arturo-ga,
As someone with a B.S. degree in biology from a major U.S. university,
I feel qualified to answer your question. I will provide you
information pertaining to factors affecting plant growth appropriate
for the 6-8th grade level. I’ll address your Question point-by-point
below.
“What sites can we go to to pull this type of info? “
I’ll cover this in a links/search strategy section at the end. Also,
as we cover the other plant topics, I’ll provide links as we go.
“First we
need info on the way plants grow…”:
Very simply, plants grow by transforming sunlight into carbohydrates
(complex molecules). To expand on this and fill in some more steps,
plants transform the radiant energy of sunlight into chemical energy
(through the process known as photosynthesis), which is then stored as
carbohydrates and other molecules. So, sunlight provides the energy
to power photosynthesis, and photosynthesis uses water and carbon
dioxide CO(2) to make carbohydrates (such as sugars and cellulose).
Note: the exact chemical equations of how these processes occur are
what grown-up biologists and botanists (botany = study of plants)
study for a living.
Take away water or carbon dioxide, and plants cannot grow even if they
have light because they can’t make (synthesize) any more
carbohydrates. Take away light, even though they have water and carbon
dioxide, and they can’t grow because they don’t have the energy to
turn the water and CO^2 into carbohydrates.
The following excerpt demonstrates one way of explaining to children
that plants need several different things in order to grow. From
[http://aspin.asu.edu/~travis/scene/redesign_scene/habitat/inquiry.html
]:
“For example, let us imagine that a student asks, "Why do plants
grow?" Variables immediately apparent are factors such as light,
water, soil, and nutrients. We might then rephrase the question into
several "what would happen if?" questions that can be investigated by
students: "What would happen if we stop giving plants water?" "What
would happen if we give plants more light?" "What would happen if we
add nutrients to the soil around a plant?" "What would happen if we
remove the plant from soil and place it in water?" As basic principles
are discovered, the investigation can be refined and made more
challenging as students try to find the optimal growth conditions for
the plants with which they are working.”
For a more detailed look at the photosynthesis process itself at the
grade school level, see the following webpage from Netwon’s Apple:
[ http://www.ktca.org/newtons/9/phytosy.html ].
A quick definition of photosynthesis (from the above site):
“Photosynthesis--The formation of carbohydrates in the
chlorophyll-containing tissues of plants exposed to light.”
Note: chlorophyll are the special pigments inside plant cells that
actually absorb/trap the sunlight.
Moving on to the next part of your Question,
“how that growth is affected by
different circumstances, eg: fertilizer, different soil, amount of
sunlight and water, etc.”:
We covered in part how the growth is affected by lack of sunlight,
water and CO(2) above. In general, there is an optimum level, or
perfect amount of each of these factors for an individual plant. When
those levels are present, the plant grows the best. If those levels
are higher or lower than the optimal, then the plant’s growth begins
to suffer. If any of the factors is missing altogether, growth will
eventually cease.
For example, although plants need water to live, too much water will
effectively “drown” a plant, by removing all the air spaces in the
soil where the roots absorb nutrients. Note that most house plants die
from over-watering, as opposed to under-watering. Too much direct
sunlight can burn a plant’s leaves. With no leaves to photosynthesize
with, the plant can’t make more carbohydrates (even though it has
light), and will stop growing and die.
Plant fertilizers can be thought of as plant “food.” They are
nutrients, such as nitrates and phosphates that the plants need to
carry out the chemical processes of photosynthesis and growth.
However, the following important distinction can be made between plant
fertilization and plant nutrition, from
[http://www.nulex.com/plantnut.htm ]:
“Plant nutrition refers to the needs and uses of the basic chemical
elements in the plant. The way the plant takes in food to promote
growth of the plant and repair damage.
Fertilization is the term used when these materials the plant needs,
but may be limited, are supplied to the environment around the plant.”
So, when you hear "nutrition, think "inside the plant itself," and
when you hear "fertilization" think "in the soil around the plant."
The manner in which different soils affect plants is largely due to
the types of nutrients the soils contain. The following link is to an
article entitled, “Plant Nutrients,” by Rod Smith, Oregon Certified
Nursery Professional:
[ http://www.rodsgarden.50megs.com/plantnutrients.htm ].
Now, on to the last part of your Question,
“What types of plants do better in these
different circumstances?”:
Some plants specialize in environmental conditions that on average are
bad for most plants. For example, cacti and succulents thrive in
low-water, high heat, dry desert environments. Plants that are adapted
for life with low water conditions are termed “xerophytes.” See full
definition and examples at this HyperDictionary.com link:
[ http://www.hyperdictionary.com/dictionary/xerophytic+plant ].
At the other extreme, a “hydrophyte” is “a plant that grows partly or
wholly in water whether rooted in the mud, as a lotus, or floating
without anchorage, as the water hyacinth”:
[http://www.hyperdictionary.com/search.aspx?Dict=&define=hydrophyte ].
In the middle we find most “normal” plants: “land plant growing in
surroundings having an average supply of water; compare xerophyte and
hydrophyte”:
[ http://www.hyperdictionary.com/search.aspx?Dict=&define=mesophyte ].
At this point I will provide you with some more links you may find of
interest:
Here’s a link to a middle school teacher resources page about plants
(from fastplant.org):
[http://www.fastplants.org/resources/middle_school.html ].
Next is a link to a page describing plant biology science projects for
grades 7 and 8 (from Resources for Teaching Middle School Science”):
[ http://www.nap.edu/readingroom/books/rtmss/2.65.html ].
Finally, here is a link to a Space Science Group webpage dedicated to
“Geotropism.” Note that “phototropism” is the tendency for plant stems
to grow toward the light. Geotropism, on the other hand, is the
tendency of plants’ roots to grow toward gravity.
From the site below, “A plant's reaction to gravity is called
geotropism.”:
[ http://www.spacesciencegroup.nsula.edu/lessons/defaultie.asp?Theme=plants&PageName=geotropism
].
Below are the search terms I used to locate the resources I presented
you with, and that you and your child can use to locate additional
resources on this topic.
Google search strategy:
Keywords,
“simple explanation photosynthesis”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=simple+explanation+photosynthesis
,
“photosynthesis”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=photosynthesis&btnG=Google+Search
,
“simple explanation plant growth”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=simple+explanation+plant+growth
,
“how do plants grow”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=how+do+plants+grow
,
“plant fertilization”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=plant+fertilization&btnG=Google+Search
“phototropism”:
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=phototropism ,
“geotropism”:
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=geotropism
"basic biology of plants":
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=basic+biology+of+plants&btnG=Google+Search
Note that clicking the “similar links” gray colored link next to each
search result main link will bring you to more content similar to that
of the last link.
I hope this proves to be more than sufficient information to provide
background material for your child’s science project. If anything I’ve
written here isn’t clear, or if I’ve left something out which is
important to you, then please don’t hesitate to ask for Clarification
to this Answer.
Sincerely,
omniscientbeing-ga
Google Answers Researcher |
,
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