Plant cells and tissues

Pages 79-82

Plant cell types

Following mitosis in meristem, two new daughter cells are formed

Small, undifferentiated, generic

Fate: remain meristematic cell, or specialize

Parenchyma

Mostly spherical in shape; living cells

Thin, pliable cell walls

Active in various metabolic functions; e.g., photosynthesis, storage of water, starch and oils

Xylem

Complex tissue: consists of more than 2 cell types

Plumbing system of the plant. Cells linked end-to-end form "pipes" through leaf veins, branches, stems and roots.

Two types of water-conducting cells, both dead when fully formed

Vessel elements: wide, short cells, open at each end, pits along sides, common in angiosperms

Tracheids: long, tapered cells, pits connect overlapping cells but no openings, found in gymnosperms

 

Phloem

Complex tissue

Conduction of dissolved sugars (sucrose)

Sieve-tube elements (long tubes called sieve-tubes)

Small pores in end walls, these walls called sieve plates

No nucleus at maturity

Companion cells (nucleated) aid sieve-tube elements in conduction

 

Phloem

Epidermis

Outermost layer of young plant body (usually one cell layer thick)

Epidermal walls covered with fatty substance called cutin

cutin forms protective layer called the cuticle

Periderm

Replacement tissue for the epidermis

Constitutes the outer bark

Cork cambium, a lateral meristem, produces cork cells

Cork cells: dead cells with suberin in cell walls

Suberin: a waxy substance, prevents water loss

Lenticels

Pockets of loosely arranged parenchyma cells

Allows for air exchange

 

Periderm

Tissues

Tissues: group of cells of the same type having a common function

Three basic types of tissues, found in all plant parts. Most composed of multiple cell types.

Dermal tissues

Protective or bounding layers

Vascular tissues

Transport materials

Ground tissues

Other functions, such as storage and photosynthesis

Primary Tissues (produced by apical meristem)

epidermis

the outer layer of cells of an herbaceous plant

primary xylem

vascular tissue for transport of water

primary phloem

vascular tissue for transport of food in solution

pith

tissue at center of the stem (parenchyma)

cortex

tissue between epidermis and vascular tissue (parenchyma)

Secondary Tissues (produced by lateral meristems)

Vascular Cambium a lateral meristem, develops between primary xylem and phloem

Secondary xylem

Tracheids

Vessel elements

Fibers

Secondary phloem

Sieve tube elements

Companion cells

Fibers

Cork Cambium, the other lateral meristem

Cork (bark)

Lenticels