Chapter 4: Tissues

General Botany

What major group or organs do plants have?

roots, stems, leaves, and often flowers

What are the organs composed of?

Tissues

What are tissues?

A group of cells performing a similar function

Monocot Seed Leaf (cotyledon)

one seed leaf

Dicot Seed Leaf (cotyledon)

2 seed leaf

Monocot Leaf Vein

-veins run parallel to each other EX: grass or corn

Dicot Leaf Vein

veins form a net-like or branched pattern EX: maple or bean leaf

Monocot Flower Part

transport tubes are scattered randomly across the stem

Dicot Flower Parts

Petals and parts usually come in multiples of four or five

Examples of monocot plants

grass, corn, rice, wheat, lilies, and onions

Examples of Dicots

beans, roses, sunflowers, tomatoes, and most trees

What are meristems?

permanent region of growth where cells actively divide

What are apical meristems?

meristematic tissues found at or near the tips of roots and shoots which increase in length as the apical meristems produce new cells

What type of growth occurs in apical meristem

primary growth

What are the three primary meristems?

Protoderm, ground meristem, and procambium

Protoderm Function

produces epidermis of plants

Ground Meristem Function

produces ground tissues

Procambium Function

develops vascular tissue system creating the xylem and phloem

Xylem Function

transport water and minerals

Phloem function

transport sugar after photosynthesis

What are lateral meristems?

cylinders of dividing cells in the stems and roots that cause them to become thicker, that is, increase the girth of roots and stems EX: vascular cambium and cork cambium

Where is vascular cambium found?

length of roots and stems in perennial and many annual plants

Vascular Cambium function?

support and conduction making it responsible for most of the increase in a plants girth as it grows

What type of tissues are produced by the vascular cambium and cork cambium?

Secondary Tissues

Why do the vc and cork cambium produce secondary tissues?

because they are produced after the primary tissues have matured

Where are intercalary meristems found?

-small plants

-monocots

-grasses

Do grasses have lateral meristem?

No, they dont have vc or cork cambium, but they do have apical meristems

Where do intercalary meristems develop?

intervals along the stems

Are intercalary meristems similar to apical meristem?

Yes, because their tissue functions to increase the length of stems

How are plants tissues classified?

structure, origin, and function

Where does mitosis occur the most in plants

meristem

What do apical meristems allow plants to do?

they allow shoots to grow upward toward light and roots to grow deeper into the soil in search of water

What is a perennial plant?

plant that lives for many years

Where is the cork cambium located in relation to the vascular cambium?

outside of the vascular cambium

Where is the cork cambium located in woody plants?

just inside the outer bark

What does the cambium produce?

outer bark

How much of a woody’s plant’s length does the cork cambium run?

almost the full length of the plant

What type of plants have cork cambium?

woody plants, such as pear, orange, and apple trees

What are the 3 types of simple tissues?

parenchyma, collenchyma, sclerenchyma

Structure of parenchyma cells

-large vacuoles

-thin pliable walls

-living cytoplasm

-primary walls

What substances may parenchyma cells contain?

starch grains, oils, tannins, and crystals

What is aerenchyma

parenchyma cells with large air spaces

What is chlorenchyma

parenchyma with many chloroplasts

Do collenchyma cells have living cytoplasm?

Yes, they have living cytoplasm

Collenchyma cell wall structure

Thick walls

Where are collenchyma cells found

beneath the epidermis

Function of collenchyma cells

provide support to growing and mature plant regions

What type of plant regions do collenchyma cells support?

Growing and mature regions

What are sclerenchyma cell walls like?

thick, tough secondary walls, usually containing lignin

What happens to sclerenchyma cells at maturity

they die at maturity

What is the function of sclerenchyma

support

What are two forms of sclerenchyma?

sclerids and fibers

Sclerids are sometimes called

stone cells

What is a characteristic of sclerids

they are gritty and hard

What causes the hardnes of nut shells

sclerids

Where can fibers be found?

roots, stems, leaves, and fruits

What is found in the center of a fiber cell?

a tiny cavity called a lumen

What are fibers used for commercially

textiles, ropes, and strings

What are complex tissues?

tissues made of two or more types of cells.

What are the 2 most important complex tissues in plants?

xylem and phloem

Why is the epidermis considered a complex tissue?

it contains parenchyma cells and other specialized cells

Xylem’s main function

chief conducting tissue in plants

What cell types make up xylem?

parenchyma cells, fibers, vessels, tracheids, and ray cells

What happens to tracheids at maturity?

they are dead at maturity

What is special about tracheid cell walls?

they have thick secondary walls

Ray cells function

food storage

What are vessel elements

individual cells that make up long vessel tubes

Which xylem cells have thick secondary walls?

tracheids

What does phloem transport?

dissolved food materials, such as sugars, to all plant parts

Where do phloem’s sugars come from?

they are produced during photosynthesis

What are the two main phloem cell types?

sieve tube members and companion cells

What other components are found in phloem?

parenchyma cells, ray cells, and fibers

How are sieve tube members arranged?

end-to-end to form a sieve tube

What do sieve tube members form?

they form the sieve tube

What is the main function of companion cells

they work with sieve tube members in phloem transport

How are sieve tubes similar to xylem vessels?

both are formed by cells laid end-to-end

How thick is the epidermis usually?

usually one cell layer thick

Where can a double-layer epidermis be found?

in some aerial roots of orchids called velamen roots

What is the function of a double layer epidermis?

protects internal cells from desiccation

What do most epidermal cells secrete?

waxy substances within and on their outer walls

What is cutin?

a substance that forms the protective cuticle layer

What is the cuticle’s function

helps protect the plant and limits water loss.

What determines how fast water is lost by evaporation?

thickness of the cuticle

What are epidermal hairs?

outgrowths of cells from the epidermis

What are uniseriate hairs?

hairs made of one cell

What are multiseriate hairs?

hairs made of many cells

What are stomata?

small pores found in the leaf epidermis

What cells border the stomata?

pairs of specialized epidermal cells called guard cells

What is the function of guard cells?

they border and regulate the stomatal pore

What replaces the epidermis in woody plants?

the periderm replaces the epidermis

When does the periderm develop?

after cork cambium begins producing new tissues

Why is the epidermis replaced in woody plants?

the stem increases in girth as it grows

What does the periderm form?

outer bark of the plant

What are cork cells like at maturity?

they are somewhat rectangular and dead at maturity

What cells form the lenticels?

loosely arranged parenchyma cells from the cork cambium

What are lenticels

openings formed by parenchyma cells through the stem surface

What is the function of lenticels?

they allow gas exchange between air and the stem interior

What is the cork cambium

a tissue that produces new tissues as woody stems grow

What does the cork cambium help increase?

the girth, or thickness, of the stem

What are hairy plants?

pubescent