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SU FOR 232 - Plant Adaptations 2

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FOR 232 1st Edition Lecture 7Outline of Last Lecture I. Why are plants green?II. LightIII. PhotosynthesisIV. Shade ToleranceV. Competition of lightVI. Morphological AdaptationsVII. PhotoperiodismVIII. ProvenanceIX. Flowering timesX. Spring phenologyOutline of Current Lecture: I. Climate and VegetationII. Leaf Size and the leaf boundary layerIII. Different thermal thresholds in plantsIV. Dark RespirationV. Different plant species have different thermal nichesVI. Water uptake through the SPACVII. Differences in drought toleranceVIII. Nutrient cycling within the SPACIX. Morphological and Physiological Adaptations of Riparian PlantsCurrent LectureI. Climate and Vegetation:a. Climate strongly influences vegetation communities precipitation and streamflowamounts, water temperature, and many other key ecosystem characteristics.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Complex and dynamic hydrology creates complex vegetation patternsc. Vegetation and Slope Aspect:i. North facing vs. south facingII. Leaf Size and the leaf boundary layer:a. Smaller and lobed leaves increase surface area for heat exchange i. Increase turbulence ii. Increased BL mixing III. Different thermal thresholds in plants:a. Rubisco is used in all photosynthetic pathwaysb. PEP-C is used in C4 plants and CAM plants, and has a higher thermal maximumc. That’s why C4 ( examples: corn, sugar cane, sorghum) and CAM plants (examples:succulents) grow well in hot climates.IV. Dark Respirationa. Dark respiration is needed for plants to complete physiological functionsb. But it’s a drain on their carbon supplyc. Note how respiration is non-linear with temperature. Above 15 degrees it rises ata greater rate.d. Respiration cuts down the amount of carbon plants can permanently fix, especially at high temperaturee. Net Photosynthesis (PS) is the height of the gross PS line above the respirationf. Net PS is the residual (what’s left over)V. Different plant species have different thermal niches:a. Acclimation to seasons:i. Some plants shift their physiology with the seasonsb. Cumulative Degree-Days to Mark Biological timei. Degree-days are an alternative way to mark development time ii. Established method in agriculture and pest managementiii. Daily degree-days: Dd = Tm – θiv. Cumulative degree-day threshold: D* = Σ°Ddc. Plant ranges can be predicted b climate degree-days related to their thermal tolerancesVI. Water uptake through the SPACa. SPAC (soil-plant-atmosphere continuum)b. Remember, water always moves down-gradient (not always downhill)c. Water is pulled by water potential forcesVII. Differences in drought tolerancea. Remember intolerant and tolerant drought species from last lectureb. Root adaptations to water scarcity i. As water becomes limiting, plants put more biomass into roots to capturea scarce resourceii. There can be drought adaptation differences within the same genusiii. Drought adapted species invests more in rootsiv. The rainforest species grows faster when water is abundantv. Higher water supply allows plants to support larger leavesVIII. Nutrient cycling within the SPACa. Leaf nitrogen concentration predicts plant photosynthetic capacityb. Plants also invest more in roots when nutrients are scarcec. Leaf nitrogen, leaf longevity and photosynthetic capacityi. Long-lived leaves have less nitrogenii. Less nitrogen means lower PS capacityIX. Morphological and Physiological Adaptations of Riparian Plantsa. Riparian zones(where land communities meet river communities) are high-energy, wet environments.b. Plants need to adapt to both long-term, chronic stress and short-term resource pulsesi. Example: flooding, sediment deposition, physical abrasion and stem breakagec. Adaptations includei. Ability to grow on unstable substrates (boulders, unconsolidated sediments LWD)ii. Establish on floodplain mineral soilsiii. Grow in saturated of flooded soilsiv. Develop seeds or plant fragments well suited for dispersal and survival in riverine areasd. Functional Adaptations of Plantsi. Invader- produces large numbers of wind and water disseminated propagules that colonize alluvial substratesii. Endure- re-sprouts after breakage f burial of either the stem or roots fromfloods or after being partially eatediii. Resister- withstands flooding for weeks during the growing season; also withstands moderate fires and disease epidemicsiv. Avoider- lacks adaptations to specific disturbances types. Life cycle often completed between disturbance events.e. Adaptations of wetlands plants to anoxic environments:i. Aerenchyma (hollow tissue for conducting nutrients and air to roots)ii. Lenticels (stem pores to allow direct gas exchange)f. Adaptations to frequent disturbances:i. BreonadiaSalicina is adapted to grow on bedrock in South Africa rivers where it can withstand substantial flooding and if severely damaged to able to re-sprout from the remaining stems and branchesg. Reproductive Strategies:i. Balancing sexual with asexual reproductionii. Mode of seed dispersal iii. Optimizing seed sizeiv. Timing of dormancyv. Seed


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