A discussion of meristems (apical meristems, vascular cambium, cork cambium, intercalary meristems) and nonmeristematic tissues (parenchyma, collenchyma, sclerenchyma, secretory tissues, epidermis, xylem, phloem, periderm) forms the body of this chapter.
Three Major Plant Organs
Root, Stems, Leaves
groups of cells performing a common function
Characteristics of Meristematic Cells:
Small, box-like cells, Large nucleus, Small vacuoles or none at all, Dense cytoplasm
Types of Meristematic Tissues
Apical, Lateral Meristems
Responsible for the increase in length of roots and stems
Located between xylem and phloem of herbaceous and woody plants
Three subdivisions of the apical meristem called primary meristems: produce primary tissues
Protoderm, Ground meristem, Procambium
Vascular and Cork Cambium
Located between xylem and phloem of herbaceous and woody plantsv (Responsible for production of tissues that increase the girth (circumference) of a plant)
Produces the outer bark of woody plants (Located near the outside of stem or root)
Found in many plants which do not have a vascular cambium (e.g., grasses) Produce increases in the length of stems and/or leaves
Permanent regions of active cell division
Composed of parenchyma cells. Tend to have large vacuoles and many contain various secretions.
Secretory Cells and Tissue
Secretory cells may function individually or as part of a secretory tissue. (flower nectar, Citrus oils, Latex etc.)
Some parts of cork cambium form loosely arranged pockets of parenchyma cells that protrude through the surface of the periderm.
Constitutes outer bark, composed of cork cells
Outermost layer of cells
Conducts dissolved food materials produced by photosynthesis throughout the plant.
Sieve Tube Members characteristics
Sieve Plates characteristics
Companion Cells characteristics
Long tubes open at each end, Made of vessel elements
Tapered at the ends with pits that allow water passage between cells.
Contain living cytoplasm and may live an extended time. (Provide flexible support for organs)
Cells with thick, tough, secondary walls, normally impregnatedwith lignin.
Parenchyma tissue with extensive connected air spaces