Plants
Plant Cell Differences
-Cell wall
-Nucleus on one side
-One vacuole
-Synthesizes Nutrients (Chloroplast)
Vascular VS Non-Vascular
Vascular: Flowers and trees, typical plants
-Tall, has plant version of blodd vessel system can moves things (water, nutrients ect) up and about
Non-Vascular: Moss
-Cannot tranpsort water or food between plant parts, must do so through asbsorption and osmosis
Must live in moist environment
short like ferris
Function of Roots (3)
-Anchors and supports plants in ground
-Absorbs soil and water
-Holds soil in place
Structure of roots (7 parts)
Root Parts:
-Root cap
-Apical Meristem
-Root hairs
-Endodermis
-Pericycle
-Phloem
-Xylem
Root hairs function
increases surface area for water and mineral absorption
Apical Meristem function
Region where new cells are produced - Root cells are developed by both elongation and cell divison causing root to grow in width and length.
Root cap
Protects the tip of the growing root
Leaf function
-Main photosynthetic organ
-Broad flat surface, increases surface area for light absorption
-Has systems in order to prevent water loss; stomata opens in the day but closes at night or when hot to conserve water, waxy cuticle on surface on leaf
-System of gas exchange, allows in and out CO2 and O2
Leaf Structure (5 parts)
Cuticle
Veins
Mesophyll
Gaurd cells
Stomata
Cuticle
Waxy layer covers upper surface of leaf, protects it against water loss
Veins
Contain Xylem and Phloem, transport water, nutrients and food, vascular tissue
Mesopyhll
Contains cells that perform phtosynthesis due to containing chloroplasts
Gaurd cells
Cells that open and close the stomata to conserve water by preventing excess water transpiraiton
Stomata
Opening in leafs surface: when open they allow TRANSPIRATION (water movement in and out of leaf) and GAS EXCHANGE (transfer of CO2 and O2 in and out of leaf)
Stem function
Support system for plant body
transport system for water and nutrients through xylem and phloem
Holds leaves and branches up
Vascular Tissue parts
Xylem: dissolves minerals, transport water
Phloem: transports sugars and proteins through stem
Cambium: Layers of cells between xylem and phloem that are able to divide
Vascular Cambium
Forms continuous cylindrical layer inside stem that can reproduce
-cells divide to form new xylem towards the inside of the stem and phloem towards the outside
Forms tree rings
Gynosperms
In vascular plants
-naked seeds - not enclosed in ovule
Ex: Pine cones
-Usually evergreens
Angiosperms
mature seeds that are surrounded by ovule
-Generally trees that shed every autumn
Flowers
-Both reproduction organs (male and female)
Pollen is used for sexual reproduction
Parts
-Receptacle
-Pistil
-Sepals
-Petals
-Carpals
-Stigma
-Styles
-Ovary, ovules
Plant reproduction
Sexual reproduction: Pollen from anther goes to stigma
Self feritilization: When sexual reproduction occurs using parts from the same flower
Cross fertilization: When pollen from a different plant fertilizes that of a different flower
Fruit
When ovules are fertalized petals fall of the flower and it developes into a fruit, fruits are vessels for plants, sometimes specialized to help transport them. (helicopters, acorns, beanpods)
Monocots and Dicots
Two types of angiosperms
-Monocts have one embryonic leaf (cotyledon) when the seed germinates
-Dicots have two embryonic leaves (cotyledons) when the seed germinates
Moncot vs dicot cells
Monocot- Vascular bundle generally not aranged in a circle but scattered throughout, no clearly defined pith, Xylem oriented towards the middle, phloem oriented towards the sides
Dicot -arranged in circle towards the middle surrounding central pith, Xylem towards the middle, phloem towards the outside, cortex outer layer of pith
Plant reproduction factors
-pollination
-fertilization
-seed dispersal
Seed dispersal factors
-Wind
-Water
-Insects
-Animals
-Fruits
Structure of seeds
-Radicle - Embryo root
-Epicotyl - Embryo shoots
-Cotyledon (contains food stores)
-testa -outer seed coat
-Mircopyle and caruncle -hole through which water enters
germination of seeds
When seed emerges from dormancy and begins to sprout
Absorption of water causes germnation by bursting seed coat so plant can produce energy
-Starts chain reaction of chemicals which cause developement of plant embryo
Seed germination reuqirements
-requires oxygen, water, temperature, water is most important as it activates enzymes necessary for cellular respiration in mature seedling, seeds generally need to be exposed to heat and light so chemical energy in seeds starch can be converted to glucose during germination
(may also be fire, light, darkness, prior animal digestion, erosion of seed coats)
Seed dormancy
blockage of complete germination of seed, delays germination until conditions are more favourable
Seed banks
-Plant strategy, to ensure all seeds do not germinate in a single year (saves species in event of catastrophe)
Seed Germination Steps (5)
-Absorption of water, causes gibberellin (horomone) or gibberalic acid (GA) to be producec
-Gibberellin causes sythesis of amylase which breaks down starch to maltase
-Maltase is transported to embryo where it becomes eitehr hydrolysed to glucose for energy or polymeralized to form cellulose (for cell wall)
-Stored proteins and lipids will also be hydrolysed by the addition of water from enzymes, triglycerides and phospholipids
-Germination uses food stored in cotyledons as an energy source until the developing seed shoot reaches the light and can begin photsynthesis
Switch to flowering
A result of light and dark periods
Floweing is controlled by phytochrome which is affected by light (photoperiodicy)
Phytochrome exists in two forms (Pr and Prf)
Pr
Absorbed red light (-660nm) is converted into Prf (far red form, -730nm)
-Non active stable form
-Predominant during the night
-In darkness Prf turns gradually to Pr
Prf
far red light (Pfr) turns into Pr
-less stable
-Active form
-Predominant during the day
Long day plants
Prf activates flowering
-Flowering is induced when the night is short so Pfr levels are high because the it has yet to fully become Pr
Short day plants
Prf acts as an inhibtor of flowering, longer nights mean more time for Prf to become Pr and so not enough Prf remains to create flowers
Day length
measured by light sensitive pigments in leaves which produces FT floweing time protein
FT
flowering time protein - triggers flowering in apical meristem which differentiates in the flower bud cells, stimulates flowering by activating certain genes in the apical meristem which results in transcription (Gene expression) allowing production of flowers
Xylem
transports minerals and water
Xylem vessels are small in diameter
xylem also have TRACHEIDS more on that later
Xylem is made up of long polymer tubes called ligin
Ligin generally forms rings or spirals
Xylem has perforated walls to allow for movement of water and gases
Tracheids
Old form of vessels
Long thin tappered ends
Liginified secondary walls
water moves cell through cell via pits
Less effective then vessels
Thick walls
Higher surface to volume compared to vessels
holds water against gravity
Vessels
-wider and shorter, are not as tapered as tracheids
-more efficient in water conduction due to the presence of perforation plates
-main conducting elements of angiosperms
Cohesion-Tension Theory of water
-Water is great for moving around cause in the xylem when the evaporated it creates negative pressure which sucks water up and replenishes the xylem
-Water is also great because its super polar and is therefore attracted to itself it forms hydrogen bonds with other water molecules and wants to stay together
-There is also adhesion with the walls of the xylem, the forms hydrogen bonds with the cell walls.
Stomata and guard cells
Guard cells take in water and swell closing the stomata
-movement of water is caused mainly be potassium ions
-light causese movement of potassium into the cell causing a movement of water in the cells with the high concentrations of potassium
-when potassium leaves the cells, the water will move out ---- flaccid cells –closed stomata
At midday, the Stomata are open, and water moves rapidly through the plant.
Water movement stops at night, when the Stomata are closed and there is no Transpiration.
Roots - later
ROOTS
-a plant hormone –abscisic acid can be produced by the roots during drought. The hormone causes the potassium ions to diffuse out of the guard cells
-water is absorbed into the root by osmosis
-the concentration of solute is higher inside the cells of the roots and water move in
-The concentration in the root in 100 times more than in the soil. The minerals ions are transported by active transport (pump protein)
-if the soil contains a higher concentration then ions can be diffuse in the root. This passive flow of water and the minerals dissolved in it is called mass flow
Sap
Phloem contains concentrated solutions of dissolved solutes mainly sugars, amino acids, hormones and metabolities
-Called sap
-Transports sucrose
Translocation
transport of sugars in the phloem
-Phloem can move stuff up or down, or both simultaineously
Sources and Sinks
summer - Source is leaves, sink is root
spring - root is source, new leaves are sink
Flowers and young buds can't yet make own energy; sinks, and roots and leaves are the source
Phloem parts
Sieve tubes
Companion cells
Sieve plates
Sieve tubes
-elongated tubes stacked end to end to form food conducting cells
-No ligin to be found
-Mature cells lack nucleus and some organelles
-Transports products of photosynthesis
Companion cells
Normal cells that handle all the cell stuff sieve cells don't do, normally near them, connected through plasmodesmata, assists in sugar loading
Sieve plates
end walls of sieve cell contained pores
Hydrostatic gradient pressure
-Solute is transported in phloem by active transport (energy from ATP) and evaporation
-Sucrose is pumped into the phloem by the companion cells, reducing water concentration in the sieve tubes, so water from the xylem osmosises in
-Uptake in water causes positive pressure which forces things (water and sugar) downwards
-Sugars are taken via active transport to sinks
-Simultaineously ions are being actively transported in the xylem from the soil
-water diffuses from phloem to xylem, water and dissolved ions are pushed up xylem, mass flow
Experiments
Puncture experiment
Aphid stylet experiment
Radioactive tracer experiment
Meristems
Meristems are regions of plants that are composed of undifferentiated cells that experience mitosis and cell division. With each division, one cell stays in the meristem
Apical meristems or primary meristems
Apical meristems or primary meristems: are found at the tips of stems and roots
Lateral meristems or secondary growth
Lateral meristems or secondary growth: is the growth in diameter which can produces the vascular tissue, cork and bark
Photoperiods
a plant ‘s response to changes in day length. (short day vs long day flowering plants)
Nutrients
inorganic substances referred as plant nutrients are need for growth
Nitrogen dificiancies
Nitrogen regulates synthesis of amino acids
Lack of it causes stunted growth, red leaf bases, long thin roots, chlorosis
Phosphorus dificiencies
Phosphorus is a component of ATP and nucleic acids
lack of it causes stunted roots, red leaf bases
Potassium dificiencies
Potassium is a part of memebrane transport, lack of it causes stundted growth and premature death
Magnesium dificiencies
component of chlorophyll, lack of it causese stunted growth and chlorosis
tropism
A tropism is a change in the direction of growth in response to stimulus. Phototropism is a change in direction of a growing plant in response to light
Gravitropism: is a change in growth direction in response to gravity
Thigmotropism: is a change in growth direction in response to touch.
Hormones
chemicals produced in small quantities that are transported to locations in the plant where they cause specific physiological or developmental responses
Cytokinins
-hormones that promote division and differentiation and are found in tissues that are actively dividing
-Cytokinins help to stimulate cell division in lateral buds when an apical bud has been removed
Gibberellins
-Gibberellins are produced in the apical regions of stems and roots where they promote cell elongation
-They also function in seed germination.
-They also play a role in flowering and fruit production in many species
Auxin
-produced in the shoot apex moves downward
-facilitates the growth of young plant cells.
-the most abundant auxins is INDOLE ACID (IAA), has a role in the control of growth in the shoot apex and promotes the elongation of cells in stems
- when in very high concentration it can inhibit growth
-the side of the plant closest to light contains less auxin than the side shaded from the light. As a result, cells on the shaded side are stimulated to elongate ( rx break bond and loosen the fiber)
-Phototropins, a photoreceptor (a protein) absorb light and it changes shape. It binds to a receptor and controls the transcription of specific genes. It seems that the genes code for a group of glycoproteins that transport the plant hormone auxin (PIN3). Those specialized membrane proteins called auxin efflux pumps move the auxins away from the sunlight. The entry of auxin into a cell is called auxin influx.
-auxin also stimulates growth in the vascular cambium and promotes the formation of new energy and die lateral meristems and new root apical meristems
-some herbicides contain auxin that causes plants to elongate too much that run out of energy and they will die
-Fruit growers spray orchard with auxin so fruit ripening can be synchronized and be picked at one time
apical dominance
is when the apical bud releases auxin and inhibits the growth in the lateral bus. Growers cut the apical bud and help the lateral buds to develop, the plant is shorter and has more branches