Studied by 11 people
What three processes does the success of plant reproduction depend on?
Pollination, fertilisation and seed dispersal
Define pollination
The transfer of pollen grains from an anther (male plant structure) to a stigma (female plant structure)
Define fertilisation
Fusion of a male gamete nuclei with a female gamete nuclei to form a zygote
Define seed dispersal
The process where the seed moves away from the parent plant, benefitting parent and offspring by reducing competition for resources
Where are the male and female nuclei in plant cells found?
Male- in the pollen grain
Female- in the ovule
Define germination
The emerging of an embryonic plant from a seed or spore after a period of dormancy
Which four main conditions does germination depend on?
Warmth, Oxygen and Moisture (and a suitable soil pH)
Which additional conditions for germination do some plants require?
Fire
Freezing
Digestion
Washing
Scarification
What is mutualism (with an example)?
Mutualism is where both species benefit from an interaction, for example:
The flowering plant gaining a means of sexual reproduction (via the transference of pollen between plants)
The animal gaining source of nutrition (plants secrete a sugar-rich substance called nectar to attract pollinators)
What is the name of substance at the apex (growing tip) of the plant?
Meristem
What are the female parts of a plant and their functions?
Stigma- the sticky, receptive tip of the pistil that is responsible for catching the pollen
Style- elevates the stigma to help catch pollen
Ovule- the structure that contains the female reproductive cells
Ovary
What is the collective name given to the female reproductive organs of a flowering plant?
Carpel (or pistil)
What are the male parts of a plant and their functions?
Anther: produces pollen
Filament: supports the anther and makes it accessible to pollinators
What is the collective name given to the male reproductive organs of a flowering plant?
Stamens
What does the xylem transport?
Water and dissolved mineral ions
Features of the xylem
Dead cells
Lined with lignin
Transport process (transpiration) is passive and requires no energy
Transpiration only occurs in one direction
What does the phloem transport?
Photosynthetic sugars/organic solutes (specifically sucrose, which is made of glucose and fructose)
Features of the phloem
Living cells
Have sieve plates between cells
Transport process (translocation) is two-directional
Translocation requires energy
What type of cells does water evaporate from in the transpiration stream?
Spongy mesophyll cells
What is the testa of a seed?
An outer seed coat that protects the embryonic plant
What is the micropyle of a seed?
A small pore in the outer covering of the seed which allows for passage of water into the seed
What is the cotyledon of a seed?
Contains the food store of the seed and forms embryonic leaves
What is the epicotyl of a seed?
The embryonic shoot (also called the epicotyl)
What is the radical of a seed?
The embryonic root
What is the difference between a monocotyledonous plant and a dicotyledonous plant?
A monocotyledonous plant bears a single cotyledon (embryonic seed leaf) whereas a dicotyledonous plant has two
How can you identify whether a seed was monocotyledonous or dicotyledonous by looking at the adult plant?
Monocots have narrow parallel veins and dicots have branching veins
Monocots have petals in multiples of three and dicots have four or five petals
Monocots have scattered vascular bundles and dicots have ringed vascular bundles
How is the structure of plant roots related to their function?
Roots branch, giving increased surface area
Root hairs further increase surface area
Mineral ions are absorbed by active transport
How is the structure of a root hair cell related to its function?
Large surface area (due to outgrowths/ extensions)
Many mitochondria for aerobic respiration
Protein pumps in the plasma membrane for active transport
Association with fungal hyphae further increase surface area
Plasmodesmata
Junctions between plant cells with a continuous cytoplasm (gaps in the cell wall)
Symplast pathway
The pathway water takes from the root hair cell to the xylem through junctions called plasmodesmata between cells with continuous cytoplasm
Apoplast pathway
The pathway water takes from the root hair cell to the xylem through the cellulose fibres of touching cell walls
Why is the movement of water on the symplast and apoplast pathways considered diffusion and not osmosis?
Because the water particles do not pass through a membrane
What is the cortex in the context of plant roots?
The cells that water passes through on its journey between the root hair cell and the xylem
What is the Casparian strip?
A strip of wax that encircles the cell next to the xylem and prevents water from continuing on the apoplast pathway
What is the Casparian strip made of?
A type of wax called suberin
What happens to water when it reaches the Casparian strip?
Water on the apoplast pathway enters the cell and continues on the symplast pathway
Which layer of the roots do root hair cells belong to?
The epidermis (outermost layer)
What is the innermost layer of the roots called?
The endodermis
What are the three main types of lignin thickening?
Annular (rings), spiral (curly) or reticular (curly wurly)
What are the individual units of the phloem called?
Phloem sieve tube elements (nb. that they’re not called cells because the elements connected performing the same function)
What instrument is used to measure rate of uptake of water?
A potometer
Why is volume of water taken up by plant roots not always equal to volume of water that evaporates from leaves?
Some water can be used in the photosynthesis reactions inside the plant
Which four factors can change the rate of photosynthesis and how?
Wind (more wind=more transpiration as water vapour is blown out of surroundings)
Humidity (more humidity=less transpiration as the concentration gradient is shallower)
Temperature (higher temperature=more transpiration as more evaporation)
Light intensity (more light=more transpiration as stomata open for gas exchange for photosynthesis)
Xerophytes
Plants that are adapted for water conservation (ie. plants that show xeromorphic adaptations)
What are some examples of xeromorphic adaptations?
Thick waxy cuticle to reduce transpiration
Absence of stomata on upper epidermis
Sunken stomata
Leaf hairs limiting movement of air over leaf surface
Modified leaves called spines
Swollen stem for water storage
Ridged structure (for self-shading)\
Extensive root system with shallow roots and deep roots
What is meant by crassulacean acid metabolism (CAM)?
An alternative biochemical pathway to the Calvin cycle. In CAM, carbon dioxide can be absorbed at night, stored as an organic acid, and then released during the day. This conserves water as stomata only need to be open during the night.
Mesophytes
Terrestrial plants that are not adapted to either very dry or very wet conditions
Hydrophytes
Plants that are adapted to live in very wet conditions
What is phototropism?
The tendency for a plant to grow towards a light source
Which plant growth substance is associated with phototropism?
Auxin
How does auxin facilitate phototropism?
Auxin accumulates on the side of the plant furthest from the light and causes cells to lengthen.
Auxin causes the fibres of cellulose to become less rigid, meaning that the cell wall becomes more flexible.
This occurs because auxin causes Hydrogen ions to be pumped into the cell wall, lowering the pH and causing bonds between glucose molecules in cellulose to break.
Which two pumps are associated with phototropism?
H+ pumps and auxin pumps
What is the meristem?
Areas of undifferentiated tissue capable of indeterminate growth, found in plants (analogous to stem cells in humans)
What is the definition of a tropism?
The turning of an organism (usually a plant) in response to an external stimulus
What is meant by photoperiodism?
The developments of plants in response to changing relative lengths of days and nights (ie.seasonal flowering)
What are phytochromes?
Photoreceptor proteins found in plants which have a role in controlling flowering
In what two forms do phytochromes exist?
Pr (inactive)and Pfr (active)
Pfr is metabolically active while Pr is metabolically inactive. What does this mean?
Metabolically active substances promote or inhibit a process. Metabolically inactive substances do neither.
When does the conversion of Pfr into Pr occur, and is it fast or slow?
During the day, quickly
When does the conversion of Pr into Pfr occur, and is it fast or slow?
During the night (absence of light), slowly
What is the difference between apical and lateral meristems?
Apical meristems promote primary growth (lengthening) including production of leaves/flowers of the plant while lateral meristems promote secondary growth (widening) including the production of bark.
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