Chapter 9 Plant transport Flashcards
What is the structure of a leaf, top to bottom?
Waxy cuticle
Upper epidermal layer
Mesophyll layer, made up of first palisade mesophyll then spongy mesophyll
Air spaces and side vascular bundle
Lower epidermal
Stoma/Guards cells
What are xerophytes? Give examples
Xerophytes are plants which have adapted to living in areas of lower water availability
e.g Cacti, Marrum Grass
State general adaptations of xerophytes
Thick waxy cuticle
Creating moist microclimate via sunken stomata, hairy leaves and curled leaves
Reduce water loss by transpiration through reduced number of leaves, stomata and losing leaves
Root adaptation of long, deep taproots and/or widespread high SA roots
Succulents
Don’t cope, die, future generation
How does the waxy cuticle prevent water loss?
Prevents loss of water through evaporation through the epidermis
What are adaptations of cacti and how do they help reduce water loss?
Sunken stomata and spines to produce a moist microclimate, reducing rate of transpiration by lowering water potential gradient
Thick waxy cuticle to reduce water loss by epidermis
Long deep tap roots to collect water metres below and widespread high SA roots to quickly take up rainwater
What are adaptations of Marram Grass?
Thick wavy cuticle to reduce water loss through epidermis
Curled leaves and hairs to produce microclimate to reducing water potential gradients and water loss by transpiration
What are succulents and how do they help reduce water loss?
Specialised parenchyma tissue used to store water when there is a plentiful supply
What are hydrophytes? Give an example
Plants adapted to a very high potential environment living in or on the surface of water, or in permanently saturated soil
e.g Water lilies
What are general adaptations of hydrophytes?
Many stomata on the upper surface of the leaf always open
Short roots as supply of water is abundant
Thin waxy cuticle
Lack of extensive support system
Wide flat leaves to increase photosynthesis
Large SA of stems and roots for increased diffusion of O2 and increased photosynthesis
Air sacs for floating
Aerenchyma
What are the main problems faced by hydrophytes?
Water logging, when air spaces filled
Need to maximise photosynthesis, e.g leaves close to the surface
What is aerenchyma? What is its function?
Specialised parenchyma with large air spaces, produced by apoptosis
Increases buoyancy
Low resistance internal pathways for movement of 02
What is the function of the air space?
Promotes efficient gas exchange
Facilitate movement of water
Mechanical support- buoyance
Thermal Insulation
What are the structures between the xylem and roots?
Endodermis, which includes the endodermal cells with casparian strip
Root cortex cells
Root hair cells
Why do plants need a transport system?
High metabolic demands, with the need to transport glucose from photosynthetic tissue to to roots, and removal of waste products, diffusion too slow
The size of plants are often very large, creating very large diffusion distances would be too slow to rely on
Low surface area to volume ratio apart from leaves, so low rate of diffusion
What are dicotyledonous plants (dicots)?
Plants which produce seeds containing two cotyledons, which are food stores for the developing embryo and form the first leaves
Name and describe the two types of dicots
Herbaceous- contain soft tissues, and have a short life cycle
Woody- lignified tissues which have long life cycles
What is the vascular system?
What is the vascular bundle?
The series of transport vessels running through the xylem and phloem
The arrangement of the xylem and phloem
How is the vascular bundle organised in stems and why?
Around the edge to give strength and support, xylem inner most
How is the vascular bundle organised in roots and why?
In the middle, as a star xylem inner most, to help withstand tugging strains of bending in the wind
How is the vascular bundle organised in leaves and why?
Midrib the main vein, many small branching veins spread through leaf for transport and support
Describe the structure of the xylem
Long, hollow structures made by several columns of cells fusing together end to end, dead
In between xylem vessels there is xylem parenchyma containing tanin which protects from attack, and nutrients
In between, there are xylem fibres which are lignified cells providing some mechanical support.
Lignins surrounds the xylem walls in spirals to provide strength. There are areas without lignin along the xylem vessels called bordered pits, which enable osmosis between xylem vessels.
Describe the structure of the phloem
Living sieve tube elements are joined together end to end
Between cells, the cell wall breaks down known as the sieve plates
As the walls have broken down and the cell fills with phloem sap, the nucleus and vacuole breakdown, only some ribosomes, which maximised space for transport
Sieve tube elements closely linked with companion cells, joined by plasmodesmata, which are very active and provides metabolic support to the sieve tubes
Between phloem vessels there is also phloem parenchyma stores nutrients
What are the function of the xylem and phloem?
Xylem- transport of water and dissolved mineral ions, and SUPPORT
Phloem- Transports organic solutes up and down, sources to sinks
What is cambium and where is it located?
Meristematic tissue between the xylem (inwards and larger) and the phloem
What are bordered pits?
Unlignified areas within the xylem which enable lateral transfer of water between different xylem vessels
How is water lost from a plant?
Transpiration- an effect of gaseous exchange where water leaves from stoma underside and top of leaf
Evaporation- through the waxy cuticle and epidermis
Reactant- photosynthesis
Cooling system
Why is a capillary tube more helpful than a calibrated pipette for potometers?
More graduations which reduces percentage uncertainty
Easier to read smaller volumes
How does osmosis enable cells to provide support to the plant?
Water moves into the vacuole via osmosis
Increases the turgor, pressure, increased pressure against the cell wall
Turgid cells provide support