Mycorrhizal infection

According to Hungria and Stacey (31) more than 4000 flavonoids have been identified within the plant kingdom and some of them have been recognized as nod gene-inducers (Table 1). In addition, root flavonoids have been suggested as molecular signals for the initiation and development of mycorrhizal infection (Chaps. 7 and 9). 

M. Ratnayake, R. T. Leonard, and A. Menge, Root exudation in relation to supply of phosphorus and its possible relevance to mycorrhizal infection. New Phytol. 81 54.3 (1978). 

R. Azcon and J. A. Ocampo, Effect of exudation on VA mycorrhizal infection at early stages of plant growth. Plant Soil 82 133 (1984). 

S. E. Smith, B. L. St John, F. A. Smith, and D. j. D. Nicholas, Activity of glutamine synthetase and glutamate dehydrogenase in Trifolium subterraneum and Allium cepa L., effects of mycorrhizal infection and phosphorus nutrition. New Phytologist 99 211 (1985). 

The growth of ectomycorrhizal trees is frequently improved by their increased phosphorus (P) accumulation (3), and this, in turn, is related to the intensity of the mycorrhizal infection. Ectomycorrhizal fungi solubilize insoluble forms of A1 and Ca phosphates as well as inositol hexaphosphates, though a wide interstrain variability has been recorded (112). These complex P forms are digested by the secretion of extracellular acid and alkaline phosphomono- and phosphodi-ester-ases. Pi in soil solutions is easily taken up by ectomycorrhizal hyphae and then translocated to the host roots. Its absorption and efflux are probably regulated... 

N. Gogala, Regulation of mycorrhizal infection by hormonal factors produced by hosts and fungi. E.xperientia 47 331 (1991). 

R. Bradley, A. J. Burt, and D. J. Read, Mycorrhizal infection and resistance to heavy metal toxicity in Calluna vulgaris. Nature 292 335 (1981). 

Figure 1. Height of Douglas-fir and ponderosa pine seedlings as a function of species mix and mycorrhizal infection.

Allen, M. F. (2001). Modelling arbuscular mycorrhizal infection is % infection an appropriate variable Mycorrhiza, 10, 255-8. 

Sparling, G. P. Tinker, P. B. (1978). Mycorrhizal infection in Pennine grassland. I. Levels of infection in the field. Journal of Applied Ecology, 15, 943-950. 

Bradley, B., Burt, A. J., and Read, D. J. (1982). Tlie biology of mycoirhiza in the Ericaceae, VIII The role of mycorrhizal infection in heavy metal resistance. New Phytol. 91, 197-209. 

As for temperate plants, it is widely assumed that mycorrhizal associations in tropical forests serve to improve the uptake of mineral nutrients, particularly phosphorus (Bolan, 1991 Koide, 1991 Smith and Read, 1997). Growth stimulations and enhanced P uptake in response to mycorrhizal infection have been reported for tropical tree seedlings (Janos, 1989 Lovelock etai, 1996, 1997). 

Read, D. J. (1986). Non-nutritional effects of mycorrhizal infection. In Physiological and Genetical Aspects of Mycorrhizae. (V. Gianinazzi-Pearson and S. Gianinazzi, Eds.), pp. 169-176. INRA, Paris. 

Mugnier, J., Mosse, B., 1987. Vesicular-arbuscular mycorrhizal infections in transformed Ri T-DNA roots grown axenically. Phytopathology 77, 1045-1050. 

Gianinazzi-Pearson V, Gianinazzi S (1978) Enzymatic studies on the metabolism of vesicular arbuscular mycorrhiza n. Soluble alkaline phosphatase specific to mycorrhizal infection in onion roots. Physiol Plant Pathol 12 45-53... 

Tisserant B, Gianinazzi-Pearson V, Gianinazzi S, Gollotte A (1993) In planta histochemical staining of fungal aJkaline phosphatase activity for analysis of efficient arbuscular mycorrhizal infections. Mycol Res 97 245-250... 

Sparling GP, Tinker PB (1978) Mycorrhizal infection in Pennine grassland D. Effects of mycorrhizal infection on the growth of some upland grasses (m y-itradialed soils. J Appl Ecol 15 951-958... 

Driige U, Schonbeck F (1993) Effect of vesicular-arbuscular mycorrhizal infection on transpiration, photosynthesis and growth of flax Linum usitatissimum L.) in relation to cytokinin levels. J Plant Physiol 141 40-48... 

Ortas I, Rowell DL (2004) Effects of ammonium and nitrate on indigenous mycorrhizal infection, rhizosphere pH changes, and phosphorus uptake by Sorghum. Commun Soil Sci Plant Anal 35 1923-1944... 

Mosse, B. C. Hepper. 1975. Vesicular-arbuscular mycorrhizal infections in root organ cultures. Physiol. Plant Pathol. 5 215-223. 

Results of these experiments were striking, and showed that the greatest inhibition occurred when pines were subject to both allelopathy and resource competition, while the effects of allelopathy and resource competition separately caused intermediate inhibition (Nilsson 1994). Other greenhouse experiments (Nilsson et al. 1993) established that aqueous extracts of E. hermaphroditum reduced N uptake by both mycorrhizal and nonmycorrhizal Scots pine seedlings, and reduced the spread of mycorrhizal infection. 

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