SBI 3UI Biology - Unit 2 (Plants)

Energy

________ is produced through the process of **cellular respiration**

Glucose

________ is produced by **photosynthesis** since plants are autotrophs

Root System

This system consists of all the __below ground__ (basal) structures that:

* **Anchor** the plant
* **Absorb water and minerals** from the ground
* **Store food** for later use

Shoot System

This system consists of all of the __above ground__ structures that are specialized for two main functions:

* **Conducting photosynthesis** or contributing substances to the process
* **Reproduce**

Three Parts of the Shoot System

1. Flowers
2. Leaves
3. Stems

Flowers

Specialized structures developed for **sexual reproduction**

* The **male** reproductive structures __produce the pollen grains__ and have modifications to ensure the pollen is distributed
* The **female** reproductive structures __accept the pollen__ and ensure it fertilizes the egg to form the seed which is contained within the fruit

Male reproductive structures (flowers)

Produce the pollen grains and ensure the pollen is distributed

Female reproductive structures (flowers)

Accept the pollen and ensure it fertilizes the egg

Hermaphroditic Plant

__Both sex structures__ are in the __same flower__

* Ex: rose, lily mango

Monoecious Plant

Have __separate male and female flowers__ on the __same plant__

* Ex: corn, cucumber, begonia

Dioecious Plant

Have __separate male and female plants__

* Ex: holly, kiwi, asparagus

Leaves

The **primary sites for photosynthesis**

Also provide:

* Support
* Protection
* Attraction of pollinators

Stems

Functions include:

* **Support** for the branches, leaves, and flowers
* **Movement of water** from the roots upward to all plant parts
* **Transportation of food** up and down where it is to be used or stores
* **Storage** of excess food
* **Protection**
* **Photosynthesis**

Leaves (Monocot)

* Have **parallel** veins
* Have **long, thin leaves**
* Ex. grasses, orchids, lilies

Leaves (Dicots)

* Have **branching** veins
* Have **broad-leaves**
* Ex: dandelions, canola, maple leaves

Modified leaves

Plants protect themselves from herbivores by having ___________ (eg. spikes on a cactus)

Roots (Monocots)

* Have a **fibrous root system** consisting of a __mat of thin roots__ spread out below the soil surface
* Ex: corn, onions, wheat

Roots (Dicots)

* Have a **taproot system** consisting of __one thick central root with thin branches__
* Ex: carrots, turnips, beets

Petals in multiples of… (Monocots)

3

Petals in multiples of… (Dicots)

4 or 5

Shoot

An **above ground structure** consisting of stems, leaves, and flowers

Nodes of a Stem

The points on the stem at which **leaves are attached**

Internodes of a Stem

The **portions** of a stem **between nodes**

Bud

An **undeveloped shoot**

Terminal Bud

Found at the **tip of a stem**

Axillary Bud

Found in the **angles (axils) formed by a leaf and the main stem**

* Growth from axillary buds forms the plant’s branches

Flower

A **specialized shoot** unique to angiosperms

Sepal

The outermost ring that **covers and protects the flower bud** before the blossom opens

Petal

Have “runway” markings that help **guide pollinators toward the flower’s reproductive parts**

Stamen

The **male** reproductive structures

Pistil

The **female** reproductive structures

Anther

The **sac located on top of each stamen**

* Within them, meiosis produces spores that develop into pollen grains

Filament

The long **stalk that supports the anther**

Stigma

The sticky **tip of the pistil**

Style

The **stalk of the pistil** that leads to the ovary

Ovary

Located at the based of each female pistil and **contains ovules**

Ovules

**Contain the egg cells**, when fertilized develop into seeds

Inflorescence

A **cluster of flowers on a branch** or a system of branches

* Ex: lily of the valley, texas milkweed

Process of Pollination

1. Pollen grains released from anthers land on the stigma of flowers
2. Once on a stigma, a pollen grain absorbs water and extends a structure called a pollen tube
3. The pollen tube, which contains sperm nuclei, grows towards the ovary through the style
4. Once the pollen tube reaches the ovule in the ovary, a sperm cell fertilizes the egg cell and forms a zygote, which develops into a plant embryo

Self-pollination

_________ occurs when pollen from the anthers is deposited on the stigma of the **same flower**

Cross-pollination

________ is the **transfer of pollen** from the anthers of one flower to the stigma of another flower

Methods plants use to attach pollinators

* Visual cues (colour)
* Scent
* Food
* Mimicry
* Entrapment

Seed Coat

**Tough outer layer** that **protects the embryo and endosperm** inside the seed

Endosperm

The **food source** for the developing embryo (may contain starch, proteins, and oils)

Cotyledon

An **embryonic leaf that stores and transfers nutrients** to the embryo

Cotyledon (Monocot)

One cotyledon

Cotyledon (Dicot)

Two cotyledons

Methods of Seed Dispersal

* Wind → carries the seeds away
* Water → carries the seeds away
* Jet propulsion → seed capsules are filled with air until they explode shooting the seeds out
* Animals → transported by attaching onto the animal’s skin or being excreted in their waste
* Raindrops → propel their spores into the air

Dormancy

When the **growth and development of a seed are temporarily stopped**

Germination

When the plant embryo within a **seed begins to grow in favourable conditions**

* In order to germinate, most seeds must soak up water (taking up water → seed expands and splits its seed coat → triggers metabolic changes in the embryo that enable it to grow)

Shoot (Monocot)

Have a **protective sheath** surrounding the shoot that penetrates the soil ahead of the shoot

Shoot (Dicot)

Have a **hooked shoot tip** that protects the delicate shoot tip by holding it downward as the shoot moves through the soil

Three Main Tissue Systems

1. Dermal Tissue System
2. Vascular Tissue System
3. Ground Tissue System

Dermal Tissue System

These cells form the **outermost layer of a plant**

* The **epidermal tissues** (epidermis) form a thin layer of cells that __cover and protect__ the surfaces of leaves, stems, and roots.
* This is the dermal tissue of non-woody plants parts

Specialized Epidermis

* Some cell are adapted for **defence by producing chemical irritants** (ex. poison ivy, stinging nettle)
* In **roots**, the epidermis has long extensions called **root hairs**. The hairs are major sites of __water and mineral absorption__
* In **leaves**, the cells produce a waxy layer called the **cuticle**. This helps to __prevent water loss__ from evaporation.
* To allow gases and water to move in and out of the leaf (gas exchange), there are openings called **stomata**. The stomata are controlled by photosynthetic cells called **guard cells**.

Root Hairs

* Are major sites of **water and mineral absorption**
* Increase the surface area of the root

Cuticle

A waxy layer on the leaves that helps prevent water loss from evaporation

Stomata

Openings that allow for gas exchange to occur

* Controlled by photosynthetic cells called **guard cells**

How Guard Cells Work (opening and closing the stomata)

Stomata are surrounded by 2 guard cells that **regulate transpiration rates** and **loss of water** through evaporation

* Day: stomata open, allows CO2 in and O2 out
* guard cells have chlorophyll, when sun out produce sugars → water moves into the guard cells, they swell, opening the stomata
* Night (or plant losing water): stomata close
* no sun, guard cells don’t make sugars → guard cells lose water, go limp, closing the stomata
* Typically more guard cells in the lower epidermis since this layer is not directly exposed to the sun and is cooler

Vascular Tissue System

These cells **transport water, minerals, and glucose around the plant**. These cells form a network of tubes that connect the roots, stems, leaves, and flowers

* 2 main types of vascular tissues: xylem and phloem

Xylem cells

* **Transport water and dissolved minerals up** from the roots
* The mature cells are hollow tubes with strong, rigid walls and no organelles  
* They are __no longer living__ cells
* They are connected to each other to form long continuous pathways
* There are two types of xylem cells: 
* **tracheids** (long cells with tapered end) and **vessel elements** (wider, shorter cells with less tapered ends)
* The ends of tracheids or vessel elements overlap, forming tubes. The tubes are hollow because the cells have died. Water passes from cell to cell through holes called pits and through openings in the ends of the vessel elements. 

Phloem

* Consists of specialized cells which **transport the sugars** produced by photosynthesis throughout the plant **in any direction**
* The plant cells use the sugar for respiration. The sugars that are not used are transported to special areas for storage.  
* Phloem cells are __living tissues__ that form the tubes
* Made up of chains of cells called __sieve-tube members__ and the end walls of these cells are like __sieves__, allowing the flow of fluid through pores.  
* In addition, __companion cells__ are linked alongside the sieve-tube members and provide proteins and other resources to those cells.

Fundamental or Ground Tissue

The **filler between the dermal and vascular tissues**. Their functions include:

* **Photosynthesize** when in the green parts of the plant
* In the __roots__, they **store carbohydrates**
* In the __stems__, they **provide storage and support**

Three Types of Ground Tissue

1. Parenchyma
2. Collenchyma
3. Sclerenchyma

Parenchyma

* Used for **food storage** in roots, fruit, and portions of the stem
* Have **thin cell walls**
* Unspecialized cells
* Have chloroplasts in the leaves and young stems
* Found in fruit and phloem cells

Collenchyma

* Used to **provide strength and flexibility** to the growing parts of leaves and stems
* Have **unevenly thickened cell walls**, elongated cells
* May have chloroplasts
* Some food storage in roots and fruits

Sclerenchyma

* have lignin-rich, **thick cell walls**
* Grow and then die in a mature plant part
* Cell walls left behind form a skeleton to **provide support**
* Have no cytoplasm when mature
* Ex: xylem cells

Vascular Tissue Arrangement - Roots

The vascular tissues are organized in the **center of the root** and is surrounded by an **endodermis**

* The xylem and phloem are found in a ring inside the endodermis
* The center part is made of ground tissue called the **pith**


* The ground tissue which makes up the **cortex**, is found between the endodermis and the epidermis 


* The **dermal tissue** forms the outermost layer (epidermis)

Vascular Tissue Arrangement - Roots (Monocot)

The vascular tissues are organized in the **center of the root** and is surrounded by an **endodermis**

* The xylem and phloem are found in a **ring inside the endodermis**

Vascular Tissue Arrangement - Roots (Dicot)

The vascular tissues are organized in the **center of the root** and is surrounded by an **endodermis**

* The **xylem forms an X** with the **phloem located in the arms of the X**

Vascular Tissue Arrangement - Stems

The xylem and phloem cells are organized as **vascular bundles**. The **xylem points toward** the center of the stem with the **phloem to the outside**

* The dermal tissues form the outmost layer (epidermis)
* The ground tissue is the **cortex** __for support__ and the **pith** __for storage__

Vascular Tissue Arrangement - Stems (Monocot)

The xylem and phloem cells are organized as **vascular bundles**. The **xylem points toward** the center of the stem with the **phloem to the outside**

* The vascular bundles are **scattered throughout the ground tissue**
* There is **no vascular cambium**

Vascular Tissue Arrangement - Stems (Dicot)

The xylem and phloem cells are organized as **vascular bundles**. The **xylem points toward** the center of the stem with the **phloem to the outside**

* The vascular bundles are arranged in a **ring around the outer circumference of the stem**
* The xylem and phloem are divided by a layer of cells called the **vascular cambium** which is able to divide to make more xylem and phloem cells

Vascular Tissue Arrangement - Leaves

The xylem and phloem are arranged in a **vein**. The veins are surrounded by a bundle sheath and ground tissue

* The ground tissue is made up of **parenchyma** cells which are responsible for __support and photosynthesis__
* The dermal tissue is the **upper and lower epidermis** which is **coated by the cuticle**. There are stomata in this later which are controlled by guard cells

Vascular Tissue Arrangement - Leaves (Monocot)

The xylem and phloem are arranged in a **vein**. The veins are surrounded by a bundle sheath and ground tissue

* The veins are **parallel**

Vascular Tissue Arrangement - Leaves (Dicot)

The xylem and phloem are arranged in a **vein**. The veins are surrounded by a bundle sheath and ground tissue

* The veins go in any direction, called a **netted pattern**

3 Stages of Transporting Water and Nutrients

1. From the soil into the roots
2. From the roots into the stem
3. From the stem into the leaves

From the soil into the roots

* Water molecules move into the roots by **osmosis** (high to low - water in root low, water in soil high, soil water move into root)
* Absorption of nutrients is done using **active transportation** (concentration of the nutrients in the plant cells > soil water, diffusion cannot work → the plant must use active transportation)
* Water and nutrients must pass through the **Casparian strip** and the **endodermis** to get to the vascular tissue
* Once inside the vascular area, nutrients are actively pumped across cell membranes into the xylem. Water and nutrients are now called **xylem sap**

Active Transportation

When **ATP** is used to move substances from **low to high** areas of concentration

Casparian strip

The _________ is made up of a __wax-like substance__ that **prevents all substances from passing through** the spaces between the endodermal cells

* P**revents substances from leaking** back into the cortex

From the roots into the stem

* Nutrients are actively pumped into the xylem, __concentration increases__, water molecules follow by __osmosis__ → creates **root pressure**, __pushes the xylem sap upward__
* Capillary action also helps the xylem sap rise
* Column of water is held together by cohesion, rises because of adhesion
* The xylem sap moves from one xylem tube to another through pits in the cell wall of the xylem cells
* The pits allow the sap to move out into the surrounding tissue
* Ensures that all cells in the plant body receive water. and nutrients

Capillary action

The tendency of a liquid in a narrow tube to rise or fall because of attractive forces between liquid molecules

Cohesion

The attractive forces between water molecules

Adhesion

The attraction between the water molecules and the sides of the tube

From the stem to the leaves

* Main driving force to get xylem sap to the top comes from the leaves
* Plants release water vapour from leaves (transpiration) → Water loss at the top of the xylem column, pulls on the water molecules creating the flow
* Transpiration causes water loss, must be enough soil water to replace it.
* If not enough water → plant wilt (not enough water pressure inside the cell vacuole - turgor pressure)
* No turgor pressure, cell sags, permanent wilting, death

Transpiration

The evaporation of water from the leaves through the open stomata located in the lead epidermis.

* Transpiration is greatest during the day (stomata open)

Turgor pressure

Water pressure inside the cell vacuole that pushes against the cell wall

Transport of Sugars (Phloem Sap)

The phloem transports sugars and other organic compounds through the plant with a process called **translocation**

* The sugars are moved from an area of production or storage, called a **source**, to an area where they are needed, called a **sink**
* Sugars can move in any direction through the plant
* Direction depends on the location of the source cells relative to the location of the sink cells

Translocation

The transportation of sugars throughout a plant

Source

Area of production or storage (of sugar)

Sink

Area where sugars are needed

From source to phloem

* Sugar moves into phloem cells by **active transportation**. As concentration of sugar increases inside phloem cells, concentration of water decreases → water moves into phloem cells from the neighbouring xylem cells by osmosis
* This forces the sugar-water solution down the phloem towards the roots. More sugar enters followed by more water to keep moving the nutrients to the roots.
* Cells along the way use the sugar as an energy source
* Excess sugars is stored in the root or fruit
* This process is called the **Source to Sink** model of sugar

From phloem to sink

* Sugar molecules leave phloem when they reach a sink cell
* Sink cells have a lower concentration of sugars than the phloem → sugars move by **diffusion** (high to low) into the sink
* Because phloem cells have a lower concentration of sugars, __water is returned to the xylem__
* The complete process is called the **pressure-flow mechanism**
* Water moves from areas of high pressure (at the source when water is drawn into the phloem) to areas of low pressure (at the sink where water is returned to the xylem)

4 Main Factors that Affect a Plant’s Growth, Ability to Reproduce and Survive

Changes in levels of:


1. Soil
2. Water
3. Salt
4. Temperature

How do plants withstand temporary stress

Plants withstand temporary stress by going dormant

* Ex: The Purple saxifrage, one of Canada’s hardiest plants, grows in a dry, rocky environment that’s frozen and dark for most of the year. The Purple saxifrage __survives by forming low dense mats that protect it from the drying wind__. Once the snow melts, it’s able to flower quickly, producing seeds within two months

Drought

A prolonged period of inadequate rainfall

Affect drought has on plants

Plants become **stressed and weakened**

* Plant may **lose more water** through transpiration than it takes up from the soil
* This shortage of water inhibits the growth of young leaves, causes the existing leaves to wilt, and reduces photosynthesis

How plants respond to drought conditions

(all reduce transpirational water loss from the plants’ leaves)

* **Conserving water by closing their stomata**, slowing down the rate of transpiration

Adaptations that allow plants to withstand drought conditions

* **Thick, waxy cuticle** that helps to retain water
* **Modified leaves** (cacti spines) instead of regular leaves that would lose lots of water through transpiration
* The stomata of many desert plants form within epidermal pits, protected by epidermal “hairs”

Affect flooding has on the plant’s environment

* Waterlogged soil **lacks the air spaces** that provide oxygen for cellular respiration in the roots.
* The **oxygen moves more slowly** through the water than through air