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Introduction to Plants

Introduction to Plants. Kingdom: Plantae Plants : Cell wall Autotroph (photosynthesis) Multi-cellular 12 Divisions (Phyla) Anthophyta = Angiosperms (flowering plants) Largest # of species (~250,000 - 90% plants) Seed plants: product seed w/in a fruit Key adaptations: flowers & fruits

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Introduction to Plants

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  1. Introduction to Plants Kingdom: Plantae • Plants: • Cell wall • Autotroph (photosynthesis) • Multi-cellular • 12 Divisions (Phyla) • Anthophyta= Angiosperms (flowering plants) • Largest # of species (~250,000 - 90% plants) • Seed plants: product seed w/in a fruit • Key adaptations: flowers & fruits • Sporophytes are trees, shrubs, herbs that flower • 2 main groups: Monocots& Dicots

  2. Monocots vs. Dicots

  3. Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells

  4. Above ground • Stems, leaves Shoot system • Underground (usually) • Roots Root system

  5. A. Roots • Anchors plant, absorbs H2O & minerals, stores sugars/starches • Root hairs – tiny extensions of epidermal cells, increase surface area for H2O and mineral absorption • Mycorrhizae: symbiosis with fungi Root hairs

  6. Fibrous Root (scallion) Taproot (carrot)

  7. Roots

  8. B. Stems • Alternating system of nodes (leaf attachment) and internodes • Function: display leaves • Terminal bud – growth concentrated at apex (tip) • Apical dominance: terminal bud prevents growth of axillary buds; growth directed upward, toward light • Axillary buds – located in V between leaf and stem; forms branches (lateral shoots) • Pinching/pruning – removing terminal bud

  9. Stems

  10. Modified stems • Runner or stolin • Aspen, strawberries, grass • Grow on surface • For asexual reproduction • Rhizome • Iris, ginger, potato, onion • Grow underground • Store food & DNA for new plant • Tuber: end of rhizome • Bulb – underground shoot • Onion • storage leaves

  11. C. Leaves • epidermis of underside interrupted by stomata (pores) • Mesophyll: ground tissue between upper/lower epidermis • Parenchyma: sites of photosynthesis • Cuticle: waxy layer

  12. Three Tissue Systems

  13. A. Dermal Tissue • Single layer, closely packed cells that cover entire plant • Protect against water loss & invasion by pathogens • Cuticle: waxy layer • Epidermis, periderm

  14. B. Vascular Tissue • Continuous throughout plant • Transports materials between roots & shoots • Xylem: transport H2O and minerals up from root • Phloem: transports food from leaves to other parts of plant stele

  15. C. Ground Tissue • Anything that isn’t dermal or vascular • Function: storage, photosynthesis, support • Pith: inside vascular tissue • Cortex: outside vascular tissue

  16. III. Cell Types • Parenchyma: most abundant • Perform metabolism, synthesizes & stores organic products • Collenchyma: grouped in cylinders, support growing parts of plant • Sclerenchyma: rigid support cell • Xylem: water conduction • Tracheids, vessel elements – dead, tubular, elongated cells • Phloem: sugar, organic cmpd. conduction • Sieve tubes, plates, companion cells – alive cells which aid movement of sugar

  17. WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS 100 µm Tracheids Vessel Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Pits COLLENCHYMA CELLS Cortical parenchyma cells Tracheids and vessels (colorized SEM) 80 µm Vessel element Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) Sieve-tube members: longitudinal view (LM) SCLERENCHYMA CELLS 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member 25 µm Plasmodesma Sieve plate Cell wall Nucleus Cytoplasm Companion cell 30 µm 15 µm Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view Sieve plate with pores (LM)

  18. Primary and Secondary Growth(apical vs. lateral meristems)

  19. Concept 35.3 Primary growth lengthens roots and shoots Root Hairs Zone of Maturation: growth & differentiation complete; fully mature cells Zone of Elongation: cells elongate; push root tip ahead Zone of Cell Division: apical meristem; new cells produced Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant

  20. Concept 35.4 Secondary growth adds girth to stems and roots in woody plants • Involves lateral meristems • Vascular cambium: produces secondary xylem (wood) • Cork cambium: produces tough covering that replaces epidermis • Bark = all tissues outside vascular cambium

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