Title: Cells and Tissues
1Cells and Tissues
2Tissues
- Tissues are groups of cells performing a common
function. Tissues are specialized. - Main tissues are dermal tissue systems, ground
tissues, and vascular tissues.
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4Primary Growth Meristems
- Apical meristems
- Location Tips of roots and stems.
- Function Produce primary growth which results in
increase in length. - Produce three primary meristems protoderm,
procambium, and ground meristem. - Young buds and leaves are produced by apical
meristems, roots by root meristems.
5Secondary growth meristems lateral meristems
- Vascular cambium
- Location Thin, branching cylinder that runs the
length of the roots and stems of most perennial
and some herbaceous annuals. - Function Produces increase in girth (width).
- Cork cambium
- Location Exterior of the vascular cambium.
Similar in structure to the vascular cambium
forming a thin ring in the roots and stems. - Function Produces outer bark of woody plants.
6Shoot and Root Apical Meristem Tissues A) Lilac
shoot B) Radish root
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9Nonmeristematic Tissues
- Cells produced by meristematic tissues that
assume a defined shape and size related to their
specific function. - Simple Tissues Composed of one type of cell
performing a specific function. - Collenchyma, Parenchyma, and Sclerenchyma-Ground
tissues - Parenchyma is the most common type
10Parenchyma
- Location Found in all parts of higher plants
- Description Many sided, thin walled, alive at
maturity no secondary wall most have large
vacuoles containing starch, oil, tannins,
crystals, and other secretions. - Function Food or water storage.
- Edible part of most fruits and vegetables is this
type of tissue.
11Transfer Cells- A type of Parenchyma with
ingrowths Facilitate movement of solutes
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13Collenchyma
- Description Similar to parenchyma (alive, no
secondary wall) but have unevenly thickened
walls. - Location Usually occur just beneath the
epidermis layer. - Function in providing flexible support to leaves
and flowers.
Rhubarb collenchyma from petiole
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15Parenchyma (below) and Collenchyma (above) Note
the difference in cell wall size
16Sclerenchyma
- Description Cells with tough, thick secondary
cell walls, usually strengthened with lignin.
Cells are dead at maturity. - Function is support and strength.
- Two types of sclerenchyma are found in plants
- 1) sclereids may be found scattered throughout
various types of tissues (seed coats, nut shells,
stony endocarps, pear fruit) - 2) fibers are long cells with a small cavity
(lumen) in the center. Over 40 types of fibers
are used in commercial use in manufacturing
textiles and similar products.
17Sclereid type of sclerenchyma
18Sclerenchyma-sclereids From water lily
Sclereids from Peach
Sclerenchyma-fibers from Basswood
19Nonmeristematic tissues
- Complex tissues Composed of two or more kinds of
cells performing a specific function. Four main
types found in plants. - Xylem-Water conducting tissue
- Phloem-Sugar conducting tissue
- Epidermis-outer skin
- Periderm-replaces epidermis in woody plants
20Xylem-Complex tissue
- Description Consists of a combination of
parenchyma cells, fibers, tracheary elements
(vessel elements and tracheids) and ray cells. - Function Plumbing of the plant. Moves water and
dissolved substances throughout the plant - Location in vascular bundles with phloem
21Tracheary Elements
- Dead at maturity, thick secondary cell walls,
openings allow water to move through - Vessel elements consist of long tubes of
individual vessel cells which are hollow with
open bars at the end of the cell. Cells are
joined at the ends. Various types of secondary
wall thickenings (annular, helical, etc) - Tracheids. Tapered at the ends. Do not have
openings at the ends. Overlap where they touch,
pits in the cell wall allow water movement. - Tracheids found in gymnosperms Vessel elements
and tracheids found in angiosperms
22Xylem
- Vessels and tracheids are responsible for the up
and down movement of water. - Ray cells move water laterally. Ray cells are
produced by the vascular cambium and radiate out
from the center of stems and roots.
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24Vascular bundle from Squash
25Secondary xylem (wood) from Oak a-c Vessel
elements, d tracheid e-ffibers
26Development of vessel element from
undifferentiated cell
27Phloem-Complex tissue
- Description Derived from vascular cambium.
Includes sieve elements, fibers, parenchyma
cells, and ray cells. Composed of sieve-tube
elements and companion cells in angiosperms. - Function the movement of dissolved food
substances.
28Development of sieve-tube element from
undifferentiated cell
29Rendition of phloem in an angiosperm
30Sieve-tube elements
- Sieve-tube elements are laid end to end. They do
not have large openings but instead, have many
small pores in the the ends (Sieve-plates). The
cytoplasm of the cells extend through the pores
and are in contact with the adjacent cells
cytoplasm.
31Phloem
- Companion cells do not directly transport
dissolved food substances but control the
activities of sieve-tube elements. Sieve-tube
elements do not have nuclei. - Can repair themselves if damaged by producing
callose, which in combination with a protein,
plugs any holes in the phloem. This is usually in
response to insect damage. - Sieve-cells, found in ferns and conifers, are
similar to sieve-tube members but do not form
continuous tubes but overlap much as in the same
manner as tracheids. Also do not have nuclei.
Have albuminous cells which function as companion
cells.
32Sieve-tube elements and companion cells Example
from an angiosperm
33Sieve Cells and albuminous cells Example from a
gymnosperm
34Development of sieve-tube elements in squash
(angiosperm)
35Epidermis-Complex Tissue
- Location Outer layer of cells, one cell thick.
- Function Exchange material with the environment
and protect internal cells. - Epidermal cells secrete cutin on the surface of
the outer walls. Cutin forms the cuticle or waxy
layer that prevents the leaf from drying out. - On leaves, four types of specialized epidermal
cells. Small pores, called stomata, which are
bordered by guard cells. - Trichomes include microscopic extensions called
root hairs which increase the absorptive surface
of the root, hairs, and glands which secrete
substances.
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37Trichome on a leaf and stomata
38Periderm
- Function Replaces the epidermis on woody plant
stems. Protects the internal tissues. - Location Outer bark of the plant
- Description Consists primarily of cork cells.
These cells are rectangular, boxy cells which are
dead at maturity. Before they die, the cork cells
secrete suberin, a waxy substance, which repels
water. - Where suberin is not laid down, there are loosely
arranged pockets of cork cells. These are
lenticels and function to allow gas exchange from
the stem with the atmosphere.
39Transverse section of periderm from apple stem
40Lenticel