Lecture notes on plant structure (download document it is in a table.)

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Angiosperms /Magnoliaphyta

Two groups

Dicots and Monocots

Are classified by following features MONOCOTS DICOTS

Seed leaves One cotyledon Two cotyledon

Leave veins Parallel Network of veins usually branched

Stems Random veins (vascular bundles)

Complex arrangement Veins (vascular bundles)are arranged in a ring

Flowers Multiples of three Multiples of four or five

Roots Fibrous root system Taproot system

(long roots)


The Root System

Root Ankers in the soil

Absorbs and transports minerals and water stores food

Root hairs Is an outgrowth of an epidermal cell

increase the surface area of the root


Is made up of stems, leaves and adoptions for reproduction

Stems Are the parts of the plant that are generally above the ground

Supports the leaves and flowers

Transport water minerals and sugar

Nodes Leaves and buds come out

(point which leaves are attached)

Internodes The portion of the stem between nodes

Leaves Main site of photosynthesis

Produces food of plant

apical bud (terminal bud) gives growth and length

(in many plats the terminal bud produces hormones that inhibit growth of the axillary buds)

Axillary buds one in each of the angles formed by a leaf and the stem

are usually dormant



Strawberry Plant Has horizontal stem (runner)

A runner is a means of sexual reproduction

A new plant can emerge form its tip

Iris Plant Have horizontal stems called rhizome(can spread and form new plants)

Store food and have buds

Potato Plant Has rhizomes that end in enlarged structures called tubers (the potato we eat)

Note: modified stem parts of the shoot system potato, iris,

Plant Cells And Tissues Are Diverse In Structure And Function

Central Vacuole Unique to the plant kingdom

Store water


Red colored pigments


Plant cell wall Made up of cellulose

Cell walls that support have a two part cell wall

Primary cell wall The primary wall is laid down first

Secondary cell wall Is more ridged between the plasma membrane and the primary wall

(has lequin)

are harder and tend to be thicker than primary cellwalls

Middle Lamella Hold the primary walls of adjacent cells together (a sticky layer)

Plasmodesmata channels of communication and circulation between adjaacent plant cells


2 cells in the phloem

conducting cell

companion cell

Primary cell wall

Secondary cell wall Thicker has lignin

Parenchyma cell (general cell) The most common cell in a plant

No specialization

Relatively small

Have only primary cell walls

Has a thin wall

Has multiple sided (like diamant 25 sides)

Thin wall


Can have storage vacuoles

Stores starch and sugars

Collenchyma cell Only have a primary wall but thickened

A alive at maturity

Becomes thick and elongated

Function: support plant that are still growing

(found at parameter of stems)

Sclerenchyma cells Rigid secondary cell walls

Hardened with lignin

Mature sclerenchyma cells cannot elongate

They occur only I regions that have stopped growing in length

When mature they are dead

(think of trees wood)

Fiber Is long and slender usually occurs in bundles

Primary walls parenchyma

Secondary wall is sclerenchyma

Hemp is a long fiber

Sclereid Or stone cell is shorter than the Fiber and has a thick irregular and very hard secondary wall

nutshell and seed coats

sclereid is scattered in the soft tissue of a pear


Two types Both having rigid , lignin-containing secondary cell wass

Tracheids Long cells with tapered ends

Water passes through pits

vessel elements Wider , shorter, less tapered

Note: Chains of tracheids or vessel elements with overlapping ends form a system of tubes that conveys water form the roots to the stems and leaves

The tubes are hollow

Because both tracheids and vessel elements are dead when mature

(the cells also function in support because of their rigid cell walls)

Food conduction cell Also known as sieve tube members

Have thin primary walls

No secondary cell wall

Remain alive during maturity

Xylem Vascular tissue contains water-conducting cells convey water and minerals upward from the roots

Phloem Vascular tissue contains sieve-tube members that transport sugars from leaves or stage tissues to other parts of the pant.


sugars (sap )




there are two cells in the phloem Conducting cell (the large one has no nucleus)

Companion cell with the nucleus

Three tissue systems make up the plants body

Epidermis The skin of the plant

Covers and protects

Defense against physical damage and infectious organisms

stem has no stomates is covered with

root has no cuticle (has root hair coming out)

Ground tissue system Cortex (consists mostly of parenchyma cells) and endodermis (innermost layer of cortex)

Fills the spaces between the epidermis and vascular tissue

Mainly parenchyma cells but usually include some collenchymas and sclerenchyma, Storage



has diverse function

Endodermis Controls entry of flow into the vascular tissue

Inside the endodermis - are mainly parenchyma cells

Lateral (axillery bud) meristern creates branch

Pith Part of dicot ground system fills the center of the stem (important I food storage

Guard Cells Regulate the size of the stomata

Vascular tissue system Xylem and phloem

Provides support and transports water and nutrients through the plant

Mesophyll Ground tissue of a leaf

Consists mainly of parenchyma cells


Meristem Unspecialized cells that dived and generate new cells and tissues

meristems At the tips of roots

And in the terminal (top)

and axillary buds of shoots

are called apical meristems

1. primary maristems shoot and root tips

result in growth and length - apical merisystem

1. Lateral-meristems

(axilery buds) In lateral buds-branches

Pericycle of roots -branched roots

2. Secondary meristems Vascular cambium

Produce, layers of xylem and poem

Secondary growth

Root cap the very tip of the root

protects the delicate cells