As autumn starts to come full swing, we start to notice numerous changes in our climate here in Kansas. One of the biggest changes we may notice just by looking around outside is the changing of leaf color and the falling of millions of leaves all over the ground. These changes in leaves are a result of the process plants undergo to produce food known as photosynthesis, or lack thereof in the case of autumn. Photosynthesis occurs in the chloroplast of plant cells. It uses energy from sunlight in order to convert carbon dioxide and water into sugar and oxygen. A pigment within the chloroplast known as chlorophyll is responsible for the absorption of the light energy needed for photosynthesis.
Image from Wikimedia Commons
During the day, plants of all types are exposed to sunlight for numerous hours which helps to drive the production of food for the plant in photosynthesis. Plants are green because of a chemical inside them known as Chlorophyll. Chlorophyll is able to capture the light energy from the sun and use it in photosynthesis. During the summer, the sun is out for nearly 15 hours a day, resulting in a lot of photosynthesis reactions within plants. During the autumn and winter however, that time slowly begins to decrease until daytime splits almost in half. Because sunlight is the driving energy of photosynthesis, as the amount of sunlight a plant has drops, the production of food for the plant slows down, resulting in the death of the leaves, or even the plant entirely. Plants known as “annuals” have a life cycle of one year. They die in the cold winter, and they leave behind a seed to sprout when spring comes along. There are also plants known as “perennials” which have a life cycle of over two years. This usually consists of larger plants and trees. These are usually the plants that drop their leaves in the autumn and winter and grow them back in the spring. When the leaves are dropped, the plant stores all of its energy in the roots, trunk and branches in order to survive the winter.
Because the production of oxygen in billions of plants around the world stops for nearly half the year, a question about oxygen levels often arises. Is there less oxygen in the atmosphere for us to breathe during winter and autumn? Technically yes. Because all of these plants have stopped converting carbon dioxide into oxygen, the carbon dioxide levels in the atmosphere rise, and the oxygen levels drop, but only by a small amount. Seasons happen at different times of year all around the world. Although oxygen production in plants might drop here in the United States because of autumn and winter, it is rising in other parts of the world like Australia as summer approaches. These opposite seasons tend to cancel each other out, and as a result, the oxygen level in the atmosphere stays fairly constant throughout, but it does decrease slightly within the region in which the leaves are dying. Just not enough for us as humans to notice or have any health problems.
- Scishowkids. “Why Do Leaves Change Colors in the Fall?” YouTube. YouTube, 16 Oct. 2015. Web. 20 Oct. 2016. <https://www.youtube.com/watch?v=Xk4-6II8l5Q>.
“Autumn Leaves: How Plants Prepare for Winter by Science Made Simple.”Science Made Simple. Science Made Simple, 2013. Web. 20 Oct. 2016. <http://www.sciencemadesimple.com/plants-in-winter.html>.