Effect of degree of soil disturbance on mycorrhizal colonization and phosphorus absorption by maize in growth chamber and field experiments

Abstract

SUMMARYPrior studies have established that phosphorus absorption by maize from undisturbed soil is greater than from soil which has been disturbed since the previous period of growth. Those experiments were conducted under controlled conditions and with only two disturbance treatments, namely disturbance of the soil by hand sufficient that it will pass a 5 mm sieve, and no disturbance at all. We present here two experiments in which additional treatments of intermediate degrees of disturbance are included.In a growth chamber experiment, cutting the soil into 1, 2 or 4 cm cubes reduced the phosphorus absorption and shoot dry matter, but the reduction was not as great as that after hand disturbance of the soil. In a field experiment, the phosphorus absorption and shoot dry matter found in a conventional tillage and no-till treatments were less than in hand-planted no-till plots, but greater than with severe soil disturbance. In both experiments increases in shoot dry mass and shoot phosphorus concentration in the less disturbed treatments were not accompanied by an increase in mycorrhizal colonization. This is inconsistent with earlier studies in which colonization was greater in undisturbed soil.Since it has now been demonstrated that increased colonization is not a necessary component in the process whereby lack of disturbance results in improved plant performance, the role of mycorrhizas in this effect should be reconsidered. If mycorrhizas are important in this respect then this can only be by means of changes in the external mycelium. However, without experimental confirmation this interpretation is speculative.

Exogenous Phytohormones Modulate Mycorrhiza-Induced Changes in Root Hair Configuration of Trifoliate Orange

“…It seems that IBA, ABA, and JA-induced AMF colonization, preferentially targeting the development of lateral root classes. Extraradical hyphae, however, influence the efficiency of mycorrhizae more strongly than root colonization in a nutrition ecosystem (McGonigle et al, 1990), due to effective increase in the volume of soil explored for nutrients extending beyond the nutrient depletion zone around the roots (Allen et al, 2003). In the present work, exogenous application of phytohormone (IBA, ABA and JA) into hyphae chamber markedly promoted the development of AM external hyphae in nylon mesh and soil, irrespective of chamber type, containing root+hyphae or hyphae alone.…”

Occurrence of Arbuscular Mycorrhizal Fungi and Fusarium in TC Banana Rhizosphere Inoculated with Microbiological Products in Different Soils in Kenya

“…Alkaline hydrogen peroxide was then poured off, the roots thoroughly rinsed with tap water and 1% hydrochloric acid (HCl) added and left for 1 h. After pouring off HCl 0.05% Trypan blue was added and the roots placed in the oven for 1 h. De-staining solution (500 mL glycerol, 450 mL of distilled water and 50 mL of 1% HCl) was added. Analysis of AM fungi colonization was done according to McGonigle et al (1990). Slides were prepared with 30 pieces of roots each 1 cm long then examined under a compound microscope.…”

Calophya latiforceps, a New Species of Jumping Plant Lice (Hemiptera: Calophyidae) Associated withSchinus terebinthifolius(Anacardiaceae) in Brazil

“…Soil disturbance also influences arbuscular mycorrhizal (AM) activity (Reeves et al 1979, MacGonigle et al 1990, Aziz et al 1995. According to Aziz et al (1995), the total number of AM propagules and spores increased in plots where the soil was completely removed compared to partial soil removal plots over a two-year period.…”