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Name: Erin
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Question:
how do plants grow in and out of sunlight. also how do plants stay alive for a while without water.


Replies:
First of all, both questions are generalizations and since there are millions of different plant species, each with different abilities and processes, these questions really can not be answered in a way that can be apply to all plants. For example, desert plants work very differently than non-desert plants in relation to water requirements and plant functioning during sunlight periods and darkness.

The first question implies that plants grow because of photosynthesis. That is incorrect. Plants use cellular respiration to provide the energy to grow and function (work). Photosynthesis only produces food and materials for the plant to grow. Cellular respiration works the same in plants and animals and is the reason why you breath and use oxygen all the time! Plants use oxygen all the time too. The oxygen is used to release useable energy from stored energy to make things happen and grow. Most plants can grow at night if conditions are fine and energy can be processed. Many plants grow their flowers at night.

Photosynthesis produces much more oxygen than the plant needs and that is why it seems that plants give off oxygen. Carbon dioxide is used only for photosynthesis only. Since animals do not make their own food, they must eat plants or animals that have eaten plants in order to get energy and materials.

As far as water goes, most plants have mechanisms to shut down water loss from the plant when conditions are dry. Some plants are extremely good at this while others are not. For example, most land plants have stomata which are openings usually found on the under side of leaves which allow for water to evaporate and gases to exchange with the environment to allow photosynthesis to work. These stomata close when conditions are dry. Photosynthesis relies upon a supply of water and so does the plant tissues in order to operate and stay alive. Different species will be able to stand long periods of dry conditions differently.

I hope this helps.

Steve Sample



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