Question

1.      Recall that carotene and xanthophyll have very similar molecular structures except for the presence of two hydroxide groups in xanthophyll. Use this information to explain the difference in Rf values for these two pigments given the substrate/solvent combination employed in this exercise.

2. Given your understanding of how deciduous trees behave in autumn, which of these pigments tends to be retained the longest before leaves fall? How do you expect photosynthesis rates to change during this time? Explain your answer by employing your observations from both of the exercises in lab this week

Answer 1

Xanthophyll is more known to be more polar than carotene. The Rf value of the xanthophyll is less (two thirds) than that of carotene because xanthophyll has an H bond with cellulose, which slows it down, and thus it less soluble in the hydrophobic (non-polar) solvent. Xanthophyll also has greater for the hydrophilic paper.

When autumn arrives and the days are shorter, deciduous trees decrease chlorophyll pigment production and other pigments become observable in the leaves resulting in non-green leaves. Thus Carotene and xanthophyll thus tend to be retained in the autumn in deciduous trees. Photosynthesis rate thus as expected would decrease greatly because of the lack of chlorophyll pigments.