Root morphology

Position 5 in Fig. lb describes the brief explosive development of biomass in an ephemeral species capable of exploiting a productive but temporary habitat. Here again morphological plasticity would be expected to predominate. In the vegetative phase, plasticity in root and shoot morphology will be an integral part of the mechanism of resource capture. 

D. B. Lazof, T. W. Rufty, M. G. Redinbaugh, Localization of nitrate absorption and translocation within morphological regions of the corn root. Plant Physiol. 100 1251 (1992). 

D. Vaughan and B. G. Ord, Extraction of potential allelochemicals and their effects on root morphology and nutrient contents. Plant Root Growth an Ecological Perspective (D. Atkinson, ed.), Blackwell, Oxford, 1991, p. 399. 

V. Groleau-Renaud, S. Plantureux, and A. Guekert, Influence of plant morphology on root exudation of maize subjected to meehanical impedance in hydroponic conditions. Plant Soil 20l 23 (1998). 

E. C. Landsberg, Hormonal regulation of iron-stress response in sunflower roots a morphological and cytological investigation. Protopkisma /94 69 (1996). 

Microorganisms at the rhizosphere are known to produce plant growth regulators using precursors released by the roots (71), which can influence root morphology (3) the degradation of these hormone-like substances could be prevented by their incorporation into humic molecules, which would preserve their chemical properties. However, definite proof is still lacking recent studies have shown the... 

G. Concheri, S. Nardi, F. Reniero, and G. Dell Agnola, The effects of humic substances within the Ah horizon of a calcic luvisol on morphological changes related to invertase and peroxidase activities in wheat roots. Plant Soil 179 65 (1996). 

However, relatively few studies have included growing plants in their experimental systems. In order to mechanistically understand the effects of pine roots on microbial N transformations rates under conditions of N limitation, l-year-old pine seedlings were transplanted into Plexiglas microcosms (121) and grown for 10-12 months. Seedlings were labeled continuously for 5 days with ambient CO concentration (350 iL L ) with a specific activity of 15.8 MBq g C. Then, soils at 0-2 mm (operationally defined as rhizosphere soil) and >5 mm from surface of pine roots (bulk soil) of different morphology and functional type (coarse woody roots of >2 mm diameter fine roots of <2 mm diameter ... 

The morphology of AM fungal structures developing outside and inside the root is conserved even in the rhizosphere of transgenic plants, where accumulation of antifungal plant defense products—such as lytic enzymes (e.g., chi-... 

Bonfante et al. (73) used monoclonal antibodies and enzyme-gold complexes to reveal pectins and cellulose at the interface between the fungal wall and the host plasma membrane in AM roots (Fig. 6), and additional wall components have been investigated with other molecular probes (74-76). These studies indicate that the interface is an apoplastic space of high molecular complexity where the boundaries of the partners are defined. The examination of other endomycorrhizal systems has demonstrated that their interface is morphologically similar but different in composition. Cellulose and pectins are present at the interface... 

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... 

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