Photosynthesis: testing a variegated leaf for starch

In 1780, the famous English chemist Joseph Priestley (right) found that plants could "." He used a mint plant, and placed it into an upturned glass jar in a vessel of water for several days. He then found that "". In other words, he discovered that plants produce oxygen.

Below are another set of pictures using a very different plant then the one above.

The actual chemical equation which takes place is the reaction between carbon dioxide and water, powered by sunlight, to produce and a waste product, oxygen. The glucose sugar is either directly used as an energy source by the plant for metabolism or growth, or is polymerised to form , so it can be stored until needed. The waste oxygen is excreted into the atmosphere, where it is made use of by plants and animals for respiration.


Light intensity and variegated leaves practical work lesson

If the whole leaf turns from yellow to blue black, light is not required for photosynthesis.

Some guidelines: This experiment will not work with a terrestrial (land) plant. An aquatic plant such as a water hydrilla or Elodea needs to be used. As the plant is placed in an aquatic environment, there is a need to supply the plant with carbon dioxide. Hence, addition of sodium hydrogen carbonate to water is necessary to provide the aquatic plant with carbon dioxide gas. There is no need to destarch the plant as we would not be testing the leaf for starch. Instead, we would be collecting the gas produced and testing if it is oxygen gas using a glowing splint.


25/03/2014 · Plants and Photosynthesis ..

Overall, our conclusion was that the white areas of variegated bhendi leaves do have stunted growth. Although the white leaves clearly receive food from the green leaves via the plant’s transport system, this is apparently not sufficient to compensate for their reduced photosynthetic abilities.

Variegated and normal geraniums make good sources of plant leaves.

We also noticed that bulges on the margins of variegated leaves corresponded to green areas (figure 3). This supports the conclusion that the intervening white areas have stunted growth. It would be interesting to see whether these observations hold for other variegated plants.

At night photosynthesis stops and the leaves respire, ..

We tested dozens of variegated bhendi leaves, and could not find a single leaf in which the half that clearly contained more white was as large as the half that contained more green, suggesting that the white parts of leaves do have stunted growth.

Ultraviolet-B component of sunlight stimulates photosynthesis and ..

The following activities provide different ways for these two hypotheses to be investigated. The activities arose from a research project to investigate how school students learn science when they ask their own questions and try to answer them by planning and doing their own investigations. We initially designed experiments based on questions that we thought students might ask when presented with a variegated bhendi. Next, we interacted informally with some students to see what questions they actually asked. We then organised a three-day workshop for students aged 11–13, during which they carried out some of the activities that we had devised and also investigated some of their own questions (including “Are white leaves thinner?” and “Do white leaves wilt faster?”).

and that's why only variegated leaves might be used.

How then do variegated plants survive? The simple answer is probably that we humans maintain them artificially. Can your students find any examples of variegated plants existing in the wild?