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Plant Structure, Growth, and Development

Plant Structure, Growth, and Development

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Plant Structure, Growth, and Development

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  1. Plant Structure, Growth, and Development Introduction The Angiosperm Body Plant Growth

  2. Introduction to Modern Plant Biology • Molecular biology is identifying crucial genes (flower development); giving a better understanding of processes such as water flow, disease resistance, shoot and root control • Structure and function is a key theme

  3. The Angiosperm Body • Problems to be solved: gravity, light, water transport, reproduction, and desiccation • Root and shoot systems

  4. The Root System • Functions: anchor, store food, absorb and conduct water and minerals • two types: taproot and fibrous root systems • role of root hairs • mycorrhizae • adventitious roots: form above ground from stem or leaf

  5. The Shoot System • Stems, leaves and flowers • growth occurs at apex • apical dominance has evolutionary importance • underground stems:bulbs and rhizomes(potatoes)-store food • leaves: main photosynthetic organ

  6. Types of Plant Cells • Function determined by protoplast and cell wall adaptations • five types of plant cells: 1. Parenchyma-synthesis and storage 2. Collenchyma-support in young plants 3. Sclernchyma-thick secondary walls, lack protoplast in mature cells?, supportive 4. Xylem-water conduction, two types: tracheids and vessel elements 5. Phloem-food conduction

  7. Tissue Systems • Three tissue systems: dermal, vascular and ground tissues • Dermal-single outside layer • Vascular-xylem and phloem, transport and support • Ground-between dermal and vascular, storage, synthesis, and support

  8. Plant Growth • Meristems generate cells; two types: apical and lateral • genetically determined life spans (most) • annuals and perennials • plants exhibit indeterminate growth • two types of growth: primary and secondary

  9. Root Growth • Primary growth divided into three zones: 1. Cell division: apical meristem, this differentiates into: protoderm, procambium, and ground meristem (primary tissues) 2. Cell elongation: elongate at least 10X, pushes tip through the soil 3. Maturation: cells complete their differentiation

  10. Primary Tissues in the Root • Protoderm: outermost layer of primary meristem, give rise to epidermis, many with root hairs • Procambium: forms stele (central cylinder) containing xylem and phloem, • Ground meristem: cortex between stele and epidermis, parechyma cells, stores food, endodermis single cell layer boundary between cortex and stele, pericycle inside endodermis

  11. Primary Growth of Stems • Apical meristem forms primary meristems (protoderm, ground meristem, and procambium) • Procambium forms vascular tissue in bundles • Ground meristem forms pith and cortex • Protoderm forms epidermal tissues

  12. Leaf Growth • Ground tissues form the mesophyll • procambium forms the veins • Protoderm forms the upper and lower epidermis, guard cells waxy cuticle

  13. Secondary Growth • Produced by growth in diameter • results from vascular and cork cambium • vascular produces xylem and phloem • cork cambium produces covering of roots and stems that replace epidermis • occurs in all gymnosperms and most angiosperms, rare in monocots

  14. Stages of Differentiation • Apical meristem • differentiates into: protoderm, ground meristem, and procambium • protoderm differentiations into epidermal structures • procambium differentiates into the vascular tissues • ground meristem produces tissues that fill in between the epidermis and vascular tissues

  15. Secondary Growth in Stems • Vascular cambium produces secondary vascular tissues: xylem--forms wood; phloem--contributes to the formation of bark and sloughs off • cork cambium produces the periderm (protective coat of plant, combination of cork cambium, layers of cork, and phelloderm,) • bark-all tissues external to the vascular cambium

  16. Secondary Growth in Roots • Vascular cambium produces secondary xylem to the inside and secondary phloem to the outside • cortex and epidermis split and are shed as the stele increases in diameter • very similar to stems, produces annual rings