Tap root system

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... 

Tliis is made up of the primary root ealled the tap root with lateral secondary roots branching out from it and, from these, tertiary roots possibly developing obliquely to form, in some cases, a very extensive system of roots (Fig. 1.14). The root of the bean plant is a good example of a tap root system. If this is split it will be seen that there is a slightly darker central woody eore, the skeleton of the root, which helps to anchor the plant and transport foodstuffs. The lateral seeondary roots arise from this central core (Fig. 1.15). Carrots and other true root crops such as... 

Flax cultivars have been selected for production of either fiber (fiber flax) or oil (oilseed flax). Location of production, climatic adaptation, and morphology of these types now differ considerably. Oilseed-type plants are usually shorter, have more branches, and produce more seeds, while fiber flax types are generally taller, have few branches, and have been seleeted for fiber (Gill, 1987). Bast fibers from flax, derived as part of the phloem, are long (4em), have high tensile strength, and have a high quality of cellulose (Deyholos, 2006). Fine flax fibers are used for linens and textiles, while coarser fibers are used for nonwoven textiles and twine. Both flax types have a short tap root system with fibrous branches. Flax is relatively shallow rooted, with only 4-7% of root mass deeper than 60 cm (Gan et al., 2009). 

Two weeks after planting in the pipes, the plants were thinned to 35 pipe per pipe each and the cups to one plant each, and the treatments begun. Each first, third and fifth day of the week for twelve weeks the pipes were flushed with three liters of tap water poured in the elbow end. The water flowed past the plant root systems and drained out the screened end of the pipes into a flask. One hundred milliliter aliquots of this water ( root exudate ) were used to water the soybean plants in the cups three times weekly. After each flushing, two liters of a low nitrogen (50 ppm N) complete nutrient solution (Peter s Hydro-sol ) were added to each pipe. The soybean plants in cups were watered as needed at other times with tap water. On alternate weeks the soybean plants were fertilized with the complete nutrient solution. At 4, 8 and 12 weeks after the root exudate treatments started eighty soybean plants (10 treatments x 2 soybean varieties x 4 blocks) were randomly chosen for analysis. The soil was washed free of the plant roots and each soybean plant was divided into roots, nodules, stems, leaves and fruits. The plant parts were dried at 105°C for four days and weighed. 

Much emphasis has been placed on the plowed layer and its contribution to crop production, and comparatively little research has been done on the subsoil. In fact, in general discussions of the depletion of soil fertility the subsoil is often ignored, even though we know that it is often higher in essential nutrients, other than nitrogen, than is the A-horizon. These mineral nutrients may be less available to plants than those in the surface layer that is constantly subject to weathering and oxidation, but nevertheless subsoils do contribute in a major way to plant feeding. The plowed layer is only 6—12 inches deep whereas the subsoil tapped by the root system may have a depth of several feet. 

To assess trichothecene effects on intact muskmelon seedlings, six week old seedlings at the 3-4 true leaf stage for each of the five genotypes were carefully removed from the soil medium. The roots were carefully washed in tap water to remove soil particles, then immersed in either solvent or 5y g ml of roridin E for 2 hr only root systems were immersed. After exposure, seedlings were washed and incubated with roots immersed in tap water for 24 hr under continuous light, then examined macroscopically for phytotoxic symptoms. Symptom severity was ranked on a scale of 0 to 5 0 = no visible symptoms and 5 = severe discoloration... 

The structural properties of the film were investigated by atomic force microscopy (AFM) performed on a XE-100 Park system equipped with 910 ACTA cantilever, operating in the tapping mode. The results were analysed in XEl software, fiom which the root mean square roughness (Rrms) value and average grain size were estimated. 

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