Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insoluble for storage. The stored starch can later be turned back into glucose and used in respiration. Oxygen is released as a by-product of photosynthesis.
In addition to producing NADPH, the light dependent reactions also produce oxygen as a waste product. When the special chlorophyll molecule at the reaction centre passes on the electrons to the chain of electron carriers, it becomes positively charged. With the aid of an enzyme at the reaction centre, water molecules within the thylakoid space are split. Oxygen and H+ ions are formed as a result and the electrons from the splitting of these water molecules are given to chlorophyll. The oxygen is then excreted as a waste product. This splitting of water molecules is called photolysis as it only occurs in the presence of light.
6.1.1 Aquatic microorganisms Stratton & Corke (1982) investigated the toxicity of permethrin andten of its degradation products on the growth, photosynthesis, andacetylene-reducing activity of two species of green algae ( Chlorella pyrenoidosa and Scenedesmus quadricaudata ) and three species of cyano-bacteria ( Anabaena spp.).
As theresult of ester cleavage and other photolytic reactions, productsformed from permethrin also included smaller or trace amounts ofmonochloro-permethrin (22) (from reductive dechlorination), 3-phenoxy-benzaldehyde (PBald) (11), 3-phenoxybenzoic acid (PBacid) (12),3-phenoxybenzyl-3,3-dimethylacrylate (23) (from diradical intermedi-ate), and benzyl alcohols (9,10), as well as their corresponding acids(15,16).
Permethrinconcentrations in the water persisted at mean levels of 0.15 µg/litre for 96 h and 0.03 µg/litre for 48 h after the first and second appli-cations, respectively (detection limit: 0.01 µg/litre).
Photophosphorylation is the production of ATP using the energy of sunlight. Photophosphorylation is made possible as a result of chemiosmosis. Chemiosmosis is the movement of ions across a selectively permeable membrane, down their concentration gradient. During photosynthesis, light is absorbed by chlorophyll molecules. Electrons within these molecules are then raised to a higher energy state. These electrons then travel through Photosystem II, a chain of electron carriers and Photosystem I. As the electrons travel through the chain of electron carriers, they release energy. This energy is used to pump hydrogen ions across the thylakoid membrane and into the space within the thylakoid. A concentration gradient of hydrogen ions forms within this space. These then move back across the thylakoid membrane, down their concentration gradient through ATP synthase. ATP synthase uses the energy released from the movement of hydrogen ions down their concentration gradient to synthesise ATP from ADP and inorganic phosphate.
So how can these factors have an effect on the rate of photosynthesis? Lets start off with the light intensity. When the light intensity is poor, there is a shortage of ATP and NADPH, as these are products from the light dependent reactions. Without these products the light independent reactions can't occur as glycerate 3-phosphate cannot be reduced. Therefore a shortage of these products will limit the rate of photosynthesis. When the carbon dioxide concentration is low, the amount of glycerate 3-phosphate produced is limited as carbon dioxide is needed for its production and therefore the rate of photosynthesis is affected. Finally, many enzymes are involved during the process of photosynthesis. At low temperatures these enzymes work slower. At high temperatures the enzymes no longer work effectively. This affects the rate of the reactions in the Calvin cycle and therefore the rate of photosynthesis will be affected.
Furthermore, I predict that if the light intensity increases, the rate of photosynthesis will increase at a proportional rate and more oxygen will be produced and therefore the oxygen levels will increase.
It will be very interesting to see how light will influence the rate of photosynthesis in plants and what will happen if they do not get the required light in order to produce starch .
During the process of photosynthesis, carbon dioxide plus water in the presence of sunlight, enzymes and chlorophyll produce glucose and oxygen as waste product.
Prediction : I predict that as I increase the distance between the light source and the Canadian Pondweed (reducing the light intensity), the volume of oxygen produced within the time limit (the measure of the rate of photosynthesis) will decrease.
Prediction: I predict that as the light source (desk lamp) is moved closer to the pondweed (Elodea), the rate of photosynthesis will increase therefore more oxygen will be produced creating more bubbles.
I believe this will happen because when the light source is nearer to the plant more of the plants surface area is coming in to contact with the light from the desk lamp therefore more photosynthesis will occur which will mean more oxygen will be produced which will create more bubbles....