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1

Meristematic tissues

Cell division or constant growth=meristematic tissue

-primary (apical). Apical meristems
•shoot
•root
•crown (i.e. Turfgrass)

-secondary (lateral). Lateral Meristems
•Vascular Cambium (veins)
•Cork Cambium (bark)

2

Permanent tissues

-simple (one cell type)
•parenchyma
•sclerenchyma
•collenchyma

-complex (more than one cell)
•xylem
•phloem
•epidermis
•cork

3

Primary Growth tissue

Happens in APICAL MERISTEMS

-occurs when length is added to a stem or root due to cell division approximately 1/10 inch from root to shoot tip

-occurs in ALL PLANTS -woody and herbaceous

-vertical "lengthening"= Apical meristems

4

Secondary growth tissue

-secondary growth tissue happens in lateral meristem tissue

-horizontal growth contributes to the wood in trees or shrubs

-happens only in woody roots and stems

-thickening or widening= Lateral Meristems

5

Primordia

*waiting for mitosis. Undetermined meristatic tissue.

•Primordia is a group of cells that represents the initial stages in development of a plant organ (plural, primordium)

•On stems, nodes containing leaf and axillary bud primordia form at regular intervals alternating with internodes (space between nodes). Primordia develop later into a leaf & auxiliary bud.

6

Permanent Meristem Tissues

*arise from apical or lateral meristem

•all initial growth comes from the meristem. BUT some cells differentiate to become either permanent

-simple tissues (parenchyma, sclerenchyma, collenchyma)

-complex tissues. (Xylem, phloem, cork)

7

3 types of permanent meristem tissue

1) Protoderm(complex) hence "derm"
2) Ground (simple)
3) Procambium (complex)

•each type is responsible for different functions of the plant

•simple tissues are made up of one cell type in a mass. Complex tissues have a mix of cell types

8

Protoderm (type of permanent meristem tissue). THINK DERM

Complex

Matures to form epidermis
-flattened irregular layer covers roots, shoots and leaves

Some of these epidermal cells specialize to become

•guard cells-help is gas exchange. Found in lower epidermis of leaves
•root hairs-emerge from the epidermal cells just above root tip and help absorptive surface of root

9

Epidermis

A single layer of cells on exterior of leaves stems, flowers and roots

•exudes a waxy material that reduces water loss

•Leaf epidermis cells may form hair
•root epidermal cells form root hairs

10

Ground (type of permanent meristem tissue).

Simple

•makes up the pith of stems and roots

*differentiates into cork cambium that makes cork aka bark for woody plants
•Ground tissue is the storage cortex inside of roots
•provides cushioningC support and fill for the plant.

11

Parenchyma (cell type in plant)

•makes up cortex of stems & roots
•makes up mesophyll layers of leaves, contains chloroplasts
•Always mesophyll
•LIVING CELLS
•Stores starches, oils, water, other sudstancds

•WOUNDS ARE FILLED WITH PARENCHYMA CELLS. PLANT PROVIDES A SEAL TO WOUND

12

Collenchyma (cell type in plant)

•living cells, dead at maturity
•cell walls thickened with cellulose
• They lack the hardening agent lignin
•often occur just under epidermis and often are found mixed with parenchyma cells to make up cortex
•provides flexible support for herbaceous stems, petioles, & leaves

13

Sclerenchyma (cell type in plant)

•tough thick walls usually reinforced with the polymer lignin
•normally dead at maturity. The cell walls harden after dying for extra strength=wood

•common in stems or bark, may occur elsewhere (protective function)
•two forms of protective
-sclerids-can protect seeds (peach pit)
-fibers-long thin cells that provide structural support. (Rope)

14

Procambium (type of permanent meristem)

Complex

THINK VEINS/ VASCULAR

•primary phloem (herbaceous and woody)
•primary xylem (herbaceous and woody)
•Vascular cambium (woody plants only)
*gives rise to lateral meristem which consists of
-secondary phloem
-secondary xylem
•Cambium is found wherever there are veins-leaves, stems and roots.

15

Function of roots

•Anchor the plant
•absorb water and minerals
•food and storage
•All roots perform similar functions

•angiosperm monocot, angiosperm dicot and gymnosperms roots do have internal structural layouts that differ slightly

16

Root cap

Jelly like substance

Root caps are designed to prevent damage to the meristem from sharp soil particles

Jelly like substance

17

Cortex cells. [in roots]

Cortex cells are for storage of waters and starch.

Parenchyma and Collenchyma cells found here !!!!!

18

Root hairs

• Extensions of epidermal cells
• vast majority of water and mineral absorption occurs through root hairs

•extremely fragile
• trees and shrubs lose 90% of the root system during transplanting including all the root hairs

Every route hair consists of one microscopic single cell!

19

Branch roots

• form from the Pericycle, which is between the endodermis and the phloem near the center of the root

-branching increases the number of root tips and absorption area
-branch roots tend to form right angles for more expansion

20

Two main types of root systems

• Fibrous

•Tap root (anchor=stronger)

21

Adventitious stems and roots

•basis of propagation by stem and leaf cuttings Roots growing from leaves

•formed my meristematic tissues

Forces one organ to grow on another
THERE ARE ADVENTITIOUS ROOTS ON CORN

22

Functions of Stems

• support leaves, flowers, fruit

•transports raw materials to leaves

•transports sugars made by leaves to other parts of plants

•Can store starches, sugars, water

23

2 types of stems

•herbaceous: only form primary vascular tissue. Primary tissue = basic xylem and phloem, not woody

•woody: forms secondary growth from lateral cambium (thickening) that becomes hardened overtime
*also called secondary xylem or vascular cambium

24

Other stem forms

•Rhizome- underground, horizontally growing stem

•stolen-horizontally growing stem just above ground level

• tuber-underground stem made primarily of storage tissue. Ex) potatoes

•corn-thickened, compressed underground stems. Ex) gladiolus

•bulb- underground stem with thick storage leaves. Ex) onion, daffodil

25

Terminal bud

Houses the apical meristem

26

Node

Attachment point for leaves and auxiliary buds

27

Axiliary bud

A subapical meristem at node, capable of growing into a new stem

28

Internode

Stem space between two nodes

29

Leaf scar

Left on stem after leaf falls off

30

Lenticel

A pore or opening in the bark

31

Bud scale

Modified leaves that wrap around buds to protect the bud from the elements

32

Bud scale scar

The scars left behind when the bud start growth after dormancy. Also called growth rings

-distance between two bud scales scars; usually one years growth

-sometimes a late frost in April can result in two sets of Bud scale scars in the same year

33

Rhizome

Underground, horizontaly growing stem

34

Stolon

Horizontally growing stem just above ground level