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why do some plants have red leaves

Most of the plants you see on a daily basis are green, but every so often you might happen upon the odd purple-leafed tree or shrub. Why do some plants have these purple parts? The answer lies with another P word: pigment. Green plants contain a lot of the pigment chlorophyll. Because chlorophyll molecules are very good at soaking up blue and red light but not so good at absorbing green light plants containing a lot of chlorophyll appear green to the human eye. Pigment is also behind a purple plant s vivid coloring. Plants that appear purple, blue or red contain a higher concentration of anthocyanin than chlorophyll. Anthocyanin is a pigment adept at absorbing green light, but less skilled at absorbing red, blue or purple light. [
Scientists believe that the purple leaves on some plants like Persian shield, oyster plant and ornamental cabbage may act as a natural , protecting the cells of the plant from too much light. Plants that experience too much sunlight can suffer from photoinhibition, a reduction in the plant s ability to carry out photosynthesis. And because high levels of anthocyanin often appear together with high concentrations of, it s possible that the purple leaves of some plants help ward off hungry herbivores.

Follow Elizabeth Palermo on Twitter @ or on. Follow LiveScience. We re also on. The vivid yellow and orange colors of fall leaves have actually been there throughout the spring and summer, but we havenБt been able to see them. The deep green color of chlorophyll, which helps plants absorb life-giving sunlight, hides the other colors. In the fall, trees break down the green pigments and nutrients stored in the leaves. The nutrients are shuttled into the roots for reuse in the spring As leaves lose their chlorophyll, other pigments become visible to the human eye, according to Bryan A. Hanson, professor of chemistry and biochemistry at DePauw University who studies plant pigments. Some tree leaves turn mostly brown, indicating that all pigments are gone. Burgundy and red colors are a different story. Dana A. Dudle is a DePauw professor of biology who researches red pigment in plant flowers, stems and leaves. Dudle said: The red color is actively made in leaves by bright light and cold.

The crisp, cold nights in the fall combine with bright, sunny days to spur production of red in leaves Б especially in sugar maple and red maple trees. Burgundy leaves often result from a combination of red pigment and chlorophyll. Autumn seasons with a lot of sunny days and cold nights will have the brightest colors. In some cases, about half of a treeБs leaves are red/orange and the other half green. Dudle says that results from micro-environmental factors Б such as only half the tree being exposed to sunlight or cold. Hardwoods in the Midwest and on the East Coast are famous for good color selections. Some of the more reliably colorful trees, Hanson notes, are liquid amber trees (also called sweet gum) that turn a variety of colors on the same tree, and sometimes the same leaf. Ash tree leaves often turn a deep burgundy color. Ginkgo trees, although not native to North America, will feature an intense yellow, almost golden, color. The colors are doing something for the plant, or they wouldnБt be there, said Hansen. But what is the colorsБ purpose?

Scientists think that with some trees, pigments serve as a kind of sunscreen to filter out sunlight. Hanson said: ItБs an underappreciated fact that plants cannot take an infinite amount of sun. Some leaves, if they get too much sun, will get something equivalent of a sunburn. They get stressed out and die. Another theory is that the color of a plantБs leaves is often related to the ability to warn away pests or attract insect pollinators. Hanson said: In some cases, a plant and insect might have co-evolved. One of the more intriguing scientific theories is that the beautiful leaf colors we see today are indicative of a relationship between a plant and insects that developed millions of years ago. However, as the EarthБs climate changed over the years, the insects might have gone extinct, but the plant was able to survive for whatever reason. Because plants evolve very slowly, we still see the colors. So leaf color is a fossil memory, something that existed for a reason millions of years ago but that serves no purpose now. Bottom line: Biologists discuss why leaves change color.

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