There were many similar threads here before (see first four references).
Hydroponic (solution culture) projects are very good for a greenhouse. The
traditional mineral nutrient deficiency experiment takes at least half a
semester. It can be varied by also doing some mineral nutrient toxicities
(especially boron, zinc, copper) and high salinity treatments.
It is often easier to use viny or rosette houseplants (piggyback plant
[Tolmiea menziesii], Wandering Jews, philodendron, pothos, etc.) to avoid
the difficulty of staking. Propagating houseplants by cuttings also is
easier and faster than seed propagation and gives clonal material (Hershey
1994). Hydroponics also can be used for transpiration measurements by
weight loss, and nondestructive plant fresh weight gain.
Another good hydroponic experiment involves iron deficiency stress
response (Hershey 2000). Some plants lower the rootzone pH when deficient
in iron and grown with all nitrate-nitrogen in the solution. This
increases iron availability, the plant recovers and the solution pH rises.
Inexpensive pocket pH meters are excellent for solution pH measurements.
Some plants lower the solution pH all the time (such as common
philodendron). Others are iron-inefficient and cannot lower the solution
pH, e.g. Tolmiea menziesii. To test whether a plant is iron inefficient,
simply grow the plant in an all nitrate-nitrogen solution such as
Hoagland's solution number 1 without iron. Coat the roots with some iron
oxide powder. Tolmiea menziesii will turn bright yellow due to iron
deficiency even with the roots coated with red iron oxide. It's very
striking.
Plant carbon dioxide deficiency is also to demonstrate using hydroponics
(Hershey 1992).
Other good greenhouse experiments involve photoperiodism and plant
hormones/plant growth regulators. Students could grow a crop of pot
chrysanthemums and incorporate both. The treatments would be:
1. Long photoperiods with water spray
2. Long photoperiod with daminozide spray
3. Short photoperiods with water spray
4. Short photoperiods with daminozide spray
Photoperiod control in a greenhouse can be a hassle because it requires
manual pulling of blackcloth or other opaque material over the plants
daily in late afternoon and removal early in the morning to assure a short
photoperiod. A long photoperiod requires a time clock and incandescent
bulbs suspended over the plants. The timer is usually set to go on from 10
pm to 2 am. A simpler photoperiod experiment can be done indoors using
fluorescent light banks and Kalanchoe daigremontiana (Hershey 2002).
Plant hormones experiments can involve GA sprays to increase height of
dwarf plants, auxins dips to promote rooting of cuttings, and auxins and
apical dominance.
Phototropism experiments can be done in a greenhouse if plants are set in
cardboard boxes to get unidirectional light. Gravitropism studies can be
done with potted plants but a greenhouse is hardly needed except to grow
the plants because the response is so rapid. Students can make simple
clinostats for gravitropism and phototropism experiments (Hershey 2005)
Plant physiology lab manuals have lots of excellent labs (Reiss 1994; Ross
1974; Witham, Blaydes and Devlin 1971)
David R. Hershey
http://www.angelfire.com/ab6/hershey/bio.htm
References
Investigative labs for plant biology. Bionet.plants.education. (August 23,
2002).
http://www.bio.net/hypermail/plant-ed/2002-August/007371.html
Inquiry-based labs for Plant Biology course. Bionet.plants.education (Dec.
2-5, 2005)
http://www.bio.net/hypermail/plant-ed/2005-December/007972.html
Phytochrome lab exercises? Bionet.plants.education (July 26, 2005)
http://www.bio.net/bionet/mm/plant-ed/2005-July/007904.html
Bionet.plants education search
http://groups.google.com/group/bionet.plants.education/search?hl=en&group=bionet.plants.education&q=plant+physiology+lab&qt_g=Search+this+group
Hershey, D.R. 1992. Plants can't do without CO2. Science Teacher
59(3):41-43.
Hershey, D.R. 1994. Solution culture hydroponics: history and inexpensive
equipment. American Biology Teacher 56:111-118.
Hershey, D.R. 2000. "Hydroponics: Iron Deficiency of Piggyback Plants" pp.
147-155. IN Gerry M. Madrazo, Jr. and Steven E. Dyche (editors). Exciting
Plant Science Activities for the Secondary Classroom Chapel Hill, NC:
University of North Carolina Press.
Hershey, D.R. 2002. Using the Kalanchoe daigremontiana plant to show the
effects of photoperiodism on plantlet formation. Science Activities
39(2):30-34.
Hershey, D.R. 2005. Time for a plant clinostat: Effects of light and
gravity on plants. Science Activities 42(1):30-35.
Reiss, C. 1994. Experiments in Plant Physiology. Englewood Cliffs, NJ:
Prentice Hall.
Ross, C.W. 1974. Plant Physiology Laboratory Manual. Belmont, CA:
Wadsworth.
Witham, F.H., D.F. Blaydes and R.M. Devlin. 1971. Experiments in Plant
Physiology. NY: Van Nostrand Reinhold.
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