Plant Ecology in a Changing World
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Page 431

Photosynthesis in succulents that I bought in the store

One of the strangest things I have done recently is to take a paper punch and punch out leaves from two succulents (Crassula smithii and Crassula nocturnus) that I bought in the store and that are growing on my window sill at home    . On each leaf punch, I measured the leaf pH and then through away the leaf punch.. The data are surprising and are provided below. Who would ever have thought that the pH of a leaf could change so much over a 24-hour period.

pH values measured on leaf punches

                        Crassula smithii          Crassula nocturnus

12 noon                       7.2                               5.4

3 pm                            7.3                               7.0

6 pm                            7.3                               7.3

9 pm                            7.2                               5.5

12 am                          7.4                               4.8

3 am                            7.5                               4.1

6 am                            7.2                               4.0

9 am                            7.4                               5.0


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Jim Ehleringer, University of Utah