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Abstract Detail

Teaching Section

Harley, Sue [1].

Forgotten Applications of Common Techniques.

     In many introductory labs on photosynthesis, students test leaves for starch to see if photosynthesis has occurred.  This simple test is often used to localize photosynthesis to chloroplasts when variegated leaves are used.  Somewhat forgotten today is that the starch test can also be used to check for C4 photosynthesis that is associated with Kranz anatomy.  Because the Calvin cycle is present in chloroplasts of the bundle sheath but not in those of the mesophyll, there is a preferential accumulation of starch in cells of the bundle sheath, analogous to the situation in variegated leaves where starch accumulates in areas where the chloroplasts are located.      
     Another common lab involves checking seed viability with TTC (2,3,5-triphenyltetrazolium chloride).  The water-soluble, colorless TTC is reduced to water-insoluble red formazan if respiration is occurring.  Often, a solution of TTC is applied to imbibed and cut maize kernels to observe respiratory activity of the embryo versus the endosperm as the formazan precipitates onto the tissue where TTC was reduced.  The TTC test can be applied more broadly than just seeds and made quantitative.  Formazan can be dissolved in ethanol or hexane.  The absorbance of this solution can be determined and used to quantify respiratory activity.  For example, when examining leaf senescence, measurement of respiration can be done to complement measurements of chlorophyll.  This provides a fuller picture of what is happening in leaves as they senescence.

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1 - Weber State University, Botany - 2504, 3772 North Campus Drive, Ogden, UT, 84408-2504, USA

C4 photosynthesis
TTC test
starch test.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PTE010
Abstract ID:777
Candidate for Awards:None

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