Phytochemical changes - Reason for green leaves to convert in brown colour (Jul/10/2008 )

What is the reason for converting green leaves in to brown coloured leaves after few days of preservation in silica gel. And also how to remove brown colour from genomic DNA.

a few keywords: plastid degradation, ethylene biosynthesis, necrosis. additionally there is no longer a energy supply. how are you isolating DNA? when you use columns you can reduce the brown color. is it affecting you somehow?