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Download 6-2.7 Summarize the processes required for plant survival (including
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Transcript
6-2.7 Summarize the processes required for plant survival (including photosynthesis, respiration, and transpiration). Photosynthesis-Plants are organisms that make their own food, a simple sugar, for survival. The process by which they make this sugar is called photosynthesis. Chloroplasts, found in the cells of the leaf, contain chlorophyll, a green pigment that absorbs the light energy from the sun. Sunlight is used to provide the energy necessary for photosynthesis to take place. During this process, plants use carbon dioxide gas from the air and water taken in through the roots to make sugar (food). During the process of photosynthesis oxygen is produced. The oxygen is released into the air, through openings, or pores, in the leaf (stomata). Photosynthesis is what provides the oxygen in the atmosphere that most living organisms need. Respiration- The food (sugar) created through the process of photosynthesis is used to provide energy needed by the plants to perform life functions. To obtain the energy from the food it produces, plants must break the sugar down in a process called respiration. In this process, oxygen from the air combines with the sugar, which is then broken down into carbon dioxide and water. During this process, energy is released. This energy can now be used by the plant to perform life functions. The carbon dioxide and water that are formed are then given off through the leaves. Transpiration- Some of the water taken in through the roots of plants is used in the process of photosynthesis. However, plants lose most of the water through the leaves. This process is called transpiration. Without a way to control transpiration, plants would wither up and die. Fortunately, plants are able to slow down transpiration. Guard cells, mostly on the underside of the leaf, open and close pores known as stomata. When the stomata are closed, water cannot escape from the leaf. 6-2.8 Explain how plants respond to external stimuli (including dormancy and the forms of tropism known as phototropism, gravitropism, hydrotropism, and thigmotropism). Stimulus: A change in the environment that causes a response or a reaction Response: The reply to the change in the environment, or stimulus •When a mature plant or seed is placed under favorable conditions and becomes or remains inactive, it is said to be dormant. Dormancy Dormancy is an inactive period of time when the plant or seed prepares for harsh conditions. Dormancy allows various species to survive in particular environments. It helps to ensure that seeds will germinate when conditions are favorable for survival of the small seedlings. Leaves fall from trees in preparation for winter; the leaf buds do not open again until conditions are favorable in the spring. •Plants can change their growth in response to their environment. These changes are called tropisms. Plants can exhibit the following kinds of tropisms: Phototropism - the way a plant grows or bends in response to light Gravitropism- the way a plant grows or bends in response to gravity Hydrotropism- the way a plant grows or bends in response to water Thigmotropism- the way a plant grows or bends in response to touch