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PROJECT A: FACTORS WHICH MIGHT AFFECT STOMATAL OPENING (LIGHT) How light affects the stomatal opening in a leaf Abstract My aim of this investigation was to check the affect of environmental factors affecting stomatal opening. My experiment was designed to check the stomata opening in light. Plants move in ways that may not seem obvious. The opening and closing of stomata is one example of this movement. There are a large amount of growth conditions that can affect a plant. One of the most important of these conditions concerns the type of availability of light present for photosynthesis. By controlling the type of light that a plant receives, its growth can be affected. I chose to measure this growth by observing the number of stomata present on the underside of leaves exposed to the dark and to sunlight. Based on the idea that there are more open stomata present on leaves exposed to the sun, my hypothesis that 'Factors which might affect stomatal opening' (Light) there will be more stomata on the plants exposed to the light. Hypothesis I believe the results of my investigations will show that the more the light source the more the stomata will open. ...read more.


The rate of gas exchange for the entire leaf is determined by the responses of all the stomatal pores on a leaf to ambient environmental conditions. Many researchers have noticed that stomatal response to seemingly identical treatments can vary considerably. Stomata, then, seem to function as separate entities which respond individually to the same environmental stimuli. The ecological implications of this "patchy stomatal response" are the focus of a great deal of current research. Knowledge of stomatal response increases our understanding of carbon dioxide assimilation and transpiration rates, as well as the nature of ecophysiological adaptations of plants to their environments. (1) The usual response of stomata to environmental factors is shown in Fig. 1.2. Closed stomata begin to open in a few minutes after exposure to light and they start to close when returned to the dark. When plants are put in CO2-free air, stomata tend to open even in the dark. Conversely, an increase in CO2 concentration above the normal level (330-340 ppm) causes stomata to close in the light. Within range of about 5-25 ? C the effect of temperature is mainly on the rate of opening and closing reactions rather than on aperture size. ...read more.


The container was labelled with this plant "DARK." 4. Both plants were placed in front of the light. Time was recorded that the plants were placed in the light on the data sheet (Table 1). Temperature was monitored next to the uncovered leaves by placing a thermometer on the leaf surface. Do not let the temperature of the plant rise above 30oC. 5. Every 15 minutes for 90 minutes, one covered leaf was removed and one uncovered leaf from each plant. The appropriate surface was painted with nail polish. The nail polish was left to dry, then cast was remove. 6. Microscope slides were prepared as before. For the easiest comparison, both casts were placed from the "LIGHT" plant side by side on one slide; both casts were placed from leaves off the "DARK" plant side by side on a second slide. Results 1. According to my observations and calculations abaxial surface of the leaf has more stomata than the adaxial surface of the leaf. This is to aid in preventing dehydration. 2. The leaves which were placed in the dark there stomata were closed while the leaves which were placed in the light there stomata were opened. 3. Bright light, leaf temperature less than 30oC, low wind speeds, and wet soil all lead to stomatal opening. ...read more.

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