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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? Roots Stems Leaves
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Figure 35.2 An overview of a flowering plant
Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Vegetative shoot Blade Petiole Stem Leaf Taproot Lateral roots Root system Shoot Axillary
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? Roots Stems Leaves What are the different varieties of roots? Tap roots – eudicots & gymnosperms – have lateral roots off of the side Fibrous roots – monocots – shallow & just below the surface What are some root modifications? Figure 35.4
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Figure 35.4 Modified roots (a) Prop roots (b) Storage roots
(c) “Strangling” aerial roots (d) Buttress roots (e) Pneumatophores
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? Roots Stems Leaves What are the different varieties of roots? Tap roots – eudicots & gymnosperms – have lateral roots off of the side Fibrous roots – monocots – shallow & just below the surface What are some root modifications? Figure 35.4 What are stems? Above ground organ with an alternating system of nodes (where the leaves attach) & internodes (stem segments between nodes) Axillary bud – structure at each node that may form a lateral shoot (branch) What are some stem modifications? - Figure 35.5
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Figure 35.5 Modified stems Rhizomes. The edible base
of this ginger plant is an example of a rhizome, a horizontal stem that grows just below the surface or emerges and grows along the surface. (d) Tubers. Tubers, such as these red potatoes, are enlarged ends of rhizomes specialized for storing food. The “eyes” arranged in a spiral pattern around a potato are clusters of axillary buds that mark the nodes. (c) Bulbs. Bulbs are vertical, underground shoots consisting mostly of the enlarged bases of leaves that store food. You can see the many layers of modified leaves attached to the short stem by slicing an onion bulb lengthwise. (b) Stolons. Shown here on a strawberry plant, stolons are horizontal stems that grow along the surface. These “runners” enable a plant to reproduce asexually, as plantlets form at nodes along each runner. (a) Storage leaves Stem Root Node Rhizome
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? Main photosynthetic organ of a plant
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Figure 35.6 Simple versus compound leaves
Petiole (a) Simple leaf. A simple leaf is a single, undivided blade. Some simple leaves are deeply lobed, as in an oak leaf. (b) Compound leaf. In a compound leaf, the blade consists of multiple leaflets. Notice that a leaflet has no axillary bud at its base. (c) Doubly compound leaf. In a doubly compound leaf, each leaflet is divided into smaller leaflets. Axillary bud Leaflet
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? Main photosynthetic organ of a plant What are some modified leaves? - Figure 35.7
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Figure 35.7 Modified leaves
(a) Tendrils. The tendrils by which this pea plant clings to a support are modified leaves. After it has “lassoed” a support, a tendril forms a coil that brings the plant closer to the support. Tendrils are typically modified leaves, but some tendrils are modified stems, as in grapevines. (b) Spines. The spines of cacti, such as this prickly pear, are actually leaves, and photosynthesis is carried out mainly by the fleshy green stems. (c) Storage leaves. Most succulents, such as this ice plant, have leaves modified for storing water. (d) Bracts. Red parts of the poinsettia are often mistaken for petals but are actually modified leaves called bracts that surround a group of flowers. Such brightly colored leaves attract pollinators. (e) Reproductive leaves. The leaves of some succulents, such as Kalanchoe daigremontiana, produce adventitious plantlets, which fall off the leaf and take root in the soil.
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? Dermal – outer protective covering Vascular – long distance transport between roots & shoots Ground – tissue between vascular & dermal
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Figure 35.8 The three tissue systems
Dermal tissue Ground Vascular
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Parenchyma Least specialized, typical plant cell Thin, flexible primary walls Do most of metabolic work Photosynthesis Storage All other cells derived from parenchyma
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Parenchyma Collenchyma Uneven & thicker primary walls than parenchyma Grouped in strands or cylinders for support of young plant Provide support without restricting growth No secondary walls & no lignin
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Parenchyma Collenchyma Sclerenchyma Thicker secondary walls with lignin for rigid support Mature sclerenchyma cannot elongate & are usually dead lacking a protoplast 2 forms Fibers – long, slender, tapered & usually in bundles – rope & flax fibers for linen Sclerids – short & irregular shaped that provide hardness to nut shells, seed coats & the gritty texture of pears
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Parenchyma Collenchyma Sclerenchyma Tracheids & vessels elements H2O conducting cells Tracheids All vascular plants Long, thin cells with tapered ends Vessel elements (angiosperms) Wider, shorter & less tapered Perforated ends & sometimes sides
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Parenchyma Collenchyma Sclerenchyma Tracheids & vessels elements Sieve-tube members Sugar-conducting cells of phloem Alive but lack nucleus, ribosomes, & vacuole Companion cells help load sugar
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Figure 35.9 Examples of Differentiated Plant Cells
PARENCHYMA CELLS COLLENCHYMA CELLS SCLERENCHYMA CELLS SUGAR-CONDUCTING CELLS OF THE PHLOEM WATER-CONDUCTING CELLS OF THE XYLEM Parenchyma cells 60 m 80 m 5 m 25 m Cell wall Sclereid cells in pear Fiber cells Cortical parenchyma cells Collenchyma cells Vessel Tracheids 100 m Tracheids and vessels element Vessel elements with partially perforated end walls Pits Sieve-tube members: longitudinal view Companion cell Sieve-tube member Sieve plate Nucleus Cytoplasm 30 m 15 m
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Where do plants grow? - Meristems
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Figure 35.10 An overview of primary and secondary growth
In woody plants, there are lateral meristems that add secondary growth, increasing the girth of roots and stems. Apical meristems add primary growth, or growth in length. Vascular cambium Cork Lateral meristems Root apical Primary growth in stems Epidermis Cortex Primary phloem Primary xylem Pith Secondary growth in stems Periderm Primary phloem Secondary Vascular cambium xylem Shoot apical (in buds) The Cork cambium adds secondary dermal tissue. The vascular xylem and phloem. Primary growth – apical meristems Secondary growth – lateral meristems
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Figure 35.12 Primary growth of a root
Dermal Ground Vascular Key Cortex Vascular cylinder Epidermis Root hair Zone of maturation elongation Zone of cell division Apical meristem Root cap 100 m
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Where do plants grow? How are leaves structured?
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Cutaway drawing of leaf tissues
Figure 35.17 Leaf anatomy Key to labels Dermal Ground Vascular Guard cells Stomatal pore Epidermal cell 50 µm Surface view of a spiderwort (Tradescantia) leaf (LM) (b) Cuticle Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy Lower Vein Xylem Phloem Bundle- sheath Cutaway drawing of leaf tissues (a) Air spaces Guard cells 100 µm Transverse section of a lilac (Syringa) leaf (LM) (c)
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Where do plants grow? How are leaves structured? Let’s consider primary & secondary growth of a stem….
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Figure 35.18 Primary and secondary growth of a stem
(a) Primary and secondary growth in a two-year-old stem Pith Primary xylem Vascular cambium Primary phloem Epidermis Cortex 1
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Figure 35.18 Primary and secondary growth of a stem
Vascular cambium 4 First cork cambium Pith Primary xylem Primary phloem Epidermis Cortex 2 1 Growth Primary xylem Secondary xylem Cork Phloem ray 3 Xylem ray Secondary phloem (a) Primary and secondary growth in a two-year-old stem
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Figure 35.18 Primary and secondary growth of a stem
Vascular cambium Pith Primary xylem Secondary xylem Secondary phloem Primary phloem Periderm (mainly cork cambia and cork) Cortex Epidermis 4 First cork cambium Secondary xylem (two years of production) 2 1 6 Growth Primary xylem Cork Phloem ray 3 Xylem ray 9 Bark 8 Layers of periderm 7 5 Most recent cork cambium (a) Primary and secondary growth in a two-year-old stem
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Chapter 35: Plant Structure, Growth & Development
What are the 3 main plant organs? What are the different varieties of roots? What are some root modifications? What are stems? What are some stem modifications? What is a leaf? What are some modified leaves? What are the 3 tissue systems of plants? What are the different types of plant cells? Where do plants grow? How are leaves structured? Let’s consider primary & secondary growth of a stem…. Where does secondary occur? Vascular cambium
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Figure 35.19 Cell division in the vascular cambium
X P Types of cell division. An initial can divide transversely to form two cambial initials (C) or radially to form an initial and either a xylem (X) or phloem (P) cell. (a) Accumulation of secondary growth. Although shown here as alternately adding xylem and phloem, a cambial initial usually produces much more xylem. (b)
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Figure 35.20 Anatomy of a tree trunk
Growth ring Vascular ray Heartwood Sapwood Vascular cambium Secondary phloem Layers of periderm Secondary xylem Bark
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