3- Tissues and the Primary.pdf

Basic Types of Cells and Tissues  Basic Types of Cells and Tissues ACTIVITY ½ yellow paper Crosswise Differentiate − Parenchyma − Collenchyma − Sclerenchyma  Basic Types of Cells and Tissues Stems, leaves, and roots all share a basic, simple organization. All plant cells belong t...

Basic Types of Cells and Tissues  Basic Types of Cells and Tissues ACTIVITY ½ yellow paper Crosswise Differentiate − Parenchyma − Collenchyma − Sclerenchyma  Basic Types of Cells and Tissues Stems, leaves, and roots all share a basic, simple organization. All plant cells belong to just three classes based on the nature of their cell wall. − Parenchyma − Collenchyma − Sclerenchyma  Parenchyma Parenchyma cells have only thin primary walls. A mass of parenchyma cells forms parenchyma tissue. − Active metabolically. − Most remain alive after they mature. Special parenchyma − Chlorenchyma − Glandular cells − Transfer cells − Phloem  Specialized Parenchyma (1 of 4) Chlorenchyma cells are photosynthetic parenchyma cells. − Thin walls allow light and carbon dioxide to pass through to the chloroplast. Pigmented cells are parenchyma. − Thin walls of parenchyma cells also allow pigments to be seen.  Specialized Parenchyma (2 of 4) Glandular cells secrete − Nectar − Fragrances − Mucilage − Resins − Oils  Specialized Parenchyma (3 of 4) Transfer cells mediate short-distance transport of material. − They have a large, extensive plasma membrane with numerous molecular pumps. Courtesy of W. W. Thomson and R. Balsamo, University of California, Riverside Courtesy of M. J. Talbot and C. E. Offler, University of Newcastle, Australia  Specialized Parenchyma (4 of 4) Phloem is parenchyma tissue that conducts nutrients over long distances. Some parenchyma cells function by dying at maturity to open areas. Parenchyma cells are relatively inexpensive to build. − Little glucose is expended in constructing such thin walls. − Most leaves are soft, composed almost entirely of parenchyma. − They are not very expensive metabolically.  Collenchyma Collenchyma cells have a thin primary wall that becomes thickened in other areas. This allows plasticity. Collenchyma tends to exist: − Beneath the epidermis − Supporting vascular bundles  Sclerenchyma (1 of 3) Sclerenchyma has a primary wall and a thick secondary wall that is usually lignified. These walls are elastic. Sclerenchyma supports the plant by its strength. Usually dead at maturity. Two types: − Conductive − Mechanical  Sclerenchyma (2 of 3) Mechanical sclerenchyma − Fibers are long and flexible. − Sclereids are short, isodiametric (cuboidal), inflexible, and brittle  Sclerenchyma (3 of 3) Small, plasmodesmata-rich areas must remain free of the secondary wall. − These become narrow pits in the secondary wall. − Two pits are called pit-pairs. Conducting sclerenchyma transports water. − Tracheary elements of the xylem POST-EVALUATION FORM