The drawback with light color experiments is that students cannot obtain
the same amount of photosynthetically active radiation (PAR) for each
color. Incandescent bulbs are rich in red but poor in blue wavelengths
while cool-white fluorescents are just the opposite. Without an expensive
PAR meter, a student cannot properly set up a light color experiment to
compare growth under equal PAR of different colors. Does anyone know a
way around this problem?
The phototropism experiments with different colored windows (red, blue,
green) in a 35 mm film canister give expected results but probably not
because the PAR is equal for each color. It would be interesting to
actually measure the PAR coming through each window under a cool white
fluorescent bulb.
******************************************************************
David R. Hershey
Snail mail: 6700 Belcrest Road #112, Hyattsville, MD 20782-1340
Adjunct Professor, Biology/Horticulture Department
Prince George's Community College, Largo, MD 20772-2199
Email: dh321 at pgstumail.pg.cc.md.us
*******************************************************************
On 22 Jan 1997, Kathleen Archer wrote:
> Regarding the question about light filters:
> I just discovered that Sigma sells disposable plastic seedling trays with
> lids which can be purchased in tinted form (Phytatray II, tinted). They
> come in blue, red and yellow tints, and Sigma provides information on what
> wavelengths are transmitted and excluded. The cost is about $25.00 for 25
> trays with lids. If you are growing seedlings non-sterilly, it might be
> possible to re-use them.
>> These might be just the ticket for student experiments where expensive light
> filters or setups are hard to come by. This way a single cool-white
> fluorescent source can be used to provide light simultaneously to plants
> getting just the desired wavelengths.
> (Sigma technical service phone # 1-800-325-5832 for questions about the
> trays, to place an order ph# 1-800-325-3010)
> Kathleen Archer
> Dept. Biology
> Trinity College
> Hartford, CT 06106
>> e-mail: kathleen.archer at mail.trincoll.edu> Ph: (203) 297-2226
>>
