by Ivan SUDNITSYN, Dr. Sc. (Biol.), leading research fellow of the Soil Science Department, Lomonosov Moscow State University; Yevgeny SHEIN, Dr. Sc. (Biol.), Head of the Chair of Soil Physics and Reclamation, Soil Science Department, Lomonosov Moscow State University
As living organisms came out of the ocean to the land surface 500 mln years ago, their major concern was to get water and retain it in their own body since water made up more than half of it. Terrestrial plants succeeded best of all because they learned to absorb moisture from soil and cut the rate of its evaporation. The mechanisms thus developed have been the subject-matter of plant anatomy and physiology for several centuries. However, specialists failed to reveal certain important details till in the early 1970s our scientists laid the foundation of a new science, the ecological hydrophysics of soils.
Passing by train or car the deserts of Central Asia (Kara Kum, Kyzyl Kum, Repetek) stretching over thousands of kilometers, you will see that bushes and even trees grow everywhere in a real scorcher. The famous saxauls also grow there. These "drought-resistant champions" manage to pierce more than a tenmeter soil column by their roots and reach the waterbearing layer. But the desired liquid turns out to be as much mineralized as seawater (or even more salty)--to drink it just try! Like it is in the sea, H2O molecules are
tightly bound by ions and molecules of dissolved substances and are inaccessible to organisms devoid of special devices for their absorption. It is not accidental that shipwreck victims die of thirst most often. But desert plants, the xerophytes, make do even with soil brines! There is another way of survival when cactuses--having no long roots-extract from almost dry soil tiny droplets of moisture (retained with great force there!) and keep them from evaporation in overly dry hot air for a long time. These are succulent plants.
But how do li ... Читать далее