The leaf of a plant plays a vital role in maintaining the health of the plant. Photosynthesis and respiration can be interrupted or even halted altogether when the temperature of the plant becomes too high or too low for photosynthesis to occur. In order to regulate leaf temperature, a process called transpiration occurs. Transpiration allows the leaves to cool themselves in warm weather and preserve energy when the temperature surrounding the plant gets too cold.
Photosynthesis is the process a plant uses to convert water, sunlight and carbon dioxide into oxygen and glucose. A special chemical called chlorophyll allows the plant to absorb sunlight while the root system draws water up from the soil and transports it to the leaves. Cells on the surface of the leaf called stomata open to take in carbon dioxide and release oxygen, in the form of water vapor, back into the atmosphere. The nutrients created by photosynthesis are then converted to food energy through respiration.
Respiration is a vital component in plant health. The sugar and oxygen produced during photosynthesis are converted to useable energy and transported throughout the plant. In order for the plant to grow and build new tissue, the amount of sugar and oxygen produced during photosynthesis must be sufficient to sustain the plant.
Transpiration occurs when the stomata of leaves open to exchange water vapor for carbon dioxide. When the temperature of the air surrounding a plant becomes too high for photosynthesis to occur, the stomata open and allow water to evaporate, essentially causing the plant to perspire. During cooler temperatures, the stomata remain closed.
The temperature surrounding a plant is the primary factor that determines the rate of transpiration. During the growing season, when the air is warmer, transpiration rates go up, allowing for a greater exchange of carbon dioxide and water vapor. In colder weather, transpiration rates go down to help the plant conserve energy. The relative humidity, or the amount of water in the air around the plant, also affects transpiration. When relative humidity is high, transpiration is low because water evaporates more easily in drier air. When the relative humidity is low, either due to temperature conditions or wind, transpiration rates will increase to raise the humidity in the air around the plant.
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