Term
| Where do root hairs develop and what are they associated with? |
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Definition
| Specialised trichoblast cells in the root epidermis. The sorptive surface of the roots is associated with the rhizosphere |
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Term
| What three factors are exceeding the planetary boundaries and safe operating space? What does this mean in regards to nutrients? |
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Definition
| Biodiversity loss, Reactive nitrogen and phosphorous levels, climate change. Excess N and P levels can act as pollutants in plant systems |
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Term
| What are the essential macronutrients and micronutrients? Which originate from air not soil? |
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Definition
Macronutrients (large amounts needed): N,P,Mg,Ca,K,S,Si
Micronutrients (small amounts needed): B,Na,Cl,Mn,Fe,Co,Ni,Cu,Zn,Mo
Air: C,O,H |
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Term
| When is a nutrient essential? |
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Definition
In it's absence, a plant can not complete its life cycle
It cannot be replaced by another element |
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Term
| What are the main fertilisers in agriculture? |
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Definition
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Term
| What are some differences between nutrient cycles in forest and agricultural systems? |
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Definition
| Farm: Less organic N in soil, N fertiliser added, less amino acids, more ammonium and nitrate, also release greenhouse gases |
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Term
| 50% of people on Earth fed as a result of synthetic nitrogen fertiliser use, true or false? |
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Definition
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Term
| What is nitrogens role in plants? |
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Definition
Determines growth and productivity
Accounts for 90 percent of plant acquired nutrients from soil
Low efficiency of fertiliser N use by crops
Results in massive pollution problems
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Term
| How to nitrogen fixing root nodules work? |
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Definition
| 'Housing estates' for specialised prokaryotes that have the enzymes to break N2 into reactive NH3 which is then converted to amino acids and proteins |
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Term
| Some plants have N fixing nodules on their stems, true or false? |
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Definition
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Term
| Which nutrients present in the soil are soluble and mobile, which are insoluble and have to be solubilised by the root, and which can be exchanged by the root from exchange sites? Why? |
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Definition
Anions such as NO3- are soluble and mobile
Cations such as Ca2+ can be exchanged by the root from exchange sites
Other nutrients such as P are insoluble andhave to be solubilised by the root.
Because soil particles mostly have a negative charge, termed 'cation exchange capacity' |
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Term
| How are nutrients transported towards root hairs? |
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Definition
Diffusion: Nutrient transport along concentration gradient
Mass flow: Transport of bulk soil solution along water potential gradient driven by transiration |
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Term
| What is the role of 'good' rhizosphere bacteria? |
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Definition
| To enhance plant growth via numerous beneficial effects including improved nutrient supply |
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Term
| What are the two main mycorrhizal symbioses? |
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Definition
Endo-mycorrhizal: form arbusculs as interface between fungus and plant INSIDE root cells, exchange soil-derived nutrients for photosynthates. Most common
Ecto-mycorrhizas: Form hartig net around root tips and hyphae grow between root cells, exchange soil derived nutrients for photosynthates |
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Term
| What is the draw of mycorrhizas on photosynthates? |
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Definition
| If well supplied with nutrients (fertilisers), plants may down-regulate fungal colonisation. This can lead to degraded soils. |
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Term
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Definition
| Dense rootlets formed by comparitively few plant species. Functionally similar to mycorrhizas? |
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Term
| What do plants rely on to access nutrients |
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Definition
Mycorrhizas (breakdown of organic matter)
Endophytic bacteria (N fixation)
Cluster roots |
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Term
How do roots alter soil in the rhizosphere?
Can exude:
H+ to acidify soil
Reductants change nutrient solubility
Chelating compounds capture nutrients
Enzymes to break down organic matter
Organic compounds including sugar, amino acids |
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Definition
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Term
| What facilitates ion transport across root cell membranes? |
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Definition
| Ion gradients and transporter proteins/channels (ATPases) requires energy |
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Term
| What types of transporters exist in ion uptake? |
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Definition
High affinity transporters (facilitate influx at low external concentrations)
Low affinity transporters (facilitate influx at high concentrations) |
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Term
| How are nutrient ions transported from soil to shoot? |
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Definition
| Via xylem flux and throughout the plant via xylem and phloem transport |
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Term
| What is the 'law of minimum' in nutrient deficiency? |
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Definition
| Growth is controlled not by the total amount of resources available, but by the scarcest resource (limiting factor) |
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Term
Which is better, high uptake of N by efficiently extracting N from soil/fertiliser
or
Efficient use of the acquired N for growth? |
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Definition
| Combining both N efficiencies is ideal |
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Term
| What is an environmentally and financially favourable alternative to adding fertiliser? |
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Definition
| Breeding crops with a better ability to acquire nutrients from the soil |
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Term
| What regulates root anatomy and root-to-shoot biomass allocation? |
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Definition
| The plants genotype and environmental triggers such as nutrient availability |
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Term
| How do plants respond to nutrient availability? |
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Definition
| By shifting allocaton of biomass to roots or shoots (roots when deficient) |
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