Gr.10 Bio(Plant tissues, organs, organ systems)

Plant tissues

Tissues: group of cells that function together to perform specialized tasks.

Meristematic tissue, epidermal tissue, ground tissue, vascular tissue

Meristematic cells

• Unspecialized plant cell that can form specialized cells.

• “permanent embryos” because of their lifelong ability to produce the cells that can become new tissues/organs in their part of a plant.

  • Plants form new organs periodically throughout their lives.

Meristematic tissue

Major functions: unspecialized tissue capable of dividing by mitosis, responsible for growing new parts of a plant.

Eg. stem tips, root tips, leaves.

Epidermal/dermal tissue

Major functions: forms a protective outer covering(barrier between plant’s internal and external environment), protects delicate inner tissues, allows the exchange of materials in and out

Eg. on top and underneath the leaf.

Specialized cells:

• Guard cells: found on the lower leaf surface; forms a stomate(pore through which CO2 enters and oxygen + water vapour exit)! Plays a significant role in transpiration(the evaporation of water from leavers).

Ground tissue

Major functions:

• In the stem: provides strength + support

• In the roots: stores food + water

• In the leaves: photosynthesis

Eg. stems, roots, leaves

Specialized cells:

• Mesophyll cells: in the leaves where photosynthesis occurs

Vascular tissue

Major functions: transports water/nutrients/sugars throughout the plant, provides physical support to plant’s body

Eg. xylem and phloem

Specialized cells:

• Sieve elements(in phloem): long cells that have pores at the end to allow easy flow of sugar.

Plant organs

Organ: structure in an organism made of cells and tissues which perform some specific function.

Roots, leaves, stem, flowers

Plant organ systems

System: a group of tissues and organs that perform a specific function.

Root system and shoot system

Root system

• Consist of roots - the organ of the plant that lies underground to convey water/nutrients to the rest of the plant.

Functions of root system:

• Absorbs and transports water/minerals from environment to stem(shoot system)

• Anchors plant to ground

• Stores food from photosynthesis in the leaves

Roots

• Anchors the plant to the ground so it can collect and transport water/nutrients from the soil

• Plant’s storage area

• Root hairs: site for water and mineral absorption.

• Cortex cells: stores starch, no chlorophyll

• Endodermis: controls transport between cortex and vascular tissues.

• Pericycle: layer of tissue that surrounds xylem and phloem

Tissues: all 4

Types of root systems

Taproot system

• Root system that comprises of one primary root and several secondary roots branching off the primary root.

• Allows plant to reach far underground for water.

• Eg. carrots, beets

Fibrous root system

• Root system that has several primary and secondary roots of similar size.

• Since roots spread out horizontally near surface —> allows plant to have large SA to take up water from surface of soil

• Fibrous roots stabilize soil + prevent erosion/landslides.

• Eg. grass, onion

Part of the root

Primary root: main/most important root in some plants.

Secondary root: roots that branch out from the primary root.

Apical meristem: found at the root tip where new cells develop.

Root cup: covers apical meristem and protects if from damage as it passes thru coarse soil particles.

Epidermis: skin cells that protect the surface of the root. Can grow root hairs: long hair-like projections which increase SA of root for more water uptake.

Vascular bundle

(Root System)

Found in the center of the root. Made of 2 transport tissues: xylem and phloem.

Xylem

• Xylem cells grow and form long straw-like tubes. The cells die but their thick cell wall remains.

  • Xylem cells are dead, hollow, and connected to form a straw that water can pass through.

• Root cells absorb minerals from the soil and pass them to the xylem.

• Water diffuses into the xylem by osmosis.

• Pressure in the xylem builds and forces water upward.

• One-way transport to leaves

  • Ends at leaves

Phloem

• Transports sugar created in photosynthesis(in leaves) to rest of plant.

• 2 way transportation(sugar down from leaves or upward from roots)

• Phloem cells are alive and actively pump the sugar where it needs to go.

Shoot system

• Supports the plant

• Performs photosynthesis

• Transports sap

Consists of: stem(w/branches), flowers, fruits, leaves

Stem

Function:

• supports leaves

• moves water, minerals, food through the whole plant

• produces food through photosynthesis(not main job but occurs in plants with little to no leaves)

• stores food that has been manufactured by plant

• contains xylem

Flower

Function:

• Reproductive structure of plant

• Produces seeds

• Male organs: stamens

• Female organs: ovary(eggs), style, stigma which are contained in the pistil

• Pollination: animals/wind transfer pollen from the male part of the flower to the female parts, allowing fertilization to occur.

Tissues: all 4

Fruit

Function:

• protect seeds - prevents them from getting dried

• fruits attract animals that feed on them allowing the seed to be dispersed

Leaf

• • Provides a large SA for photosynthesis

  • Transports sugar to other parts of plant

  • Upper/middle leaf: upper epidermis protects leaf and lets sunlight pass through to the mesophyll tissue where palisade cells perform most photosynthesis and spongy parenchyma cells allow gas exchange within the leaf. Vascular bundles ensure every cell in leaf is close to a supply of water + nutrients.

  • Lower leaf: lower epidermis contains guard cells and stomata, which play a significant role in transpiration.

Epidermis

• Top/bottom layer of tough cube-shaped epidermal cells

• Function: protection

• No chloroplasts —> no photosynthesis

  • Sunlight passes through epidermis to photosynthesis cells

• Covered by cuticle(waxy coating)

  • Protect inner tissues from drying out by reducing water loss

• LOWER EPIDERMIS:

  • critical for exchanges of gas between leaf and external environment.

  • contain guard cells/stomata

Mesophyll

• Palisade layer:

  • Contain most of plants chloroplasts, site for photosynthesis.

  • Column-shaped mesophyll cells

  • Top of the cells are arranged to meet the Sun’s rays head on, so the rays pass through the length of the cell.

  • Very active —> lots of mitochondria

• Spongy layer:

  • air spaces connect with stomata to allow gas exchange.

Stomata

• Tiny poors that allow for gas exchange

• Underside of leaf to prevent excessive water loss by closing

Vascular Bundle

(Shoot system)

• Xylem + phloem

• Sheath cells: surround bundles in leaf

• Found in leaves - form veins

Transpiration

1. Water moves into roots from the soil by osmosis which replaces water moving up stem

2. Water moves up through stem and into leaves to replace water lost by evapouration

3. Water is lost from leaf by evaporation through open stomata

Stomata controls transpiration

• Closed at night or when water is limited

Cohesion vs adhesion

Cohesion: ability of water molecules to cling together

Adhesion: ability of water molecules to cling to the wall of the xylem

Adhesion

ability of water molecules to cling to the wall of the xylem

Bud

Swelling of the stem that contains meristem for new undeveloped tissues.

Terminal bud: most active growth

Lateral bud: dormant/inactive but have the potential to produce new branches/leaves/flowers.

Auxin

Plant hormone created by cells in active growing areas.

This hormone holds back the development of the cells below and behind them.

Plant galls

• Galls: An abnormal growth of plant tissue caused by insects/micro-organisms.

• These insects/micro-organisms use the plant’s resources to support themselves/their offspring.

• Gall growth is contained and doesn’t spread to other tissues.

Tobacco mosaic virus(TMV)

Virus that is highly destructive. Attacks leaves of plants and often lowers crop yields dramatically.
This was the first major plant virus whose structure was investigated because easy to work with, produced clear symptoms, had major scientific value, and was highly destructive.

Plants with too little vs too much water

Plants can’t survive without water because:

1. Minerals need to be dissolved in water to be absorbed and move up the xylem in the form of sap.

2. 2. No water = no photosynthesis

Plants with too much water:

1. If the soil has too much water, there will be no room for oxygen —> root cells won’t have enough oxygen for cellular respiration.

Plants without soil

Hydroponics: type of agriculture that uses a nutrient solution instead of soil.