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Photosynthesis increases linearly with light intensity at low intensity, but at higher intensity this is no longer the case (see Photosynthesis-irradiance curve). Above about 10,000 lux or ~100 watts/square meter the rate no longer increases. Thus, most plants can only use ~10% of full mid-day sunlight intensity. [6]
Light supply: The rate of transpiration is controlled by the stomatal aperture, and these small pores open especially for photosynthesis. While there are exceptions to this (such as night or CAM photosynthesis), in general, a light supply will encourage open stomata. Temperature: Temperature affects the rate in two ways:
The light compensation point (I c) is the light intensity on the light curve where the rate of photosynthesis exactly matches the rate of cellular respiration.At this point, the uptake of CO 2 through photosynthetic pathways is equal to the respiratory release of carbon dioxide, and the uptake of O 2 by respiration is equal to the photosynthetic release of oxygen.
This fact allows measurement of the light reaction of photosynthesis by using chlorophyll fluorometers. [42] Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature, and proportion of carbon dioxide in the atmosphere, and can vary from 0.1% to 8%. [43]
In botany, a light curve shows the photosynthetic response of leaf tissue or algal communities to varying light intensities. The shape of the curve illustrates the principle of limiting factors; in low light levels, the rate of photosynthesis is limited by the concentration of chlorophyll and the efficiency of the light-dependent reactions, but in higher light levels it is limited by the ...
The Emerson effect is the increase in the rate of photosynthesis after chloroplasts are exposed to light of wavelength less than 680 nm (deep red spectrum) and more than 680 nm (far red spectrum). When simultaneously exposed to light of both wavelengths, the rate of photosynthesis is higher than the sum of the red light and far red light ...
The visible-light part of the action spectrum was found to have a peak in the red-light region, suggesting that chlorophylls act as photoreceptors of photoinhibition. In the 1980s, photoinhibition became a popular topic in photosynthesis research, and the concept of a damaging reaction counteracted by a repair process was re-invented.
Of the 150 kWh falling on the crown, 1% is used for photosynthesis, 10% reflected as light energy, 5 to 10% as sensible heat with the remaining 79 to 84% entering the process of transpiration. [3] If a larger tree has a sufficient water supply, it can evaporate more than 100 L of water a day.