Answer: B - lipid
Lipids are a group of naturally occurring molecules that include fats, oils, waxes, and steroids. In plants, lipids play an important role as the waxy covering on the surface of leaves, stems, and other plant parts. This waxy coating is called the cuticle, and it serves several important functions for the plant.
First, the cuticle helps to reduce water loss from the plant by slowing down transpiration, which is the process by which water evaporates from the plant surface. Lipids' hydrophobic (water-repelling) nature makes the cuticle an effective barrier to water evaporation. This helps to conserve water, which is especially important in arid or drought-prone environments.
Second, the cuticle also protects from physical damage and parasites. The tough, waxy surface of the cuticle is difficult for herbivores to penetrate, and it can help to deter feeding and damage from insect pests.
Third, the cuticle can regulate plant temperature by reflecting or absorbing light and heat. This helps the plant to maintain an optimal temperature range for growth and survival.
The cuticle is composed of a complex mixture of lipids, including long-chain fatty acids and alcohols, and often contains additional compounds such as pigments, essential oils, and resin. The cuticle's exact composition varies among plant species and can be influenced by environmental factors such as temperature, humidity, and exposure to UV light.
