Phytotechnology and Photosynthesis
From a practical standpoint, phytotechnology is the use of plants in environmental biotechnology applications, and draws on many of the characteristics which have already been described. In this respect, it does not represent a single unified technology, or even application, but rather is a wider topic, defined solely by the effector organisms used.
Plants of one kind or another can be instrumental in the biological treatment of a large number of substances which present many different types of environmen-tal challenges. Accordingly, they may be used to remediate industrial pollution, treat effluents and wastewaters or solve problems of poor drainage or noise nui-sance. The processes of bioaccumulation, phytoextraction, phytostabilisation and rhizofiltration are collectively often referred to as phytoremediation. Although it is sometimes useful to consider them separately, in most functional respects, they are all aspects of the same fundamental plant processes and hence there is much merit in viewing them as parts of a cohesive whole, rather than as distinctly dif-ferent technologies. It is important to be aware of this, particularly when reading a variety of other published accounts, as the inevitable similarities between descrip-tions can sometimes lead to confusion. Moreover, the role of phytotechnology is not limited solely to phytoremediation and this discussion, as explained above, is more deliberately inclusive of wider plant-based activities and uses.
Despite the broad spectrum of potential action exhibited by plants in this respect, there are really only three basic mechanisms by which they achieve the purpose desired. In essence, all phytotechnology centres on the removal and accumulation of unwanted substances within the plant tissues themselves, their removal and subsequent volatisation to atmosphere or the facilitation of in-soil treatment. Plant-based treatments make use of natural cycles within the plant and its environment and, clearly, to be effective, the right plant must be chosen. Inevitably, the species selected must be appropriate for the climate, and it must, obviously, be able to survive in contact with the contamination to be able to accomplish its goal. It may also have a need to be able to encourage localised microbial growth.
One of the major advantages of phytotechnological interventions is their almost universal approval from public and customer alike and a big part of the appeal lies in the aesthetics. Healthy plants, often with flowers, makes the site look more attractive, and helps the whole project be much more readily accepted by people who live or work nearby. However, the single biggest factor in its favour is that plant-based processes are frequently considerably cheaper than rival systems, so much so that sometimes they are the only economically possible method. Phy-toremediation is a particularly good example of this, especially when substantial areas of land are involved. The costs involved in cleaning up physically large contamination can be enormous and for land on which the pollution is suitable and accessible for phytotreatment, the savings can be very great. Part of the rea-son for this is that planting, sowing and harvesting the relevant plants requires little more advanced technology or specialised equipment than is readily at the disposal of the average farmer.
The varied nature of phytotechnology, as has already been outlined, makes any attempt at formalisation inherently artificial. However, for the purposes of this discussion, the topic will be considered in two general sections, purely on the basis of whether the applications themselves represent largely aquatic or terrestrial systems. The reader is urged to bear in mind that this is merely a convenience and should be accorded no particular additional importance beyond that.