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Lecture # Date _____ Chapter #35~ Plant Structure and Growth
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Angiospermophytes: Flowering Plants!
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Angiosperm structure Three basic organs: 1) Roots (root system)
fibrous: mat of thin roots taproot: one large, vertical root Branching and Root hairs increase surface area for mineral ion and water uptake. 2) Stems axillary bud: between leaf and stem, potential to form branch shoot usu. dormant in young plants. terminal bud: apex (tip) of young shoot, where most shoot growth occurs apical dominance: terminal bud inhibits axillary bud growth (prune?) 3) Leaves Blade (flattened) Petiole (Stalk)
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Angiosperms: MONOCOTS VS. DICOTS
(Seed leaf) Mono vs. dicot Fibrous root system taproot usu. present
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Tissue Distribution in Dicot Stems
Vascular bundles (xylem and phloem) Surrounded by ground tissue (xylem faces pith and phloem faces cortex in dicots) Be able to draw and label!
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Tissue distribution dicot leaf
Be able to draw and label!!
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Primary Tissues of Leaves
Epidermis/cuticle (protection; prevents desiccation) Stomata Guard cells Mesophyll: ground tissue between upper and lower epidermis palisade (most photosynthesis) spongy (gas circulation)
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Structure and Function of leaves
Explain the relationship between the distribution of leaf tissues and their functions: Absorption of light Gas exchange Support Water conservation Transport of water and products of photosynthesis
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Modified roots, stems and leaves
Storage roots– roots swollen with food. (ex. Carrot) STEMS Stem tubers= parts of the stem that grow down into the ground and are used for food storage (ex. Potato) LEAVES Bulbs= leaf bases– used for food storage (ex. Onion, tulip) Tendrils= outgrowths from leaves that allow plants to vine. (ex. Vining plants)
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Dicots have… Meristems (perpetually embryonic parts that make new cells for plant growth) apical: tips of roots and buds; primary growth (height of plant) lateral: cylinders of dividing cells along length of roots and stems; secondary growth (girth of plant); Produce wood
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Control of Plant Growth
Plant growth is controlled by hormones: Ex. Auxin and phototropism Other factors also affect growth… ex.
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Terrestrial Plant Support
Thickened cellulose Cell turgor Lignified xylem (lignin– a hardening agent found in wood)
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End of IB STUFF
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Secondary Growth Two lateral meristems
(TREE RINGS) Two lateral meristems 1. vascular cambium ~ produces secondary xylem (wood) and secondary phloem (diameter increase; annual growth rings) 2. cork cambium ~ produces thick covering that replaces the epidermis; produces cork cells; cork plus cork cambium make up the periderm; lenticels (split regions of periderm) allow for gas exchange; bark~ all tissues external to vascular cambium (phloem plus periderm)
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Plant tissue Systems Dermal tissue system (epidermis): single layer of cells for protection Cuticle– waxy coating secreted by epidermis of leaves Root hair epidermis used for absorption Vascular tissue system (material transport) xylem: water and dissolved minerals from roots to shoots 2 cell types: tracheids & vessel elements: elongated cells dead at maturity phloem: food from leaves to roots and fruits sieve-tube members: phloem tubes alive at maturity capped by sieve plates (porous); companion cells (nonconducting) connected by plasmodesmata to sieve tube member. P.681 Ground tissue system– makes up most of the young plant (photosynthesis, storage, support): pith and cortex
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Plant Tissue Cell Types
Parenchyma primary walls thin and flexible; no secondary walls; large central vacuole; most metabolic functions of plant (chloroplasts) Collenchyma unevenly thick primary walls used for plant support (no secondary walls ; no lignin– a hardening agent) Sclerenchyma support element strengthened by secondary cell walls with lignin (may be dead; xylem cells); Two types = fibers (long, occur in bundles) and sclereids (shorter, irregular, nutshells etc.)
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Plant Growth Life Cycles annuals: 1 year (wildflowers; food crops)
biennials: 2 years (beets; carrots) perennials: many years (trees; shrubs) Meristems (perpetually embryonic) apical: tips of roots and buds; primary growth lateral: cylinders of dividing cells along length of roots and stems; secondary growth (wood)
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Primary growth Roots root cap~ protection of meristem
zone of cell division~ primary (apical) meristem zone of elongation~ cells elongate; pushes root tip zone of maturation~ differentiation of cells (formation of 3 tissue systems)
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Primary Tissues of Roots
Stele~ the vascular bundle where both xylem and phloem develop, (also, the entire collection of vascular tissue in roots and stems) Pith~ central core of stele in monocot; parenchyma cells Cortex~ region of the root between the stele and epidermis (innermost layer: endodermis) Lateral roots~ arise from pericycle (outermost layer of stele); just inside endodermis, cells that may become meristematic
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Leaf structure
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Summary of primary & secondary growth in a woody a stem
PRIMARY PRIMARY LATERAL SECONDARY MERISTEMS TISSUES MERISTEM TISSUES Protoderm Epidermis Secondary phloem Primary phloem Vascular Procambium cambium Secondary Primary xylem xylem Ground meristem Ground Pith & tissue: Cortex Cork cambium Cork Apical meristem of stem Periderm
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Hydrophyte Characteristics
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