The Plant Health Care concept is based on maximizing the vigor and thus the appearance and resistance of the plant. Since plants largely obtain sustenance and moisture through the root system and soil, much of the emphasis of PHC is placed on creating soil conditions conducive to healthy root systems. This root/soil relationship is receiving a great deal of attention by researchers seeking to enhance plant appearance and health. This area is on the cutting edge of new plant physiology knowledge. New discoveries are opening up our knowledge and technologies that are finding their ways into the market place. To be able to adequately implement strategies that utilize this technology we need to gain our own appreciation of this knowledge.
Roots function as portals for water and nutrients to enter the plant as well as support and storage organs. How well roots serve the portal functions largely determine if the plant survives and how it handles stress. Healthy functioning root systems can draw in copious volumes of water and absorb adequate levels of nutrients to support the other maintenance and growth functions of plants. Plants seem to be better at the previous function than the latter. Because plants can only take up nutrients in certain chemical combinations, many naturally occurring soil nutrients are unavailable to plants. Even thought the essential element is present, it is sometimes bound up in or by chemical compounds that are too large or of the wrong configuration to pass through the cell walls of root cells.
This is where other soil dwelling organisms play a roll in PHC. Other organisms in the soil assist in making nutrients available to plant roots. Decomposition organisms, primarily saprophytic fungi and bacteria, "feed" on organic matter in the soil and metabolize complicated molecules into simpler ones. For the most part these saprophytes are harmless to living tissue, and thus don't infect plant roots. But plants do benefit from the availability of previously unavailable nutrients. These organisms generally exist in soil where organic matter and adequate air and moisture are present regardless of the presence of plants.
Some fungi, however, have refined this relationship, so that they derive a portion of their energy from plant respiration products. The mycorrhizae fungi have formed symbiotic relationships with plants, whereby both organisms benefit. In return for access to these discarded energy sources, mycorrhiza absorb and metabolize nutrients into forms the plant can use. These mycorrhizae fungi form fillamentacous mats in the rhizosphere (root area of the soil) in close association with the root systems. Some tend to be rather species or genus specific while others will co-exist with a wide range of plant "hosts". Ecto-mycorrhiza live only in close proximity to plant roots.
