chapter 35 plant structure, growth, and development
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Chapter 35 Plant Structure, Growth, and Development. Shannon Nugent Austin Wetterau Erin Strong. Anatomy of a Plant. 3 Basic Organs: Roots, Stems, Leaves Absorb water from below and CO 2 from above Root system and Shoot System Both depend on each other - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 35Plant Structure,
Growth, and Development
Chapter 35Plant Structure,
Growth, and Development
Shannon Nugent
Austin Wetterau
Erin Strong
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Anatomy of a PlantAnatomy of a Plant
• 3 Basic Organs:
• Roots, Stems, Leaves
• Absorb water from below and CO2 from above
• Root system and Shoot System
• Both depend on each other
• Roots starve without photosynthesis
• Shoot system depends on water and minerals absorbed
• 3 Basic Organs:
• Roots, Stems, Leaves
• Absorb water from below and CO2 from above
• Root system and Shoot System
• Both depend on each other
• Roots starve without photosynthesis
• Shoot system depends on water and minerals absorbed
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RootsRoots
• Multicellular organ acting as an anchor, absorbs nutrients, and stores carbs
• Most gymnosperms or eudicots have a Taproot - main root
• Lateral roots - roots linked to main taproot
• Monocots - many small roots (fibrous root system)
• Multicellular organ acting as an anchor, absorbs nutrients, and stores carbs
• Most gymnosperms or eudicots have a Taproot - main root
• Lateral roots - roots linked to main taproot
• Monocots - many small roots (fibrous root system)
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StemsStems
• Stem - an organ consisting of system of nodes where leaves attach with internodes
• Axillary bud - in angle of stem and leaf (branch)
• Apical bud - developing leaves
• Buds describe dormancy
• Possible Food storage and asexual reproduction
• Stem - an organ consisting of system of nodes where leaves attach with internodes
• Axillary bud - in angle of stem and leaf (branch)
• Apical bud - developing leaves
• Buds describe dormancy
• Possible Food storage and asexual reproduction
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LeavesLeaves
• Main photosynthetic organ
• Monocots - parallel major veins
• Eudicots - branched network of veins
• Help taxonomists diversify many different plants
• Main photosynthetic organ
• Monocots - parallel major veins
• Eudicots - branched network of veins
• Help taxonomists diversify many different plants
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35.235.2
• Intermediate growth - most plants grow continuously
• Plant life cycle: Annual, Biennial, Perennial
• Meristems make intermediate growth possible
• Initials - sources of new
• Derivatives - new cells from meristem
• Intermediate growth - most plants grow continuously
• Plant life cycle: Annual, Biennial, Perennial
• Meristems make intermediate growth possible
• Initials - sources of new
• Derivatives - new cells from meristem
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35.3• Growth of Roots
– Primary growth produces the Primary plant body: parts of roots and shoot systems produced by apical meristems
– Tip of root is covered by the root cap: protects apical meristem during primary growth
– zone of cell division includes apical meristem & 3 primary meristems (protoderm, procambrium, & ground)
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35.3 cont.
• Growth occurs in 3 stages:
– zone of cell division (where new root cells are produced)-
– zone of elongation: root cells elongate
– -zone of differentiation: zone of maturation, become distinct cell types
• Primary growth produces epidermis, ground tissue, and vascular tissue
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35.3 cont.
• Growth of Shoots
– vascular tissue runs through stem in strands called vascular bundles
– dicots = vascular bundles in ring, pith inside ring, cortex outside
– monocots = vascular bundles scattered through ground tissue
– Leaves develop from Leaf primordia: projections along side of apical meristem
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35.3 cont.
• Tissue Organization
– Epidermis has stomata: tiny pores controlled by guard cells that allow gas exchange
– Ground tissue is located in the mesophyll
– Vascular tissue contains xylem and phloem
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35.4• Secondary growth occurs in stems and
roots of woody plants
• Secondary Plant Body: tissues produced by vascular cambium and cork cambium-
– vascular cambium: cylinder of meristematic cells that forms secondary vascular tissue, increases vascular flow and support for shoots
– cork cambium: produces a tough, thick covering that protect the stem from water loss and invasion
• Primary and secondary growth occur simultaneously
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35.4 cont.
• Vascular Cambium and Secondary Vascular Tissue
– As meristematic cells divide, they increase circumference of vascular cambium and add layers of secondary xylem (wood) to its interior and secondary phloem to exterior
– Some parts of vascular cambium are elongated & other parts are shortened and produce vascular rays: radial files of cells that connect the secondary xylem with secondary phloem
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35.4 cont.• A year’s growth appears
as a distinct ring in tree trunks and roots
• Heartwood= old layers of secondary xylem that no longer transport water and minerals
• Sapwood= newest, outer layers of secondary xylem, transports xylem sap
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35.4 cont.• Cork Cambium & Production of Periderm
– During secondary growth, epidermis is falls off and is replaced by two tissues produced by the first cork cambium
– Cork tissue functions as a barrier that protects stem/root from water loss, physical damage, and pathogens
– Periderm: consists of cork cambium plus the layers of cells it produces
– Lenticels: dot the periderm and enable living cells within a woody stem or root to exchange gases with outside air
– Bark: all tissues external to vascular cambium
– Components of bark = secondary phloem, most recent periderm, and old layers of periderm
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35.5- Growth, Morphogenesis, and Differentiation Produce
the Plant Body
• Scientists believe that if they identify each gene’s function in a plant, they can discover a blue print of how plants develop
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35.5 cont.• GROWTH
– When cell numbers increase, cell divisions in meristems increase the potential for growth
– Most increase in growth comes from cell expansion or elongation
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35.5 cont.• Preprophase band
– Concentrated ring of microtubules. Disappears before metaphase, but predicts the future plan for cell division
• Water uptake accounts for 90% of plant cell expansion
• Vacuoles fill quickly from the water uptake & take up a lot of space in cells, letting the plant grow rapidly
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35.5 cont.• Enzymes weaken the cross-links in
cell wall, letting it expand as water diffuses into the vacuole by osmosis
• Morphogenesis must occur for plant to develop properly– Cells must be organized into
multicellular arrangements of tissues and organs
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35.5 cont.• Pattern formation- Development of
specific structures in specific locations
• Positional information is communicated by signals that continuously indicate to every cell its location in the developing structure– Ex. Hormones, proteins, mRNAs
provide positional info.
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35.5 cont.• Critical step in morphogenesis
is proper establishment of axial polarity
• Morphogenesis is under the control of homeotic genes (master regulatory genes that over see major events in development)
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35.5 cont.• Cellular differentiation depends on
the control of gene expression• Positional information is important to
all stages of development (growth, morphogenesis, and differentiation)
• Phase changes- When internal or environmental changes cause a plant to switch from developing one part to another