PLANTS

1. PLANTS Chapters 26, 28 - 30

2. Characteristics of Kingdom Plantae • Multicellular • Eukaryotic • Cell Walls of cellulose • Photosynthetic containing chlorophyll a & b • Contain peroxisomes (organelles with enzymes to degrade hydrogen peroxide) • Surplus carbohydrates stored as starch

3. Importance to the Ecosystem • 290,000 different species of plants within very varied environments. • Most plants are terrestrial • They stabilize and build soil • Are habitats for many organisms • Release O2 and absorb CO2 • Are the Producers of food, mainly; rice, beans, soy, corn, grasses and wheat • Moderate surface temperature • Are used as fiber and building material • And they are really pretty!

4. To adapt from an aquatic to a dry ecosystem, terrestrial plants faced a few problems: • Prevent water loss • With a waxy cuticle (cutin) – a water tight sealant that covers above ground plant structures • Stomates with guard cells & stoma that close to prevent water loss (in all but liverworts)

5. Defies gravity • For water transport • Rigid enough to not fall over with gravity and wind Answer Vascular tissue!!

6. Tracheophytes Vascular– possess vascular tissue Make up 93% of all land plants • Xylem (water) and Phloem (food) for transport • Lignified (supported) transport vessels • Roots for water absorption & anchoring plant • Leaves for photosynthesis • Life cycle dominated by Sporophyte (2N) generation

7. Two branches of Tracheophytes • Seedless plants produce spores (Seed- “is a baby plant, inside a box, with its lunch” an embryo with stored nutrients & a protective layer) Ferns,Lycopodia, Horsetails and Whisk ferns

8. Seed Plants - Produce seeds Gymnosperms - have naked seeds (not enclosed inside fruit) on modified leaves forming cones - needle-shaped leaves with thick cuticles Spruce, pines, fir, cedar, larch, redwoods, Sequoia

9. Angiosperms – Flowering plants 90% of all plants Flowers (for scent and color) to attract pollinators Have: Ovaries which will mature into fruit Ovules will develop into a seed Fruit protects dormant seeds and aids in seed dispersal Maple tree seeds

10. Further divided into Dicot vs Monocot

11. Plant Structures

12. Roots: • Absorb water & minerals • Anchorage for plant • Food storage in the form of starch • Transport of water and nutrients • Stems: • Conduct water, minerals and food • Hold leaves upright • Support fruit and flowers • Photosynthesis in some cases (succulents & cacti) • Food storage in some • Leaves • Photosynthesis • Flowers & Fruits • Sexual Reproduction

13. Leaves Organized to maximize photosynthesis & sugar production Acts as a solar collector Four basic layers: • Cuticle– Waxy • Upper epidermis – cells w/o chloroplasts • Palisades mesophyll cells – w/ chloroplasts. Thin narrow cells tightly packed together 4. Spongy mesophyll cells – w/ chloroplasts Loosely packed cells for gas exchange Vein located here with xylem & phloem cells • Lower epidermis withstomates

14. Functioning of the Stomates 90% of the water a plant loses escapes through the stomates Guard cells – modified epithelium w/ chloroplasts and a thickened inner wall. Controls the opening and closing of the stoma. When photosynthesizing, water builds up in guard cells’ central vacuole causing turgidity and opening the stoma. When not photosynthesizing, cells become flaccid and stoma closes

15. Control of stomates to open: • Depletion of CO2within air spaces of leaf • Increase in Potassium ions to guard cells, lower water potential, causing water to diffuse into cells • Blue light receptors in cells triggers proton pump in plasma membrane of guard cells, which promotes uptake of K+ ions causing stomates to open • Active transport of H+ out of the guard cells Control of stomates to close: • Lack of water • High temperatures – stimulates cell respiration & CO2 buildup • Abscisic acid – produced in mesophyll cells in response to dehydration. Signals guard cells to close up

16. Flowers Male: Stamen with anther and filament Female: Carpel (Pistil) made up of the stigma, style and ovary Ovaries contain ovules Receptacle supports carpel Sepals are flower “leaves” for protection Pedicle is flower stem

18. Flower DissectionAlstroemeria, Lily of Peru • Take petals off and count them • Remove stamen (male parts) and count • Determine if it is a mono or dicot • Using a scalpel, cut anther in a drop of water to release pollen. Put a cover slip over. Observe pollen • Isolate pistil/carpal. Feel stigma, see the style and then… • cut pistil down the center through the ovary and observe ovules under the microscope

20. An overview of Angiosperm Reproduction Sporophyte (2N) produces haploid spores by meiosis. Spores (1N) divide by mitosis giving rise to Gametophyte(1N) within pollen grain and ovules Pollination – process of bringing pollen grain to stigma by wind, water, or animal. Gametes(1N) formed by Gametophyte– sperm and egg. Fertilization results in (2N) zygote which divides by mitosis to produce (2N) Sporophyte Sporophytedevelops into embryo and then seed, while ovary becomes the fruit.

22. Gametophyte Development & Pollination

23. Double Fertilization • After landing on stigma, pollen grain begins to germinate, producing a pollen tube extending down to the ovary • Pollen grain nucleus divides by mitosis to form two sperm nuclei • Tip of pollen tube enters ovaryand enters ovulethrough the micropylereleasing the two sperm nuclei • One sperm nucleus fertilizes the egg to produce thezygote • The second sperm nucleus combines with the two polar nuclei to form a 3N nucleus at the center of the embryos sac. This will become theliquidy endosperm (nutrient for the developing seed) Great animation

24. From zygote to seed Each ovule develops into a seed enclosed in a fruit Embryo develops from the zygote Endosperm will be replaced by cotyledons Embryo and cotyledons are protected by seed coat Embryo structure: Hypocotyl – embryonic stem Radicle – embryonic roots Epicotyl – embryonic leaves Cotyledons are high in starch Dicots have two cotyledons like in beans Monocots have one cotyledon - corn

25. From Ovary to Fruit

27. From Seed to Seedling – aka: Germination • Imbibitionis the uptake of water due to low water potential of dry seed. • Seed coat softens and cotyledons expand. Enzymes begin digesting starch. Energy is now available to developing embryo • Radicle is first to emerge from seed. • Hypocotyl forms a hook and when stimulated by light and phytochrome, pulls seed up through soil. • Epicotyl&cotyledonsrise up on strengthened hypocotyl • Epicotyl spreads first true leaves & begins photosynthesizing. • Cotyledons (seed leaves) shrivel and fall off

29. Transport in PlantsHow does water get up to the top of a coastal redwood that is 300ft tall? Movement of water & minerals goes against gravity 3 mechanisms for moving water & minerals: • Transport of water & minerals by individual cells like root hairs –Root pressure • Short distance transport from cell to cell moves the water and minerals around it • Long distance transport within xylem & phloem throughout the entire plant – Transpirational pull

30. Root Pressure – fluid in xylem is pushed up Results from water flowing into stele from soil as a result of osmosis due to a greater water potential in the soil than in the root cells Only good for a few meters as a result ofcapillarity Guttationon the tips of plants in the morning • Transpirational pull – water in xylem is pulled up Transpiration – is the evaporation of water through the stomatescausing negative pressure to develop in xylem from roots to leaves. Cohensionpulls water column up xylem. Transpirational pull-coheshion tension theory – “for every molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in at the root to replace it” Absorption of sunlight drives transpiration due to evaporation of water Regulates plant temperature Increase on sunny, hot, dry, windy days. Rate decreases on humid days A really good animation

31. Transpiration Lab #9 • Procedure: • Select 6 plants that are approximately the same size • Water the plants until the soil is saturated but not draining • Get 6 plastic bags and write #1, #2, etc on each and your teams’ initials • Over plant #1, place a bag that has been misted over the plant and tie it in place, covering the entire plant, leaves, soil and pot. • For #2 - #6, slip the bags onto the base of the plant (the pot) and then wrap the plastic bag with string around the base of the plant. Do not tie it too tightly or you may damage the plant • Mass the plants and record the data in the chart marked Day I. • Place plant #1 in the designated humidity location • Place plant #2 in the designated control area for natural light – Control 1 • Place plant #3 in the designated dark location – Control 2 • Place plant #4 in incandescent artificial light • Place plant #5 in fluorescent artificial light • Place plant #6 in front of the fan as the designated wind location • Get the temperature at each location and record this on the data table • Mass your plants are subsequent days and record the data in the chart provided.

34. % Water loss: Day I – Day II = X/Day I mass Day I – Day III = X/Day I mass

35. % Water loss: Day I – Day II = X/Day I mass Day I – Day III = X/Day I mass

36. Plot your data and the class means for each of the conditions on graph paper. (Condition versus % water loss) • For your formal lab write-up, the following should be included: • Descriptive title • Background • Purpose • Data table • Graph (bar graph) • Discussion

37. Plant Responses - Tropisms • Phototropism – response to light • Gravitropism – response to gravity • Thigmomorphogenesis – change in plant form due to a mechanical disturbance • Thigmotropism – response to gravity. Roots grow down • Hydrotropism • Heat stress • Cold stress • Salt stress • Drought • Flooding Gravitropism

38. Phototropism Controlled by: • Blue light – increases plant growth • Phytochromes – regulatory pigment • Change in light, temperature and humidity • Circadian rhythms – Biological clock in a 24 hr period without regard to environmental changes. (Wake-up time) • Photoperiodism – physiologic response to relative length of night & day to promote flowering. Morning glories • Short-day, long-day, & day-neutral plants – flower in response to the length of darkness they receive • Poinsettias in winter with ~6 hrs of light • Summer plants flowering with 14 hrs of light

40. Onion Root tipApical meristem is high in cytokinins & auxins while cells in the zone of elongation hasgibberillins

41. Experiments on Coleoptiles & Role ofAuxins AColeoptileis a protective sheath enclosing the shoot tip and embryonic leaves of grasses Light causes the auxinto collect away from the light, allowing the cells on the opposite side of the light to elongate and “grow” towards the light due to unequal distribution of the auxins

42. Defense mechanisms Plants have no immune system to pathogens • Cuticle and epidermis • Hairs on leaves • Thorns • Distasteful chemicals and poison – poison ivy, foxglove

43. The Ultimate – “I got you” • Plants can “recruit” predatory animals to aid in their defense such as the Parasitoid wasp. • When caterpillar takes it leaf meal, the plant releases a volatile chemical attractant to signal the parasitoid wasp. • The parasitoid wasp lays and injects its eggs right into the caterpillar’s body • As the larvae hatch, they eat the caterpillar from the inside out. The caterpillar is alive while this is happening but paralyzed!