Physiology The study of life processes

Transcription

1 Physiology The study of life processes John Punches Oregon State University Plant Life Functions Transpiration (water movement) Photosynthesis (energy capture) Respiration (energy release) Tissue Synthesis (growth) Maintenance, Storage, Defense 1

2 Transpiration = water movement Water Vapor Water Xylem = plant plumbing Water is pulled through xylem under negative pressure (tension or vacuum) 2

3 Transpiration in Leaves water water vapor Stoma & Guard Cell Taiz & Zieger Plant Physiology, 3 rd Ed. Stoma Guard Cell 3

4 Transpiration requires soil moisture functional root system functional stem & branch plumbing functional leaves Transpiration Rate Transpiration rate is controlled by stomatal aperture in response to relative humidity temperature light wind under constraint of water availability plant nutrition 4

5 Water Vapor Water Stomatal Control Open Closed 5

6 Diurnal Fluctuation of Stomatal Aperture Stomata Open Closed 6 am noon 6 pm 9 pm Time Transpiration is Responsible for... Transporting water throughout plant Transporting minerals throughout plant Cooling plant (evaporative cooling) Moving some sugars and plant chemicals Maintaining cell firmness 6

7 Photosynthesis = food production Water + CO 2 are combined to produce simple sugars Water transpiration O 2 is a byproduct CO 2 O 2 Photosynthesis requires light water carbon dioxide green stuff 7

8 Photosynthesis in Leaves water O 2 & water vapor CO 2 photosynthetic products Taiz & Zieger Plant Physiology, 3 rd Ed. Chloroplast 8

9 A Chloroplast Taiz & Zieger Plant Physiology, 3 rd Ed. Photosynthetic Apparatus Taiz & Zieger Plant Physiology, 3 rd Ed. 9

10 Photosynthetic Pathway Taiz & Zieger Plant Physiology, 3 rd Ed. Solar rays reaching earth Wavelength in Nanometers 10

11 Capturing Light Photosynthetic Pathway Taiz & Zieger Plant Physiology, 3 rd Ed. 11

12 The Calvin Cycle RUBP CO 2 + H 2 O ADP Carboxylation Regeneration 3-phosphoglycerate ATP Taiz & Zieger Plant Physiology, 3 rd Ed. Glyceraldehyde-3- phosphate Sucrose, Starch Reduction ADP ATP + NADPH + P i NADP Photosynthetically Active Radiation 0 Percentage of Transmitted Light Reflected Light Absorbed Light Transmitted Light Wavelength (nm) Percentage of Reflected Light Visible Spectrum Taiz & Zieger Plant Physiology, 3 rd Ed. 12

13 Plants can t use all the solar energy available to them. solar energy reaching plant Reflection-transmission Nonabsorbed wavelengths 8% loss 60% loss Heat dissipation 8% loss Metabolism 19% loss 5% Carbohydrate Taiz & Zieger Plant Physiology, 3 rd Ed. Shade Leaf Upper epidermis Palisade mesophyll Water vapor Lower epidermis Carbon dioxide 13

14 Deeper palisade mesophyll Sun Leaf Waxy cuticle Thicker epidermis Water vapor Fewer stomata Carbon dioxide Can photosynthesis occur when water is limited? water O 2 & water vapor CO 2 photosynthetic products 14

15 Factors that Affect Photosynthetic Rate Light Carbon dioxide (CO 2 ) H 2 0 Temperature Light Photosynthesis increases at higher levels of light intensity Photosynthesis decreases at lower levels of light intensity 15

16 CO 2 and H 2 0 Low levels reduce photosynthetic rate High levels increase photosynthetic rate Temperature o is optimum range Decreases dramatically above or below that range 16

17 Respiration = energy release Simple sugars consumed to produce energy O 2 is required Respiration in Leaves O 2 CO 2 17

18 Respiration is Complex! Storage, Phloem transport Pentose phosphate pathway Pentose-P Sucrose Hexose-P Triose-P Starch Hexose-P Triose-P Pentose phosphate pathway Pentose-P CO 2 NADPH Organic acids Photosynthesis CO 2 NADPH Storage ATP Glycolysis NADH ATP Lipid breakdown Citric acid cycle CO 2 Mitochondrion NADH FADH 2 Taiz & Zieger Plant Physiology, 3 rd Ed. Oxidative phosphorylation O 2 Respiration must occur in all living tissues 18

19 Respiration requires carbohydrates oxygen functional carbohydrate transport Transport in Stems Herbaceous Monocot Herbaceous Dicot 19

20 Sugars move through phloem from source to sink H 2 O H 2 O Active loading of sugars into phloem Phloem transport H 2 O Sucrose H2O drawn in to balance solute potential Transpiration H 2 O Pressure driven flow H 2 O Active unloading of sugars Sucrose Taiz & Zieger Plant Physiology, 3 rd Ed. Respiration Rate Temperature O 2 concentration Soil condition 20

21 Temperature Respiration rate increases with increasing temperature May increase to the detriment of the plant Oxygen Low levels reduce respiration rate 21

22 Soil Condition Dense, compacted and water logged soils reduce the amount of oxygen available for respiration A Comparison Photosynthesis produces food stores energy uses water uses carbon dioxide releases oxygen occurs in sunlight Respiration uses food releases energy produces water produces carbon dioxide uses oxygen occurs in dark and light 22

23 Plants use carbohydrates for: Respiration (energy) Growth Reproduction Storage Defensive Compounds Vacuole Nucleus Ribosomes Rough endoplasmic reticulum Mitochondrion Smooth endoplasmic reticulum Taiz & Zieger Plant Physiology, 3 rd Ed. Chloroplast Golgi body 23

24 Storage Membrane protein synthesis Lipid synthesis & membrane assembly DNA Protein synthesis Respiration Photosynthesis Taiz & Zieger Plant Physiology, 3 rd Ed. Poly & Oligosaccharide Synthesis Element Use - Carbohydrate carbon HO CH 2 OH O oxygen hydrogen HO OH OH 24

25 Element Use - Protein O O O O CNHCHCNHCHCNHCHCNHCH R R R R nitrogen Element Use - Chlorophyll HC CH 2 CH 3 magnesium H 3 C H 3 C H N N H Mg II N N CH 2 CH 3 CH 3 O O O C O OCH 3 25

26 Essential Mineral Nutrients Macronutrients carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, magnesium, calcium Micronutrients iron, boron, zinc, copper, manganese, molybdenum, chlorine Mineral Functions in Plants N, S part of carbon compounds (amino acids, proteins ) P high energy molecules, carbohydrate distribution regulation Si, B cell wall structure and formation K, Ca, Mg, Cl, Mn, Na ions involved in regulation, cofactors for enzymes Fe, Zn, Cu, Ni, Mo oxidation & reduction reactions (photosynthesis, respiration, nitrogen fixation) 26

27 Relative Use of Elements Mo 1 Ni 2 Cu 100 Zn 300 Na 400 Mn 1,000 B 2,000 Fe 2,000 Cl 3,000 Si S P Mg Ca K N 30,000 30,000 60,000 80, , ,000 1,000,000 O 30,000,000 C 40,000,000 H 60,000,000 Major Environmental Factors 27

28 Major Environmental Factors Water Atmosphere Temperature Light Soil Water Essential to plant life raw material for photosynthesis carries dissolved nutrients Requirements vary by: species time of year temperature soil environment 28

29 Atmosphere Above ground environment Gaseous elements (CO2, O2, H, pollutants) Relative humidity Temperature Affects many chemical reactions Plants have a temperature range Optimum varies by species Coolseason Warmseason 29

30 Light Required for sustained growth photosynthesis Plants only use light between nm ~60% of sunlight is out of a plant s range How Light Influences Plant Growth Phototropism - plant growth toward light Photoperiodism - affect of the duration of light exposure on growth and development 30

31 Phototropism Normal Erect Growth Plant Bending Toward Light Photoperiodism Long-night (short-day) Hours Cocklebur Short-night (long-day) Henbane 31

32 Soil Moisture Nutrients (mineral elements) Oxygen Microorganisms ph & Nutrient Availability Strong acidity Moderate acidity Iron Manganese Boron Copper & Zinc Slight acidity Nitrogen Phosphorus Potassium Sulfur Slight alkalinity Calcium Magnesium Moderate alkalinity Molybdenum Strong alkalinity 32

33 Environmental Interactions Temperature and Light flowering senescence dormancy cold hardiness Environmental Interactions Water and Temperature stress cold hardiness winter leaf desiccation 33

34 Plant Processes in Balance Water Uptake vs Transpiration Photosynthesis vs Respiration Carbohydrate allocation Nutrient allocation Growth vs Storage vs Reproduction vs Defense Light Energy Above ground = Photosynthesis & Respiration CO 2 O 2 Below ground = Respiration, No Photosynthesis O 2 C 2 Water Vapor Carbohydrate allocation Water Nutrient allocation 34