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Question Video: Defining the term "Hormone" In Plants Biology

Auxins are a group of hormones found in plants. Which of the following best defines hormones? [A] Hormones are chemical messengers that travel throughout an organism to act on target cells or organs. [B] Hormones are electrical signals that travel throughout an organism via the nervous system to act on target cells or organs. [C] Hormones are soluble carbohydrates that communicate changes in stimuli between the external and internal environments of an organism. [D] hormones are biological catalysts that speed up the rates of chemical reactions without being used up.

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Video Transcript

Auxins are a group of hormones found in plants. Which of the following best defines hormones? (A) Hormones are chemical messengers that travel throughout an organism to act on target cells or organs. (B) Hormones are electrical signals that travel throughout an organism via the nervous system to act on target cells or organs. (C) Hormones are soluble carbohydrates that communicate changes in stimuli between the external and internal environments of an organism. Or (D) hormones are biological catalysts that speed up the rates of chemical reactions without being used up.

To answer this question, let’s look at what a hormone is and what it does. And to do this, we’re going to remove the answer options for now. Hormones are chemical messengers. And, as the question tells us, they can be found in plants. Plants, like this one, do not have nervous systems, so instead they need some kind of chemical messenger to send signals around the body. These hormones can cause changes in the organism’s body and can communicate between organs and tissues and allow them to respond to their external environment.

Let’s take a look at a few of these responses in plants. Hormones are responsible for triggering blossoming of flowers, are responsible for pores on the leaves called stomata to open and close and allow the exchange of gases. Hormones can even promote root growth and the growth of the other parts of the plant too. In fact, some hormones can have multiple effects in different areas of the plant. For this reason, hormones need to be able to travel around the body of an organism to act on target cells where they’re needed.

Let’s bring back all our answer options so we can eliminate those that we know are not correct and find our correct answer. As we now know, plants do not possess a nervous system, but plants do possess hormones. Therefore, we can eliminate option (B), as if plants don’t have a nervous system, hormones can’t be electrical signals that travel via a nervous system in a plant. The term biological catalyst is used to describe a structure called an enzyme rather than a hormone. So option (D) is also incorrect.

While option (C) does describe the fact that hormones can communicate changes between an external and internal environment of an organism, hormones are usually not carbohydrates. In fact, they’re most often derived from proteins or lipids. So option (C) is also incorrect. This leaves us with option (A), which accurately describes hormones as chemical messengers that travel throughout an organism to act on target cells or organs.

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