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About the Plant Wars Reading Passage
Plant Wars is a practice IELTS Reading passage that examines chemical warfare strategies in the plant kingdom. It covers how plants compete for light, water, and nutrients, and how they defend themselves from herbivores using allelopathy, primary and secondary metabolites (including the cyclic hydroxamic acids DIBOA and DIMBOA), and by recruiting ant colonies. The passage also connects these plant defense mechanisms to research on human cancer cells. The Cambridge source for this passage is not specified in the existing article.
You should spend about 20 minutes on Questions 1–14, which are based on the passage below.
This passage contains three question types: Sentence Completion (Q1–7), Diagram Labelling (Q8–12), and True/False/Not Given (Q13–14).
Plant Wars: Full Reading Passage
Paragraph A
Mention the words "chemical warfare" or "deployed armies" in any conversation, and your interlocutor might immediately assume you're talking about wars between humans. In reality, however, there are other kinds of wars out there where these techniques are employed far more frequently and in a far more intricate manner: those waged in the plant kingdom.
Paragraph B
We might not normally think of plants this way, but much like humans and animals, they too have to fight for survival on a daily basis. Nutrients, light, and water are the three things any plant needs in order to grow; unfortunately, none of these is ample in supply, which means that the competition between plants can grow fierce. Some plants and trees are at an architectural advantage: taller trees have greater access to natural light, while plants with deeper roots have the ability to absorb more water and nutrients. Others, though, manage to defend their territory through "allelopathy", or chemical warfare.
Paragraph C
So how does this chemical warfare work exactly? As Dr. Robin Andrews explains, plants convert the nutrients they absorb from the ground to energy with the aid of a type of organic compound known as metabolites. These metabolites can be divided into two categories: primary and secondary. Primary metabolites are what allows a plant to live, playing a direct role in its growth and development, and are thus present in every plant. Secondary metabolites, on the other hand, can vary from plant to plant and often play the role of a defense mechanism against neighboring competitors.
Paragraph D
Out of these secondary metabolites, there are two that are incredibly interesting: DIBOA and DIMBOA. These two cyclic hydroxamic acids were at the forefront of a study conducted by researchers at the University of Bern in Switzerland. Their research showed that DIBOA and DIMBOA are the primary agents responsible for allelopathic activity in wheat, rye, and maize. These chemicals are released into the soil through the roots of the plant, and then move through the soil to reach the roots of nearby plants. Once there, they inhibit growth by blocking a molecular mechanism that is essential for the development of other plants.
Paragraph E
The relationship between plants and herbivores is another area where chemical warfare comes into play. Plants cannot run away from predators, so they have developed a different kind of defense. Some produce chemicals that, in small doses, are harmless to all herbivores; but in larger quantities, these substances become toxic. Others produce chemicals that are not toxic at all herbivores but affect only certain species. And then there are plants that produce substances that are immediately lethal, even the smallest contact with these chemicals can be fatal to an animal.
Paragraph F
Some plants take a more sophisticated approach and form alliances with insects in order to protect themselves. The acacia tree, for instance, is home to colonies of ants that live in the tree's hollowed-out structures. In return for shelter, the ants actively protect the acacia from herbivores. The relationship is so strong that acacia ants have been known to attack even large animals like giraffes in order to defend their host tree.
Paragraph G
Beyond their role in plant defense, allelochemicals have caught the attention of medical researchers. Some of these chemical compounds have been found to affect cancer cells in humans without harming healthy tissue. Researchers at the University Clinics Tübingen have been conducting clinical trials to assess the potential of plant toxins as treatments for cancer patients. If these trials prove successful, the weapons that plants have developed over millions of years of evolution could one day serve a very different purpose.
Plant Wars Reading Questions & Answers
Sentence Completion: Questions 1–7
Complete the sentences below. Choose NO MORE THAN THREE WORDS from the passage for each answer.
1. Plants need nutrients, water, and ________ to survive, just like ________.
2. Tall trees are able to gain more access to ________.
3. Chemical warfare in plants is known as ________.
4. Metabolites convert absorbed nutrients into ________.
5. A metabolite is a kind of ________.
6. DIBOA and DIMBOA are able to ________ by blocking an important molecular mechanism.
7. DIBOA and DIMBOA inhibit growth by disrupting a/an ________.
Diagram Labelling: Questions 8–12
Label the diagram below. Choose NO MORE THAN THREE WORDS from the passage for each answer.
8. Toxic chemicals are harmless when administered in ________.
9. Some toxic chemicals do not affect ________.
10. Some plants produce chemicals that are ________.
11. Ants live in the tree's ________.
12. Acacia ants have been known to attack animals as large as ________.
True/False/Not Given: Questions 13–14
Do the following statements agree with the information given in the passage?
Write:
- TRUE if the statement agrees with the information
- FALSE if the statement contradicts the information
- NOT GIVEN if there is no information on this in the passage
13. Allelochemicals have been found to affect human cancer cells.
14. Plant biologists and medical researchers are cooperating on research into plant toxins.
