Plant Growth Responses to Vesicular‐arbuscular Mycorrhiza

Abstract

Light and temperature greatly influenced the development of vesicular-arbuscular mycorrhiza and growth of onions in a phosphate-deficient soil. There were more large arbuscules and host growth was stimulated more with 25,000 lux than with 13,000 lux at 23° C and in a 14-23° C diurnal cycle. At 14° C and 13,000 lux mycorrhiza caused no growth stimulation even in three low-phosphate soils. At 18° C infection was much sparser in a 6 h daylength than in 12 and 18 h. Mycorrhizal plants kept in daylengths of 6 h at 13,000 lux were 3.5 times heavier than their non-inoculated controls. The effect of infection increased in longer daylengths and higher light intensities to 14.2 times the weight of controls with 18 h at 25,000 lux. The addition of soluble phosphate stimulated growth to the same extent as mycorrhizal inoculation did in the highest light conditions but phosphate stimulated growth more than did mycorrhiza under intermediate light conditions. The amounts of soluble carbohydrate in the roots of plants given phosphate and in those that were mycorrhizal did not differ significantly, but there was more soluble carbohydrate in plants growing in most light. Plants both with and without mycorrhiza contained much glucose, fructose, sucrose and an unidentified sugar with a low RF value, but there was no indication of fungal carbohydrates such as trehalose and mannitol.

Regulation of Arbuscular Mycorrhization by Carbon. The Symbiotic Interaction Cannot Be Improved by Increased Carbon Availability Accomplished by Root-Specifically Enhanced Invertase Activity

“…However, constant (instead of decreasing) hexose or Suc levels in mycorrhizal tobacco and Medicago roots indicate the sufficient availability of carbohydrates in wild-type plants under normal growth conditions. In contrast, according to previous experiments that show a reduced mycorrhization upon limiting light intensity (Hayman, 1974;Tester et al, 1985;Son and Smith, 1988), suppression of AM could be observed if the root was severely undersupplied with carbohydrates as shown for NT rolCTppa plants. During the disturbed inorganic pyrophosphatase-dependent uptake of Suc into the phloem cells and translocation of Suc to the sink tissue (Lerchl et al, 1995), the formation of AM was characterized by less density of fungal storage organs, indicating a deficiency of carbon.…”

“…Moreover, higher carbon availability was shown to stimulate the phosphate allocation (Bü cking and Shachar-Hill, 2005). Conversely, limiting light intensity reduced mycorrhization and lead to decreased growth and phosphate uptake (Hayman, 1974;Tester et al, 1985;Son and Smith, 1988).…”

“…Conversely, limiting light intensity reduced mycorrhization and lead to decreased growth and phosphate uptake (Hayman, 1974;Tester et al, 1985;Son and Smith, 1988).…”

Fungos micorrízicos arbusculares nativos e doses de fósforo no desenvolvimento do amendoim RUNNER IAC 886

“…Outro aspecto relevante é estudar a eficiência dos FMA nativos que além de ser fácil e rápido de se obter esse inóculo puro, seus benefícios têm sido relatados (HAYMAN, 1982;LAMBERT et al, 1980). O uso de inóculo misto, composto por espécies com diferentes estratégias, pode apresentar resultados melhores para plantas hospedeiras e pode, conseqüentemente, ser mais adequado do que a introdução de uma única espécie de fungo (DAFT, 1983 O substrato utilizado no experimento foi proveniente de uma amostra de solo classificado como Neossolo Quartzarênico (EMBRAPA, 2006) misturado com uma parte de areia de rio lavada (2:1).…”

Inoculum production of arbuscular mycorrhizal fungi native to soils under different forest covers

“…In addition to this monosporic inoculant, it is possible to produce inoculant with different native species with greater ease and speed (Lambert et al, 1980;Hayman, 1982). In comparison with the commercial inoculant, it has a low cost, higher taxonomic diversity, and the use of locally adapted species (Schwartz et al, 2006;Douds Jr. et al, 2010), which increases the chances of positive effects on the plant (Klironomos, 2003) and avoid the introduction of exotic species (Ijdo et al, 2011).…”