Nitrogen
Needed for vegetative growth, essential component of both proteins and chlorophyll.
Nitrates are very soluable and easly washed out of the soil. Flooding, drought, and low temprerues call all effect nitrate avalibility (washed out or poor conditions for nitrifying bacteria).
Nitrogen deficency results in slow or stunted growth and chlorosis (yellowing of the follage).
Phosphorus
Important for root development, crop maturity and seed production, and an essential ingredient in the conversion of ADP to ATP in photosynthesis. It is also a major component of plant DNA and RNA, and used my numerous enzymes.
Often associated with healthy root growth and important for mitosis.
Potassium
Required for the activation of over 80 enzymes, it promotes general health and vigor in plants and is needed for photosynthesis. Controls water uptake in the roots, and loss from the leaves.
Promotes flowering and fruiting in plants.
Deficiency leads to yellowing or purple leaf tints and poor flowering or fruiting.
Plant micronutrients
- boron (B)
- copper (Cu)
- iron (Fe)
- molybdenum (Mo)
- zinc (Zn)
- chlorine (Cl)
- manganese (Mn)
- cobalt (Co)
- nickel (Ni)
- sodium (Na)
In addition to NPK, what 4 other macronutrients are critical for plant grow?
- Ca (Calcium): Used by plants in cell membranes, at their growing points and to neutralize toxic materials.
- Mg (Magnesium): An essential part of chlorophyll.
- S (Sulfur): A component of many proteins.
- Si (Silcon): Strengthens cell walls, improves resistance to drought, pests, disease, and frost. Used by many grasses to deter grazers, eg the high Si level in pampas grass gives the leaves a sharp edge.
What are the 3 tenets of cell theory?
- All living organisms are composed of one or more cells.
- The cell is the basic unit of structure and organization in organisms.
- Cells arise from pre-existing cells.
However, the first of these tenets is disputed, as non-cellular entities such as viruses are sometimes considered life-forms
What prevents a turgud cell from bursting?
Cellulose
What gives a plants secondary cell wall strenght?
Secondary walls are much thicker than the primary wall, and consist of 45% cellulose, 30% hemicellulose, and 25% lignin. It is the lignin that gives the cell wall its strength.
Label the diagram
- Cell Wall
- Nucleus
- Mitochondrion
- Chloroplast
- Vacuole
- Endoplasmic reticulum
What is the equation for photosynthesis?
6CO2 + 6H2O ⟶ C6H12O6 + 6O2
- Carbon Dioxide = CO2
- Water = H2O
- Glucose = C6H12O6
- Oxygen = O2
Describe the light-dependent reaction in photosynthesis
- Light hits pigment molicules, energising the electrons within it.
- On return to their gound state energy is released by driving a chemical reaction.
- Two chemical reactions:
- ADP (adenosine diphosphate) to ATP (adenosine triphosphate)
- Splitting water into Hydrogen and Oxygen (the waste product). The free H atoms are combined with NADP to form NADPH2.
Describe the light-independent reaction in photosynthesis
The dark reaction or Calvin Cycle
- The reaction occures in the stroma of the chlotoplast
- ATP and NADPH2 are converted back into ADP and NADP, and recycled back into the light reaction stage.
- This drives a reaction that converts CO2 into sugars
What are the 5 main plant hormones?
- Auxin: Influences bud and leaf formation, growth towards light, and often found in rooting powders.
- Gibberellin: Cell elongation, seed germination, and flowering.
- Cytokinins: Cell division.
- Ethylene: Fruit ripening (banana)
- Abscisic acid: Stress response
Other major hormones now recognised include:
- brassinosteroids
- jasmonates
- salicylic acid
- strigolactones
What are the 4 main types of stem cuttings?
- Softwood
- Greenwood
- Semi-ripe
- Hardwood
Name the parts of the flower
- Pistal
- Stamen
- Stigma
- Style
- Ovary
- Anther
- Filament
- Petal
- Ovule with Embryo Sac
- Sepal
- Receptacle
- Peduncle
What is cross-pollination?
pollination of a flower or plant with pollen from another flower or plant
What is self-pollination?
The pollination of a flower by pollen from the same flower or from another flower on the same plant.
What is self-incompatibility?
A mechanism that prevents pollen from one flower from fertilizing other flowers of the same plant.
when a pollen grain produced in a plant reaches a stigma of the same plant or another plant with a similar genotype, the process of pollen germination, pollen-tube growth, ovule fertilization and embryo development is halted at one of its stages and consequently no seeds are produced. SI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants, and it is considered as one of the causes for the spread and success of angiosperms on the earth.
How is a seed formed?
- After fertalisation the overy is refered to as the fruit, and the ovule the seed.
- The seed consists of seed coast, the embryo, and endosperm.
- In berries and drupes (stone fruit) the overy wall develops in to a fleashy pericarp
- As the seed matures it looses most of its water, going from 90% mass to 10-15% mass.
Why do some seeds show a dormancy stage?
To ensure that premiture germination cannot takeplace, and that germination occues with the best conditions for survival.
- Maturity: The seed needs to be fully developed. This is Morphological Dormancy.
- Right season: Eg. no point in germinating just before winter.
- Location: Allow for dispersal away from main plant
- Availability: Light, water, heat,
How can you break seed dormancy?
- For mechanical or physical dormancy (the seedling is unable to break out of the seed coat) try scarification. This may mimic natural processes of decay, chewing, ect. Scarification can be done with a small file, or for small seeds a jar containing some sandpaper.
- For chemical Dormancy try soaking. This can washout chimical the are inhbiting the development of the seed. Soak in warm water for 24 hours, and disguard any floaters.
- For physiological dormancy use stratification, place the seeds in a fridge for a month, then sow in a heated propagator.
What does a seed need to germinate?
- Water: The seed needs to rehydrate by taking in water through the micropyle.
- Oxygen: Required for arobit respiration enabling cells to metabolise and burn energy.
- Temprerature: Varies from plant to plant, but essential to have correct.
- Light: Not all seeds are light dependent, but some require light to trigger the germination process. Light dependent specis are often woodland plants like Foxgloves.
Describe the germination process
- Cell Division:
- The radicle (embryonic root) is the first to emerge
- cell division occures in the epicotyl, at the base of the radicle
- The fine root hairs of the radicle begin to take in water and minerals
- Enlargment:
- The plumule starts to grow up
- The growth centre of the plumule is the hypocotyl
- Differentiation:
- epigeal germination: the radicle grows forcing the seed and cotlydons out of the ground (eg. pumkins and courgettes)
- hypogeal germination: cotlyedons stay underground as the plumule elongates (eg. peas)
