B8 Flashcards
What are living things and non living things composed of?
The same types of chemical elements.
What is a mechanistic view?
Life is chemically based and obeys universal, physical, and chemical laws.
What elements make up 98% of the mass of every living organism?
C, H, N, O, P, S
What are Na and K essential for?
Nerves and function.
What is Ca function?
Biological signalling
What is iron important for?
Important component of Haemoglobin
What do plants need molybdenum for?
Incorporate nitrogen into biologically useful substances.
What are macro and micronutrients?
Macronutrients - required in large amounts
Micronutrients - required in trace amounts.
Molecular weight is determined from atomic mass
All contain the same number of entities (atoms/ions/molecules) - avogadros number
What are the macronutrients obtained from water or CO2?
Hydrogen, carbon, oxygen
What are the macronutrients obtained from soil?
N, P, K, Ca, Mg, S, Si
What are the micronutrients obtained from soil?
Cl, Fe, B, Mn, Na, Zn, Cu, Ni, Mo
What is the prevalence of nitrogen?
Proteins, nucleic acids, chlorophyll, deficiency = chlorosis
What is the prevalence of potassium?
Enzyme activator, concentrates in meristems, stomatal regulation, deficient = chlorosis and brown tips.
What is the prevalence of calcium?
Middle lamella, movement of substances through cell membranes, deficiency = terminal bud dead, young leaves hooked and withered, roots die.
What is the prevalence of phosphorus?
Respiration, cell division, high energy compounds, deficiency = stunted growth, leaves darker green, lower leaves purple.
What is the prevalence of magnesium?
Chlorophyll, enzyme activator, deficiency = yellowing of leaves between veins
What is the prevalence of sulfur?
Part of some amino acids e.g. cysteine, Fe-S proteins important in electron transfer, deficiency = chlorosis, dead spots, veins lighter in colour.
What is the prevalence of iron?
Respiration, chlorophyll formation, deficiency = large veins remain green but chlorosis in remainder
What is the prevalence of manganese?
Enzyme activation, photolysis, deficiency = dead spots, veins remain green, chlorosis effects on young leaves
What effects the amount of essential elements plants get?
Often one limiting nutrient, uptake influenced by environmental conditions. Soil pH, saturation. Can also be harmful in high amounts.
How does uptake of inorganic nutrients occur?
Uptake takes place through epidermis of root and is usually an active process requiring the expenditure of metabolic energy. Uptake often aided by mycorrhiza, particularly through phosphorus uptake. Transport across root appears to be mainly along symplast pathway (protoplast to protoplast via plasmodesmata). Evidence suggest that ions are loaded into xylem vessels.
Uptake of inorganic nutrients - cation exchange capacity?
Cations attracted to negative charged soil particles. K+ higher in roots therefore harder to uptake - active transport against conc gradient.
How is ion uptake an active process?
Mineral composition of roots is different to the soil e.g. higher K+ conc in root. Thus ion uptake is selective e.g. ratio of k+:na+ higher in roots. Some ions are taken up against a chemical potential gradient which requires an input of energy I.e. active. Nitrate and phosphate must be transported against an electrochemical gradient - they are both anions.
How are inorganic nutrients transported to the shoot?
Mineral nutrients are transported upwards in xylem (transpiration stream). Some nutrients move laterally from xylem into surrounding tissue of roots and shoots. Others transported to leaves. Active transport systems supply specific cells with nutrients. Mg, Fe, and N needed to build chlorophyll in leaves. Nutrients imported into leaves via the xylem may be exchanged with the phloem and translocated with sucrose.
What is mycorrhiza?
Intimate, mutualistic, symbiotic association between root and fungus. Helps roots obtain mineral nutrients, fungus gets sugars in return. 2 types - ectomycorrhiza, important to forest trees, endomycorrhiza, present on the roots of most plants.
Endomycorrhiza
The fungus penetrates the outer cortex and makes intimate contact with the cell membrane but does not enter protoplasm. Phosphorus is supplied to the plant cells via arbuscules. Vesicular-arbuscular mycorrhiza are very common in herbaceous plants.
Ectomycorrhiza?
Fungus forms a sheath around the root and grows between cells to form hartig net. Form mushroom fruiting bodies.
What are orchid mycorrhiza?
Orchidaceae family has more than 20,000 species. All mycoheterotrophic at one stage - usually as seeds, seeds very small with no nutrient reserves. Fungal symbiont provides carbon during germination.
What relationship do wintergreen, willow, and girdled knight have?
Pyrola minor has ectomycorrhizal association with tricholoma cingulatum and salix caprea. The fungus is like a pipe allow nutrients to pass between the willow tree and wintergreen.
What sites have unique soil properties?
Brownfield sites
What forms of nitrogen are available to plants?
Nitrate (NO3-) - important in many ecosystems, and for crops
Ammonium (NH4+) - in acidic soils
Nitrogen (N2) - only plants that have symbiotic relationship with N-fixing prokaryotes.
Organic nitrogen - parasites, carnivorous plants.
What happens in nitrate (NO3-) assimilation?
What happens in nitrate (NO3-) assimilation?
NO3- -uptake> NO3- -2e- nitrate reductase> NO2- -6e-> NH4+ -2e-> amino acids -> proteins, nucleoid acids, other organic N. Requires energy and reducing power. Reduced ferredoxin required.
What happens in Nitrogen fixation (N2 fixation)?
Root symbiosis - legumes : rhizobium. Lead symbiosis - gunnera
What is nitrogen fixation catalyse by?
Nitrogenase
Nitrogen fixation - what is nitrogenase?
A large protein complex associated with the prokaryote partner. It contains Mo and Fe and catalyses the following reaction.
N2 + 8H+ + 8e- + 16ATP -> 2NH3 + H2 + 16ADP + 16 Pi
Requires lots of energy supplied by plant
Requires reduced ferredoxin
Requires anaerobic conditions
What happens with nitrogen fixation in legumes?
Nitrogenase activity is inhibited by oxygen. Nodule cells make leghaemoglobin, which binds to oxygen. Rhizobium forms an infection thread through root hair, root cells undergo mitosis to form nodule.
What are the impacts of nitrogen pollution?
Historically limits plant growth. Human activity increased N emission and deposition. Short term acts as fertiliser. long term disruptive effects. Disrupt natural cycle C:N ratios. Bryophytes most sensitive. Eutrophication and acid rain. Favours growth of invasive species. Phase shifts of plant communities, global problem.
