Abstract
Plants regularly face dry conditions. Not having enough water poses a serious threat to a plant’s ability to grow and develop or even just survive! If plants die, we will not have enough food to eat! How do plants manage to survive during water shortages? They must somehow be able to sense, respond, and adapt to changes in water availability. They do this through a range of techniques that allow for a plant to combat water shortages. A plant’s structural “armor” helps it to decrease the amount of water it loses to the environment and increase water storage. Plants respond to water shortages in very complex ways. These responses can include changes in the plants’ growth and in their ability to protect themselves against toxic chemicals that accumulate in the plant during dry periods. All of a plant’s responses are directly controlled by the plant’s genes. If we can understand the genes that are involved in protecting plants against drought, in the future we might be able to make genetically modified crops that can tolerate global warming and climate changes.
Have you heard people speaking about global warming and climate change? Do you know what these terms mean? These terms basically imply that the earth is getting hotter every year. These higher temperatures lead to unexpected and unusual weather patterns. One of these extreme weather patterns is frequent and severe droughts. Droughts are very long dry periods without any rain. What do severe droughts mean for plants? Well, plants are sessileAn organism that can’t move and stays in one place, like a plant., which means they stay in one place and can’t move around like we can. They can’t pull up their roots and relocate to a shady or damp spot. Therefore, plants somehow need to deal with these ever-increasing drought conditions, or they will simply die. Remember, plants are our food. We eat plants raw or cooked (those vegetables your mom insists you eat!) or processed, like your favorite box of breakfast cereal [which is made from wheat or maize (corn)]. So, if plants die because of droughts, we will not have enough food to eat!
If there is no water around, what can plants do to survive? Amazingly, all plants seem to have a number of genes for drought-defense strategies encoded in their DNA. Genes are small sections of DNA, like chapters in a book. How they use these genes determines their ability to survive drought.
Some plants are drought-resistant. When we talk about drought-resistant plants, we mean plants that can withstand dry conditions without dying. A drought-resistant plant can survive drought by using three defense strategies: escaping, avoiding or tolerating the loss of water [1]. Drought tolerant plants are quite rare in nature and can endure long periods with no water at all. Some of the most spectacular drought tolerant plants are called resurrection plants. Resurrection plants are able to survive long periods (up to 3 years!) without any water. However, give them a little water and they will spring back to life in a day or two. Other drought-resistant plants may not be as spectacular, but they too can survive short periods of drought using special techniques and defense strategies.
Some Plants Have Special Structures That Help Them to Survive in Drought Conditions
Some plants are able to survive droughts because of their unique structures. These structural features include the external armor of plants that protects them against water loss, as well as tools to help the plants absorb and store water. Drought-resistant plants can be specially adapted to live and survive in very dry environments. These plants often look quite different from plants living in areas where water is easily available. The drought-resistant plants normally have special “avoidance” (one of the defense adaptations!) features to make sure less water is lost to the environment or that more water gets absorbed and stored in the plant. Plants called desert succulentsPlants that have thickened and fleshy leaves and stems, in which water can be stored. are a good example of plants that have drought avoidance strategies [2]. Desert succulents have thick fleshy leaves, which often don’t resemble leaves at all, and they have a thick waxy layer to prevent water loss. Desert succulents also have extensive root systems that search for water under the dry desert soil (Figure 1). Some succulents have specialized roots that form large bulb structures, which are actually underground water reservoirs for the plant. These plants can survive years of drought using the water stored in their bulbs.