Test 2 Study Guide Plant Physiology – Bielenberg 2/6/2017 Mineral Nutrition What do plants need to grow other than water? Basic concepts- What are they, What’s essential, Deficiency and Toxicity WhaIf you want to learn more check out phsc 101 towson
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t plants are made of [dry mass] -C from the atmosphere dominates the mass of a plant -other essential requirements discovered by developing methods of experimental science Important bc of the close link to agricultural well being -famines/population pressure were a recurring threat -in the early days they had no synthetic fertilizer Availability of fertilizer -as population goes up , the nitrogen we put into the atmosphere goes up -Haber-Bosch Process- N from atmosphere can be used to make fertilizer -all other sources have to be mined (K and P) If it doesn’t come from plants, it comes from rocks Mineral- acquired from the environment in inorganic forms -defined by quantity or role in plant, macronutrients, micronutrients(trace), beneficial elements (nonessential) Plants don’t mirror the mineral content of soil, they actively select what goes in Methodology- new ways to do thingsMineral Nutrient Research -Hydroponic Growth System -Nutrient Film Growth system -Aeroponic Growth System -Ebb and Flow system Defining essentiality -irreplaceable in function of metabolism -direct involvement -deficiency and toxicity -cant complete a life cycle if it not provided Mineral Groups -1- part of carbon compounds -2- important for energy storage or structural integrity -3- remain in ionic form -4-involved in redox reactions Nickel essentiality experiment- plants grown in Ni-free env. survived for generations, until it ran out Some minerals don’t move well in the phloem (ability to be moved around by the plants) Deficiency and toxicity Concentration of nutrient in the tissue- way more important than what is in the soil, etc- plants can only take up what is dissolved in soil Deficiency zone, adequate zone, toxic zone- these all depend on the nutrient and its role in the plant Critical concentration- minimum tissue concentration of a mineral that allows for optimal growthToxicity can occur by a wide variety of mechanisms and the symptoms depend on the nutrient and species in question -transporter competition, oxidative stress Finding Nutrients in the Environment -Nutrient presence vs availability -Nutrient distribution in the environment -Plant exploration of the environment -Symbioses to assist exploration of the environment CEC- Cation Exchange Capacity- measure of the capacity for a soil to absorb and exchange ions Nutrient availability dependent on the pH of the soil Nutrient movement to roots- laterals, root hairs, root system morphology Exploring the soil volume Laterals- enable a greater soil volume to be explored by the root system and allow for local proliferation of roots in nutrient rich patches Root hairs0 cellular extensions of epidermal cells that extend the effective radius of the root for nutrient uptake Root system morphology- species specific, environmental plasticity, optimized for nutrient and water uptake Interception by root- root moves towards the nutrient and takes it in Mass flow- all the water you take from the soil directly around the root also pulls water from further away parts of the soil (and everything dissolved in the water comes with it) Diffusion Depletion zones- for around the roots as a result of the absorption of nutrients Mycorrhizal symbiosesFunctions Exploration- can explore much farther Exchanges- plants usually give C in exchange for N,P, etc from fungi (most useful in lower soil nutrient levels) Diversity Vesicular-arbuscular mycorrhizae- grows within cortical cells, gives P Ectomycorrhizae- grows btwn cortical cells and outside root gives N&P 2/15/17 Ion Transport Ion entrance into roots Symplasmic- through the intracellular spaces of the root Apoplasmic- through the extracellular space of the root Passage cells- (in the endodermis) method to bypass the casparian band Mechanisms by which nutrients cross membranes Simple Diffusion- no energy used, through membrane by conc. gradient Facilitated Diffusion- rapid, passive, protein-assisted Channel proteins- open pores through which transported molecules pass that have selectivity because of biophysical properties(size/charge) (very rapid) Carrier proteins- transported molecules are bound the protein and released from the protein on the other side of the membrane Active transport Primary Pumps- membrane transport proteins that move solutes against the gradient (req. input) ATP-binding cassette (ABC) transporter Group that bind ATP to transport a variety of molecules Major detox mechanism- once molecules are put into the vacuole it wont affect the phys of the cytoplasm or transport Secondary- tying the movement of one ion to the movement of another (no direct E consumption) Symport- protein uses the gradient of H+ to move a substrate against the gradient into the cell Antiport- protein uses the gradient of a substrate to move H+ ions into the cell Michaelis-Mentin Kinetics- find out which type of transport protein is used Graphs rate / external conc. Of transported molecule Channels – linear rate of transport- dependent on external conc. Carriers- bind molecules and display saturation from occupation of all available rxn sites Bent curves tell us that there are multiple transport systems to cover the whole conc. Range Electrochemical potential- depends on conc. Difference between inside and outside of a compartment, charge of the solute Nernst equation ΔEj = (2.3 R T/ zj F) * log10 (Cjo / Cji) Simplified: zjΔEi = 59 * log10 (Cjo / Cji) If ions are at concentrations EQUAL or BELOW that predicted by the Nernst equation: 1. Ions may use PASSIVE diffusion to enter cell, and 2. Ions are excluded, possibly actively removed from cell If ions are at concentrations ABOVE that predicted by the Nernst equation 1. ACTIVE uptake must occur, and 2. Ions can diffuse out of the cell with no energy input Vacuole has a very low pH (comparable with outside the cell) Lots of different transporters are used to move molecules across membranes, which follows the electrochemical potential gradient Ion movement across membranes is determined by electrochemical potential (what is charge across membrane? Nutrient uptake is driven by membrane potential, which depends upon ATP production by the mitochondria, which is affected by oxygen concentration, temperature, and energy supply Transport system (antiport, symport, etc?) We can explain a plants ability to move ions, by the species ability to tolerate the different soil environment (specialized for their environment) Cultivars have figured out that plants with certain transporters adapt it differently to high or low-nutrient environments and have different efficiencies at difference nutrient availability levels (being good at performing well in low nutrient environment OR being good at performing great in perfect conditions) • Examples of transporter complexity for sodium resistance – Root cell exclusion – Root cell sequestration to vacuole – Removal from xylem stream – Re-transport to roots in phloem – Shoot cell sequestration to vacuole Not all species do all of these 2/17/17 Light as energy- Photons are the particular nature of light Energy of a particular photon is called a quantum Iridescent coloration in insects and plants- is it an indicator for pollinators? Ridges on the back of a CD reflect light as a rainbowish thing Objects don’t have colors Have different absorption and reflection of ambient radiation Ridges on leaves and petals, etc.- light bounces off at weird angles so you see dif colors at dif angles Humans only have 2 receptors in their eyes; some organisms have up to 12 (mantis shrimp) Measurement of light- quantity, quality, timing and duration of light treatment Quantity- fluence rate Photon fluence- total number of incident photons Energy fluence(irradiance)- total number of incident energy Visible light relevant to photobiological processes are referred to as photosynthetically active radiation (PAR) Interested in how fast photons come in- energy/sec or photons/sec What happens to light energy that hits a leaf?- very little is captured Three routes of heat loss from leaves Reradiation- the sun is a black body radiator- emits light bc it is really hot- largest energy input into our atmosphere+ Sensible heat loss- boundary layer effects Transpiration- stomatal conductance, boundary layer, vapor pressure deficit- is main way plants shed off heat Everything emits radiation- heat, etc Latent heat of vaporization-Temp needs to be regulated in leaves Photosynthesis “Synthesis using light” General reaction: 6 CO2 + 6 H2O → C6H12O6 + 6 O2 3 stages of photosynthesis: Light capture and conversion to chemical energy To convert light energy into reducing agents such as ATP and NADPH Capture by pigments; pigment color dependent on preferential absorption of particular wavelengths of light and the reflection of others Electrons have many excitation states, which are at specific energy intervals; if the energy of a photon matches that of the energy interval of a particular molecule, that molecule can absorb that photon Pigments have different absorption spectrums depending on molecular makeup – chlorophylls are green pigments- a and b are slightly different but cover different parts of the spectrum CO2 fixation of step Carbon cycling- rearrangement of C compounds into what the plant needs