Plant Tissues

Plant structures are composed of 4 main tissues. They are:

Epidermis – outer layer of cells which protect the plant from water loss and from fungi and bacteria

Vascular Tissues – transport water, sugars and other materials through the plant

Ground Tissues – tissues that the vascular tissue is embedded in…. usually storage cells

Meristematic – cells that divide

Plant Tissues

• Meristematic- growth

• Epidermal- protection

• Parenchyma- storage

• Sclerenchyma- strengthen and support

• Vascular- transportation

– xylem = water + nutrients

– phloem = plant products in solution

http://www.lima.ohio-state.edu/biology/images/zeaxs.jpg

Plant Tissues

In Most Plants

• Glucose is produced in the leaves through photosynthesis.

• The glucose is converted to sucrose (by dehydration synthesis) for transportation.

• The sucrose is converted to starch and stored.

RootsRoots have many functions.

1. anchor the plant

2. bind soil… stops erosion

3. absorb water and minerals

4. store food (usually as starch)

Root Types

Taproots• look large and fleshy, • are mostly found in plants

with two seed-leaves (dicots),

• grow deep into the ground to search for food,

• are able to store food, which is particularly necessary for perennial plants during periods of dormancy.

Fibrous roots• lie close to the surface of

the soil, • are mostly found in plants

with one seed-leaf (monocots)

• collect precipitation before it sinks deep into the ground,

• can often be found growing side by side with taproots- the two types of roots combine efforts to maximize efficiency.

Adventitious roots

• are common in both dicots and monocots

• develop to help the plant climb: for example, ivy

• help develop modified underground stems, such as bulbs

Aerial Rootsmodified to absorb water from the air

Aerial roots of an Orchid Orchids in bloom

Root Hairsare actually epidermal cells

adapted to absorb water

* Water enters the cells by Osmosis

* Minerals enter by Active Transport

Root Hairs

Regions of the root tip• Region of Maturation - Most cells

differentiate into various distinctive cell types. – Root hairs form.

• Region of Elongation - Cells become several times their original length. – Vacuoles merge

• Region of Cell Division - Composed of apical meristem in the center of the root tip. – Most cell division occurs at the edge of

the inverted cup-shaped zone.• Root Cap - Thimble-shaped mass of

parenchyma cells covering each root tip. – Protects tissue from damage. – Function in gravity perception.

The Root Tip

The Function of Root Tissues• Epidermis – outer layer of cells, provide protection from drying

out, water loss and infection.• Cortex – area made up of parenchyma cells. Parenchyma

cells are usually storage cells• Endodermis – regulates materials entering the center of the

root.• Pericycle –the outermost layer of cells of the stele• Xylem – transports water• Phloem – transports sugar• Stele – Also known as the “Vascular Cylinder”…… made up of

the xylem and phloem• Pith – tissue located in the center of the stem• Apical Meristem - (Meristematic Tissue) – tissue that in a

constant state of growth… apical means “located at the tip”• Meristem accounts for the increase in length of the roots and

stems.

Dicot Root X-section

Monocot root X-section

Dicot root X-sectionMost Dicot roots have an “X” of xylem cells in the center of the root.

The Casparian Stripregulates the movement of water into the root

Stele