Do oranges have traces of starch?

This is for a chemistry experiment, so I just want to know if there are small traces of starch in oranges, and not whether or not I should eat an orange for its starch content, or something to that extent.

According to Healthy Eating, oranges contain 8.98g of sugar but does not contain any starch:

The natural sugar found in fruits doesn't create such a big response because it's balanced by the fruit's fiber content. One banana has 14.43 grams of sugar, compared to only 8.98 grams in an orange. The biggest difference between the two is in the amount of starch each contains. The orange doesn't have any, while the banana has 9.42 grams of starch.

Sources are varied. This paper studies starch in oranges (I can't access full paper). However, here authors mention that oranges contain practically no starch (beware, images are upside down). They refer to work by

Stahl A.L., Maturity studies of citrus fruits, 1938

and quote this work saying "starch content was measured to be 0.07-0.13%" in pulp of Pineapple oranges. Compare that to 22% of potato starch amount (dry mass).

Do oranges have traces of starch? - Biology

Metabolism is the sum of all chemical reactions in a living organism. These reactions can be catabolic or anabolic. Anabolic reactions use up energy to actually build complex biomolecules (think of anabolic steroids building muscle mass). The energy for anabolic reactions usually comes from ATP, which is produced during catabolic reactions. Catabolic reactions break down complex biomolecules, such as carbohydrates and lipids and release the energy stored within.

Think about It

  1. Is cellular respiration anabolic or catabolic? Explain.
  2. Is photosynthesis anabolic or catabolic? Explain.

Enzymes are proteins that facilitate chemical reactions in living systems by acting as catalysts in biochemical reactions. Enzymes speed the rate of the reaction by either bringing the reactants into close proximity or by binding to a single reactant and splitting it into smaller parts. Enzymes have a property known as specificity, which simply means that each enzyme catalyses a specific biochemical reaction. Enzymes are indispensable molecules of life. Enzymes are functional within a given range of temperatures and pH values for that enzyme.

Ripening and Vitamin C

Using a starch-iodine solution, students will measure the amount of vitamin C in ripe, half-ripe and unripe oranges. They will learn about the instability of vitamin C.

Research Questions:

  • Is there more vitamin C in ripe oranges or unripe oranges?
  • Is there more vitamin C in oranges that have been sitting out on the counter vs oranges stored in the fridge?
  • What is the consequence of purchasing old produce?
  • How can I measure the vitamin C in foods?

Vitamin C (also known as ascorbic acid) is highly unstable and has short shelf-life. While unripe fruits have high concentrations of vitamin C, this diminishes as the fruit ripens. As ripe fruits age, the vitamin C continues to disappear.

Students can evaluate these phenomena using a starch and iodine solution. Iodine reacts to starch by becoming purple unless vitamin C is present which is why the deep purple starch iodine solution turns clear when students drip it into the orange juice. While the clarity dissipates by the adding additional iodine starch solution, higher concentrations of vitamin C will require more iodine-starch solution to prevent the mixture from clearing.


  • Triple beam or scale balance
  • Corn starch
  • 2 gallons distilled water
  • Two one-gallon glass jugs (such as apple cider is sold in)
  • 50 ml concentrated HCl
  • 13 g iodine
  • 20 g potassium iodide
  • One 250 or 500 ml Erlenmeyer
  • Graduated cylinder
  • 1 liter beaker (other types of glass container will do)
  • 250 ml beaker
  • Burette
  • Funnel
  • Clamp and stand for holding burette
  • Ripe, half ripe and unripe oranges
  • Juicer (optional)

Although reagents and glassware can be obtained from a lab supply house, hopefully students can borrow these from their schools. Distilled water is available in large grocers or from your school lab. Cornstarch is available from grocery stores. It may be easier to get unripe oranges if you live in Florida or California where you can get them from a tree.

Experimental Procedure:

Before starting the experiment, make two solutions: (1) the starch reaction solution and (2) 0.01 N iodine.These two solutions are made as directed below.

Starch Solution

  1. Weigh out 1.2 g cornstarch powder and transfer it to a small saucepan.
  2. Make slurry of the cornstarch powder and 20 ml of distilled water.
  3. Add 180 ml to the slurry.
  4. Bring to a boil and stir (this can be done over the kitchen stove).
  5. Fill a one-gallon glass jug with a half gallon of distilled water.
  6. Add 47 ml of concentrated HCl to the one-gallon jug.
  7. Add 20 ml of the cornstarch solution to the one-gallon jug.
  8. Fill the jug with another half gallon of water.
  9. Stir. Cover with a lid and label.

0.01 N Iodine Solution

  1. Measure 12.7 g iodine and 20 g KI (potassium iodide) and transfer them to a 1 l beaker.
  2. Dissolve the reagents in 100 ml distilled water. Stir.
  3. Bring the total volume of the solution up to 1000 ml.
  4. Using a graduated cylinder, measure 378 ml of the solution made in steps 1 &ndash 3 and transfer to a gallon glass jug. Cover with a lid and label.

Starch-Iodine Solution

  1. Measure 50 ml of the starch solution and transfer to an Erlenmeyer flask.
  2. Measure 50 ml of the iodine solution and transfer to the Erlenmeyer flask, stirring it together with the starch solution until thoroughly mixed. Cover with cork. Label

Experimental Protocol

  1. Clamp your burette to a ring stand. Place a 250 ml beaker under the burette. Make sure the stopcock on the burette is closed.
  2. Using a funnel, add the starch-iodine solution to the burette, making sure that it does not over-fill. Practice opening and closing the stopcock so that you can easily count drops that come out when the stopcock is opened.
  3. Prepare your first orange sample by peeling the unripe orange and putting it in a juicer or manually squeezing the juice from the unripe orange into a beaker. Make sure you have at least 100 ml of juice in a beaker, using additional unripe oranges if necessary.
  4. Place the orange juice beaker under the burette and very gradually add the starch-iodine solution, counting the number of drops as you go. With each drop, the solution will react with the vitamin C and temporarily become clear. Once all the ascorbic acid is neutralized, the addition of the starch-iodine solution will not become clear, but will instead retain its dark color. Record the total number of drops it take to reach this point.
  5. Repeat this experiment using a half-ripe orange and a ripe orange. Consider repeating the experiment to compare ripe fruit that has been left on the counter with ripe refrigerated fruit.

Terms/Concepts: Vitamin C (ascorbic acid, Using a burette and making solutions, Concentration of vitamin C as a function of ripeness and age of fruit Chemical stability

Hobbs, Christopher & Elson Haas. Vitamins for Dummies. For Dummies Press (1999)

Katherine M. Phillips et al. &ldquoStability of Vitamin C in Frozen Raw Fruit and Vegetable

Homogenates&rdquo Journal of Food Composition and Analysis. 23 253&ndash259 (2010)

Linus Pauling Institute: Vitamin C

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In this science project, you will learn an interesting method for determining the amount of vitamin C in a solution. The technique you will be using is called titration.

Titration is used to determine the unknown concentration of a chemical in a solution. In a titration, a carefully measured amount of a second chemical is gradually added to the solution. The added chemical reacts with the original chemical, whose concentration is unknown. The original chemical is called the titrand, and the added chemical whose concentration is known is called the titrant, or titration solution. The titration solution reacts with the titrand, and the progress of this reaction is carefully monitored. When 100% of the original compound has reacted with the added chemical, the titration is complete. Now the concentration of the original chemical can be determined from the amount of titration solution that was added.

So you can better understand how a titration works, let us look at the specific example of determining the concentration of vitamin C. Vitamin C, also known as ascorbic acid, is the titrand in this case (because its concentration is unknown). You start with a measured volume of the titrand. The titrating solution that will added to the titrand is iodine. You will start out by using your iodine solution to titrate a known amount of vitamin C, using a solution prepared from a vitamin C tablet. You will carefully measure the amount of iodine solution needed to titrate the known amount of vitamin C. You will know when the titration is complete because you will add a third chemical&mdashsoluble starch&mdashto the solution. The starch acts as an indicator: the starch changes the color of the solution when the iodine/vitamin C reaction is complete. As soon as the solution changes color, you will stop adding iodine solution. Once you have calibrated your iodine solution with a known amount of vitamin C, you can then repeat the procedure to determine how much vitamin C there is in samples of fresh-squeezed orange juice.

The chemical reaction of iodine with vitamin C is called an oxidation-reduction reaction (chemists often use the shorthand 'redox reaction' to refer to this type of reaction). The ascorbic acid is oxidized to dehydroascorbic acid, and the iodine is reduced to iodide ions. Oxidation-reduction reactions always occur in pairs like this. The molecule that loses electrons is oxidized, and the molecule that accepts the electrons is reduced.

In this chemistry science project, you will investigate how different storage times affect the amount of vitamin C in fresh-squeezed orange juice. How do you think the amount of vitamin C will change over time, if it changes at all? Get ready to do some titrations to find out for yourself.

Do oranges have traces of starch? - Biology

Lakyn Allen, Landon Fox, Gina Thomas, Paola Ruiz , Christine Carroll

Proteins, Simple Sugars, Lipids, and Starch: An Experiment

Researching the Existence of These in Lemonade and Crackers

Abstract. Finding whether the components (proteins, simple sugars, lipids, and carbohydrates) were apparent in these foods (lemonade, crackers) were examined in an experiment designed by Kim Wootton. The process for finding proteins includes mixing the item with 30 drops of copper sulfate (CuSO 4 ) and 3 drops of sodium hydroxide(NaOH). A positive test result would appear as a deep blue, almost purple, color. The process for finding whether the food item contains simple sugar includes putting the food item in a test tube, mixing it with Benedict's Solution, and heating the entire tube up in a boiling water bath. A positive test would be indicated by a blue to orange color change. To find if lipids were present, we put 2 drops of our created solution (lemonade, or water/cracker mix) onto a drop of brown paper. Translucence indicated a positive test result. Finally, to test for starch, we put our item in a test tube and mixed in a drop of iodine. A positive result was indicated by a blue tinge in the tube. (Wootton 2014). Our collected data revealed a presence of simple sugar in both items, a presence of protein in only the lemonade, an appearance of lipids in neither, and an appearance of starch in just the cracker. This report will show this process and data results through pictures and words.

In this lab we explore the biochemistry of the components needed for life. All living things are made of 4 organic compounds: carbohydrates, lipids, proteins, and nucleic acids. We use these organic compounds daily in our bodies. Lipids are used for energy storage in organisms and also provide protection and insulation. Abundant proteins are enzymes, which regulate chemical reactions. Organisms use these compounds in the process called metabolism. This process consists of creating muscle tissue (anabolism) and breaking down substances like digesting food for energy (catabolism).

In order to find out the many different ways we as organisms obtain these essential organic compounds, we can test common food items we consume. For this lab we decided to test lemonade and crackers for lipids, starch, simple sugars, and proteins. This gave us a better understanding of what common foods could contain and how they interact with our inner biochemistry when we consume them.

This study was conducted at New Tech High @ Coppell, on September 11, 2014. We conducted four tests to two different edible items to see which what organic compounds were present. The four tests we conducted included simple sugar, starch, protein, and lipid. Our controlled group was a test tube of water. For each test, we started with two test tubes one filled with a diluted cracker liquid and one filled with country time lemonade. Then, we would add various amounts of different solutions, and recorded which kind of reaction each mixture had. We could tell a positive reaction took place if the initial color changed. If there was a negative reaction taking place, there would be no color change.

Overall, the results of the experiment we conducted were as expected. The only unexpected outcome when testing the lemonade mix was the Protein Test, which had a very slight positive reaction. The nutrition label states that there were 0 grams of protein in the mix, so the positive reaction could be due to residual in the test tube we used from previous experiments. Both the Lipids and Starch Tests had no reaction in the lipid test, there was not a translucent spot because the lemonade evaporated, and in the starch test, there was no reaction because the color did not change once iodine was added. In the simple sugars test, once we added 5 drops of Benedict’s and heated the test tube in a boiling water bath, the color of the mixture turned orange indicating a positive reaction. When testing the crackers, both the protein and lipids test had a negative reaction, because in the lipid test there was not a translucent spot (the mixture of crushed up crackers and water had evaporated), and in the protein test the color did not change. The simple sugars and starch tests had positive reactions, since the color in both mixtures changed once their experiments were completed.

Through our experiments, we discovered that Countrytime Lemonade contains simple sugars, but not lipids and starch. We received a weak positive result in the protein test. This was unexpected, but it is our belief that this was a false-positive due to poor instrument cleaning by the group before. The indication of simple sugars was expected as lemonade generally contains lemonade. When we tested the cracker, we found that it does contain simple sugars and starch, however it did not contain lipids or protein, which was expected.

The purpose of this lab was to determine the nutritional value of a few common household items that most of us use and are exposed to. We now know that Countrytime Lemonade mix does not contain lipids, starch or protein (although there was a discrepancy in our data regarding protein), while it does contain simple sugars. We also discovered that crackers do not contain protein or lipids, but do consist of simple sugars and starch. Discerning this type of information about the foods we take in is crucial for the promotion of a healthy lifestyle and better quality of life overall.

Reece, J. B. (2015). Campbell Biology: Concepts & Connections (Vol. 8). Upper Saddle River, New Jersey: Pearson Education.

Sample Lab Report-Ecology 101. (2004, September 22). Retrieved September 11, 2014.

Amylase on Starch Lab

In this experiment you will observe the action of the enzyme amylase on starch. Amylase changes starch into a simpler form: the sugar maltose, which is soluble in water. Amylase is present in our saliva, and begins to act on the starch in our food while still in the mouth.
Exposure to heat or extreme pH (acid or base) will denature proteins. Enzymes, including amylase, are proteins. If denatured, an enzyme can no longer act as a catalyst for the reaction.
Benedict’s solution is a test reagent that reacts positively with simple reducing sugars like maltose, but will not react with starch. A positive test is observed as the formation of a brownish-red cuprous oxide precipitate. A weaker positive test will be yellow to orange.

Add 1g of cornstarch to a beaker containing 100ml of cold distilled water. While stirring frequently, heat the mixture just until it begins to boil. Allow to cool.

1. Fill the 250-mL beaker about 3/4 full of water and place on the hot plate for a boiling water bath. Keep the water JUST AT BOILING.

2. Mark 3 test tubes A, B and C. “Spit” between 1 and 2 mL of saliva into each test tube.

3. Into tube A, add 2 mL of vinegar. Into tubes B and C, add 2 mL of distilled water. Thump the tubes to mix.

4. Place tube B into the boiling water bath for 5 minutes. After the five minutes, remove from the bath, and place back into the test tube rack.

5. Add 5 mL of the starch solution to each tube and thump to mix. Allow the tubes to sit for 10 minutes, occasionally thumping the tubes to mix.

6. Add 5 mL of Benedict’s solution to each tube and thump to mix. Place the tubes in the hot water bath. The reaction takes several minutes to begin.

Tube A: Starch + saliva treated with vinegar (acid)

What does this indicate?__________________________________________________

Tube B: Starch + saliva and water, treated in a boiling water bath

What does this indicate?__________________________________________________

Tube C: Starch + saliva

What does this indicate?__________________________________________________

1. What is the function of an enzyme?

2. Where does a substrate attach to an enzyme?

3. If an enzyme is present in a reaction, less ________________ _________________ will be needed to get the reaction started.

4. What is a common suffix found at the end of most biological enzymes?

5. Most enzymes are macromolecules called ________________.

6. Define denaturation of proteins.

7. Name 3 things that can denature or unfold an enzyme.

8. In this lab, what weak acid denatured the protein?

9. What was the purpose of placing one test tube in a hot water bath?

Phadebas in Forensic Biology

Phadebas has been used within Forensic Biology for many years. The original article that described the usefulness of Phadebas® in forensics was written already back in 1974*. It all started in UK but usage is now global. Originally the test was used for presumptive testing of suspicious stains, i.e. Tube test, but some labs started to crush Phadebas Amylase Testablets and spray them on filter paper. These papers were used as searching devices to localise hidden saliva stains on items, complementary to the Tube test that could only test visible stains.

This method spread but such a technical procedure caused big variations between labs. To solve this issue, Magle in cooperation with some Forensic Biology labs started a project to develop industrially pre-manufactured Phadebas coated papers. In 2007, Phadebas Forensic Press Test was launched to ensure that all papers

  • Are applicable directly from package
  • Include Batch number and Expiry date
  • Are easy to handle and use
  • Have negligible batch variations
  • Give no difference between labs and consequently have higher credibility as evidence material
  • Are produced in clean facilities to avoid the risk of contamination.

The principle behind the test is that Phadebas®, consisting of starch microspheres with a blue dye cross-linked to the starch, are immobilised on filter paper sheets. In the presence of amylase the starch is digested, releasing the water soluble dye, which diffuses through the pores of the filter paper. The resulting blue colour is visually observed on the non-reagent side of the Phadebas® paper. The Press test is performed when it is necessary to localise an amylase positive area on an item. If a very strong reaction is obtained with the Press test and there is no other obvious contaminating material, this is interpreted as an indication of saliva. The following link illustrates the methodology and simplicity with an Overview of Phadebas Forensic Press Test. For detailed instructions please follow Phadebas Forensic Press Test Instructions.

In-house testing at several independent forensic laboratories has determined that no other forensically relevant body fluid (sweat, semen and vaginal secretion) will react within 10 minutes using the current protocol, even after repeated deposition. The exception is faecal stains that may contain levels of amylase as high as those found in saliva. For this reason positive observations within areas obviously contaminated with faeces should not be interpreted for the presence of saliva. The presence of potential faecal material on an item should be recorded in the examination notes. In an independent trial performed in UK it was demonstrated that saliva from the most common pets did not give rise to any false positives.

To assure selectivity for saliva, the papers must not detect stains with an amylase activity below 2000 units/L within 40 minutes testing time. It has been demonstrated in several scientific articles that saliva dilute 1:100 can be easily be detected. For further info, please visit the Phadebas Archive.

The Phadebas Forensic Tube Test is more sensitive than the press test and used semi-quantitatively for the presumptive testing of saliva deposits. If it is suspected that the stain to be tested is a weak saliva stain, or if testing the supernatant from an extracted stain or swab, Phadebas tube test offers a better method than using Phadebas paper. A tube test may also be carried out if amylase is detected (using the Phadebas® Forensic Press test) in an area that exhibits other staining such as semen, blood or heavy vaginal deposits. The Tube test is used in two ways qualitative and quantitative. The qualitative test relies in the observable colour difference between the positive test and a blank whereas the quantitative test makes use of absorbance spectrophotometry to exactly measure the α-amylase activity.

* An Improved Test for the Detection of Salivary Amylase in Stains, Willott, G. M., Journal of the Forensic Science Society 1974 14: 341-344

Salty Science: Is There Iodine in Your Salt?

Have you ever noticed if the salt you're using says it's "iodized"? Iodine is a micronutrient, which means we need it in small quantities to be healthy. Because iodine is relatively rare in many people's normal diets, it's added to table salt. Then when people salt their food, such as tasty turkey, stuffing and mashed potatoes, they're also getting iodine. In this science activity you'll use some kitchen-friendly chemistry to investigate which types of salt have iodine and which don't. Then when you sit down to your Thanksgiving dinner, you can know whether to also give thanks that you're helping combat iodine deficiency.

Micronutrients, such as iodine, are types of nutrients that people need in small amounts. Iodine is important for a person's thyroid to function normally. (The thyroid is a gland in the neck that makes key hormones.) It is found in small amounts in other foods, including saltwater fish, seaweed, shellfish, yogurt, milk, eggs, cheese and a handful of other edibles. If a person doesn't consume enough iodine, they can become iodine deficient. The lack of this micronutrient can cause different medical problems (usually due to hypothyroidism caused by a thyroid that does not make enough hormones). These conditions include goiter (a visible swelling of the thyroid) as well as serious birth defects. In fact, iodine deficiency is the most common preventable cause of mental retardation.

Iodine (in the form of iodide) is added to table salt to help prevent iodine deficiency. Since the 1980s there have been efforts to have universal salt iodization. This has been an affordable and effective way to combat iodine deficiency around the world, but not all salt contains iodine, however. You'll investigate whether different salts have iodine by mixing them with laundry starch, which forms a blue-purple&ndashcolored chemical with iodine. (Vinegar and hydrogen peroxide are added to the salt solution to help this chemical reaction take place.)

&bull Disposable plastic cups that are 10 ounces in size or larger. (Alternatively, you could use smaller cups and scale down the activity.)
&bull Distilled water
&bull Measuring cups
&bull Measuring spoons
&bull Laundry starch solution, also called liquid starch (Alternatively, you could make a suitable starch solution by dissolving one cup of starch-based biodegradable packing peanuts in two cups of water.)
&bull Iodine antiseptic solution (optional) (Use either an iodine tincture or povidone-iodine solution, found in the first aid section of grocery stores and drugstores. If the iodine doesn't come with a dropper, you'll also need a medicine dropper.)
&bull Disposable plastic spoons
&bull At least three different types of salt to test&mdashfor example, plain (noniodized) table salt, iodized table salt, pickling salt, rock salt, kosher salt, "lite" salt and sea salt (If you aren't using the iodine antiseptic solution, include iodized table salt.)
&bull 3 percent hydrogen peroxide
&bull White vinegar

&bull If you are using an iodine antiseptic solution, you can prepare a positive control cup so you know what the reaction between iodine and starch should look like. To do this, pour one half cup of distilled water into a disposable cup, add one half teaspoon (tsp.) of laundry starch solution and then add five drops of the iodine antiseptic solution. Be careful when handling the iodine because it can stain.
&bull Stir well with a disposable plastic spoon. What happens to the liquid when the iodine is added?

&bull Pick one of the types of salt you want to test and measure out four tablespoons (tbsp.) into a clean, plastic, disposable cup. Add one cup of distilled water to the salt and stir well for about a minute with a clean, disposable plastic spoon. You do not need all of the salt to dissolve.
&bull Then add one tbsp. of white vinegar, one tbsp. of hydrogen peroxide and one half tsp. of starch solution. What do you think the purpose of the starch is?
&bull Stir the salt solution well with the disposable plastic spoon and then let the solution stand for a few minutes. What happens to the solution after you stir it? Does it become a blue-purple color?
&bull Repeat this process using the other, different types of salt you want to test. For each type, be sure to use a different, clean disposable cup and spoon. Do any of the other salt solutions become a blue-purple color?
&bull Based on your results, which salts do you think contain iodine (in the form of iodide) and which do not? Do your results agree with the labeling on the salt packages, which often say whether the salt contains iodide or not?
&bull Extra: Try this activity with even more different types of salts. For some ideas, see the Materials list above. Which types of salt contain iodine and which do not? Do your results agree with their labeling?
&bull Extra: In this activity you added vinegar because it is an acid and helps the chemical reaction take place. Try testing the iodized salt solution again but this time leave out the vinegar. Does the reaction still take place, turning the solution a blue-purple color? If the reaction occurred, did it take a longer amount of time to happen?
&bull Extra: Temperature often affects chemical reactions. You could try this activity again, but test an iodized salt solution at different temperatures (by heating or cooling the distilled water). How does changing the temperature of the solution change how the color-changing reaction takes place?

Observations and results
Did the iodized table salt solution change to a blue-purple color when you mixed in the starch? Did the "lite" table salt similarly change color whereas most of the other salt types did not?

In this activity you should have seen that the iodized table salt and the "lite" table salt solutions both changed to a blue-purple color (as did the iodine antiseptic solution, if you used it). This indicates that iodide is present in these types of salts. You likely saw no color change for the solutions made using the noniodized salt, rock salt, kosher salt or sea salt because these varieties do not typically contain iodide.

The starch solution was used in this activity because it forms a blue-purple&ndashcolored chemical when combined with iodine. Because the solution&rsquos original pH needs to be changed for this chemical reaction to effectively take place, vinegar (an acid) is also added. Hydrogen peroxide is used to turn the salt's iodide into iodine, which the starch reacts with.

Be sure to thoroughly wash any measuring spoons or other utensils that came into contact with the solutions made in this science activity. You can dispose of the solutions by pouring them down the drain.

More to explore
Micronutrient Information Center: Iodine, from the Linus Pauling Institute, Oregon State University
Micronutrient Deficiencies: Iodine Deficiency Disorders, from the World Health Organization
Testing for Iodide in Table Salt ( pdf ), from Stephen W. Wright, Journal of Chemical Education
Determining Iodide Content of Salt, from Science Buddies

This activity brought to you in partnership with Science Buddies

Top 8 Experiments on Translocation in Plants

The following points highlight the eight experiments on translocation of plants. Some of the experiments are: 1. Demonstration of Upward Translocation from Germinating Seeds 2. To Show the Downward Translocation of Food in a Woody Stem (Or Effect of Ringing Upon Food Movement) 3. Demonstration of Translocation from Leaves 4. Demonstration of Upward Translocation of Food in Woody Stem and Others.

Experiments # 1

Demonstration of Upward Translocation from Germinating Seeds:

About 100 seeds of pea or gram or Vicia seeds are soaked in distilled water. The seeds are divided into two lots. One lot of seeds is taken out at the stage when seed coats can be removed. The fresh weight, dry weight and ash weight of this lot are determined.

The other lot is allowed to grow in dark.

As soon as the primary leaves appear in this lot, the cotyledons are separated from a few seedlings:

(i) The average dry weight of the cotyledons and the shoot,

(ii) The average ash weight and

(iii) The average loss or gain of the cotyledons and the shoots are sep­arately determined.

(i) Percentage loss of dry weight and ash weight of the cotyledons and

(ii) The corresponding percentage increase of dry and ash weights of the shoot are calculated from the data.

The cotyledons are the storehouse of growing embryo. As the embryo grows to a seedling, reserved food material is translocated to the seedling from cotyledons. So long the leaves are not formed, photo­synthesis cannot take place and seedlings remain entirely dependent on the cotyledons for their nourishment and growth.

In this experiment the seedlings are grown in dark in order to preclude the possibility of getting nourishment of the seedlings from the photosynthate.

Decrease of the food materials from the cotyledons and concomitant increase in the shoot indi­cates that food materials are translocated upward to the shoot at the cost of cotyledons. Some amount of food materials is lost by way of respiration or other catabolic processes in both cotyledons and shoots which may be taken here as insignificant.

Experiments # 2

To Show the Downward Translocation of Food in a Woody Stem (Or Effect of Ringing Upon Food Movement):

The experiment is to be performed with a woody plant in which the apical growth has ceased. It is best performed in growing season. One or more stems or branches are selected which have no side branch for 50 cm or more and which are several centimeters in diameter.

Ring is made by removing the bark and phloem tissue approximately in the middle of the clear portion. The removed rings of bark should be about 1 cm wide and ringing should be done carefully so that the xylem is not damaged.

The exposed surface of the xylem should be carefully scrapped with a sharp knife so that all traces of cambium are removed. The ex­posed surface is covered with paraffin wax. After three weeks, final growth measurements are taken.

Sections are cut 25 to 50 cm from the regions immediately above and below the ring and following data are taken:

(i) Sections from just above and just below the ring are tested for starch with iodine solution and compared.

(ii) The volumes of 100gm of tissue from below and above the ring is determined by displacement of water and compared.

(iii) The percentage of dry matter in each tissue is determined and compared.

Results are tabulated or plotted to show the effect of ringing upon translocation of food material based on the above three indices.

Food materials are synthesized in leaves and translocated downwards through the phloem. Removal of phloem tissue hampers this downward translocation and accumulation of food materials above the ring occurs. This experiment indicates that organic solutes flow downward through the phloem into root and other organs, when the above the indices below and above the ring are compared.

Experiments # 3

Demonstration of Translocation from Leaves:

Several seedlings of kidney bean (Phaseolus vulgaris) are chosen on which the first pair of primary leaves is well developed. Three sets of plants are exposed to bright sunlight until the leaves show heavy starch accumulation on test with 1% iodine.

One petiole of each pair of leaves is then treated by the following methods, leaving the second petiole and leaf intact as control:

(i) One petiole is cut off and kept in water for comparison with control leaf

(ii) Killing a portion of one petiole by a hot forceps (heating any other portion of the plant is avoided the leaf may be kept in position with the help of a thread) and

(iii) A portion of one petiole is anesthetised with chloroform or ether soaked in cotton. All the plants are kept in dark in a moist chamber at 20°C for 24 hour’s. Chloro­phyll is removed from the leaves with alcohol and a few drops of lactic acid and tested for starch with 1 % iodine solution.

The untreated leaves show little or no response with iodine test compared to treated ones.

Marked loss of starch from a leaf is taken as an evidence of downward translocation. Considerable retention of starch in a treated leaf indicates that starch has not been translocated due to interference in the translocatory path. The experiment thus shows that food material is translocated from leaves.

Experiments # 4

Demonstration of Upward Translocation of Food in Woody Stem:

The experiment can be best performed in growing season. Four approximately uniform twigs on a woody plant are selected. Potted woody plants or even cut branches with their basal ends immersed in water can be used in this experiment. When tested with iodine they show considerable quantity of starch.

Smooth-barked species with rather stout stems and with true terminal buds are most suitable If possible twigs should be selected from plants which bear no side branches for a distance of about 40 cm back from the terminal bud.

The selected branches are numbered. Twig number 1 is ringed about 5 cm, twig number 2 about 20 cm, and twig number 3 about 40 cm below the respective terminal buds. Twig number 4 is kept as control.

During ringing, a strip of bark is re­moved 0.5 cm wide and the exposed wood is carefully scrapped to remove all traces of cambium avoiding any damage to the xylem.

The exposed wood is coated with paraffin wax. Leaves and lateral buds are removed from the portions of the twigs above the rings as fast as they emerge from the stem.

On the control stem all the leaves and lateral buds which start to develop about 40 cm below the original location of the terminal bud are removed. The twigs are observed from time to time as growth proceeds from the terminal bud, noting especially differences in the rate of longi­tudinal growth.

After three weeks the stem elongation which has occurred from the terminal bud of each stem is measured and recorded in millimeters. Cross sections are cut from above and below the ring of each stem and tested for starch with iodine solution.

The rate of growth above the ring in case of number 1, 2 and 3 twigs is very much checked as compared with control. The growth that has occurred in the ringed stems is only due to upward translocation of food materials through xylem.

In case of control twig the upward trans­location has taken place both through xylem and phloem. It is also evident from the experiment that the more is the distance of the ring from the terminal bud, the less is the rate of growth above the ring. The accu­mulation of starch is always maximum just below the ring.

N.B. From the above experiment a correlation with translocation and growth may be made. The influence of phloem upon translocation and growth may also be studied by removing different amounts of phloem tissue from a particular region on the stem.

Experiments # 5

To Demonstrate the Exudation from Phloem Tissue:

Cucurbita seedlings are grown under favourable condi­tions until they have attained a length of 30 cm. The stem of one of the plants is cut off with a sharp scalpel from 5 to 10 cm above the soil surface. The cut end of the excised portion of the stem is held in an inverted position and observed under a powerful hand lens or binocular microscope for exuda­tion.

Exudation may also be studied by puncturing a sharp needle through the bark to a sufficient depth to just reach the inner layer of phloem.

It is observed from what tissue (xylem or phloem?) the exudate comes. If exudate cannot be discerned clearly in the excised by stem the first drop of exudate is blotted with a filter paper and the cut end is re-examined.

It is clear from the study that the sap comes out mainly through the phloem tissue in the form of droplets.

Experiments # 6

Demonstration of Translocation of Food into Developing Fruits:

Suitable species of fruit trees on which fruits of consider­able size usually develop are selected. The experiment should be started when the fruits on the tree are half-matured.

At least ten fruits are tagged and numbered and their circumferences are carefully measured. The fruits are isolated from the main phloem system of the plant by means of proper ringing. Rings may be made at the base of fruiting branch or both above or below its point of attachment on the stem.

All precautions are followed in ringing the stem. The circumferences of an equal number of fruits from un-ringed branches are also measured to serve as controls. From time to time both sets of fruits are measured and rates of growth in diameter of the fruits from the ringed and un-ringed branches are com­pared.

The rates of growth in diameter of fruits in ringed and control sets are recorded and compared.

The developing fruits are the active centres of mobilisation of carbohydrate from other regions of the plant. Since phloem is the principal path of translocation of food materials to the developing fruits, removal of phloem tissue greatly hampers this transport of carbohydrate to the growing fruits. Hence the growth rate of the ringed fruits is much less compared to controls.

Experiments # 7

Demonstration of Upward Translocation of Mineral Salts In-Woody Stem:

This experiment can be performed with potted woody plant as in Expt. 4. Three sets of at least five comparable branches on the plant are selected. In one Set all of the branches are ringed 5 cm below the base of each terminal bud. Rings are made about 0.5 cm wide, the ex­posed wood is carefully scrapped to remove all traces of cambium and the exposed surface is covered with paraffin wax.

In the second set all the branches are removed from the plant by making a sharp cut at the point corresponding to that at which the branches of the first set were ringed, i.e., 5 cm below each terminal bud. This set is used as ‘starting’ control.

In the third set all the branches are tagged at a point 5 cm below the terminal bud. At the end of three weeks the branches of the girdled set and the tagged set which is to serve as ‘end’ control are removed by cutting them off at the point of girdle and at the point of tagging respectively.

The ash content of the branches of the ‘starting’ control is determined at the beginning of the experiment and that of the ‘end’ control and of ringed branches at the end of the experiment, as follows.

The sample of stems to constant weight is dried in an oven at about 80°C and its dry weight is determined. Each sample is ground and mixed thoroughly. The ground dry tissue from each set of stem is weighed and heated to constant weight in a muffle furnace at about 600°C.

The estimated ash contents are expressed as percentages of the dry weight and fresh weight of stems.

The mineral from the soil solution is carried through the xylem in transpiration stream, though some amount of mineral is trans­located through phloem. As minerals are mainly translocated through the xylem, the removal of phloem tissue from the ring will not debar the stem above the ring from the supply of mineral nutrients.

When the ash content of the stems of three sets is compared, it becomes clear that percentage of ash content is maximum in case of the set where the branches were origin­ally removed 5 cm below the terminal bud and minimum in case of the set where branches remained intact. This shows that translocation of mineral solutes takes place mainly through xylem.

Experiments # 8

Demonstration of the Effects of Inhibitors on the Uptake, Distri­bution and Translocation of 32 P in Plants:

One-month-old bean seedlings grown in sand culture may be suitably employed in this study. The plants are removed from the culture taking sufficient care not to injure the roots.

Roots are then washed well to remove the adhering particles. These are then selected for treatment. Two such plants are taken and the roots are inserted in each of the six test tubes containing the following solutions (10 ml) and three test tubes may be bubbled for aeration.

Now from each leaf, discs are prepared with the help of a corkborer at different intervals, dried under infra-red lamp and its radio-activity is measured in a Geiger-Muller Counter. After 1 to 2 hr. the plants are taken out, roots are washed well with carrier phosphate (0.01 M Na2HPO4) and the distribution of radio-activity is determined by autoradiography as follows.

The plant is kept for sufficient time in contact with a suitable film in a dark room under some uniform pressure. [Half-life of 32P is to be taken into consideration (14.3 days)]. After exposure the film is developed and the spots of radio-activity are determined.

Exposure time = 10 7 / x min.

+3 days, where x is the count per minute (CPM) during experiment.

The uptake of 32 P by plants as affected by aeration, sodium arsenate and sodium azide is noted and data are tabulated.

The above experiment clearly demonstrates the transloc­ation of radio-active phosphorus to different organs of the plant. The translocation of phosphorus is a function of time and distance from the roots as indicated by the radio-activity in different plant parts.

Again metabolic inhibitors like azide or arsenate inhibit the rate of translocation indicating that it is regulated by the metabolism of living cells. Increased translocation with aeration suggests that respiratory energy is also involved in the translocation of phosphorus.


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