plant lights vs sunlight

john markwell markwell at
Sun Jul 31 08:56:12 EST 1994

twallace at (Todd A Wallace) writes:

>I have noticed that when I grow seedlings under my grow light they grow
>tall and thin, and eventually topple over. If I grow them next to the
>window, they grow stronger but shorter. Why is there a difference?

>|    Todd Wallace               |  "A pessimist is surprised   |
>|    twallace at    |   as often as an optimist,   |
>|-------------------------------|   but always pleasantly."    |
>| Expatriate Midwesterner (tm)  |            - Robert Heinlein |

I suspect that the problem is the light intensity.  Just measuring the
wavelengths able to drive photosynthesis (~400 to 700 nm), sunlight 
would normally contain 1000 to 2000 micromoles of photoms per sq. 
meter per second.  With fluorescent lamps, it is difficult to achieve 
over 350.  Since the light intensity (actually, we measure something 
called the photon fluence rate when dealing with plants) tends to 
decrease with the square of the distance from the source, you might 
try moving the plants closer to the lamps.

I hope this helps


John Markwell			Phone: 402-472-2924
Dept. Biochemistry		FAX:   402-472-7842
University of Nebraska		Internet: markwell at
Lincoln, NE  68583-0718

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