Limit to avoid acute mortality 4 Mid-summer, when strong thermal stratification develops in a lake, may be a very hard time for fish. Water near the surface of the lake - the epilimnion - is too warm for them, while the water near the bottom - the hypolimnion - has too little oxygen.
It is also described as the degree of brightness that a plant is exposed to. In contrast to light quality, the description of the intensity of light does not consider wavelength or color.
One footcandle is equal to However, the units footcandle and lux are merely based on visual sensitivity and do not provide information on the energy or photon content of light.
It describes the number of photons of light within the photosynthetic waveband that an area of 1 sq meter receives per second. It can be measured using a light meter.
Another unit of measurement is the mol m-2d-1 which describes the total number of photons received by an area of 1 sq meter in 24 hours.
The following intensity values in footcandle are given for some light conditions Janick High light intensity means it is brighter compared to low light intensity. Factors Affecting Light Intensity The intensity of light can change with the time of the day, season, geographic location, distance from the equator, and weather.
Light intensity is also affected by dust particles and atmospheric water vapor, slope of the land, and elevation Edmond et al. This causes a slight variation in the amount of light and heat that the earth receives. According to Manakerthe amount of natural light that may enter a building is affected by the location of windows or glass surface through which light enters, the presence of trees and shrubs, roof overhangs, window screens and awnings, and the tint and cleanliness of the glass.
Within a building, the amount of light, whether natural or artificial, will be further affected by curtains and blinds, surface textures, and reflectance from wall coverings, furniture, and other furnishings. Further, leaves on a single plant differ in the amount of light that they receive.
The amount of light incident on a leaf decreases as sunlight passes downward through the canopy. Leaves on the upper part of the canopy tend to shade and reflect light away from the lower leaves.
However, different plants have optimum requirements and both deficient and excessive light intensities are injurious. Subject to physiological limits, an increase in the intensity of light will result to an increase in the rate of photosynthesis and will likewise reduce the number of hours that the plant must receive every day Manaker During summer when light supply is abundant and almost continuous in Alaska, potatoes and cabbages of enormous sizes have been produced Janick According to Chapman and Carterthe minimum limit for the process of photosynthesis in most plants is between and fc.
But light intensity of as low as 10 lux 0. Deficient light intensities tend to reduce plant growth, development and yield. This is because low amount of solar energy restricts the rate of photosynthesis. Below a minimum intensity, the plant falls below the compensation point.
Photosynthesis significantly slows down or ceases while respiration continues. Compensation point is the metabolic point at which the rates of photosynthesis and respiration are equal so that leaves do not gain or lose dry matter. Etiolation, a morphological manifestation of the adverse effect of inadequate light, is described by Chapman and Carter in the following manner: Likewise, excessive light intensity should be avoided.
It can scorch the leaves and reduce crop yields. This reduces the rate of light absorption and the rate of photosynthesis; 2 Excess light intensity is associated with increase in the temperature of leaves which in turn induces rapid transpiration and water loss.
The guard cells lose turgor, the stomates partially or completely close, and the rate of diffusion of carbon dioxide into the leaves slows down.
Sugars accumulate and the rate of photosynthesis slows down. Alaska Science Forum Feb. Installation, Maintenance, and Management. Crop response to light variations.
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The rate of photosynthesis was measured every five min under light colors of white, green, red, blue and yellow under a light intensity of lux.
The rate of photosynthesis was measured by the spinach disk method in which we replaced the air from the disks with sodium bicarbonate using a vacuum. Rate of photosynthesis: limiting factors Limiting factors The main factors affecting rate of photosynthesis are light intensity, carbon dioxide concentration and temperature.
In any given situation any one of these may become a limiting factor, in other words the factors that directly affects the rate at which photosynthesis can take place masking the effects of the other factors.
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Effects of CO 2 and O 2 on photosynthesis are discussed in Part I of this guide. Temperature and light quality are two other conditions that must be carefully controlled when measuring photosynthesis. The students can be allocated to investigate a particular factor that affects the rate of photosynthesis, or they can choose from this list, or they can develop their own ideas.
Light intensity or distance of the Elodea from the lamp. (Light intensity is proportional to 1/distance 2. Temperature of the water; Carbon dioxide concentration.