Download as PDF, PPTX
Seed germination2.pdf
- 1. Plant Growth: anirreversible change in the size of a cell, organ or whole organism. Differentiation: Cells taking on specialized form and function. Plant Development: the orderly and progressive change from seed germination through juvenility, maturity, flowering and fruiting.
- 2. Seed Seedling Mature plants Flowering Fruiting Plant LifeCycle (1) How is a seed formed? (2) How does a seed become a seedling? (3) How is shoot formed? (4) How is root formed? (5) How is a flower formed?
- 3. (1) How isa seed formed? (2) How does a seed become a seedling? (3) How is shoot is formed? (4) How is root is formed? (5) How is a flower formed?
- 4.
- 5.
- 6. Male and FemaleGametophyte Gametophyte – embryo sac Gametophyte – anther Gamete – egg Gamete – two sperm cells (in pollen grain or tube) Male Female
- 7. 21-14 Anther Tapetum (nutritive) Epidermis Raven et al.,1999; Biology of Plants Anther (lily) Pollen sac Pollen mother cells (Microsporocytes)
- 8. Tetrad (n) Free microspores (n) Mature pollen (n) Nucleusof vegetative cell Generative cell Pollen mother cell (Microsporocyte) (2n) Meiosis Pollen Development “„diploid‟” “„haploid‟”
- 9. Ovule Development micropyle funiculus outer integument inner integument nucellus20.8 Esau, 1977; Anatomy of Seed Plants embryo sac
- 10. Megasporogenesis (2n) (n) (n)(n) Meiosis Megasporocyte (mother cell) “Megasporogenesis”
- 11. Egg Cell Differentiation Buchananet al., 2000’ Biochemistry and Molecular Biology of Plants
- 12. Haploid Egg Antipodal cells Eggcell Synergid cells Central nuclei
- 13.
- 14. Double Fertilization Antipodal cells Centralnuclei Egg cell Synergid cell Sperm nuclei Endosperm Embryo
- 15.
- 16. Simplified Structure ofA Mature Seed Seed coat Embryo Endosperm Seed coat is dead tissue. It protects everything inside it. Embryo is a minute plant . Endosperm provides energy for seed germination and early seedling growth.
- 17. (1) How isa seed formed? (2) How does a seed become a seedling? (3) How is shoot formed? (4) How is root formed? (5) How is a flower formed?
- 18. Dry seeds Imbibedseeds Water Uptake: the First Event in Germination
- 19. Bewley, Plant Cell EventsOccur during Seed Germination
- 20. Water Relations andSeed Germination High water availability Medium water availability Low water availability
- 21. Temperature and SeedGermination
- 22. Some Seeds RequireLight for Germination Dark Dark Light
- 23. Tomato Seed Anatomy Endosperm Seedcoat Embryo 0.5 mm
- 24.
- 25.
- 26. Involvement of ExpansinGenes in Seed Germination LeEXP4 Dissecting seed LeEXP8
- 27. Organic Seed Dormancy •Endogenous • embryo characteristic prevents germination-epicotyl, hypocotyl, radical • Exogenous • characteristic of structures - seed coats, fruit walls, including endosperm or perisperm prevents germination
- 28. Types of SeedDormancy • Physiological • Morphological • Morphophysiological • Physical • Physical & physiological • Chemical • Mechanical
- 29. Physiological Dormancy • Nondeep •Intermediate • Deep
- 30. Causes of Physiological Dormancy •Covering restricts oxygen • Inhibitors in coverings • Embryo cannot break through physical barriers • Endosperm restrict embryo growth • Interaction between embryo and covering • Abies alba, Castanea sativa, Corylus avellana, Euonymus europaeus, Juglans nigra, Juglans regia, Juniperus, Prunus avium,Rhamnus frangula, Vaccinium myrtillus • Carpinus requires warm followed by cold stratification • Elaeagnus umbellata- chemicals shortened prechilling & increase germination
- 31. Nondeep Physiological Dormancy • Germinateover a narrow range of temperatures • Excised embryos usually grow • Broken by short periods of prechilling • Require germination temperature above 15°C • Broken by chemicals- potassium nitrate, thiourea, kinetin, ethylene, gibberellins • Light required for germination • Arbutus unedo –can germinate in dark • Ulmus glabra- no prechill • Vaccinium- long period of light required, GA reduces length of light
- 32. Intermediate Physiological Dormancy •Excised embryos will grow • As much as 6 months prechilling needed • Gibberellins, kinetin, thiourea can shorten prechilling requirement • Acer negundo, Acer pseudoplatanus, Acer saccharum, Corylus avellana, Fraxinus americana, Fraxinus pennsylvanica • Fagus sylvatica – ethylene accelerated and increased germination at 15°C, at 5°C chemicals no better than water soak on germination, GA3 increased germination of unchilled seeds at 15°C, 10 weeks prechill negate chemical effect (Seed Sci 2004, p21-33)
- 33. Deep Physiological Dormancy •Excised embryos do not grow or produce abnormal seedlings (Prunus will) • Long prechill requirement • Chemicals do not affect germination of intact seeds • Sorbus aucuparis – secondary dormancy induced above 20°C, germinates best at 1-3°C • Acer platanoides, Acer tartaricum, Malus domestica, • Prunus persica – 90 days prechill • Prunus mahaleb – 100 days prechill • 3 to 5°C best germination temperature for Prunus mahaleb, Prunus padus
- 34. Morphological Dormancy • Morphologyof embryo not developed • Temperate families- Apiaceae, Ranunculaceae • Tropical families – Annonacease, Arecaceae, Degeneriaceae, Lactoridaceae, Monimiaceae, Myrsticaceae, Winteraceae
- 35. Morphophysiological Dormancy • Underdevelopedembryos • Embryo growth and dormancy break required • Embryo grows first then dormancy broken or both at same time • Vary warm, moist and cold stratification periods • Viburnum- epicotyl dormancy, warm for radical then cold for epicotyl • Fraxinus excelsior, Magnolia acuminata
- 36. Physical Dormancy • Presentin 15 angiosperm families • Large embryos with food reserve in embryo not endosperm • Hilum impermeable in Cercis siliquastrum • Impermeable in seed coats- micropyle, hilum, chalazal area, impermeable palisade cells • Embryo is not dormant • Air drying during development intensifies hardness • Cytisus scoparius – dry heat(65°C) for 2 minutes, or acid for 30 minutes • Crataegus in warm climates only endocarp dormant • Robinia pseudoacacia, Laburnum anagroides
- 37. Physical & PhysiologicalDormancy • Embryo dormancy usually broken first • Germinate at low temperatures (5, 10, 15°C) • Prechilling breaks physiological dormancy • Hot water, acid, or mechanical scarification effective before prechilling • Cercis siliquastrum – 16 weeks prechilling = 77% germination(Jordan source)(2004 Seed Sci p 255-260) • Cersis canadensis, Cotinus coggygria, Cotinus obovatus, Sambuscus • Tilia- endosperm is inhibitor, excised embryos grow • Crataegus – 3 month periods of cold-warm-cold- warm-cold=55% germination, apomixis common
- 38. Chemical Dormancy • Inhibitorsin embryo, endosperm, seed coat • Leaching or seed coat removal • Seed may have physiological dormancy too so need prechilling • Abscisic acid inhibits germination when applied exogenously • Nickel (20 mg/liter) increased germination of Picea abies
- 39. Mechanical Dormancy • Stonyendocarps • Embryos with deep physiological dormancy - require long prechilling • Anacardiaceae, Cornaceae, Juglandaceae, Nyssaceae, Oleaceae • Cornus sanguinea – 94% germination at 12 weeks prechilling, 81% germination at 12 weeks warm + 12 weeks cold stratification(2004 Seed Sci p 1-4) • Cornus mas- 18 week warm + 15-18 weeks cold stratification (Tylkowski 1991) • Cornaceae not morphologically dormant • Elaeagnus angustifolia – snip both ends • Rosaceae - warm maturation temperature prior to collection reduced dormancy
- 40. Mattoral Germination Conditions • Meanoptimum germination temperature for trees about 21°C – during cool season when soil is moist • Mean optimum germination temperature for shrubs about 19°C • Shrub seed germinate in light and dark • No shrub seed has morphological dormancy (underdeveloped embyros)
- 41. Boreal & NorthTemperate Subalpine • Pinus cembra- 90-270 days of prechilling • No morphological, morphophysiological, physical dormancy in species • Pinus mugo, Picea abies – nondormant
- 42. (1) How isa seed formed? (2) How does a seed become a seedling? (3) How is shoot formed? (4) How is root formed? (5) How is a flower formed?
- 43.
- 44. Formation of SAM Taizand Zeiger, Plant Physiology
- 45. CZ: central zone;PZ: peripheral zone; RZ: rib zone Shoot Apical Meristem (SAM) Taiz and Zeiger, Plant Physiology
- 46. Leaf Formation: LeafPrimordium
- 47.
- 48. Leaf Anatomy Taiz andZeiger, Plant Physiology
- 49. From: PM Ray,“The Living Plant” Apical dominance is a phenomenon in which the apical bud tends to “dominate” stem growth in the sense that all of the axillary buds immediately below it do not grow out to form branches. Thus the stem grows tall, not wasting resources by growing wide. The idea is that auxin produced in the apical bud is transported down the stem and suppresses the outgrowth of the lateral (axillary) buds. If the tip is cut off the auxin source is removed and the buds begin to develop into branches.
- 50. (1) How isa seed formed? (2) How does a seed become a seedling? (3) How is shoot formed? (4) How is root formed? (5) How is a flower formed?
- 51. Root Systems Taproot system:characterized by having one main root (the taproot) from which smaller branch roots emerge. When a seed germinates, the first root to emerge is the radicle, or primary root. In conifers and most dicots, this radicle develops into the taproot. Fibrous root system: characterized by having a mass of similarly sized roots. The radicle from a germinating seed is short lived and is replaced by adventitious roots. Adventitious roots are roots that form on plant organs other than roots. Most monocots have fibrous root systems.
- 52. Root tip has4 developmental zones Root cap: Protects RAM and push Meristematic zone: Primary root Elongation zone: Rapid cell elongation, rate of division decreases with distance from meristem Maturation zone: Cells get their mature differentiated features. No lateral organs produced from apical meristem to avoid hindrance in soil penetration Branch roots arise from non growing region Root System development
- 53. Cells of theroot epidermis develop projections called root hairs. These elongate by “tip growth” and increase surface area for water and mineral uptake. Root hairs are found away from the root tip, in the region of maturation. Note that the root hair develops as an outgrowth from individual epidermal cells; that is, the root hair is not a cell separate from the epidermal cell. The Figure shows (bottom to top) four stages of root hair development: cell specification, root hair initiation, tip growth, and maturation.