Plant Structure & Function Project

Objective

• summarize information on page 535-547

Requirements

• a clearly marked section for each structure ( leaf, stem, root) that includes:

1. What the structure does to support plant function
2. How the structure works
3. Details of the secondary structures involved and what they do
4. Labeled diagram or illustrations

Summary

1. Roots absorb water + dissolved minerals from the soil


2. Water + minerals are transported upward from roots to shoots= xylem sap


3. Transpiration ( loss of water from leaves through stomata) creates a force within leaves that pulls xylem sap upward


4. Through stomata leaves take in carbon dioxide and release oxygen. The carbon dioxide provides carbon for photosynthesis ( process of which plants make their own food) while oxygen is used for cellular respiration ( the air we breathe)


5. Sugars are produced by photosynthesis in the leaves


6. Sugars are transported as phloem sap to roots and other parts of the plant


7. Roots exchange gases with the air spaces of soil, taking in oxygen and releasing carbon dioxide. In cellular respiration, oxygen supports the breakdown of sugars

The Root

ROLE

1. keep the plant in the soil


2. hold the stem in place


3. holds the soil to prevent erosion ( water washes away soil)
   
   

FUNCTION

• brings nutrients in the plant

1. Roots absorb water by photosynthesis and replace water by transpiration


2. Roots absorb dissolved minerals and regulate the quantity of these minerals entering the rest of the plant


3. Roots store starch made from the food produced by the leaves. Some of this stored food is used by the cells of hte root itself= transported to other plant parts that require it
   

SECONDARY STRUCTURES

• outer surface of root= absorbing function


• root systems are divided and subdivided into networks of roots to increase surface area


• roots absorb the most when their external surface area is enlarged

EPIDERMIS

• protects + enclose the interior root structures


• absorb water and dissolved minerals from soil


• root hairs enlarge surface area for absorption


• perform cellular respiration= food
  

SECONDARY STRUCTURES

• contain no chloroplasts= can't make food

• glucose used for cellular respiration comes from starch stred in the cortex layer of the root
  

CORTEX

• contain large vacuoles for food storage


• vacuoles are made from starch= consists of carbohydrate made by leaves
  
• cortex makes up a proportion of the volume of the root, particularly in young roots, where it functions in the transport of water and ions from the epidermis to the vascular (xylem and phloem) tissues. In older roots it functions as a storage tissue

ENDODERMIS

ROLE

• determines what enters the vascular system for tranport to the rest of the plant
  

SECONDARY STRUCTURES

• special cells in the endodermis makes sure that materials in the centre of the root are filtered
  
• filtering keeps harmful substances out= allowing nutrients and water into the root's vascular tissue= nutrients and water transports to the rest of the plant
  
• selectively permeable membrane of an endodermis cell= pathway into the root's vascular tissue
  
• membrane of an endodermis cell= blocks passage of large particles which get through the endodermis if the cell membrane selects them= endodermis makes sure which minerals and how much of it gets through the vascular tissue at the centre of the root
  

VASCULAR TISSUE

SECONDARY STRUCTURES

• vascular cylinder= contains both phloem + xylem
  
• xylem= transport water+ minerals+ other dissolved materials absorbed by the root to the upper parts of the plant


• phloem= conduct dissolved food
  
• phloem conducts dissolved food into the root= leaves manufactre extra glucose
  
• phloem conducts dissolved food out of the root and upward into the plant's stem and other structures= food storage
  

In result

• xylem= conducts water and minerals from the roots upward and throughout the plant


• phloem= transports dissolved foods in all directions within the plant.

The Stem

water from this willlow's roots must travel upward.sideways, and downward through its stems to reach the most distant leaves. Food produced by the outermost leaves travel up, across, and down to reach the roots.

ROLE

• brown, rigid stems= long life span for plant

• vascular bundles in monocots are scattered throughout the stem cross section

• vascular bundles in dicots are gathered together in orderly rings
  
• supports and gives nutrition to the plant

• holds plant's leaves up to the sun

FUNCTION

1. water + dissolved mineral nutrients are transported from the roots to the leaves ( performed by the xylem)
   
2. newly manufactured food molecules are transported from the leaves to the roots for storage ( performed by the phloem)
   
3. food stored in the root is transported to any plant part that needs it ( performed by the phloem)
   

SECONDARY STRUCTURES

Stolons

• above-ground horizontal stems

• produce new plants where the nodes in the stem touch the ground

Rhizomes

• underground, horizontal stems
  
• have long and thin stems or thick and fleshy stems
  


• reproduces asexually= node of the stems has a bud
  
• have enlarged sections called tubers

Corms

• a short, thickened, underground, upright stem where food is stored

EPIDERMIS
ROLE

• layer of cells that protect the inner tissues

SECONDARY STRUCTURES

• covered by a cuticle

• stomata allows gases to enter and exit
  
• contains chloroplasts to perform photosynthesis
  

CORTEX AND PITH

ROLE & FUNCTION

• region of ground tissue between the epidermis and the vascular bundles is the stem cortex; the region of ground tissue in the center of the stem is the pith

• cortex= cells are irregular in shape and arrangement

• pith= cells walls are thin and there are more air spaces among the cells

• cortex stores food in the form of starch

• pith stores water and small amounts of food
  
• the cortex and the pith don't transport food and water
  

SECONDARY STRUCTURES

• turgor helps keep stems straight

The Leaf

ROLE OF THE LEAF

1. convert light into food= photosythesis
2. provide shade and camouflage for other organisms
   
3. fallen leaves provide habitat+ food for decomposers ( ex. fungi&bacteria)
   
4. add beauty to environment

EPIDERMIS

What is an epidermis?

• the epidermis is the external cells that protect the leaf from underneathe


• acts as a barrier to invaders such as fungi and bacteria

• cell margins fit tightly together

Secondary Structure: Cuticle

• since the epidermis is not completely waterproof, the cuticle performs this job
  
• a thin waxy covering on the top layer of leaves


• blocks gases through the cells of the epidermis

Result: both the cuticle+ epidermis are transparant= allows light through the leaf

STOMATA

What is a stomata?

• allows gases to enter and leave for photosynthesis ( process of which plants make their own food) and cellular respiration ( the air we breathe)

• stomata is an opening or pore in leaves that is surrounded by guard cells
  
• stomata are tiny holes within the epidermis
  

Secondary Structure: Guard Cells

• work together in pairs and possess thick walls

regulate rate of gas exchange by controlling the size of the stomata

• large opening of stomata= faster the leaf can exchange oxygen and carbon dioxide

guard cells surround the stomata and are shaped like two cupped hands= changes within water pressure causing the stoma( singular of stomata) to open or close= when guard cells are full of water they swell up and bend away from each other= opening the stoma

during dry times= the guard cells close

when guard cells swell= stomates close

when guard cells shrink= stomates open

plants respond to changes in temperature and humidity by opening or closing their stomata

in result, guard cells regulate the opening and closing of the stomata+ control the exchange of gases between the leaf and the surrounding atmosphere

SPONGY LAYER

Located beneath the palisade layer, its cells are irregular in shape and loosely packed. Although they contain a few chloroplasts, their main function is the temporary storage of sugars and amino acids synthesized in the palisade layer. They also help in the exchange of gases between the leaf and the environment. During the day, these cells give off oxygen and water vapor to the air spaces that surround them. They also pick up carbon dioxide from the air spaces. The air spaces are interconnected and open to the outside through the stomata (singular stoma).

VASCULAR TISSUE

What is a vascular tissue?

• found in the veins of a leaf which consists of xylem ( transports water& minerals from roots-->stem--->leaves) & phloem ( transports sugar/food)
  
• veins conduct water & dissolved minerals in and out of the leaf

• to secure CO2 and release O2
  (and the reverse in the dark)

Veins in a leaf perform 3 fluid- conducting functions

1. conduct water into the leaf
   
2. conduct dissolved minerals into the leaf
   
3. conduct dissolved carbohydrates ( nutrients) out of the leaf
   

Secondary Structures

• leaf cells produce food by photosynthesis= dissolved carbohydrates exits the leaf= food is brought to the non-photosynthesizing parts of the plant
  

PALISADE CELLS

• palisade cells are found in leaves
  
• produce sugars by photosynthesis
  
• contain lots of chloroplasts to absorb light
  
• cells are block shaped so that many can be packed into the leaf

• top layer is exposed to the light & bottom layer is exposed to the gases in the spongy layer= energy + raw materials are available to each cell= maximizes light to make photosynthesis work

Glossary

LEAF
STEM

ROOT

Corms
- a short, thickened, underground, upright stem where food is stored



Cortex
- layer of tissue between the epidermis and the vascular tissue of the plant; irregular in shape and arrangement



Cuticle
- waterproofing function of the leaf



Endodermis
- located inside the cortex where it filters material in the root



Epidermis
- external cells that protects the plant



Palisade Cells
- leaf tissues that is within the mesophyll in leaves of dicots



Pith
- soft and spongy tissue in the center of a stem



Stolons/ Runners
- a horizontal, underground stem



Stomata

- an opening or pore in leaves that is surrounded by guard cells



Tubers
- Underground food storage organ of a plant



Turgor
- status of water content of a plant cell



Vascular Cylinder
- cylinder of vascular tissue of the root which is clumped together( contains phloem+xylem)


Veins
- vascular bundles in a leaf