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CELLS? Syllabus Theme A Plant Structure and Function TISSUES? A1: The plant body consists of cells and tissues Campbell & Reece Chap. 35 pp. 712, 717-721 Tissue – group of cells with a common structure and function Organ – several types of tissues that work together to carry out particular functions ORGANS? Three basic organs: roots, stems, and leaves Organized into a root system and a shoot system Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Shoot system Leaf Vegetative shoot Blade Petiole Axillary bud Stem Taproot Lateral roots The Three Tissue Systems: Dermal, Vascular, and Ground Root system Ground tissue system Forms the cortex and pith in roots and stems the mesophyll in leaves Includes various cells specialized for functions such as storage, photosynthesis, and support Three basic cell types: Dermal – Forms function? Vascular – function? Ground – variety of functions Parenchyma Collenchyma Sclerenchyma Dermal tissue Ground tissue Vascular tissue 1 PARENCHYMA CELLS Chlorenchyma 60 µm Thin primary walls Flexible Aerenchyma Large central vacuole Functions? PARENCHYMA CELLS COLLENCHYMA CELLS SCLERENCHYMA CELLS PARENCHYMA CELLS SCLERENCHYMA CELLS 5 µm 80 µm Sclereid cells in pear 25 µm Cell wall Fiber cells Have lignin Unevenly thickened primary walls Primary and secondary walls Long strands near stem surfaces and along Two types: Sclereids – short, isodiametrical cells Fibers – long, slender cells in groups (bundles) leaf veins Function? A C Vascular tissue system Carries out long-distance transport of materials between roots and shoots Consists of two tissues, xylem and phloem B 2 Xylem Vessel Tracheids Phloem 100 µm Pits Tracheids and vessels – conduction Fibers – strength Parenchyma cells storage Sieve-tube members: longitudinal view Sieve-tube elements – conduction Companion cells Fibers – strength Parenchyma cells storage Companion cell Sieve-tube member Sieve plate Tracheids and vessels Nucleus Vessel element Vessel elements with partially perforated end walls 30 µm 15 µm Tracheids Cytoplasm Companion cell Dermal tissue system Epidermis Outermost layer of cells Covers and protects Variations: Trichomes / root hairs Stomata, surrounded by guard cells Produces a waxy cuticle Dermal tissue system Plant growth Annual Periderm Replaces epidermis in woody plants cells and cork parenchyma cells Functions? Cork Perennial Biennial 3 Plant growth Plant growth Plants exhibit localized growth at meristems All cell division – mitosis cell elongation - central vacuole fills with water cell differentiation- specialization into the different cell types Primary growth in length of plant plants grow this way Secondary growth Increase in diameter of a plant woody angiosperms and gymnosperms grow this way Only Secondary growth Occurs at apical meristems Located: Primary growth Increase Growth includes Lateral meristems Add thickness to woody plants through secondary growth Vascular cambium tips of roots and in the buds of shoots Produce wood (secondary xylem) and inner bark (secondary phloem) Cork cambium Form periderm (outer bark) Primary growth in stems Shoot apical meristems Epidermis Cortex Primary phloem Lateral meristems add secondary growth Vascular cambium Cork cambium Primary xylem Lateral meristems Pith Secondary growth in stems Apical meristems add primary growth Periderm Cork cambium Pith Primary xylem Root apical meristems Cortex Primary phloem Secondary xylem Secondary phloem Vascular cambium 4
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