Plant Structure and Function Study Guide – Period 6 TRANSPORT IN THE XYLEM OF PLANTS Basic Leaf Structure: o Water lost in the form of gas from the leave through openings called stomata o Transportation is the loss of water vapour from leaves and other aerial parts of the plant o Water absorption replaces the water that is lost from the plant’s upper structures o Leaves consist of a flat part called the blade and a stalk that is called the petiole. o Leaves have a layer of wax as their outermost layer that protects against water loss and insects. o Just like stems and roots the leaves have vascular tissue that includes a xylem and phloem o The xylem brings water to the leaves. The phloem carries the products of photosynthesis to the rest of the plant o A densely packed region of cylindrical cells are in the upper portion of the leaf called the palisade mesophyll. These cells contain a large amount of chloroplasts to carry out photosynthesis. o Bottom of leaf is composed of spongy mesophyll (loosely packed with less chloroplasts) o Stomata occur on the bottom surface of leaves and they allow oxygen and carbon dioxide exchange between the leaf and surrounding areas o As oxygen and CO2 are exchanged, water is lost from the plant. o Specialized guard cells control the openings and closing of the stomata Plant Water and Mineral Movement Xylem is actually a complex tissue composed of many cell types It is involved in supporting the plant as well as being the specialized water-conducting tissue of terrestrial plants The two cells types largely involved in water transport are tracheids and vessel elements Tracheids are dead cells that taper at the ends and connect to one another to form a continuous column. Vessel elements are the most important xylem cells involved in water transport They are attached end to end to form continuous columns, like the tracheids The end of the vessels have perforations in them, allowing water to move freely up the plant. Water passes from one tracheid to another through thin regions called pits In vessel elements, water passes through the pits in the primary wall areas and through the end walls. Stomata and Guard Cells Stomata open and close because of changes in the turgor pressure of the guard cells that surround them. Stomata can only be closed on a short term basis because CO2 must enter for photosynthesis Guard cells are bulge when they’re are full of water and swell causing the stoma to open Vice versa… guard cells sag towards each other when when they lose water causing the stoma to close.
Transcript
Plant Structure and Function Study Guide – Period 6
TRANSPORT IN THE XYLEM OF PLANTS
Basic Leaf Structure:
o Water lost in the form of gas from the leave through openings called stomata
o Transportation is the loss of water vapour from leaves and other aerial parts of the
plant
o Water absorption replaces the water that is lost from the plant’s upper structures
o Leaves consist of a flat part called the blade and a stalk that is called the petiole.
o Leaves have a layer of wax as their outermost layer that protects against water
loss and insects.
o Just like stems and roots the leaves have vascular tissue that includes a xylem and
phloem
o The xylem brings water to the leaves. The phloem carries the products of
photosynthesis to the rest of the plant
o A densely packed region of cylindrical cells are in the upper portion of the leaf
called the palisade mesophyll. These cells contain a large amount of chloroplasts
to carry out photosynthesis.
o Bottom of leaf is composed of spongy mesophyll (loosely packed with less
chloroplasts)
o Stomata occur on the bottom surface of leaves and they allow oxygen and carbon
dioxide exchange between the leaf and surrounding areas
o As oxygen and CO2 are exchanged, water is lost from the plant.
o Specialized guard cells control the openings and closing of the stomata
Plant Water and Mineral Movement Xylem is actually a complex tissue composed of many cell types
It is involved in supporting the plant as well as being the specialized water-conducting
tissue of terrestrial plants
The two cells types largely involved in water transport are tracheids and vessel elements
Tracheids are dead cells that taper at the ends and connect to one another to form a
continuous column.
Vessel elements are the most important xylem cells involved in water transport
They are attached end to end to form continuous columns, like the tracheids
The end of the vessels have perforations in them, allowing water to move freely up the
plant.
Water passes from one tracheid to another through thin regions called pits
In vessel elements, water passes through the pits in the primary wall areas and through
the end walls.
Stomata and Guard Cells
Stomata open and close because of changes in the turgor pressure of the guard cells that
surround them.
Stomata can only be closed on a short term basis because CO2 must enter for
photosynthesis
Guard cells are bulge when they’re are full of water and swell causing the stoma to open
Vice versa… guard cells sag towards each other when when they lose water causing the
stoma to close.
Plant Structure and Function Study Guide – Period 6
Gain and loss of water in guard cells is due to the transport of potassium ions. K+ are
pumped into the cells when blue light triggers ATP - powered protein pumps.
When Potassium ions passively leave cells water also leaves.
closure. Ths hormone is produced in roots during times of water deficiency.
Other factors, (CO2 circadian rhythms) affect stomatal opening and closing
The cohesion-tension theory of plant fluid movement
Process Explanation
Water moves down
concentration gradients
The spaces within a leaf have a high concentration of water
vapour. Water moves from this location to the atmosphere,
which has a lower water concentration
Water lost by transportation
is replaced by water from the
vessels
Replacing water from the vessels maintains a high water
vapour concentration in the air spaces of the leaf
The vessel water column is
maintained by cohesion and
adhesion
Cohesion involves the hydrogen bonds that form between
water molecules
Adhesion involves the hydrogen bonds that form between
water molecules and the sides of the vessel; adhesion
counteracts gravity
Tension occurs in the
columns of water in the
xylem
This is because of the loss of water in leaves and the
replacement of that lost water by xylem water. The water
columns remain continuous because of cohesion and adhesion
Water is pulled from the root
cortex into xylem cells
Cohesion and adhesion maintain the columns under the
tension created by transpiration
Water is pulled from the soil
into the roots
This happens because of the tension created by transpiration
and the maintenance of a continuous column of water
Roots and Fluid movement in plants:
Main function of roots is to provide mineral ion and water uptake for the plant
Roots are very efficient because of an extensive branching pattern
Specialized epidermal structures called root hairs help with water absorption
Root hairs increase the surface area which the water and mineral ions are absorbed by a
factor of nearly 3
The three root zones indicate regions of cell development
o Zone of cell division: where new undifferentiated cells are forming corresponding
with the M phase of the cell cycle
o Zone of elongation: where cells are enlarging in size, corresponding with the G1
phase of the cell cycle.
o Zone of maturation: where cells become a functional part of the plant
Plant Structure and Function Study Guide – Period 6
Water abosorbs from the soil to the root hairs because the hairs have a higher solute
concentration and a lower water concentration than the soil around it.
Water moves through the plasma membranes into the root hair cells
Most of the water entering a plant comes through by osmosis. Once inside the root, water
moves to the vascular cylinder which is where the xylem and phloem is.
Mineral Ions
It’s essential that mineral ions move into the root as well as water.
3 major processes allow mineral ions to pass from the soil to the root:
1. Diffusion of mineral ions and mass flow of water in the soil that carries these ions
2. The action of fungal hyphae
3. Active transport
Passive flow of water and minerals dissolved in it occurs when a higher concentration of
mineral is dissolved outside the root than inside this is referred to as bulk flow or mass
flow.
Active transport is required when there is a higher concentration of minerals outside a
plant than inside.
Plants also use energy to bring in ions that can only pass through certain proteins and not
the lipid bilayer.
Potassium ions move through specialized proteins called potassium channels.
The result of active uptake of mineral ions is a high solute (hypertonic) concentration
within the root. Because of this, the amount of water absorbed from the soil by the root
through the process of osmosis is increased.
Plant adaptations for water conservation
Environmental effects on transpiration in most plants
Environmental
factor
Effect
Light Speeds up transpiration by warming the leaf and opening
stomata
Humidity Decreasing humidity increases transpiration because humid
air near the stomata is carried away
Wind Increases the rate of transpiration because humid air near the
stomata is carried away
Temperature Increasing temperature causes greater transpiration because
more water evaporates
Plant Structure and Function Study Guide – Period 6
Soil Water If the intake of water at the roots does not keep up with
transpiration, turgot loss occurs and the stomata close, and the
transpiration rate decreases
Carbon Dioxide High carbon dioxide levels in the air around the plant usually
cause the guard cells to lose turgor and the stomata to close
Xerophytes are plants adapted to arid climates with adaptations to reduce transpirational
water loss. Some of those adaptations are:
Small thick leaves reduce surface area
Reduced number of stomata decreases the number of openings for water to escape
Stomata are located in pits causing higher humidity near the stomata
Waxy cuticle reduces water loss by acting as a barrier
Hair-like cells on the leaf surface trap water vapor maintaining higher humidity near the
stomata.
Shed leaves or become dormant in dry months
“Succulent” plants such as cacti store water in fleshy, watery stems
Xerophytes can use alternative photosynthesis processes CAM and C4.
o CAM plants close stamota close stomata during the day and incorporate CO2
during the night.
o C4 plants have a stomata that open during the day but take in carbon dioxide more
rapidly than non-specialized plants.
Halophytes are plants adapted to grow in water with high levels of salinity. They are a promising
source of biofuel because they don’t compete with food crops for resources. They have more
adaptations
Many store water becoming succulent diluting the salt concentration
Several species secrete salt
Some species can compartmentalize Na+ and Cl- in their vacuoles
Halophytes and Xerophytes share some adaptations to conserve water. One final adaptation they
share is to simply close stomata using the action of guard cells.
Plant Structure and Function Study Guide – Period 6
Phloem Overview: Phloem transports everything that xylem cannot (like larger macromolecules). Phloem can transport in various direction, unlike the xylem/(it occurs in all parts
of the plant). Phloem transports these materials from a source to a sink using a process
called translocation. Translocation depends on the hydrostatic pressure of the xylem.
Process of Translocation
Translocation is how plants transport organic molecules from a source to a sink
Source: organ in the plant that produces sugar
Sink: organ in the plant that uses sugar
Water dissolves the organic molecules and turns them into phloem sap- This sap includes sugar, amino acids, plant hormones, and small RNA
Pressure-flow Hypothesis (The movement of sap during translocation)
1. The xylem vessel inputs water to the sieve tube to help create hydrostatic pressure
2. The source cell inputs sugar to the phloem sieve tube, and the phloem begins to flow from the source to the sink
3. The hydrostatic pressure is diminished at the end when the sugar reaches the sink
4. The xylem carries the almost-pure water back to the source
This process requires energy!
Plant Structure and Function Study Guide – Period 6
Two Different Types of Angiosperms: Monocotyledonous Plants & Dicotyledonous Plants
Monocot Dicot
Leaf venation
Veins usually parallel Veins usually netlike
Flowers Floral organs usually open in multiples of three
Floral organs usually open in multiples of four or five
Embryos One cotyledon Two cotyledons
Stems Vascular tissue scattered Vascular tissue arranged in a ring
Roots Root system fibrous, which means that there is no main root
Taproot
Pollen One opening in pollen grain Three openings in pollen grain
Plant Structure and Function Study Guide – Period 6
Angiosperm - a plant that has flowers and produces seeds within its carpel. Carpel: consists of stigma, style, and ovary
Gymnosperm - a plant that has seeds unprotected by an ovary or fruit. Reproduce by cone and pollen. The pollen is the male reproductive part and the
cone is female.
Plant Structure and Function Study Guide – Period 6
PLANT GROWTH
Structure
Tissue types o Dermal tissues- outer covering that protects against physical agents and
pathogenic organisms, prevents water loss, and may have specialized structures for various purposes
o Ground tissues- thin-walled cells that function in storage, photosynthesis, support, and secretion
o Vascular tissues- consist of xylem and phloem that carry out log-distance conduction of water, minerals, and nutrients within the pant, and provide support
“Whats up bro?” - Mr. Madden Meristems
o Meristematic tissue is groups of cells that have the same function as stem cells o They are able to divide and differentiate into different parts of the plant o There are two different categories of meristematic tissue groups, which depends
upon their location in the plant Apical meristems (primary meristem) develop at the tips of roots and
stems, and they allow for further growth in length of the roots and stems. This growth results in herbaceous, non-woody stems and roots
Lateral meristems allow for growth in thickness (secondary growth). They are often times seen in woody plants like trees and shrubs. There are two types of lateral meristems
Vascular cambium produces secondary vascular tissue. These include secondary xylem—a major component in wood—on the inside and secondary phloem on the outside
Cork cambium produces cork cells in the outer bark of a plant
Chemical Activity and Phototropism
Plant Tropism (growth or movement influenced by external stimuli) Stimuli include gravity, touch, light, and chemicals Phototropism - Plant growth in response to light
Plant Structure and Function Study Guide – Period 6
Negative phototropism (away from light source) - Plant Roots Purpose of phototropism is to cultivate more productive photosynthesis through
exposure to sunlight Essential for growth
Plant Hormones - facilitate coordination between plant cells, instrumental to growth, allow for interaction with external stimuli
Auxin - Plant hormone that facilitates phototropism Increases flexibility of plant cells, allowing for elongation by buildup between cells
that are distanced from light source As cells are exposed to sunlight, Auxin Pumps remove Auxin and transport it to a
higher concentration in cells with less sunlight and inactive pumps
Plant Hormones Animal Hormones
Coordinate and regulate activity Influences reproduction Channeled through interaction between
hormone and receptor Balances of several simultaneously present
hormones influence function
Coordinate and regulate activity
Influences reproduction Channeled through
specialized gland secretion Single present hormone
influences function
Growth
Indeterminate Growth - Continual pattern of growth (MAIN TYPE) Determinate Growth - Growth ceases after a certain size has been reached (only
happens within some plant organs such as leaves)
Three Types of Life Cycles o Annual life cycle
Plant completes life cycle in one year and then dies Ex. Corn, Rice, etc.
o Biennial life cycle Plant completes life cycle in two years before dying Ex. Onions, Parsley, etc.
o Perennial life cycle Plant lives for many years and death is usually caused by infection or
other environmental factors Ex. Deciduous, Evergreen, etc.
Factors that affect plant development and growth: o Environmental factors, such as day length and water availability
Plant Structure and Function Study Guide – Period 6
o Receptors, which allow the plant to detect certain environmental factors o The genetic makeup of the plant o Hormones, which are chemical messengers
Study Guide: Flower Reproduction Angiosperms/Flower Structure Reproduction creates variety Angiosperm- any plant that has a flower Monocotyledonous (Monocots) Plants versus Dicotyledonous (Dicots) Plants
Monocots Dicots
Parallel venation (the system of veins) in leaves
Netlike venation pattern in leaves
Three flower parts, or multiples of three Four or five flowers parts, or multiples of four or five
Seeds contain only one cotyledon (seed leaf)
Seeds contain two cotyledons
Vascular bundles arranged throughout the stem
Vascular bundles arranged as a ring in the stem
Root system mainly fibrous Root system involves a taproot (main root)
Pollen grain with one opening Pollen grain with three openings
Division between the angiosperms is based on morphological characteristics.
Plant Structure and Function Study Guide – Period 6
Flower structure and function:
Flower Part Function
Sepals Protect the developing flower while it is in the bud
Petals Often colorful to attract pollinators
Anther Part of the stamen that produces the male sex cells (pollen)
Filament Stalk of the stamen that holds up the anther
Stigma Sticky top of the carpel, on which pollen lands
Style Structure of the carpel that supports the stigma
Ovary Base of the carpel, in which the female sex cells develop
Produces the plant gametes by mitosis o Sperm form in male gametophytes o Eggs form in female gametophytes
Sporophyte Generation
Produces spores by Meiosis
Plant Structure and Function Study Guide – Period 6
Two Forms: 1. Pollination 2. Fertilization
Pollination
Pollination is the process by which pollen is placed on the female stigma o It is the first step in the progression towards fertilization and the production of
seeds
Pollination vectors include:
o Insects o Wind o Birds o Water o Other animals
Vector attractions in flowers:
o Red Flowers - Birds o Yellow/Orange Flowers - bees o Odourless flowers - Wind
Plant Structure and Function Study Guide – Period 6
Self Pollination
Pollen from the anther of the same plant falls upon its own stigma Results in less genetic variation
Cross Pollination
Pollen is carried from the anther of one plant to the stigma of a different plant of the same species
Increases genetic variation and results in better fitness The only problem with cross pollination is the female stigma may not receive the male
pollen due to long travel distances
Artificial Pollination
Botanists can select plant genetic characteristics by controlling the process of pollination
Fertilization
Fertilization happens when the male and female sex cells unite to form a diploid zygote o The female sex cells that are fertilized by the pollen are present within the ovules
of the flower o The ovules are present within the ovary of the carpel o Once the pollen grain adheres to the stigma, a pollen tube begins to grow
Pollen tube growth and fertilization occur in the following sequence:
1. Pollen germinates to produce a pollen tube 2. The pollen tube grows down the style of the carpel
Plant Structure and Function Study Guide – Period 6
3. Within the growing pollen tube is the nucleus that will produce the sperm 4. The pollen tube completes its growth by entering an opening at the bottom of the
ovary 5. The sperm moves from the tube to combine with the egg of the ovule to form a
zygote
Once the zygote is formed, it develops with the surrounding tissue into the seed As the seed develops, the ovary around the ovule matures into a fruit to protect the seed
Seeds
Seeds are the means by which an embryo can be dispensed to different locations It’s the protective structure for the embryo
Parts of the seed
Testa: The tough, protective outer coat Cotyledons: seed leaves that function as the nutrient storage structure Micropyle: a scar at the seed opening where the pollen tube entered the ovule Embryo Root and Embryo Shoot: becomes the new plant during germination
Germination: the development of the seed into a functional plant
Once the seed is formed, it matures
o Seed dehydrates until water is 10%-15% the weight o Goes into its dormancy period
Dormancy period: where the seed has a low metabolism and no growth or development.
Variable for different seed types.
General Conditions for Germination
Water: rehydrates dried seed tissues Oxygen: allows aerobic respiration to produce ATP Appropriate Temperature: important for enzyme action
Plant Structure and Function Study Guide – Period 6
Many plants have other, specific conditions that must be met before germination to start.
Some need the testa to be broken before water can be taken in Some have to be exposed to fire or smoke
Light isn’t usually mentioned in seed germination because it has variable effects
Initial Process of Germination
Absorption of water Release of growth hormone Gibberellin or Gibberellic Acid
o Causes the production of amylase, which hydrolyses starch into maltose o Maltose is hydrolysed into glucose, which can be used in cellular respiration
Glucose can be converted into cellulose so new cells can produce cell walls
Germination is uncertain- the seedling is fragile and will be exposed to harsh weather,
parasites, predators, etc. o Plants produce many seeds because many of them won’t produce a functional
