Last week, we learned that plants can get viral, bacterial and fungal diseases too. However, did you know that plants have in-built mechanisms to fight these off? Read on to find out more about the super-strength of plants.
There are three types of these in-built responses within plants:
Physical responses
Chemical responses
Mechanical responses
These are plants’ defenses when being attacked. What do they get attacked by though? Last week, Tobacco Mosaic Virus and rose black spot were mentioned. These are diseases caused by microorganisms: viruses and fungi respectively. Additionally, they can get attacked by insects (also known as aphids) or other animals as well.
Physical responses
If you look at any plant cell, they all have a thick cell wall made of cellulose. This is very hard to penetrate for microorganisms such as viruses, bacteria and fungi.
Additionally, all leaf cells have a waxy cuticle. You may have heard of it! A waxy cuticle is a waxy layer that covers the outermost tissue layer of a plant. The cuticle is secreted by the epidermis, and helps prevent water loss and infection by parasites. This also protects plants from attack by microorganisms.
The final physical defense are layers of dead cells on plants. For example, bark - a strong barrier found in trees to defend from attacks.
Chemical responses
Plants can also release antibacterial chemicals and poison. These will kill bacteria, thus, defending against attack. Poison will deter other life forms like herbivores.
Mechanical responses
Thorns are an example of mechanical defense. Once any animal gets close enough to eating the plant, these thorns will sting them as they are very sharp. The most famous example is the thorny rose.
Another mechanical response that you may have come across is the use of excessive numbers of hairs on a plant. If you have ever tried to pick a hairy plant, you will soon know that they are really uncomfortable to touch. For herbivores, they are uncomfortable to eat, so they will leave the plant alone.
You may have also heard of the stinging nettle, but do you know what a white dead nettle is? White dead nettles utilize the mechanical response of mimicry to defend themselves. Below, you can see how they look almost exactly like stinging nettles that sting any herbivores when touched. But, it has no sting. Just because they look similar, white dead nettles can defend themselves against predators.
Surprisingly, some plants even scare herbivores into not attacking them. For example, when the Mimosa Pudica, commonly known as the sensitive plant (or a touch-me-not), is touched by another organism, its leaves fold in upon themselves and its stems droop. This is to scare any herbivores!
By: Hemlata Pant
Sources:
“GCSE Science Revision Biology ‘Plant Diseases 2’ (Triple).” YouTube, uploaded by Freesciencelessons, 5 Oct. 2017, www.youtube.com/watch?v=02Mx7s8gIig.
Srivastava, Samriddhi. “From Curing Wounds To Itchy Skin, Here Are Some Amazing Benefits Of Touch-Me-Not Plant.” HerZindagi English, 1 May 2020, www.herzindagi.com/health/amazing-benefits-of-touch-me-not-plant-curing-wounds-itchy-skin-article-156440.
Team, AskNature. “Leaves Fold in Response to Touch : Herbe Sensible.” AskNature, 20 July 2017, asknature.org/strategy/leaves-fold-in-response-to-touch/#:%7E:text=Leaves%20of%20mimosa%20plant%20fold,leaf%20in%20a%20few%20minutes.&text=When%20the%20Mimosa%20pudica%2C%20commonly,themselves%20and%20its%20stems%20droop.
“Waxy Cuticle.” TheFreeDictionary.Com, www.thefreedictionary.com/Waxy+cuticle#:%7E:text=Botany%20A%20waxy%20layer%20that,loss%20and%20infection%20by%20parasites. Accessed 2 Sept. 2020.
“White Dead-Nettle | NatureSpot.” Www.Naturespot.Org, www.naturespot.org.uk/species/white-dead-nettle. Accessed 2 Sept. 2020.
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