Chapter 5: Tissues, Organs, and Plant Structures PDF

Chapter 5: Tissues Organs and Tissues Organs: Roots, Stems, Leaves and Flowers Each organ composed of tissues A group of cells performing a similar function May be more than one tissue per organ Meristems Tissues (Apical Meristems) Meristems; Permanent regions of growth active cell division ”stem ce...

Chapter 5: Tissues Organs and Tissues Organs: Roots, Stems, Leaves and Flowers Each organ composed of tissues A group of cells performing a similar function May be more than one tissue per organ Meristems 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 degree growth) Primary Meristems; develop from apical meristem Protoderm Ground meristem Procambium Primary meristem produce primary tissues Parent cells Tissue System Components Protoderm Dermal Tissue Epidermis and Periderm (in older stems and roots) Protection Prevention of water loss Ground Meristem Ground Tissue Parenchyma Collenchyma Sclerenchyma Photosynthesis Food storage Regeneration Support and structure Protection Procambium Vascular Tissue Vascular Bundles -Xylem tissue -Phloem Tissue Transport water and minerals Transport Food 4 Regions: 1. Root Cap a. - Thimble- shaped, parenchyma cells covering each root i. Protect tissues from damage as root grows ii. Secretes lubricating mucilage 2. Region of cell division Functions a. Composed of apical meristem in the center of root tip i. Subdivided into 3 meristematic areas: 1. Protoderm - gives rise to epidermis 2. Ground meristem - gives rise to cortex and pith 3. Procambium - gives rise to primary xylem and primary phloem 3. Region of cell elongation 4. Region of maturation Meristematic Tissues: Lateral Meristems (Lateral Meristems) Produce 2 degree tissues that increase the girth of roots and stems (= 2 degree growth). ○ Vascular cambium - produces 2 degree 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. 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 ○ May remain alive a long time ○ Multipurpose Photosynthetic Storage Secretory ○ Can differentiate into other cell types 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 degree cell wall unevenly thick Pliable and Strong ○ Providing flexible support, often in herbaceous plants ○ Most abundant in stems and long leaf veins 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 Sclereids (aka Stone cells) ○ Scattered in tissue ○ Cell as long as wide ○ Found in pears, stone fruit pits, gives nut shells hardness Fibers ○ Much longer that wide and contain lumen (tiny cavity) 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 vessels elements ○ Vessel elements: Thick secondary cell walls Open at both ends Secondary walls develop irregularly Perforation plate between end walls Tissues Produced by Meristems: Complex Tissues Tracheids ○ Tapered ends ○ Pairs of pits that allow water to pass from cell to cell Pits area without secondary cell ○ Dead at maturity ○ Thick secondary cell walls ○ May have spiral thickenings on cell walls 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 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 Tissue Patterns in Stems: Herbaceous Dicotyledonous Stems Herbaceous dicots have discrete vascular bundles arranged in cylinders. Vascular cambium arises between primary xylem and primary phloem Function in lateral conduction and food storage ○ Composed of long-lived parenchyma cells. 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 Cutin; fatty substance on the surface of out walls of epidermis that forms waxy cuticle. ○ Wax secreted on cuticle ○ Prevent water loss by evaporation ○ Provides bacterial and fungal resistance Root epidermal cells produce root hairs ○ Increase absorptive area of root surface Leaves have stomata boarded by pairs of guard cells 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 tissue: 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 eh surface of periderm Allows for gaseous exchange Common on fruit trees