WEWilliams at osprey.smcm.edu
Mon Feb 5 12:57:27 EST 2001
>I am teaching a course on plant ecology this semester and would welcome
>suggestions for lab exercises, particularly on water relations (using a
>pressure chamber) and photosynthesis (using an IRGA). Thanks.
We often begin our plant-physiology course labs with a survey of the
differences between shade- and sun-grown sunflowers. (We just grow
the sun-grown on top of a greenhouse bench and the shade-grown on the
floor underneath the same bench.) They show very obvious differences
in overall morphology, chl a:b ratios, and photosynthetic light
curves (we've been using O2 electrodes, but an IRGA would be at least
as good -- what are you using?). Water relations are a bit trickier
because, as you undoubtedly know,it's very difficult to water-stress
a plant growing in a small pot without killing it. We sometimes see
pretty clear differences between noon and pre-dawn water potentials
in the sun-grown sunflowers, though; you might try that.
William E. Williams
Saint Mary's College of Maryland
18952 E. Fisher Rd.
Saint Mary's City, MD 20686-3001
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