turn yellow

“Just like tea, it will bleach and turn yellow — and people say it might also get an off-flavor — if exposed to sunlight,” she said.

When exposed to excessive darkness the leaves of the mutant, COG-free plants began to turn yellow, wrinkled, and thin -- signs the plants were dying.

"The damage is enormous because the trees have been infected by bacteria… You can see this tree, it is green, but the leaves are starting to turn yellow, which means it may be diseased."

Some leaves gradually turn yellow and drop.

Finally, the leaves turn yellow in the fall.