Botany Ch 4

Plant Tissues

4 Major Types of Plant Organs

Roots, stems, leaves, flowers

Tissue

Group of cells performing a singular function

3 Basic Tissue Patters in Roots and Stems

Woody Dicots, herbaceous dicots, monocots

Meristems

Permanent regions of growth and active cell division. cells are typically small, 6-sided, box-like, with very large nuclei and small or absent vacuoles

Apical meristems

found at the tips of roots and shoots. Roots and shoots increase in length as it produces new cells. Embryo leaves and buds and 3 primary meristems (protoderm, ground meristem, and procambrium) develop from this.

Primary meristems

protoderm (epidermis), ground meristem, procambrium (vascular tissue). Produce primary tissues

Protoderm

epidermis

procambrium

vascular tissue

Lateral meristems

secondary growth. Produce secondary tissues that increase the girth of roots and stems. Include the vascular cambium and the cork cambium.

Vascular cambium

produces secondary tissues that function primarily in support and conduction. composed of a thin layer of brick-shaped cells that extends the length of stems and roots. tissues produced are responsible for most of the increases in girth as a plant grows.

initials and derivatives

individual remaining cells of the cambium, and their sister cells

Cork cambium

a thin cylinder that runs the length of roots and stems of woody plants. Lies outside vascular cambium just inside the outer bark. produces bark.

Intercalary meristems

present in grasses and related plants. occur in vicinity of nodes (leaf attachment area) along stems. Add to stem length.

Simple tissues

composed of one type of cell

complex tissues

composed of 2 or more cell types

parenchyma

composed of parenchyma cells

parenchyma cells

thin, pliable walls. usually 14-sided at maturity. living cytoplasm, often containing large vacuoles and various secretions. may remain alive a long time. have spaces between them.

Characteristics of Collenchyma Cells

living cytoplasm. may remain alive a long time. cell walls thick, with uneven thickness. pliable and strong, thus provide flexible support.

Types of parenchyma tissues and cells

aerenchyma, chlorenchyma, transfer cells

Aerenchyma

parenchyma tissue with extensive connected air spaces, usually in aquatic plants

Chlorenchyma

parenchyma cells containing chloroplasts that function in photosynthesis

Transfer cells

develop irregular extensions of inner wall that greatly increase surface area of plasma membrane

Sclerenchyma cell characteristics

thick, tough, secondary walls, normally impregnated with ligin. Dead at maturity. Function in support. 2 types: Sclereids, fibers

Sclereids

Scattered in tissue. Cells as long as wide. Include stone cells (pears)

Fibers

Found in roots, stems, leaves, and fruits. Much longer than wide and contain lumen (tiny cavity). Lots of human uses!

categories of complex tissues

xylem and phloem, epidermis, periderm

Xylem and Phloem

transport water, ions, and soluble food through plants

Epidermis

a protective layer covering all plant organs. consists of parenchyma or parenchyma-like cells. Includes specialized cells that regulate the movement of gases in and out of the plant, secretory glands, hairs, crystal-isolating cells, and cells that increase the surface area of roots

Periderm

comprises the outer bark of woody plants. consists mainly of cork cells. has pockets of parenchyma-like cells.

Xylem

chief conducting tissue for water and minerals that are absorbed by the roots. composed of parenchyma cells, fibers, vessels, tracheids, and ray cells.

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

Tracheids

tapered at the ends with pairs of pits that allow water to pass from cell to cell. dead at maturity. thick secondary cell walls. may have spiral thickening on cell wall.

pits

areas without secondary cell

rays

function in lateral conduction and food storage. composed of long-lived parenchyma cells. produced in horizontal rays by ray initials of the vascular cambium. In woody plants, they radiate out from the center like spokes of a wheel

Phloem

conducts dissolved food materials produced by photosynthesis through the plant. composed of sieve tube members, companion cells, fibers, parenchyma cells and ray cells.

companion cells

narrow, tapered cells associated with 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

callus plug

prevents leaking of sieve tube contents when cell is injured

cutin

fatty substance on the surface of outer walls of epidermis that forms cuticle.

root epidermal cells

produce root hairs. increase absorptive area of root surface.

trichomes

found in some above-ground plants. outgrowths consisting of one to several cells

lenticels

Loosely arranged pockets of parenchyma cells formed by cork cambium that protrude through the surface of periderm. Allows for gaseous exchange.

periderm

replaces epidermis when cork cambium beings producing new tissue. constitutes outer bark. primarily composed of cork cells. dead at maturity. while still alive, cytoplasm secretes suberin (fatty substance) into walls. Makes cork cells waterproof and helps protect phloem.

secretory cells and tissue

cells may function independently or as part of a secretory tissue: flower nectar, citrus oils, glandular hair mucilage, latex, resins