Trichomes are tiny hairs found on the leaves and stems of plants. These structures are crucial for drought resistance, drought resistance, and herbivore defense. Students will use an inquiry-based activity to investigate the leaf hairs of various plants in the schoolyard. There will be two hypotheses: one about whether or not all plants have leaf hairs, and the other about whether or not most plants are heavily or moderately pubescent (hairy). Leaves will be collected and classified into three categories. Students will compile their data into a data table and bar graph, which they will then present to the class. The teacher will try to pique the students’ interest in the topic by offering some theories about why plants have leaf hairs in the conclusion.
How Plants Use Trichomes to Defend Against Insects
Trichomes are hairs found on the leaves, stems, and fruits of plants. These hairs serve as a strong defense against a variety of herbivorous insects in truly fascinating ways. But trichomes have other functions, too. When it is particularly hot, for instance, they serve as a canopy to provide shade, lower water loss, and shield the plant from the sun’s ultraviolet radiation. But the most intriguing aspect is how they protect themselves from insects. There is a great deal of variation in the size, shape, and quantity of plant trichomes (Figure 2). A densely packed mat of trichomes on the leaf surface can delay caterpillar feeding [3], which means that it takes longer for caterpillars to locate a spot or to chew through the trichomes to reach the epidermis—the first nutrient-rich leaf layer—if a plant has more trichomes. Some trichomes are also sharp, and they can pierce through the caterpillars’ supple bodies (Figures 2A,D). Unexpectedly, some plants will even put more trichomes on their young leaves if their older leaves are being eaten, protecting the young leaves from harm in the future.
Generally speaking, there are two types of trichomes: non-glandular and glandular. Non-glandular trichomes are sharp, pointed, spiny appendages that act as a physical barrier to stop the movement of herbivorous insects (Figures 2A,D) [4, 5]. In many cases they look like stars. Additionally, the hard materials silica and calcium carbonate added to these pointed needles can blunt caterpillars’ teeth, making it difficult for them to chew. Trichomes limit the caterpillars’ ability to eat, but once they get inside their guts, they can also be destructive. They make holes in the intestinal wall, which allows food and blood to mix. This can result in harmful infections and boost the caterpillar’s defense mechanisms [6].
Contrastingly, glandular trichomes have enlarged globular heads that resemble water tanks and contain poisonous or sticky substances that can either trap or kill herbivores when ingested (Figures 2A–C). These globular heads occasionally also produce noxious compounds that deter herbivores. As a result, we can state that these miniature water tanks discharge toxins as soon as any type of insect attack sends out a danger signal. In conclusion, trichomes—the seemingly innocuous hairs on plant leaves—can shield plants in a number of ways prior to, during, and following an attack by caterpillars or other insects.
Here are some potential benefits of hairiness in leaves that may explain why young leaves of so many trees are hairy. No reason exists to believe that just one of these explanations is accurate. Many organs, tissues and processes in plants serve multiple functions.
The hairs spread out and lose their luster as the leaf ages and grows. The hairs gradually fall out once the epidermis is fully developed, especially from the leaf’s upper surface.
Although I’m sure readers can think of other reasons for why leaves are hairy, these are the most prevalent ones, and they are all backed up by some experimental data.