Zone root system

Figure 11 Root systems as simulated by the computer program Simroot. The systems display herriitgbone architecture (a) dichotomous architecture (b) and bean root architecture (c). The bean root system (c) is shown in

Remediation with plants requires that the contaminants be in contact with the root zone of the plants. Therefore, root morphology and depth directly affect the depth of soil that can be remediated or the depth of groundwater that can be influenced. A fibrous root system such as that found in grasses has numerous fine roots spread throughout the soil and provides maximum contact with the soil because of the high surface area of the roots. A tap root system (such as in alfalfa) is dominated... 

It is assumed that the primary root waU is completely impermeable to O2 in the zone covered with laterals. In fact the root wall is not completely impermeable in this zone but the resulting flux is small compared with that from the rest of the root system and no serious error arises from ignoring it. 

Another factor rarely considered is the zone of the root system subjected to the microbial metabolite. It is likely that the metabolites will only be formed in particular regions of the soil where there are suitable substrates for producer micro-organisms and it is unlikely that the entire root system will come under the influence of a metabolite. For example, acetic acid is a coinnon microbial fermentation product of cellulose and is phytotoxic ( 5,... 

They are considered to be the trees and bushes growing in the saline Intertidal zones of sheltered coastlines. Their root systems are thus regularly inundated with saline water however, dilution by flooding may occur once or twice annually O). Four vascular plants associated with tidal mangrove swamps in Southeast Asia have been utilized by local inhabitants for their toxic properties. The natural sap or aqueous extract from the leaves and bark is used to stupefy fish, as poison for spear and arrow tips, and applied to tooth cavities and skin to deaden aches and pain. 

Evidence was obtained recently that pesticide vapors may enter the air by still another mechanism, involving plant circulation and water loss (57). Rice plants were found to efficiently transport root-zone applied systemic carbamate insecticides via xylem flow to the leaves, eventually to the leaf surface by the processes of guttation and/or stomatal transpiration, and finally to the air by surface volatilization. Results from a model chamber showed that 4.2, 5.8, and 5.7% of the residues of carbaryl, carbofuran, and aldicarb, respectively, present in rice plants after root soaking vaporized within 10 days after treatment. The major process was evaporation of surface residues deposited by guttation fluid. 

Much of what we know about the nutrient stocks of secondary forests is based on soil measurements made to depths of only 0.1 to 1.0 m (Uhl and Jordan, 1984, Buschbacher et al., 1988, Koutika et al. 1997, Neill et al. 1997). However, water balance studies and direct measurements of deep soil moisture and roots provide evidence that forests across much of seasonally dry Amazonia depend upon root systems that extend well beyond this conventional sampling depth to absorb water during the dry season (Nepstad et al. 1994, Jipp et al. 1998, Hodnett et al. 1997, Holscher et al. 1997). The occurrence of root systems extending to 18 m depth in Amazonian forests (Nepstad et al. 1994) demands a re-examination of our thinking about the nutrient stocks of these ecosystems, and the recovery of these nutrient stocks in secondary forests. If the rooting zone of Amazonian forests extends to several meters depth, instead of several centimeters depth, are these forests less vulnerable than previously believed to nutri-... 

Certain plant species are known as cesium pollution indicators, but the uptake by each individual plant can be very different. In the first place, it depends on the presence of free cesium in the species root system zone and competitive effects of potassium [5-10]. Different soil types show differences in the ratio of sorbed to fixed cesium, in soil size fractions, in pH value, and content of organic matter, as well as in Cs vertical distribution profiles and, consequently, in cesium transfer from soil to plants [11-18]. 

In the logging industry it refers to a standing tree that presents a hazard to employees due to certain conditions including, but not limited to, deterioration or physical damage to the root system, trunk, stem or Umbs, and the direction and lean of the tree. Danger Zone... 

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