War of the Plants
Read War of the Plants and check the IELTS Reading answers. The general perception of plants is that they are defenceless when faced with threat from animals (including man), insects and other plants. This, however, is not the case. Plants are able to defend themselves against attack from their env…
Passage preview
The general perception of plants is that they are defenceless when faced with threat from animals (including man), insects and other plants. This, however, is not the case. Plants are able to defend themselves against attack from their environment in many ways. There are two major features of plants that ensure their continuation as species. One of these relates to their physical attributes. Spinifex grass, a plant native to Australia, provides a notable example. Adapted to life in the hot, desert inland, spinifex has developed tightly rolled leaves which reduce the effects of drought stress. The hairs, or trichomes, which are found on the inner surface of the rolled-up spinifex leaf are believed to assist in minimising water loss. Trichomes also have defensive roles against predators. Many plants, such as the sunflower, have hairy leaves which are rough to the touch. When the plant is bitten by a grazing animal, the sensation is unpleasant on the tongue and the animal normally moves on to find more palatable food.
Vocabulary from this passage
12 words worth learning before you sit the test, each with the sentence it appears in.
- allelopathy noun
The chemical inhibition of one plant species by another, through the release of biochemical substances.
Forest ecologists studied how allelopathy allows certain tree species to dominate forest understories.
- deter verb
To discourage or prevent someone or something from taking action through fear or doubt.
Bright warning coloration on certain insects helps to deter potential predators from attacking them.
- diminish verb
To make or become less, smaller, or weaker over time or in degree.
The effectiveness of the traditional pesticide began to diminish as the insects developed genetic resistance.
- epidermis noun
The outermost layer of cells covering the primary body of a plant, providing environmental protection.
The plant's epidermis is coated with a thick waxy cuticle to prevent excessive moisture loss.
- harness verb
To control and utilize a natural resource, force, or process for a productive purpose.
Modern agricultural science seeks to harness natural plant defenses to minimize synthetic chemical usage.
- inhibit verb
To hinder, restrain, or prevent an action, process, or the growth and development of something.
Certain agricultural weeds produce compounds that actively inhibit the germination of crop seeds.
- palatable adjective
Pleasant to taste, or acceptable and satisfactory to the mind or sensibilities.
The grazing cattle avoided the bitter weeds, searching for more palatable grasses instead.
- residual effect noun
A remaining or lingering consequence, impact, or trace left behind after the primary cause has ceased.
Organic farmers prefer natural pesticides because they break down quickly without leaving a harmful residual effect.
- suppression noun
The act of forcibly putting an end to or inhibiting the growth, development, or activity of something.
The chemical runoff caused the complete suppression of native flora along the riverbank.
- synergistic adjective
Relating to the interaction of multiple agents to produce a combined effect greater than the sum of their individual effects.
The combination of the two herbicides produced a synergistic impact that eliminated resistant weed populations.
- synthetic chemical noun
A man-made substance produced through artificial chemical synthesis rather than occurring naturally.
Consumers are increasingly willing to pay higher prices for food grown without any synthetic chemical inputs.
- trichome noun
A small hair or outgrowth from the epidermis of a plant, often serving protective or absorptive functions.
Microscopic analysis revealed that the plant's trichomes secrete a sticky substance to deter insects.
Answers with explanations
- 14. D
Paragraph D discusses the thorn apple weed, noting that **chemicals are released from the seed during the early stages of germination**. Germination is the biological reproductive process of a plant growing from a seed, precisely matching the description in the prompt.
- 15. B
Paragraph B outlines how some plants use a **natural adhesive** to trap insects so they are **held onto the plant, unable to depart**. "Natural adhesive" directly paraphrases the phrase "a kind of glue" from the prompt.
- 16. A
Paragraph A introduces **physical attributes** (non-chemical methods) of defence. It provides exactly two examples: the **tightly rolled leaves** of the spinifex grass to prevent water loss, and the hairy leaves (**trichomes**) of plants like the sunflower to deter grazing animals.
- 17. C
Paragraph C provides the formal definition of the term, explicitly stating that **Chemical interactions that occur between plants are known as 'allelopathy'**. This directly matches the requirement to find the "definition of the term".
- 18. B
Paragraph B provides multiple descriptions of chemical defence against predators, such as insects encountering a **toxic chemical which will deter it from feeding**, or animals receiving an "irritant chemical" from the nettle plant to deter future threats.
- 19. F
Paragraph F focuses extensively on the practical benefits of plant chemicals for farming. It highlights how harnessing these "natural herbicides" can **reduce this enormous bill** (financial benefit) and offer **real advantages in addressing environmental concerns** by replacing synthetic chemicals.
- 20. E
Paragraph E systematically lists the characteristics of allelopathic chemicals, noting they are **active in small quantities**, **effective only with certain other plants**, and that they **act by disrupting the plant's natural processes**. This directly satisfies the request for a description of their characteristics.
- 21. A
Paragraph A gives the example of the spinifex grass, which has **tightly rolled leaves** and specific hairs that **assist in minimising water loss**. Minimising water loss is the exact equivalent of conserving water, making this paragraph the correct match.
- 22. TRUE
The statement claims the nettle's 'syringes' are glandular trichomes. Paragraph B introduces the concept of **glandular trichomes** and then states that in the nettle plant, **these trichomes resemble miniature hypodermic syringes**. The text confirms they are indeed the same thing, so the statement is TRUE.
- 23. NOT GIVEN
The statement claims allelopathic plants grow more successfully than those relying only on physical features. The text states weeds are more **physically and chemically aggressive**, but it never directly compares the overall growth success of allelopathic plants *against* plants that rely *only* on physical features. Thus, the information is NOT GIVEN.
- 24. FALSE
The statement says research into synthetic herbicides focuses largely on *individual* chemicals. Paragraph E states that the **development of synthetic herbicides** targets synergistic effects—where **two or more such substances may combine**. Because they target combinations rather than individual chemicals, the statement is FALSE.
- 25. FALSE
The statement claims herbicides cost over A$200 million a year. Paragraph F clarifies that the **A$200-million annual cost** applies to *all* crop protection, and that **at least half** of that total is spent on herbicides. Half of $200 million is $100 million, which contradicts the claim. Therefore, the statement is FALSE.
- 26. D
The article discusses physical and chemical defences in the first few paragraphs, and then transitions into how allelopathy (chemicals found in weeds) can be used to create **natural herbicides** for agriculture. Option D captures this overarching theme that these weed chemicals have **real advantages** and practical benefits for the farming industry.