This is a question I am commonly asked. I am the first to admit that I am ‘no’ expert on these wonderful plants, but I did learn something remarkable about them last year in a college Biology class at my local extension college. Mainly, the enzymes, proteins, and processes of the cells that are key to photosynthesis in succulents are actually radically different from the ones in ‘regular’ plants. Thus, this makes them even more magical and special to me. To read more about this, please read more here, copied directly from the Cactus and Succulent Society of America webpage. Enjoy.
What is a Succulent?
by Artie Chavez Reprinted from the Cactus Chronicle, Newsletter of the Los Angeles Cactus & Succulent Society You must own at least one cactus or succulent, or you would not be reading this. Everyone’s first question seems to be “How do I take care of this?” If you’re afraid to ask this question, you should not be, because answering this question is tougher than one would think, and is also the first question the experts ask when they receive a new plant. With this question in mind let’s try to examine how to answer it. The following is a common conversation that we all have experienced, being on one end or the other, “How do I take care of this thing?” Our first instinct is to discuss watering, when and how much. But in order to answer this we need to know what is being watered, so we ask with all the encouragement and patience as possible, “What is it?” The reply we get, “Well, it’s green and has spines, and OH! It’s that one that flowers!” Well we asked, obviously we need more information. Our next question, “Is it a cactus or succulent?” That will clear everything up, right, WRONG, the response is that of a blank stare. OK, here it is, the opportunity to show just how much knowledge we have and as we blurt out “Well a cactus is a succulent, but A succulent is now a cactus.” Where did that come from? Who knows, but boy did it sound good. Our attention returns to the person that we were trying to help, and we thought we had a blank stare before. The next bit of wisdom we are about to share will clear everything up, after all it came from an esteemed botanist, we begin to recite “A cactus has spines and a succulent has thorns, or is it the other way around?” Before we know it we are standing alone. Seriously, it is true that a cactus is a succulent, what we need to explore is what makes a plant a succulent. Most simply put, succulents increase their drought tolerance in two simple ways. First, the word succulent means to have juicy tissues. The juice refers to the ability of the plant to store water. Succulents store water in a number of different places in their anatomy, such as their leaves, stems, bodies, trunks (caudex), and roots. Second, succulents have the ability to conserve water in several ways, the most unusual of which, is the CRASSULACEAN ACID METABOLISM (CAM), this is considered a high evolutionary feature. First described in the Crassulacean Family. This process is related to the transformation process of photosynthesis and respiration. Like foliage plants, succulents need to make food in order to live and to grow. Photosynthesis is the process in which plants convert carbon dioxide and water in the presence of sunlight, and the green pigment known as chlorophylla, to form sugars, oxygen, and water. Water and salts enter through the roots, them are pulled up to the photosynthesizing tissues. Air enters through special valves called stomata. When opened it allows the intake of Carbon Dioxide and allows the release of oxygen and water vapors, the stomata open during the day and close at night, ending photosynthesis. At night another process begins that of respiration, which reverses the process of photosynthesis, breaking down rather than building up sugars in the presence of water and oxygen, releasing the energy to the plant. In succulents the daily cycle is the same, photosynthesis still occurs during the day, but the opening of the stomata is reversed. The stomata remain closed during the day and open at night to allow the intake of air. With the stomata opening at night the evaporation of the plant’s moisture vapor is minimized in the cool of the evening. This reversal also has two other effects, it requires that Carbon Dioxide be stored over night awaiting daylight for photosynthesis and it slows the plants growth rate. This was a quick lesson in understanding what a succulent is. With all of these interesting modifications these plants will survive under the harshest conditions by conserving and reserving their resources.