragmoplast present absent

lysosomes absent present

Central vacuole present absent

plastids present absent

cilia absent present

*Animals have vacuoles but they are smaller than the central vacuole and has a different function.

Cell Cycle

• Phases1.Karyokinesis – nuclear division

1.Cytokinesis – cytoplasmic division

Mitosis• Interphase - not a resting phase; metabolically active cells- nucleolus very visible- presence of nuclear envelope- uncoiled chromosome = chromatin

• Events1.G1 – presynthesis phase; growth and normal

metabolic process occur2.S – synthesis phase; DNA replication happens3.G2 – premitotic phase; preparing for cell

division

• Prophase- disintegration of nuclear

envelope - Disappearance nucleolus- densely thick chromosomes (2

sister chromatids)- formation of spindle fiber- Centromere (point of attachment of

the 2 sister chromatids

• Metaphase- presence of metaphase

plate- chromosomes (2 sister

chromatids) are aligned in the center

• Anaphase- chromosomes (1 chromatid)

have migrated to the opposite poles

- # of chromosomes have doubled

Metaphase- presence of metaphase plate (imaginary plane)- chromosomes are aligned in the center

• Telophase- opposite of prophase- formation of cell plate phragmoplast,

vesicles, cell wall

- The cell divides into two- The chromosomes

uncoil.- The nucleus reforms.- The spindle apparataus

disassembles.

Plant tissues

• Meristematic tissue• Fundamental tissue

Meristematic Tissue

• Region where there is new cell formation and growth initiation

A.Apical Meristem- for the shoot and root elongation or increase in length

1.Root apical meristem – Allium cepa l.s.2.Shoot apical meristem – Coleus blumei l.s.

The Root cap is composed of irregular, nondividing cells. The purpose of the root cap is to protect the apical meristem.The apical meristem is composed of dividing cells.

B. Lateral Meristem – for increase in girth

1.Vascular cambium – produce xylem and phloem

2.Cork cambium – produce cork cells and phelloderm

Vascular cambium

cork cambium

Tilia sp. stem

Simple/Fundamental tissue

1. Parenchyma• thin walled; for storage2. Collenchyma• unevenly thickened walls; for plastic support3. Sclerenchyma• for elastic support, rigidity and strengthening1. Fibers- thickened walls2. Sclereids- isodiametric in shape

C P

Apium graviolens stem

Collenchyma

Parenchyma

Coleus blumei

Sclereid (Stone cells) in Pyrus malus

Bundle cap(Fibers)

Helianthus sp.

Bundle sheath(Fibers)

Zea mays

Complex Tissue• Xylem – conduction of water1. Trachieds – narrow with tapered ends2. Vessels – thick and wide with perforations*both have secondary thickenings composed of

LIGNIN

• Phloem – conduction of food and nutrients1. Companion cells- nucleate, regulates metabolism

of sieve tubes2. Sieve tube element – enucleate, conduction of

food* Only have 1° wall unlike xylem.

2°XYLEM

vessel tracheid

•Pinus sp. only have trachieds because they are non-flowering•Helianthus sp. both have vessels and tracheids since they are flowering plants

Monocot• Zea mays stem – scatterd type of vascular

bundle distribution

(Bundle sheath)

Zea mays vascular bundle

Dicot

• Helianthus sp. – concentric type of vascular bundle distribution

Bundle cap

xylem

Vascular Cambium

Phloem

Collateral Vascular Bundle of Helianthus sp.

Cucubita sp. stem

P

P

X

VC

VC

Bicollateral vascular bundle of Cucurbita sp.

Trichomes

Function

• Anti-herbivory• Defense of plants• Creates a layer of immobile air next to the leaf

which allows water that diffused to bounce back in

• Shades leaves

Epidermis

• Cuticle protects the epidermis from desiccation or water loss

Stomatal Apparatus

The guard cells are the only epidermal cells that have chloroplasts. The other cells in the epidermis do not possess chloroplast.

• The Guard cells control the stomatal openings in the epidermis of the leaf. It regulates the exchange of CO2, oxygen and water vapor.

• Three environmental factors regulate these cells. These factors are light, CO2 concentration and water availability.

• When the guard cells are activated, K+ pumps actively transport K+ into the guard cells, resulting in a high [K+] in the cells.

• As a result, water enters the cells by osmosis. This causes the guard cells to swell. The one side of the guard cells is thicker than the other and does not stretch. As the guard cells swell up they bend.

Some tips for the exam

• Be sure to know your manual by heart.• Know everything that you’ve answered in the manual• Know the structures, functions and specimens

(including scientific names) where they can be found.• Read the pre-lab part• Bring a calculator :D

Good luck in your exam. Study hard … - jedayao