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For a science fair project, my niece is growing lima beans and studying how light will affect their growing habits. She has 3 plants. She keeps one of them in darkness all the time, one of them in sunlight for only 5 hours then it goes into a dark room with the first plant, and the last stays outside all of the time.
So far, the one in darkness hasn't grown at all which I expected. However, the plant that's outside for only 5 hours a day has grown twice as tall as the plant that's outside all of the time.
This isn't normal, right? Her hypothesis was that the plant outside all of the time would grow the tallest and thats what I thought as well.
The last time we measured, outside plant was 9cm tall and inside/outside plant was 17.5cm. They've all been growing for about two weeks now.
For better results, she should have grown multiple plants under each condition...but nonetheless: harsh sunlight can severely distress some plants. I've noticed that my lawn always grows taller under the shade of a picnic table. That's the great thing about experiments and scientific observation. The results you get may not always be what you'd expect. And, with science, all such experiments should be able to be replicated with the same results before forming conclusions.
Proving that her hypothesis is incorrect is not "wrong"--it's learning.
But she needs to note the condition of the plants, too. Just growing taller is not necessarily better if they're spindly and weak. Those characteristics need to be noted as well.
JackMichigan that was a nice explanation. It's rare to see someone with a scientific approach these days.
FlaKid you don't say your niece's age/grade so I don't want to be too critical of the experiment. I suspect, however, the result was correct based on more in depth knowledge of how plants grow and science experiments...... but first let me explain a few things.
A science experiment needs to limit variables that can effect the growth of a plant. One example of a variable would be moisture: if the plants were kept consistently moist to the same degree. Amount of water each plant received (a whole other experiment by the way) is very important. Water is lost from transpiration; a plant left completely out doors all the time will need more water. If it dries out it will stop or slow its growth. Outdoor vs indoor is another variable that needs to be controlled for to limit wind and pollutant differences; outdoor conditions are very different from indoor in many ways for a plant and she may well have seen a difference between a plant left in a protected "box" out doors from a plant left in the open (another experiment all by itself).
As far as why I suspect the experiment has turned out correctly? Many sprouts will actually become taller when there is reduced sunlight but they are not healthier or "better" plants and will eventually succumb to pests/disease and when they reach the stage of flowering and seed/fruit will lag behind the plant that has better sun exposure. Height was only one variable she has measured and she may want to go back and look at the "health" of each sprout. I suspect the tall one is actually quite leggy or spindly and less green than the shorter all sun sprout. There is a built in tendency in many plants to grow towards light as fast as they can in order to get enough energy to reproduce based on plant hormones. Most people recognize the spindly tree growing sideways out from under another larger one as an example of this.
A couple of things. First, a plant that does not receive enough light will change its "growth strategy", such that the cells making up the stem become more elongated and narrow rather than shorter and wider. In nature this would have the effect of getting the low light plant into a zone with better light, as for example, if it had germinated in the shadows and was growing out toward an area of better light. Secondly, many plants are very sensitive to the length of the day, and grow differently when the day is short (5 hr) vs. long. Often the plant growth hormones are changed in relative amounts, which affects the appearance of the plant, and also frequently the plant is either put on the "flowering plan" or the not flowering plan". In fact, just opening the door to where the plant is in "continuous darkness" is enough to affect the flowering readiness of that plant even though it is not healthy enough to do it.
For those wondering, my niece is in 5th grade and to be honest I really wanted her to pick a difference project since this would take so long. Her project is due in a week so we don't have the time to grow another plant.
When she first started doing this, we were deciding whether or not keep them all outside using a box to create darkness but went with the dark room instead. As far as them being in direct sun and shade, when their outside in the morning, they both get the same amount of direct sunlight. The rest of the day the outside plant is in the shade as its on the front porch which doesn't get direct sunlight after noon.
Outside of the locatoin, everything about the experiment is consistant including the amound of water they each get (1/8 cup). Maybe we should start giving outside plant more water but it might be too late for that.
For those wondering, my niece is in 5th grade and to be honest I really wanted her to pick a difference project since this would take so long. Her project is due in a week so we don't have the time to grow another plant.
When she first started doing this, we were deciding whether or not keep them all outside using a box to create darkness but went with the dark room instead. As far as them being in direct sun and shade, when their outside in the morning, they both get the same amount of direct sunlight. The rest of the day the outside plant is in the shade as its on the front porch which doesn't get direct sunlight after noon.
Outside of the locatoin, everything about the experiment is consistant including the amound of water they each get (1/8 cup). Maybe we should start giving outside plant more water but it might be too late for that.
Anyway thanks for the help.
You should take a moisture reading and keep that variable constant. Also understand the variable of temperature is also probably having a much larger impact and that should be measured daily.
But again as you pointed out she is only in 5th grade. LOL
You should take a moisture reading and keep that variable constant. Also understand the variable of temperature is also probably having a much larger impact and that should be measured daily.
But again as you pointed out she is only in 5th grade. LOL
Yea it would be pretty hard for her to explain all of those things when she presents it to the judges.
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LOL
