Why leaves are red in autumn

Due to the yellow color attracting the attention of harmful insects, many plants deal with their own red leaves to reduce losses in the fall, adding to the colorful romance of this season of the year .

Leaf color change is one of the phenomena that signals the arrival of autumn, but why do some species' leaves turn red? This question confused biologists for decades. Now Dr. Thomas Doring, lecturer at Imperial College London (UK) proposed a new explanation.

Thomas and his two colleagues hypothesized that the leaves produced red pigment because avoiding yellow color attracted the attention of harmful insects such as aphids. The yellow pigment is present on leaves in both spring and summer, but we only see it in the fall when the leaves stop producing green chlorophyll before it falls.

The red color is produced by a type of pigment called anthocyanin. Many species of plants produce this pigment in their autumn purchases before the leaves fall.

To test the hypothesis, the three scientists investigated the tendency to choose the color of aphids when they reached the tree in the fall to mate and lay eggs. They applied 70 different colors to 140 discs and filled them with water to track the number of aphids per each disc.

Two weeks later, the team found that the number of aphids on blue plates was three times more than the red ones, but the yellow disc attracted four times more bugs than the green disc.

Red helps plants repel insects in the fall.Photo: tinypic.com.

Later, Dr. Thomas used the colors of several hundred types of leaves from many plants to apply on the plate and repeat the test. The results showed that the red leaves did not attract many aphids with green and yellow leaves. From this experiment, the team identified leaves of some red plants to fight aphids. If the insect lands on leaves to lay eggs in large numbers, its growth may slow down and its health will decline.

The benefits of red are clear, but why do leaves of some plants still turn yellow when autumn comes? 'In theory, plants suffer losses for turning red. If the damage caused by insects is greater than the losses arising from the production of red pigments in the fall, the leaves will tend to turn red. In contrast, if the damage caused by insects is lower, the tree will retain the yellow color on the leaf, ' explains Dr. Thomas.

Thomas and his two colleagues will continue to explore the effects of aphids on leaf health and the behavioral differences of aphids when perched on red, blue and yellow leaves. According to many experts, the above findings of scientists have great significance. At least people understand that, if you want to scare away pests from the field in the fall, we should plant a lot of red leaf trees.