Science Buddies: "Ask an Expert"

i have a idea, but i don't know will it work or not.
my idea is that will the plant grow faster or slower if it received sunlight at different period of time in a day? will the sunlight cause any different if it's in the morning? noon? afternoon? sunset? will it then affect the growth of plant? ok~this is what i am going to do..~please help me!!~thanks!!

That's an interesting idea, sanhkyeung! I have a couple of questions which might help you focus your ideas:

How would a plant (or any organism) 'know' what time of day it is? You might want to look up 'circadian rhythm' on Google or Wikipedia. My suggestion would be to provide the plants with a low level of light all day but only put some in direct sunlight in the morning, afternoon, or evening--otherwise the plants may react as if it were morning regardless of what time of day you allowed them to get sunlight. You probably also want a group of plants that have the low level of light all day but don't get put into direct sunlight at all.

I hope that helps! Let me know if you have any questions.

hi~your suggestion is great!!~but i want to to know that how can i sure that the level of light is low??is the light from lamp ok? also, will the sunlight be different at different period of time? thanks for answer my question!!~i think i will go ahead and do this experiment~^^

I don't know a whole lot about plants so maybe someone else can chime in, but I'm pretty sure that incandescent (not flourescent) lights are not very good for plants. Perhaps you could put the plants in a room lit only by one of these bulbs. If you could get a lamp at a store where you could adjust the light level, you could keep the light level even lower. Of course, you'd need to make sure that you had a room where it was okay if you turned the lights on and off at the same time every day.

Depending on what your budget for this project is, there are special instruments that measure the exact light level in a location. For example, here's a page with several: http://www.gemplers.com/a/pages/ilightlevels.asp. They're fairly expensive, though, but maybe you could find one you could borrow.

or do u think i should just testing the sunlight at different period of time in a day?? rather using the indoor light?? and then i will compare the growth of plants in the morning light, afternoon light, or something like that??

sanhkyeung,

That's another good idea: comparing growth rates of plants exposed to only morning, only afternoon, or only evening light. It's slightly different from the question you were asking first because you would be determining if there is a difference in the quality of sunlight at the various times of day whereas in the first experiment, you would be assuming the quality of sunlight was the same and determining if the plants process sunlight differently at different times of day. (Actually, now that I think about it if you do decide to do the first experiment, you should try to hold light quality constant and put them under growing lamps rather than in sunlight just in case there are differences in sunlight quality at different times of the day.)

It's up to you--you might want to think about how easy it will be to do each experiment and which one excites you more!

hey there

from what i know...it depends on some plants because if you compare a plant that grows in the tropics...it is usually greater and sometimes more colorful in size than compared to plants in the temperate zones...this also applies to animals and insects that grow within both areas

Light is only one driver of plant growth. Temperature is an important consideartion in plant growth. Some plants are adapted to high temperatures (tropics) and others to cool seasons (cabbage/broccoli).

Available nutrition and water availabilty also affect plant growth.

In an experiment varying light intensity the temperature, nutrition and moisture levels must be controlled.
Matt Mulanax