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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

Tissues

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

Apical Meristems

Responsible for the increase in length of roots and stems

Lateral Meristems

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

Lateral Meristems

Vascular and Cork Cambium

Vascular Cambium

Located between xylem and phloem of herbaceous and woody plantsv (Responsible for production of tissues that increase the girth (circumference) of a plant)

Cork Cambium

Produces the outer bark of woody plants (Located near the outside of stem or root)

Intercalary Meristems

Found in many plants which do not have a vascular cambium (e.g., grasses) Produce increases in the length of stems and/or leaves

Meristems

Permanent regions of active cell division

Parenchyma

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.)

Lenticels

Some parts of cork cambium form
loosely arranged pockets of parenchyma
cells that protrude through the surface of the periderm.

Periderm

Constitutes outer bark, composed of cork cells

Epidermis

Outermost layer of cells

Phloem

Conducts dissolved food
materials produced by photosynthesis
throughout the plant.

Sieve Tube Members characteristics

Large, cylindrical

Sieve Plates characteristics

Porous region

Companion Cells characteristics

Narrow, tapered

Vessels

Long tubes open at each end, Made of vessel elements

Tracheids characteristics

Tapered at the ends with pits
that allow water passage between cells.

Rays characteristics

Lateral conduction

Collenchyma

Contain living cytoplasm and may live an extended time. (Provide flexible support for organs)

Sclerenchyma

Cells with thick, tough, secondary walls, normally impregnatedwith lignin.

Sclerids characteristics

Stone cells

Fibers characteristics

Contain Lumen

Aerenchyma

Parenchyma tissue
with extensive connected air spaces

Chlorenchyma

Parenchyma cells containing chloroplasts.

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