Question
hello,
i did an experiment where i kept a plant in darkness and it turned yellow.
please help me understand the science behind this.
thank you
dou

Answer
Dou,

This sounds like a homework question and I am not supposed to answer homework questions so my answer will be very brief. Yellowing of leaves is called chlorosis. The green pigment in plants is
chlorophyll. In most plants, chlorophyll synthesis requires light. Gymnosperms,such as pines, are an exception and can form chlorophyll in the dark.

For most plants, no new chlorophyll can be made in the dark. The existing chlorophyll has a limited life and eventually degrades. When the chlorophyll degrades, it reveals the yellow cartenoid pigments that were there all along but just masked by the green chlorophyll. The degradation of chlorophyll is also the reason why tree leaves change color in the fall.

If you need details of the biochemistry of chlorophyll synthesis, do a google.com search for chlorophyll biosynthesis.

Good luck.

Darlene