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AP Biology Chapter 35 – Plant Structure, Growth, and Development Plant Organs, Tissues, & Cells • Organs: Roots – Stems – Leaves • Root System • Taproot • Eudicots • Gymnosperms • Stores Nutrients • Fibrous Roots • Monocots Plant Organs, Tissues, & Cells • Organs: Roots – Stems – Leaves • Shoot System • Stem • Nodes • Leaf Attachment • Internodes • Axillary Bud • Grows Branches (Lateral Shoot) • Terminal Bud • Growth of Stem Plant Organs, Tissues, & Cells • Organs: Roots - Stems - Leaves • Shoot System • Leaves • Photosynthetic Organ • Blade • Petiole • Joins Leaf to Stem • Not in Many Herbaceous Monocots (Grasses) • Veins • Branched in Eudicots • Unbranched in Monocots Simple Compound Doubly Compound Plant Organs, Tissues, & Cells • Modified Leaves Plant Organs, Tissues, & Cells • Tissues: Dermal – Vascular – Ground • Dermal • Epidermis • Single Cell Layer • Periderm • In Woody Plants • Vascular • Xylem – Water & Dissolved Minerals • Phloem – Sugars • “Cylinder” in Root, “Bundle” in Stem and Leaf • Ground • Pith – Internal to Vascular • Cortex – External to Vascular “stele” Plant Organs, Tissues, & Cells • Cells • Parenchyma • Thin, Flexible • Least Specialized • Perform All Basic Functions • Collenchyma • Grouped in Strands or Cylinders • Thick Walled • Support • Sclerenchyma • Secondary Walls - Rigid • Dead at Maturity Plant Organs, Tissues, & Cells • Cells • Cells of the Xylem • Tracheids • Long, Thin, Tapered • Protoplast desiccates • Water Moves through Pits Between Empty Dead Cells • Vessel Elements • Short, Wide • Aligned End to End • Allows Water Movement Between Dead Cells Plant Organs, Tissues, & Cells • Cells • Cells of the Phloem • Sieve Cells • Sieve Tube Members • Alive, but No Nucleus or Ribosomes • Sieve Plates » Between Cells » Pores Allow Flow • Companion Cell • Nucleus and Ribosomes Also Serve the Sieve Cells Meristems • Indeterminate vs. Determinate Growth • Growth Throughout the Life of the Plant • Animals and Plant Leaves Reach Maturity • Annuals • Single Year Life Cycle • Biennials • Two Year Life Cycle • Growth – Dormancy – Flower (Reproduction) • Perennials • Unlimited Life Meristems • Perpetually Embryonic Tissues • Apical • Tips of Roots and Shoots • Enable Growth in Length (1o Growth) • Most Growth in Herbaceous Plants • Non-Wood • Lateral • Growth in Girth (2o Growth) • Vascular Cambium • Adds 2o Xylem & Phloem • Cork Cambium • Replaces Epidermis with Periderm Meristems • Three Year’s Growth Primary Growth – Roots • Produces 1o Plant Body • Root Cap • Protects Apical Meristem • Zone of Cell Division • Zone of Elongation • 10x Original Length • Extend Root Tip • Zone of Maturation •Cortex??? Primary Growth - Roots • Eudicot • Monocot •Vascular Bundle •Eudicot •Scattered •Monocot •Ring Primary Growth - Roots • Lateral Pericycle Primary Growth - Shoots • Terminal Bud Tissue Organization - Stems • Eudicot Monocot Tissue Organization - Leaf Secondary Growth • 2o Plant Body • Lateral Growth • Growth in Girth • Vascular Cambium • Adds 2o Xylem & Phloem • Cork Cambium • Replaces Epidermis with Periderm Secondary Growth • Cell Division & Accumulation of 2o Growth • C – Vascular Cambium • D – Differentiated Cell • P – 2o Phloem X – 2o Xylem Secondary Growth • Bark • Tissues External to Vascular Cambium • 2o Phloem, Cork Cambium, Cork • Heartwood • Old 2o Xylem • No Transport • Sapwood • Active Xylem Differentiation & Morphogenesis • Plant Molecular Genetics • Model Organism – Arabidopsis thaliana • Completely Sequenced • Many Genes Previously Known (Dros.) Differentiation & Morphogenesis • Preprophase Band • Microtubule Ring Orients Plane of Cell Division Differentiation & Morphogenesis • Cell Division Increases Number of Cells • Cell Expansion Increases Plant Mass • In Meristems • Asymmetrical Cell Division • One Cell Receives More Cytoplasm Differentiation & Morphogenesis • Cell Expansion • 90% from Water – Allows for Rapid Growth • Expansion Oriented Along Plant’s Main Axis • Water in Vacuoles • Vacuoles Centralize • Microfibrils Orient Vacuole Formation Differentiation & Morphogenesis • Pattern Formation • As with D. melanogaster (Ras Gene?) • Positional Information • Signals Each Cell as to Its Position in the Plant • Intercell Signaling Wild-Type Seedling • Arabidopsis FASS Mutant Mature Mutant Mutant Seedling (Random Orientation vs. Axial Orientation) Differentiation & Morphogenesis • Pattern Formation • Polarity • ID of Root End and Shoot End Along a Well Developed Axis • Initial Polarization into Root and Shoot ends Normally Determined by Initial Asymmetrical Division of the Zygote (gnom Mutant) Differentiation & Morphogenesis • Gene Expression • Remember…All Genes Present in Every Cell, Only Specific Genes Expressed • Differentiation from Expression Wild-Type Tomato Leaves KNOTTED-1 Mutant Tomato Leaves Differentiation & Morphogenesis • Phase Changes • Meristem can Change from One Developmental Phase to Another • ex. Juvenile State to Mature State • May Produce Change in Morphology • A branch with juvenile leaves may actually be older than a branch with mature leaves. Differentiation & Morphogenesis • Flowering • Apical Meristem Terminates 1o Growth of that Shoot Tip and Develops into the Flower’s Organs • Expression of Floral Mutant Arabidopsis Meristem Identity Genes • Floral Organ Identity Wild-Type Arabidopsis Genes • Regulate Floral Pattern
