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Page repaired and totaled 10/30/09. If you put something in that is not there please see me ASAP. Mr F

 

Overview:

Leaves - what do they do, and how do they do it -

     Leaves are the food and energy conversion source of the plant. They are the factories that produce food for a tree/plant from sunlight, carbon dioxide and water (photosynthesis). This complex process needs all of these factors to carry on, if one is absent or not there then photosyntesis will not work. One of the factors that is necessary to this process is water. The roots of a tree or a plant embed themselves deeply into the ground supplying a firm base for the plant. But they also bring water from the soil up to the leaves of the plant/tree. To do this there is xylem which pulls water up the plant and to the leaves and there is phloem which flows water down the plant. Another factor is sunlight which is also necessary for photosynthesis. The more sunlight that is shined on the plant the faster it can photosynthesize because it converts that energy from the sun into energy it can use. The final necessity for the process is carbon dioxide which enters the plant through the mocroscopic opening called the stoma located on the bottom of most leaves.

 

 

Leaf Anatomy

 

Cuticle- A thick wazy layer that protects the leaf from water loss and injury. Tends to be thicker on the top of the leaf than it is on the bottom. Composed of an insoluble cuticular membrane, and covered with soluble waxes

Upper Epidermis- Helps deter water loss, layer of plants protection. Permits most of the light that touches it to pass through

Palisade Mesophyll Cell- Filled with chlorplasts, carries out most of the photosynthesis in the leaf. The cylindrical shape allows a large amount of light to be absorbed by the chloroplasts

Bundle Sheath cell- a layer of cells in a plant leaf that forms a sheath surrounding the vascular bundle

Xylem- Supplies water and minerals

Phloem- transports nutrients and carbs down the plant

Lower Epidermis- A layer of plant's protection

Spongy Mesophyll-The site of gaseous exchange for photosynthesis and respiration

Guard Cell-speciailized cell in the epidermis of plants that controls the opening and chlosing of stomata by responding to changes in water pressure

Stoma-opening in the underside of a leaf that allows carbon dioxide and oxygen to diffuse into and out of the leaf

Vein-a cluster of vascular tissue in leaves

 

This diagram does a great job of showing everything we are studying in very basic terms. You'll notice that all of the things in this diagram are terms that we need to know and it is easy to follow and see exatly where everything fits. It even shows how CO2 and O2 travel in and out of the Stoma.

 

An extremely easy way to determine whether you are looking at the top or bottom of a leaf is to locate the stoma.  The stoma is always at the bottom.

 

The following is the anatomy of the leaf.

 

The chloroplast, shown in the bottom right of this picture is where photosynthesis takes place in plants.  It contains saclike membranes called thylakoids.  A granum is a stack of thylakoids.  These thylakoids contain clusters of chlorophyll and other pigments and protein known as photosystems that are able to capture the energy of sunlight.  The stroma is the space outside the thylakoid membrane.  The thylakoid membrane serves as home to light-dependent reactions (1st stage of photosynthesis) and the stroma serves as home to the light-independent reaction (or Calvin Cycle), which is the 2nd stage of photosynthesis. 

 

Cross Section Diagram:

This diagram labels all the parts of the inside of a typical leaf, including xylem, phloem, guard cells, cuticle, upper and lower epidermis, and the pallisade mesophyll/ spongy mesophyll.

http://www.tutorvista.com/content/biology/biology-iv/plant-water-relations/opening-closing-stoma.php

This link is a video that explains the anatomy of a leaf, focusing specifically on the stoma and guard cells. It explains the opening and closing of the guard cells in an interactive way.

Photosynthesis Reactants/Products:

CO2 + H2O---> Glucose + O2

 

The reactants and products get in and out of leaf due to gradients. CO2 diffuses into the leaf, is used in the reaction to produce oxygen and then oxygen diffuses out 

 

http://www.cartage.org.lb/en/themes/sciences/botanicalsciences/PlantsStructure/AnatomyLeaf/AnatomyLeaf.htm

This website has really detailed explanations of what each part of the leaf does. It also has another, simplified diagram of a cross section of a leaf and shows how stoma work.

 

 

 

 

  

 

          This is a very good diagram that not only shows the parts of the leaf, but also shows their function. 

 

The orange arrow is the sun getting into the leaf.  It goes straight through th upper epidermis and into the palisade mesophyll cells, as shown in the diagram. 

 

The blue arrow represent the xylem.  The arrow shows the passage going into the leaf.  This is because the xylem transports water into the leaf to help it with photosynthesis.

 

The purple arrow reprsents the phloem.  It is leading out of the cell because that is that is where the products travel through down the plant.

 

The pink arrow represents carbon dioxide.  The carbon dioxide goes into the leaf through a stoma, and gets into the leaf.  The carbon dioxide will be used for photosynthesis.

 

This is a good video representation of a 3D model of photosythesis occuring by Virtual Cell Animation Project http://www.youtube.com/watch?v=hj_WKgnL6MI  

 

     Adding on to what the last edit had to say involving the leaf diagram, this video was very helpful to me regarded the way light effects pigments and chloroplasts in a leaf. This clip also introduces some terms which I do not believe we have learned aboutjust yet, but it clearly lays out how light effects pigment in a leaf and in turn affecting the color of the leaf.

 

 

 

This video shows a really cool digital animation of the processes of photosythnsis.

 The picture above breaks down the color spectrum and graphs that with the wavelength as the x axis and absorbance as the y. It goes along with the lab we did last week.

 

October 27, 2009 at 7:47:22 pm by bartsobczyk@yahoo.com

The upper part of the leaf is made up of three parts. The cuticle, the upper epidermis, and the palisade mesophyll cells.The cuticle is a transparent lining on the top of the leaf. It is waxy in order to prevent water loss. It is also transparent so that the suns rays can get through. Below the cuticle is the upper epidermis. The epidermis is made up of cells that prevent water loss, regulate exchange, and absorb water and mineral nutrients. It is also transparent so that the suns rays can get through. The cuticle and upper epidermis are both transparent so that light can get through to the palisade mesophyll cells. These cells perform photosynthesis. The light gets through into the cells where there are chloroplasts to absorb the light. This whole process helps the cells with photosynthesis.

 

October 27, 2009 at 7:55:35 pm by bartsobczyk@yahoo.com

There are also spongy mesophyll cells in the middle of the leaf. These cells have chloroplassjust like the palisade mesophyll cells. These cells though have less chloroplasts, because most of the light is absorbed by thepalisade mesophyll cells. They do have a few chloroplasts because these cells also perform photosynthesis. This means that they absorb water and gases just like any other cells in order to help with the plants processes.

 

October 27, 2009 at 8:07:08 pm by bartsobczyk@yahoo.com

Another important part of the leaf are the veins. The veins have a very important role in the leaf, because they transport things through the leaf and the plant. The veins are covered by bundle sheath cells. These cells cover the vein, and also help with photosynthesis. Inside of the veins are two other parts of the leaf. These parts are the xylem and the phloem. They each serve similar, but opposite roles. The xylem transports water from the bottom of the plant, and brings it up to the leaves and all the other parts of the plant. The phloem doesn't bring a reactant, it gives away the products. The phloem transports the sugars made by the cells through photosynthesis, down the plant, instead of up.

 

October 27, 2009 at 8:15:47 pm by bartsobczyk@yahoo.com

At the base ofthe leafis the lower epidermis. The lower epidermis is also a set ofcells that protect the leaf, covered by the cuticle. In some parts of the lower epidermis,there are little holes. The little holes are stoma. Themain function of the stoma is to let gas through.Mostly carbone dioxide. This is important for the function of the plant, because it needs carbone dioxide in order to perform photosynthesis.Because the stoma allows things toenter into the cell, there are also guard cells. These cells do exactly whatyou would expect, they guard thestoma. They make sure things that are supposed to stayout ofthe cell, stay out.

 

 

October 28, 2009 at 9:41:53 pm by Conor Brooks

the veins (pictured above). The

[ minor edit referring to existing graphic]

 

October 28, 2009 at 9:44:34 pm by Conor Brooks

the leaf (pictured in the bottom half of the cross section above). These

[ minor edit referring to existing graphic]

 

October 28, 2009 at 9:46:27 pm by Conor Brooks

lower epidermis (pictured and labeled above).

[ minor edit referring to existing graphic]

 

 

PIGMENTS

Xanthophyll: Xanthophyll is a yellow pigment found in most plants that is similar to chloropyll and is responsible for the production of carbohydrates by photosynthesis. This yellow color could be seen in Thurdsay's chromotography experiment. The pigment is from the 'cartenoid group' meaning that their molecular structure is based on carotenes, orange pigments, that have been oxidized to a yellow color. Animals cannot produce xanothphyll and therfore must come from diet or food intake.

 

Carotene: Carotenes are orange pigments necessary for plants to perform photosynthesis. They come from the carotenoid family, but represent the cartenoids without oxygen. There are two main types of Carotene: Alpha carotene and Beta carotene. Beta carotene is what is found in yellow, orange or green plants. The carotene protects the plant from ultraviolet light and are a form of Vitamin A for animals that consume plants high in beta carotene. Carotene traveled the furthest up the paper as seen becasue it is near the top. It did this because it is the lightest molecule (between, xanthophyll, chlorophyll, chloropyll b) therefore it was able to travel with the water all the way to the top.

 

Chlorophyll A: Chlorophyll is necessary for plants to perform photosynthesis. The 'A' pigment is a blue-green pigment. Chlorophyll A is the most common and most efficient form of chlorophyll that can be found in plants since it abosrbs light most efficiently; absorbing optimally at wavelenghts of light around 400-450 nm. Obviously Chlorophyll A is obviously not capable of absorbing light in the green and yellow part of the spectrum since green and yellow is what is reflected back to our eyes.

 

Chlorophyll B:  Chlorophyll B is the yellow-green chlorophyll pigment and differs from Chlorphyll A due to a minor differnce in a sidechain in its molecule. Chlorophyll B abosrbs optimally between 450-500 nm and 600-650 nm on the spectrum. Chlorophyll B is found mostly in plants and is considered an 'accessory pigment'.

 

 

<--- This is a visual on the pigments that were seperated

 

* all of the colors that were seperated in the picture are color pigments that leafs contain. Notice that there are not any purple or blue, which is logical since we do not see any purple or blue trees, even in the fall.  

 

Carotene weighs the least out of all the four pigments so therefore it rises up to the top of the slip of paper, and the chlorophyl b weighs the most so it stays at the bottom of the page.  This is shown in the following video..

http://www.youtube.com/watch?v=THqmpLdUaBA

                 

 

               This video does a good job of describing the pigments.  Not only does it explain them but it shows real life examples.  the guy in the video explains the pigments really well.  He names each of the one at a time and shows an example.  This  is a very good video and if you want to learn the pigments, this video will do it very easily

 

 --->Why are Plants Green?

Inside every leaf, there are millions and millions of tiny chlorophyll, which allow plants to perform photosynthesis and give them their green color. Chlorophyll absorb blue and red light--this means that the greens and yellows are reflected back, making plants appear green.  

 

To see a picture of what is happening inside the leaf when the chlorophyll absorbs blue and red light, follow this link: www.ebiomedia.com/BioGalleries/Inside-the-Cell-CHLOROPHYLL-ABSORPTION-SPECTRUM.html

 

Here are some of the notes I took during the class review game today.  These should help you study for the quizzes:

~During chromotography, which molecules go the farthest? : Carotene molecules, because it is the lightest molecule.                               

~Why are some leaves red? : Because the pigment carotene reflects the red light,.

~How many carbon dioxide molecules make two glucose molecules? : 12 (one carbon per molecule, 12 carbons in 2 glucose molecules)

~Why is maple syrup harvested in the fall? Explain: In the fall, phloem is carrying nutrients down the tree's tube systems which are close to the surface, and during the spring, xylem is bringing the nutrients up.

~What do guard cells guard against? : Dehydration

 

 

 

 

 

Futher Types of Pigment Found in Leaves:

 

Plants make an amazing variety of pigment molecules, far more than animals. After all, plants are creatures of light. They sense light to control their growth and rapid responses to the environment, and they use light as their source of energy. Plants produce pigments to advertise rewards for animals which pollinate flowers and disperse seeds. Thus, pigments may have physiological and/or biological functions.There are three different types of pigments that are found during the aging of leaves: chlorophylls (which were already discussed in detail), carotenoids, and anthocyanins.

 

• CAROTENOIDS

 

Carotenoids are very long-chain water-repelling pigments that are synthesized in the plastids of plant cells. In the sunflower, a common carotenoid, ß-carotene, is produced in the chromoplasts of the ray flowers to produce bright yellow-orange colors. These pigments primarily absorb in the blue wavelengths, allowing the longer wavelengths to be scattered and producing the yellow color. In autumn foliage, the carotenoids are left over in the chloroplasts and revealed from the loss of chlorophyll.

 

 

• CHLOROPHYLLS

 

The chlorophylls, a and b, are the pigments of photosynthesis. They are produced in chloroplasts in the photosynthetic tissues of the leaf. The chlorophyll molecules are very water repelling, partly because of the long phytol tail in the molecule. The closed ring of the molecule is similar to the hemoglobin of our blood, but holds a magnesium ion rather than iron. It is a large and expensive molecule to make, partly because each ring contains four nitrogen atoms. Chlorophyll is normally broken down towards the end of the leaf life span, and much of the nitrogen is resorbed by the plant.

  

 

• ANTHOCYANINS

 

Anthocyanins are water-soluble pigments produced via the flavonoid pathway in the cytoplasm of the colored plant cell. The attachment of the sugar molecule makes them particularly soluble in the sap of the vacuole, where these molecules are stored…..once they are launched. These are responsible for the pink-red colors of most flower petals, of most red fruits (like apples) and almost all red leaves during the autumn. Anthocyanins absorb light in the blue-green wavelengths, allowing the red wavelengths to be scattered by the plant tissues to make these organs visible to us as red.

 

 

 

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Identification of Leaves

SHAPE:

 

 

Leaf Blade

One way to identify a plant is by the shape of its leaf blade.

The main part of a leaf is the blade.

There are nine major shape categories:

Linear
narrow, with parallel or nearly parallel sides	Examples

 

Lanceolate
lance shaped, longer than broad and tapering to a point at the tip	Examples

 

Oblong
much longer than wide, with nearly parallel sides	Examples

 

Elliptic
shaped like an ellipse, wider at the center and tapering to equal tips	Examples

 

Ovate
egg-shaped, broader at the base than the tip	Examples

 

Cordate
heart-shaped, either the leaf shape or base	Examples

 

Reniform
Kidney-shaped	Examples

 

Spatulate
In the shape of a spatula or spoon	Examples

 

Orbicular
Round	Examples

 

 

GROUPING:

 

After you determine the leaf shape, you need to examine how the leaves are grouped on the stem.

Simple
Some leaves are simple, meaning they appear alone Examples ,

There are three main types of Simple leaf groupings:

Entire
Examples ,

 

Palmately lobed
Examples ,

 

Pinnately lobed
Examples ,

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Compound
	Other leaves are compound, meaning that they appear in groups and are made up of leaflets. Examples

 

Three kinds of compound leaves are:

Palmate
Examples
	Leaflets form a fan shape.

Pinnate
Examples
	Leaflets are opposite each other on the stem.

Bipinnate