Effect of VA mycorrhizal fungi and rhizosphere microorganisms on root and shoot morphology, growth and water relations in maize

Abstract

SUMMARYMaize {Zea mays L.) was grown in fertilized calcareous soil in pots which were separated by 30 fim nylon nets into three compartments, the central one for root growth and the two outer ones for hyphal growth. The size of each compartment was 40 x 25 x 3 cm. The treatments comprised of sterilized soil, either inoculated witb rhizosphere microorganisms (other than VA mycorrhizal fungi), with rhizosphere microorganisms together witb a VA mycorrbizal fungus [Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe] or remained non-inoculated (sterile control). As inoculum for rbizospbere microorganisms the roots with adhering rhizospbere soil of nonmycorrhizal maize plants was used.Compared to the non-inoculated (sterile) control, inoculation with rhizosphere microorganisms did not affect shoot dry weight and morphology, but increased total root length (17 %) and root length per unit root dry weight (35%). The additional inoculation with VA mycorrhizal fungi had no influence on tbe shoot dry weight but increased area and dry weight of the leaf blades by about 30% and the ratio leaf blade:leaf sheath + stem (w/w) by 41 %. Tbe most profound effect of VA mycorrhizal fungi inoculation was on root growth and morphology. Compared to the non-inoculated control, root dry weight was decreased by 16%, root length by 31 % and root hair density and length by 41 and 43 %, respectively.In mycorrhizal plants the transpiration rates per plant were about 30 % higher than in the other treatments and this is attributed to tbe larger leaf area. Water uptake rate per unit root length and per unit time was about twice as high in mycorrhizal plants. For several reasons a substantial hyphal water transport seems unlikely. The results stress the necessity of detailed studies on root morphology for interpretation of effects of mycorrhizal fungi on mineral nutrient uptake and water relations in plants.

Impact of endomycorrhizal fungi and other bioinoculants on growth enhancement of Glycine max (L.) Merrill

“…The leaf area enhancement is due to potential of the arbuscular mycorrhizal fungi to improve water and phosphorus uptake as suggested by Harley and Smith (1983) and Sieverding (1991). Similar results were found in the case of corn (Kothari et al, 1990), lettuce (Tobar et al, 1994) and maize (Subramanian et al, 1995). The increase of the leaf area with AM inoculation would be beneficial by maintaining a higher photosynthetic rate (Auge et al, 1987;Panwar, 1993).…”

Alterações morfológicas no sistema radicular do milho induzidas por fungos micorrízicos e fósforo

“…Da matéria seca da parte aérea obtiveram-se os extratos para a determinação do P após digestão nitroperclórica (Sarruge & Haag, 1974). O número de raízes seminais e adventícias (nodais e laterais de primeira ordem) foram contadas, e o número de pêlos absorventes foram determinados segundo Kothari et al (1990). A porcentagem de colonização micorrízica foi determinada segundo Giovanetti & Mosse (1980), após clarificação com KOH e coloração com azul de tripano segundo Phillips & Hayman (1970).…”

“…Outro fator importante envolvendo os fungos micorrízicos e o teor de P no solo, são seus efeitos sobre a morfologia das raízes. O reduzido crescimento dos pêlos absorventes e o reduzido comprimento radicular do milho com inoculação de fungos micorrízicos estão relacionados negativamente com a concentração de P nos tecidos das plantas (Kothari et al, 1990). Entretanto, alguns trabalhos mostraram que inoculação com fungos micorrízicos aumenta a produção de raízes (Hodge et al, 2000), o peso total de raízes (Mane et al, 1993;Hernandez & Cardenas, 1994) e o comprimento das raízes (Isopi et al, 1995).…”

Potential agricultural benefits through biotechnological manipulation of plant fungal associations

“…Mycorrhizal fungi can improve water uptake and retention in crops under drought conditions [15]. For example, corn plants with mycorrhizal fungi had a 30% higher rate of transpiration, and water uptake in relation to root size was double that of control plants [15].…”

“…For example, corn plants with mycorrhizal fungi had a 30% higher rate of transpiration, and water uptake in relation to root size was double that of control plants [15]. Fungal inoculation was also shown to improve water uptake in red clover, apple, rose, and rangeland grass [15]. It is thought that colonization of plant roots by soil fungi increases stomatal efficiency of plants.…”