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1. Japanese Bitter Orange (Citrus trifoliata or Poncirin trifoliata)

citrus trifoliata (1) square.jpg

Please note, the latin name listed for this tree is visible from the southmost pathway of the inner garden, by the wall. The label reads 'Poncirin trifoliata'.

Secondary metabolites don’t help with growth or reproduction, but they do help plants communicate, compete with others, and defend themselves. These molecules are often what make plants have certain smells, through aroma compounds like citronellol for citrus fragrance. They might also make plants have certain tastes, like menthol for minty flavour, or certain colours through pigments, like chlorophyll for green.

Having certain smells, tastes and colours might not seem like something that gives a plant an advantage, but they can both help to attract some and keep away other animals and insects in their environment. The molecules behind these smells, tastes, and colours also shape contact between microbes and the plant. They can attract microbes that help the plant, say by coating its roots and protecting it from parasites, like Pseudomonas bacteria do for tomato plants.

What does that mean? Some secondary metabolites are natural antimicrobials. As we go along to the next stop in the trail, you’ll see how these have been used by humans and animals through history.

Magnifying Glass smallDo you think it’s bad for plants to kill microbes?

When we talk about ethics, we’re talking about what’s bad or good, what we should or shouldn’t do, in a moral sense. We all have gut feelings about questions like whether it’s bad for plants to kill microbes, and there’s no decided right or wrong answer for this or any of the other Spotlight on the Ethics questions you’ll read. But it’s good to think about what might lie behind your gut feeling.

Do you think it’s bad for plants to kill microbes because microbes are living things too, and living things have rights? Or do you think it’s okay, because only living things that can feel things can have rights, and microbes probably can’t feel things?

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