Ep. 02 - Fall Colors

Episode Notes:

When discussing branching, Steve and Bill wondered whether Horsechestnut (Aesculus hippocastanum) was native. While some members of this genus are native to North America, the Horsechestnut (AKA Horse-chestnut or Conker Tree) is an imported species native to the Balkans.


     Steve had mentioned that there was only one genus in the Aceraceae, or maple family. This is wrong. That fool neglected the two species within the genus Dipteronia that are endemic to mainland China.

      Additionally, Steve also said, “we’ve slowly been knocking out all these different genes that code for all these different hormones”, which may have been misleading. Plant hormones are not transcribed directly from DNA; instead they are later synthesized by the products of specific genes. If the genes responsible for the synthesis of a particular hormone are “knocked out,” the plant will no longer be able to synthesize that hormone.             

         Also when Bill was describing how the abcisssion layer forms, he said that the separation layer gets thicker and pushes against the separation layer. What he meant to say was that the protection layer (the layer closer to the twig) gets thicker and pushes against the separation layer (the layer closer to the leaf). Here is a more complete description of the process: 

Abcission cells start to collect where the stem meets the branch. Two layers form – the separation layer and a protection layer. In the separation layer, the cells are short with thin walls. So, this area becomes weak and a tear starts to form. The protection layer is closer to the tree – a kind of nodule starts to grow. It cuts off all water and nutrients to the leaf, and, as the nodule grows, it pushes the leaf farther and farther from the branch until the separation layer is so brittle, it breaks. 

Work Cited: 

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Archetti, Marco. "Classification of hypotheses on the evolution of autumn colours." Oikos 118.3 (2009): 328-333.

Bolser, Jessica A., et al. "Birds select fruits with more anthocyanins and phenolic compounds during autumn migration." The Wilson Journal of Ornithology 125.1 (2013): 97-108.

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Landi, M., M. Tattini, and Kevin S. Gould. "Multiple functional roles of anthocyanins in plant-environment interactions." Environmental and Experimental Botany 119 (2015): 4-17.

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