B4 Organising Animals And Plants Flashcards
How plant organs are involved in the transport system
Xylem and phloem transports the products of photosynthesis including sugars and amino acids
Why transport in plants is important
Plants transport all the nutrients and water it needs for survival from its roots to the tips of the leaves
Dermal (epidermal) tissue
Covers and protects the plant
Vascular tissue
Transports water, minerals and sugars
Ground tissue
A site of photosynthesis
Xylem tissue
Transports water and mineral salts from the roots up to other parts of the plant
Phloem tissue
Transports sucrose and amino acids
Describe evidence for movement of water through xylem
Root pressure pushes water up
Examples of plant organs
Roots
Stems
Leaves
How the rate of transport through a plant can be measured
By measuring the distance travelled by an air bubble in a capillary tube over a given time
Function of stomata
Regulates gas exchange between plant and environment and control of water loss
How a potometer can be used to estimate the volume of water lost by a plant
By recording the time taken for a bubble in the tube to move a set distance
Mass potometer
Measures transpiration through loss of mass
Factors that affect transpiration
Temperature
Humidity
Air movement
Light intensity
Transpiration
The evaporation of water vapour from the leaves
Why temperature affects the rate of transpiration
As temperature rises, water evaporates faster
Water molecules in leaves gain more energy. This increased energy causes water to evaporate more quickly
Why humidity affects the rate of transpiration
Easier for water to evaporate into dryer air than into more saturated air
Why light intensity affects the rate of transpiration
Plants open their stomata in response to light, allowing water vapour to escape from the leaves
Why amount of air flow affects rate of transpiration
Increased movement of the air around a plant will result in a higher transpiration rate
How the opening and closing of stomata is controlled by guard cells
The turgor pressure in the guard cells controls the opening and closing of the guard cells
How transpiration maintains the movement of water from roots to leaves
Transpiration is tranported to the leaves through the xylem
How stomata control transpiration
Guard cells increase or decrease the size of the pore with changes in their turgor status
Function of roots
To take in water and nutrients
Function of leaves
Turns sunlight into food
Function of stem
Support leaves, flowers, and fruits
How to use a light microscope to view a cross-section of a leaf
Add a drop or two of water over the leaf section and then covering it with the coverslip
Look through eyepiece lens
How the structure of xylem is adapted to its
function
Has no end walls so xylem forms a continuous hollow tube
Strengthened by lignin providing strength and support
Consists of dead cells which don’t have organelles filling them up allowing more capacity for transporting water
How the structure of phloem is adapted to its
function
Sieve plates enable easy and efficient flow of phloem sap between cells
Companion cells help in loading and unloading sugars into sieve tube elements
Flexible sieve tube elements and supportive fibers helps phloem withstand stretching and bending as plant grows or moves
How would you suggest functions for unknown
plant tissues
Cell shape and size :
Elongated cells may suggest role in transport or support
Rounded cells might be storage or metabolic
Cell wall thickness:
Thick cells may indicate a structural role (support, protection)
Thin walls suggest role in transport or metabolic activities
How structure of dermal tissue is related to its function
Dermis structure provides strength and flexibility
Blood vessels help maintain your epidermis by transporting nutrients
How structure of vascular tissue is related to its function
Make up of 2 specialized conducting tissues
Xylem provides structural support
Phloem transports sugars from sits of photosynthesis to other parts of plant
How structure of ground tissue is related to its function
Structural support for stem and vascular tissue
Storage for water and sugars
Evaluate drinking from a straw as a model for transpiration
Tension created by transpiration pulls water in the plant xylem, drawing water upward in almost same way you draw water upward when you suck on a straw
Examples of plant tissues
Epidermal, palisade mesophyll, spongy, xylem, phloem, meristem
Function of palisade mesophyll tissue
The part of the leaf where photosynthesis occurs
Function of spongy mesophyll tissue
Contains big air spaces to allow gases to diffuse in and out of cells
Function of meristem tissue
Found at growing tips of shoots and roots and able to differentiate into lots of different types of plant cell allowing plant to grow
What tissues do leaves contain
Epidermal
Mesophyll
Xylem
Phloem
Why is epidermal tissue covered with a waxy cuticle
Helps reduce water loss by evaporation
Why is upper epidermis transparent
So loght can pass through it to palisade layer
Why does palisade layer have lots of chloroplasts
Means they’re near the top of leaf where they can get most light
Why do xylem and phloem form a network of vascular bundles
They deliver water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis
They also help support the structure
Function of air spaces in spongy mesophyll tissue
Increase rate of diffision gases
Function of stomata on lower epidermis
Lets CO2 diffuse directly into leaf
Structure of phloem tube
Made up of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
Translocation
The transport of dissolved material within a plant
Differences between transpiration and translocation
Transpiration is process by which water is absorbed by roots of plant
Translocation movement of organic substances
Transpiration involves movement of water and dissolved minerals
Transolcation movement of organic molecules and other nutrients
Transpiration occurs through xylem
Translocation occurs through phloem
Similarities between transpiration and translocation
Both processes are involved in the transport of essential substances within the plant
Both processes use vascular tissue to transport substances
Both processes can be affected by temperature, light intensity and humidity
Factors that affect translocation
Light intensity
Temperature
Concentration of solutes
Water available
Nutrient availability
How does temperature affect translocation
Increases the speed of translocation increases kinetic energy of molecules involved in the process
How does light intensity affect translocation
As light intensity increases, rate of photosynthesis increases, rate or growth increases and more food is translocated
How does concentration of solutes affect translocation
A higher concentration of solutes can create a higher pressure potential
This drives the movement of substances through the phloem
How does water availability affect translocation
In conditions of water scarcity, the pressure in the phloem may decrease, slowing down or stopping translocation
How does nutrient availability affect translocation
If soil is deficient in certain nutrients, the plant may not be able to produce the necessary sugars for translocation
If soil is rich in nutrients, the plant may produce more sugars, leading to a higher rate of translocation
What is transpiration caused by
By evaporation and diffusion of water from a plant’s surface
Why is more water drawn up from the rest of the plant through xylem vessels
To replace it as evaporation creates slight shortage or water
How is there a constant transpiration stream of water through a plant
More water is drawn up from the roots
How to calculate the mean number of stomata on a given area of leaf
Use microscope
Count number of stomata in the field of view
Then slightly move slide and count number of stomata in a different field of view
Make at least five random counts, then calculate a mean
How to use sampling to estimate the number of stomata on a leaf
Calculate mean
Why do plants have different numbers of stomata
To help them survive better in a higher range of temperature
Each individual stomata will be able to bring in more carbon dioxide
Bubble potometer
Measures the rate of water loss from a plant by transpiration
Differences between a moving bubble potometer and a mass potometer
Moving bubble potometer measures water taken up by the plant from a tube
Mass potometer measures water lost by whole setup
Moving bubble potometer requires more complex setup
Mass potometer requires simple set up
Adaptations to control water loss and how they work
Thick waxy cuticles - create barrier to evaporation
Narrow leaves with fewer pores - reduce amount of water escaping
Identify variables when investigating rate of transpiration
The factors affecting transpiration
Make a prediction using scientific knowledge when investigating rate of transpiration
If environmental conditions sush as temperature humidity increase transpiration increases
What is the use of a potometer to measure the rate of transpiration
