How Does Enviromat Survive With Such Little Water?
Years of research and development have gone into making Enviromat such a remarkably versatile yet drought tolerant product. The specially formulated substrate, or growing material, keeps the plants as healthy as possible by retaining moisture without letting the roots get soggy; There’s enough substrate for the plants to survive indefinitely and because it contains no organic material whatsoever, it won’t rot away or need topping up.
The plants themselves are specially chosen members of the sedum plant family: They’re all happy to grow and flourish in the British climate and in fact some of the species are native to this country. Sedums were chosen because they have an amazing ability to survive where other plants struggle. But how do they do it? Why is it that sedums seem to thrive where the soil is thin, even when the weather is hot and dry and other plants are wilting all around them?
The reason that sedum plants – and their cousins from the Crassulacea (pronounced crass-you-lay-see) family are so good at resisting drought, is that they have developed a survival mechanism, known to scientists as Crassulacean Acidic Metabolism or CAM.
In simple terms, CAM is the plants’ way of making sure that as little water as possible can escape through the pores on its leafs and stems, and it does that by effectively “holding its breath” all through the heat of the day and only opening its pores at night when the air is cooler and the water stored within the body of the plant is less likely to evaporate away.
If we compare CAM plants such as sedums or house leeks, to plants that don’t have this special adaptation – lettuces for example, we can see how it is that Enviromat tolerates a drought for longer periods of time and also understand why our ancestors thought so highly of these very special plants.
All green plants use a process called photosynthesis (pronounced foto-sin-the-sis) to make energy food from carbon dioxide gas, water and sunlight. The by-product of this process is oxygen, which is why, without plants to do this, our planet would be uninhabitable – but that’s another story.
Photosynthesis can only happen during the day, as the chemical reaction inside the leaf cannot happen without sunlight. The other ingredients for the reaction are water and carbon dioxide. Carbon dioxide is all around us as one of the gasses in air. The plant absorbs this gas through pores in the leaf surface which are known as stomata (stoma is the Greek word for “mouth” or “opening”), trouble is, when the stomata are open to let carbon dioxide in, they also let water vapour escape. When the soil is dry, the plant can’t replace this water and it will wilt and die. But not if it is a CAM plant…
CAM stands for Crassulacean Acidic Metabolism. “Crassulacean” after the plant family it was first discovered in; and “Acidic Metabolism” to describe what is happening inside the plant.
CAM plants keep their stomata closed daylight hours so that water vapour doesn’t escape in the heat of the day. Instead, they open their stomata at night, take in the carbon dioxide and store it in the form of malic acid. In daylight, they turn the malic acid back into carbon dioxide and use it for photosynthesis. That’s how they survive for so long in arid conditions and it’s also why (as noticed by Roman apothecaries) that sedum plants taste bitter first thing in the morning and not quite so nasty by the afternoon.