There are two main plant responses that involve light they are called phototropism and photoperiodism. Phototropism is the growth and response to a light stimulus. The plant has a hormone called auxin that reacts when phototropism occurs. The auxin causes the plant to have elongated cells on the farthest side from the light. There are two types of phototropism. The first type is called positive phototropism which is when the plant grows toward the light. The second type is called negative phototropism which is when the plant grows away from the light. For example plant shoots show positive phototropism and the plant roots show negative phototropism. The mechanism of control for phototropism is the tip of the shoot which is where the direction of light is detected. This is supported by an experiment done by Darwin. He placed tin foil on the tip of one shoot of a plant and didnt place tin foil on the other. After a couple days the plant with the tin foil grew directly up and the other one without grew towards the light. Photoperiodism is the developmental responses of plants to the relative lengths of the light and dark periods. The mechanism of control for photoperiodism is the circadian system. Night break experiments show that measuring night length is one of the mechanisms used for photoperiod assessment.
In conclusion, phototropism and photoperiodism are two main plant responses to light. Phototropism is the growth to the light and photoperiodism is the developmental responses of plants to the relative lengths of the light and dark periods.
Monday, November 28, 2011
1961 : Movement of Water Essay
The process of water movement through the xylem and out the stomates is called transpiration. During transpiration water moves from the soil through a vascular plant. There is four major contributers that take place during transpiration. They are the tissues being traversed, the processes and forces involved, enviromental factors which are conductive to a high rate of transpiration, and the effects of the process upon the plant.
The plant tissues that are being traversed is the symplast and the apoplast. The functions of the symplast and the apoplast is transporting water and minerals through the plant. The difference between symplast and apoplast is that apoplast is the continuum of cell walls plus extracellular spaces and the symplast is the continuum of cytosol connected by plasmodesmata.
The processes and forces involved in transpiration is transpirational pull. This is when water vapor in the airspaces of a leaf diffuses down its water potential gradient and exits the leaf via stomata. Transpiration produces negative pressure in the leaf which exerts a pulling force on water in the xylem, pulling water into the leaf.
The enviromental factors which are conductive to a high rate of transpiration is air temperature, relative humidity, and wind speed, . Plants transpire faster in higher temperatures and in more sunlight. Humidity causes increase in diffusion and it happens more rapidly. Wind can reduce the rate of transpiration because it can carry humid air away and replace it with drier air.
Lastly the effects of transpiration on plants. The plant can get dehydrated because each day the plant rehydrates as the soil dries out and this rehydration is not complete causing it not to get enough water. Then this can affect the plant's growth, photosynthesis and transpiration.
In conclusion, I have learned that transpiration is the evaporation of water particles from plant surfaces, especially from the surface openings, or stomates, on leaves. Stomatal transpiration accounts for most of the water loss by a plant, but some direct evaporation also takes place through the surfaces of the epidermal cells of the leaves. Water movement is very important during this process. Transpiration causes pressure in the plant making water shoot up into the xylem. Also many things can affect this process like enviromental factors for instance temperature can increase this process rapidly. Transpiration can also effect the plant by drying it out causing the plant to wilt. As you can see transpiration can be a complicated process buts its how plants get water to move through them.
The plant tissues that are being traversed is the symplast and the apoplast. The functions of the symplast and the apoplast is transporting water and minerals through the plant. The difference between symplast and apoplast is that apoplast is the continuum of cell walls plus extracellular spaces and the symplast is the continuum of cytosol connected by plasmodesmata.
The processes and forces involved in transpiration is transpirational pull. This is when water vapor in the airspaces of a leaf diffuses down its water potential gradient and exits the leaf via stomata. Transpiration produces negative pressure in the leaf which exerts a pulling force on water in the xylem, pulling water into the leaf.
The enviromental factors which are conductive to a high rate of transpiration is air temperature, relative humidity, and wind speed, . Plants transpire faster in higher temperatures and in more sunlight. Humidity causes increase in diffusion and it happens more rapidly. Wind can reduce the rate of transpiration because it can carry humid air away and replace it with drier air.
Lastly the effects of transpiration on plants. The plant can get dehydrated because each day the plant rehydrates as the soil dries out and this rehydration is not complete causing it not to get enough water. Then this can affect the plant's growth, photosynthesis and transpiration.
In conclusion, I have learned that transpiration is the evaporation of water particles from plant surfaces, especially from the surface openings, or stomates, on leaves. Stomatal transpiration accounts for most of the water loss by a plant, but some direct evaporation also takes place through the surfaces of the epidermal cells of the leaves. Water movement is very important during this process. Transpiration causes pressure in the plant making water shoot up into the xylem. Also many things can affect this process like enviromental factors for instance temperature can increase this process rapidly. Transpiration can also effect the plant by drying it out causing the plant to wilt. As you can see transpiration can be a complicated process buts its how plants get water to move through them.
Transpiration: Water Loss Essay :)
c. The concept of water potential is used to account for the movement of water from the plant stem to the atomosphere during transpiration because the concept of water potential is water moving from a high concentration to a low concentration and thats exactly what water does when it goes from the plant stem to the atomosphere. This is because water travels through the plant where there is high concentration and onto the leaf where there is low concentration.
In conclusion there are many factors that affect transpiration; wind, temperature, light, and humidity. The factors can either increase or decrease the the of transpiration but in the end water is always going from a high to low concentration.
Sunday, November 20, 2011
The Lightest Material in the World
http://www.sciencedaily.com/releases/2011/11/111117154643.htm
Scientists have created a material that is 99.99% air. The new material redefines the limits of lightweight materials because of its unique "micro-lattice" cellular architecture. This material could be used for battery electrodes and acoustic, vibration or shock energy absorption. This is important because it introduces nano and micro designs for the future.
Scientists have created a material that is 99.99% air. The new material redefines the limits of lightweight materials because of its unique "micro-lattice" cellular architecture. This material could be used for battery electrodes and acoustic, vibration or shock energy absorption. This is important because it introduces nano and micro designs for the future.
Birth of a Famous Blackhole
http://www.sciencedaily.com/releases/2011/11/111117144045.htm
Amazingly scientists have poduced a complete description of a blackhole. The scientists have traced back its history from when it was born which was 6 million years ago. This discovey gives us information about how the blackhole was born and how fast it was spinning. They believe the blackhole was created by a super nova explosion.
Amazingly scientists have poduced a complete description of a blackhole. The scientists have traced back its history from when it was born which was 6 million years ago. This discovey gives us information about how the blackhole was born and how fast it was spinning. They believe the blackhole was created by a super nova explosion.
Friday, November 4, 2011
Sabor-Tooth Squirrel or "Scrat" from Ice Age? :)
http://www.sciencedaily.com/releases/2011/11/111102161050.htm
A professor has discovered 2 skulls from the first known mammal of the early Late Cretaceous period of South America. This discovery provides new clues on the early evolution of animals. This new mammal looks like a sabor-tooth squirrel and its called Cronopio. Cronopio was shrew-sized, about 4-6 inches in length, and was an insectivore with a diet of the insects, grubs and other bugs of the time. This discovery was so important because it was the first time they found this type of mammal.
A professor has discovered 2 skulls from the first known mammal of the early Late Cretaceous period of South America. This discovery provides new clues on the early evolution of animals. This new mammal looks like a sabor-tooth squirrel and its called Cronopio. Cronopio was shrew-sized, about 4-6 inches in length, and was an insectivore with a diet of the insects, grubs and other bugs of the time. This discovery was so important because it was the first time they found this type of mammal.
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