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.
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