ABSTRACT
The plant consists of about 95 per cent water, which is the main constituent of protoplasm or living matter. When the plant cell is full of water, or turgid, the pressure of water enclosed within a membrane or vacuole acts as a means of support for the cell and therefore the whole plant, so that when a plant loses more water than it is taking up, the cells collapse and the plant may wilt. Aquatic plants are supported largely by external water and have very little specialized support tissue. In order to survive, any organism must carry out complex chemical reactions, which are explained, and their horticultural application described, in Chapters 6 and 7. Raw materials for chemical reactions must be transported and brought into contact with each
other by a suitable medium; water is an excellent solvent. One of the most important processes in the plant is photosynthesis, and a small amount of water is used up as a raw material in this process.
