Salts as Potential Environmental Pollutants, Their Types, Effects on Plants and Approaches for Their Phytoremediation

Abstract

Demand for food dramatically increases as the world gets populated, and this problem is of central attention all over the world. Under these circumstances, the balance between food production and consumption depends on the agricultural productivity. However, an increase in the world population and decrease in the agricultural areas due to many reasons such as industrializations, global warming, use of marginal water etc. have been forcing us to use arable lands efficiently as well as saline-prone areas. Low fertile agricultural areas or non-agricultural areas have to be included into agricultural areas if the food production is to be increased. For this reason, many breeding and amelioration strategies have been evaluated so far, however, a few of them have been found successfully in achieving the goals. Physiological, genetical and biochemical mechanisms in plants are quite complex, therefore, it is very difficult to breed a resistant or tolerant plant against stress. To date, breeding or amelioration strategies have followed one direction, either chemical or biological, they then concentrated on either soil or plant itself, have been tested on a few plants in a few local research stations, e.g., use of mycorrhiza. An amelioration strategy both on soil and plant, which could possibly increase the crop production in saline or polluted areas, enable us to improve soil conditions for a long period of time with little effort and expenses. Salt concentration in the soil could be reduced via drainage as well as using high quality water. On the other hand, economically important crop plants have been bred for their resistance to disease and non-pathogenic stress agents such as drought and salinity and some of them have been made commercially available. However, this has not solved the problem globally, especially for the many crop plants which have to be grown in moderate saline conditions, therefore, an effective alternative approach must be found. In recent years, a new method called "bioreclamation" or "phytoremediation" has been introduced in many scientific works and reports. It is one of the efficient methods to improve crop production and quality in saline areas aiming to grow halophytes as companion plants with the crop plants. In this chapter, the effect of salt on plants and plant metabolisms and their phytoremediation strategies have been evaluated so that halophytes could possibly be used as companion plants with crop plants without retarding their growth in saline areas.

The Use of Halophytic Companion Plant (Portulaca oleracea L.) on Some Growth, Fruit, and Biochemical Parameters of Strawberry Plants under Salt Stress

“…uptake salt ions through their roots and store them in their leaves. It is quite possible that these plants could be used as companion plants with crop plants, especially salt-sensitive glycophytes, to reduce the negative effects of NaCl through the uptake of toxic ions [14,15]. For example, Portulaca oleracea L. (purslane) (which is a member of Portulacaceae), is a drought-and salt-tolerant annual plant.…”

Phytoremediation of Salt-Affected Soils Using Halophytes

“…The physiological and metabolic processes could be disturbed in plants. The symptomatic responses associated with these changes include various physiological parameters such as decreases in leaf area, increases in leaf thickness, succulence, abscission of leaves, necrosis of root and shoot, and decrease of internode lengths (Parida and Das 2005;Dikilitas and Karakas 2010). Under high salt stress, plants cannot get enough water, and turgor pressure significantly decreases, and therefore, stomata of plants are closed to conserve water (Kader and Lindberg 2010).…”

“…These plants could also be used as companion plants with other crop plants especially with salt-sensitive glycophytes due to their biology and physiology. Phytoremediation techniques used as salt reclamation or as companion plants have two main advantages for the growers: first, no farmers have to purchase any chemical amendments, and secondly, financial or other benefits such as landscape or animal or human nutrition from the crops are expected during the amelioration process Dikilitas and Karakas 2010). It is clear that halophytes are capable of providing satisfactory yields under high salt conditions.…”

“…Widespread occurrence of salt-affected soils in agriculture took great attention for the future of agricultural productivity. Salt-induced land degradation is the most common land degradation process where rainfall is low to maintain a proper agriculture especially in arid and semi-arid regions (Dikilitas and Karakas 2010). Therefore, use of halophytes under these harsh circumstances might have great benefits.…”

“…Electrical conductivity measurement and salinity classes and crop response(Richards 1954; Soil Survey Division Staff 1993;Smith and Doran 1996;Dikilitas and Karakas 2010) …”