Some books on hydroponics give the reader a crash course on biology complete with diagrams. I would prefer that you get your own biology text, if you feel it's necessary in order to produce good cucumbers. It seems to make more sense to relate biology directly to hydroponics and the nutrients that make plants grow.
Each plant is a natural workshop that builds organic matter in the form of roots, stems, leaves, fruit and seeds. Air and water provide more than ninety-seven per cent of this matter, while the remainder comes from plant nutrients. A plant cannot take up any organic substance; rather it absorbs inorganic mineral salts. That is, the vegetable kingdom feeds directly on the mineral kingdom.
This is why there is no conflict between organic gardening and hydroponics. The difference is, however, that in organic gardening it is the soil that is fed with dead plant and animal matter, not the plant. Soil acts as a natural fertilizer factory that goes to work on these organic substances with its soil bacteria in league with weathering. It breaks these substances down into their inorganic parts (chemicals, if you like), so that the plants can feed on them.
In hydroponics there is no soil, and the plants are fed directly with the same minerals that healthy organic soil produces. The plant does not know, or particularly care, whether its mineral food was made by man or nature. It does care, though, that it is well fed, and a nitrate is a nitrate whether it comes from a nutrient solution or a dead mouse.
A plant uses two basic processes in order to grow. The first, osmosis, takes up water and minerals through the roots. The second, photosynthesis, uses light and the atmosphere for transforming the water and minerals into plant tissue. Roots need air as well, in order to breathe, and this is one of the reasons that hydroponics works so well. The loose, chunky hydroponic growing medium, the aggregate, as it is called, allows plenty of air to reach the roots. On the other hand, natural soil often requires a lot of work and time to assure satisfactory aeration.
Fijiure I. A simple hydroponic system.
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