BIO 1010 – Unit 3 - Chapter 4 Tissues.pdf

Chapter 5: Tissues BIO 1010: DOLAN UNCP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organs and Tissues Plants have three or four major groups of organs: – Roots, Stems, Leaves, Flowers Each organ is composed of tissues. – a group of cells performing a...

Chapter 5: Tissues BIO 1010: DOLAN UNCP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organs and Tissues Plants have three or four major groups of organs: – Roots, Stems, Leaves, Flowers Each organ is composed of tissues. – a group of cells performing a similar function. – may be more than one tissue per organ. Meristematic Tissues Apical Meristems Meristems: Permanent regions of growth – active cell division – “stem cells” – Apical Meristems (AM) – at tips of roots and shoots – Roots and shoots increase in length as the AM produce new cells (= 1° growth). Meristematic Tissues: Apical Meristems – Primary meristems develop from apical meristems. Protoderm Ground Meristem Procambium – Primary meristems produce primary tissues. Basic Plant Tissues: Develops from Meristem Tissue Parent Cells Tissue System Components Functions (1° meristem) Protection Prevention of water loss Protoderm Dermal Tissue Epidermis Periderm (in older stems and roots) Ground Meristem Ground Tissue o Parenchyma Photosynthesis o Collenchyma Food Storage o Sclerenchyma Regeneration Support and structure protection Procambium Vascular Tissue Vascular Bundles Transport water and Xylem tissue minerals Transport Phloem tissue food Plant Cells  Tissues  Organs 4 regions: 1. 2. 3. 4. Root cap Region of cell division Region of cell elongation Region of maturation Root Cap - Thimbleshaped, parenchyma cells covering each root tip –Protects tissues from damage as root grows –Secretes lubricating mucilage Root Structure Region of Cell Division - Composed of apical meristem in the center of root tip – Subdivided into 3 meristematic areas: Protoderm – Gives rise to epidermis Ground meristem - Gives rise to cortex and pith Procambium - Gives rise to primary xylem and primary phloem Meristematic Tissues: Lateral Meristems Lateral Meristems Produce 2° tissues that increase the girth of roots and stems (= 2° growth) – Vascular Cambium - Produces 2° vascular tissues that function primarily in support and conduction. Composed of a thin cylinder of brick-shaped cells that extends the length of stems and roots – Cork Cambium - Lies outside vascular cambium just inside the outer bark Produces bark Meristematic Tissues: Lateral Meristems Vascular and Cork Cambium Meristematic Tissues: Intercalary Meristems Grasses and related plants do not… – vascular cambium or cork cambium Do have Intercalary meristems. Tissues Produced By Meristems: Ground Tissues: Parenchyma  Simple Tissues - Consist of only one kind of cell Parenchyma cells: – Most common cell and tissue type – Thin, pliable walls – Living cytoplasm, often containing large vacuoles and various secretions – May remain alive a long time – Multipurpose Photosynthetic Storage Secretory – Can differentiate into other cell types Parenchyma cells Tissues Produced By Meristems: Simple Tissues – Types of parenchyma tissue and cells: Aerenchyma – Have extensive connected air spaces, usually in aquatic plants Chlorenchyma - containing chloroplasts Transfer cells - Develop irregular extensions of inner wall that greatly increase surface area of plasma membrane – Nectaries of flowers Tissues Produced By Meristems: Simple Tissues: Collenchyma Long lived, with living cytoplasm Often elongated, 1° Cell walls unevenly thick Pliable and strong – providing flexible support, often in herbaceous plants – most abundant in stems and long leaf veins Collenchyma cells Tissues Produced By Meristems: Simple Tissues: Sclerenchyma Sclerenchyma cells: Thick, tough, secondary walls Impregnated with lignin – Dead at maturity, Function in support – Two types: sclereids and fibers Tissues Produced By Meristems: Simple Tissues: Sclerenchyma o Sclereids (aka Stone Cells) Scattered in tissue Cells as long as wide Found in pears, stone fruit pits, gives nut shells hardness Tissues Produced By Meristems: Simple Tissues: Sclerenchyma – Fibers » Much longer that wide and contain lumen (tiny cavity) Tissues Produced By Meristems: Complex Tissues Complex tissues - Composed of two or more kinds of cells – Vascular tissues include xylem and phloem. Complex Tissues: Vascular Tissue: Xylem Vascular tissues include xylem and phloem. Xylem -conducting tissue for water and minerals absorbed by the roots – Composed of: parenchyma cells fibers, vessels tracheids ray cells Complex Tissues: Vascular Tissue: Xylem: Vessels – Vessels – Long tubes made of vessel elements Vessel elements: – Thick secondary cell walls – Open at both ends – Secondary walls develop irregularly – Perforation plate between end walls Vessels elements Spiral thickenings on vessel walls Tissues Produced By Meristems: Complex Tissues – Tracheids Tapered ends Pairs of pits that allow water to pass from cell to cell – Pits - Areas without secondary cell Dead at maturity Thick secondary cell walls May have spiral thickenings on cell walls Tracheids Complex Tissues: Vascular Tissue: Phloem  Phloem - Conducts dissolved food materials produced by photosynthesis throughout plant Composed of: sieve tube members companion cells Fibers parenchyma cells ray cells Complex Tissues: Vascular Tissue: Phloem: Sieve Tube Members – Sieve Tube Members: Lack secondary cell walls and nuclei Lay end to end to form sieve tubes Walls have sieve plates with small pores Callose forms callus plug Prevents leaking of sieve tube contents when cell injured Companion cells - Aid in conduction of food Phloem Tissue Patterns in Stems Herbaceous Dicotyledonous Stems Herbaceous dicots have discrete vascular bundles arranged in a cylinder. Vascular cambium arises between primary xylem and primary phloem. – Adds secondary xylem and secondary phloem Complex Tissues: Vascular Tissue: Rays Function in lateral conduction and food storage – Composed of long-lived parenchyma cells Tissue Patterns in Stems: Woody Dicotyledonous Stems Complex Tissues: Epidermis Epidermis- Protective layer that is one cell-layer thick covering all plant organs – Composed mostly of parenchyma cells, guard cells of stomata, secretory glands and hairs Leaf cross section Complex Tissues: Epidermis: Cutin – Cutin - Fatty substance on the surface of outer walls of epidermis that forms waxy cuticle Wax secreted on cuticle prevent water loss by evaporation, Provides bacterial/fungal resistance – Root epidermal cells produce root hairs. Increase absorptive area of root surface – Leaves have stomata bordered by pairs of guard cells. Complex Tissues: Epidermis: Trichomes Complex Tissues: Epidermis: Secretory Cells may function individually or as part of a secretory tissue. – Flower nectar – Citrus oils – Glandular hair mucilage – Latex – Resins Complex Tissues: Periderm  Replaces epidermis when cork cambium begins producing new tissue Constitutes outer bark Primarily composed of: – Cork cells (phellem) – Cork Cambium (phellogen) – Cork Parenchyma (phelloderm Complex Tissues: Periderm: lenticels – – – – Loosely arranged pockets of parenchyma cells Form by cork cambium protrude through the surface of periderm. Allows for gaseous exchange Common on fruit trees 44 Review Organs and Tissues Meristematic Tissues – Apical Meristems – Lateral Meristems – Intercalary Meristems Tissues Produced by Meristems – Simple Tissues – Complex Tissues