Life: The Natural World Week 8 Notes, Chapter 6
Life: The Natural World Week 8 Notes, Chapter 6 Biol 1012
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This 3 page Class Notes was uploaded by Madison Lovegren on Thursday October 13, 2016. The Class Notes belongs to Biol 1012 at University of Northern Iowa taught by Barton L Bergquist in Fall 2016. Since its upload, it has received 4 views. For similar materials see Life: The Natural World in Biology at University of Northern Iowa.
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Date Created: 10/13/16
Chap. 6 Part A Net Photosynthesis= Gross photosynthesis respiration Rates vary with temp. Chemical bonds Covalent Hydrogen weakest Ionic Leaf Shape More lobes= more surface area, more effective heat loss than those with unlobed shapes Air flow past/through lobes of the leaf helps dissipate heat Net carbon gain is the result of net photosynthesis and net respiration throughout the entire plant Leaves contribute to gain Root and stems, if nonphotosynthetic contribute to loss Plants and even leaves on a single plant vary in their light compensation and light saturation points relative to their sun/shade environment Comparisons between sun and shade grown plants clearly demonstrate the adaptations for each condition Part B Leaves receive more resources and grow larger, but thinner, when less light is available a compensation enabling more photosynthesis under those conditions Phenotypic plasticity Shade tolerant species can adapt to high light levels, but shade intolerant species can’t adapt to low light levels Water Stress Effects 1. Closed or partially closed stomata 2. Reduces water loss, but also reduces CO2 uptake, photosynthesis and heat dissipation 3. Some plants curl leaves, others wilt both reduce surface area and heat gain 4. Prolonged water stress leaves lose chlorophyll and yellow 5. Still more water distress drop leaves, oldest first, dieback of twigs and branches C4 Plants do Photosynthesis using 2 sites, 2 diff. types of cells 1. CO2 enters mesophyll cells 2. Reacts with PEP, produces, OAA 3. OAA becomes malic acid (MA) and aspartic acid (AA) 4. MA & AA transported to vascular bundle (VB) cells and broken into CO2 5. CO2 then goes through C3 cycle Advantages 1. Bypasses inhibitory Where there is less water and/or more heat, C4 plants do better Crassulacean Acid Metabolism (CAM) Pathway 2 pathways like C4 pants, these are in the same mesophyll cell, but operate at diff. times of day avoids In response to less water, plants can grow more roots and get more water And of lesser resources go to build leaves, smaller leaves, less water loss Even related species can show differences in root mass/leaf area ratio and biomass gain relative to water availability The maximum rate of photosynthesis for C4 species occurs at higher temps as compared to C3 species Cold Tolerance Cold (Frost) Hardiness Plants become more hardy as seasons change but this is lost when the plants start to grow in the spring, then less frost hardy In experimental conditions: Some trees have survived 196 degrees C Some seeds have survived temps. a few degrees above absolute zero Macronutrients needed in large amounts carbon, C hydrogen, H oxygen, O nitrogen, N calcium, C phosphorus, P magnesium, Mg sulfur, S sodium, Na potassium, K chlorine, Cl 10/13 Nitrogen uptake by roots increases with nitrogen concentration in the soil Nitrogen uptake influences the amount deposited in the leaves Maximum rates of net photosynthesis are proportional to leaf nitrogen concentrations Fertilizing with nitrogen can be important for maximum photosynthetic rates resulting in more plant growth and crop yield Growth responses to nitrogen vary with species Species from a normally low nitrogen environment benefit by continuing to grow more relative to N availability Species with longer lived leaves have lower leaf nitrogen and lower rates of photosynthesis. Building leaves is “costly”” so keeping “low photosynthetic” leaves longer gives more time to pay back the cost Advantage can avoid stress under lownutrient conditions
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