It also includes topics on leaf arrangements, leaf types, leaf structure, leaf color, abscission, and importance to humans This tutorial elaborates on the effect of light on plant growth. It describes how different plants require different amounts of light in a day. The amount of time that a plant requires is called the critical period.
Learn more about this topic in this tutorial Plants need to regulate water in order to stay upright and structurally stable. Find out the different evolutionary adaptations of plants in terms of structure e. Lentic or still water communities can vary greatly in appearance -- from a small temporary puddle to a large lake. Baum explained that the analysis of chloroplast genes shows that it was once a member of the group cyanobacteria , "the one group of bacteria that can accomplish oxygenic photosynthesis.
In their article, Chan and Bhattacharya make the point that the formation of secondary plastids cannot be well explained by endosymbiosis of cyanobacteria, and that the origins of this class of plastids are still a matter of debate. Pigment molecules are associated with proteins, which allow them the flexibility to move toward light and toward one another. A large collection of to 5, pigment molecules constitutes "antennae," according to an article by Wim Vermaas , a professor at Arizona State University.
These structures effectively capture light energy from the sun, in the form of photons. Ultimately, light energy must be transferred to a pigment-protein complex that can convert it to chemical energy, in the form of electrons. In plants, for example, light energy is transferred to chlorophyll pigments.
The conversion to chemical energy is accomplished when a chlorophyll pigment expels an electron, which can then move on to an appropriate recipient. The pigments and proteins, which convert light energy to chemical energy and begin the process of electron transfer, are known as reaction centers.
The reactions of plant photosynthesis are divided into those that require the presence of sunlight and those that do not. Both types of reactions take place in chloroplasts : light-dependent reactions in the thylakoid and light-independent reactions in the stroma. Light-dependent reactions also called light reactions : When a photon of light hits the reaction center, a pigment molecule such as chlorophyll releases an electron.
The released electron manages to escape by traveling through an electron transport chain , which generates the energy needed to produce ATP adenosine triphosphate, a source of chemical energy for cells and NADPH. The "electron hole" in the original chlorophyll pigment is filled by taking an electron from water. As a result, oxygen is released into the atmosphere. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons.
This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules. Inside the plant cell are small organelles called chloroplasts, which store the energy of sunlight. Within the thylakoid membranes of the chloroplast is a light-absorbing pigment called chlorophyll, which is responsible for giving the plant its green color.
During photosynthesis, chlorophyll absorbs energy from blue- and red-light waves, and reflects green-light waves, making the plant appear green.
While there are many steps behind the process of photosynthesis, it can be broken down into two major stages: light-dependent reactions and light-independent reactions. The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence the name light- dependent reaction.
The light-independent stage, also known as the Calvin Cycle , takes place in the stroma , the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence the name light- independent reaction. C3 and C4 photosynthesis. Not all forms of photosynthesis are created equal, however. There are different types of photosynthesis, including C3 photosynthesis and C4 photosynthesis.
C3 photosynthesis is used by the majority of plants. It involves producing a three-carbon compound called 3-phosphoglyceric acid during the Calvin Cycle, which goes on to become glucose. C4 photosynthesis, on the other hand, produces a four-carbon intermediate compound, which splits into carbon dioxide and a three-carbon compound during the Calvin Cycle.
A benefit of C4 photosynthesis is that by producing higher levels of carbon, it allows plants to thrive in environments without much light or water. Used by the majority of plants, it involves producing a three-carbon compound called 3-phosphoglyceric acid during the Calvin Cycle, which goes on to become a sugar called glucose.
Send us feedback. See more words from the same year. Accessed 12 Nov. More Definitions for photosynthesis. See the full definition for photosynthesis in the English Language Learners Dictionary. Nglish: Translation of photosynthesis for Spanish Speakers. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!
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