Effects of vesicular‐arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrations

Abstract

Effects of vesicular-arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrations. -Physiol. Plant. 76: 211-215.Relations between cytokinin concentrations and effects of P and vesieular-arbuscular mycorrhizal (VAM) infection were investigated in Plantago major L. ssp. pleiosperma Pilger. Both mycorrhizal infection by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe and P addition increased the shoot to root ratio, specific leaf area (SLA), and P concentrations of shoot and roots, and decreased the percentage of dry matter in the shoot during the experiment. In general, P concentration in the shoot and roots of each treatment correlated positively with the shoot to root ratio and specific leaf area, and negatively with the pereentage of dry matter in the shoot. Cytokinin concentrations in the tissue of shoots and roots were determined using an enzyme-linked immunosorbent assay. Concentrations of zeatin and zeatinribosides in the free base and nucleotide fractions had increased more after P addition than in the case of mycorrhizal infection in both shoot and roots, whereas the P concentrations had increased less. It is suggested that zeatin and zeatin-ribosides are not the primary growth-substances involved in mediating VAM effects.

Phosphorus nutrition‐mediated effects of arbuscular mycorrhiza on leaf morphology and carbon allocation in perennial ryegrass

“…If this is the case, the improvement in P capture could have altered the number of active meristems and thus increased the sink strength (Pieters et al, 2001). In our study the increase in LMR was completely caused by an increase in shoot mass ratio, representing a common response associated with increasing P-supply rates (Baas & Lambers, 1988;Wright et al, 1998;de Groot et al, 2001), as the lamina : shoot ratio is a quite conserved quantity in grass species. However, LMA was decreased to a much greater extent than the positive change in LMR.…”

“…A still unsolved aspect is whether AMF influence on growth is entirely mediated by changes in plant P status, or whether there are P status-independent AMF effects. It is known that both P addition and AMF colonization could promote plant growth by increasing the leaf area per unit of plant biomass (leaf area ratio, LAR) (Baas & Lambers, 1988), which contributes to an increase in the C assimilation on a whole-plant basis (Lambers & Poorter, 1992). But are AMF and P supply effects on growth and its morphological determinants quantitatively equal?…”

Impact of arbuscular mycorrhizal fungi on N and P cycling in the root zone

“…Arbuscular mycorrhizal fungi might be able to withdraw cytoplasm from their hyphae when they senesce and leave only their cell wall material to decomposers. If we consider that mycorrhizal colonization of plants may reduce the production of roots relative to that of shoots (Baas and Lambers 1988;Lambais and Cardoso 1990) as well as root exudation (Schwab et al 1983), we can see that AMF could reduce the net amount of C released to soil by a root system. Thus, depending on the plant, the fungus and the conditions of an arbuscular mycorrhizal association, the presence of AMF could increase or decrease C input to soil.…”

Localized elongation of roots of cotton follows establishment of arbuscular mycorrhizas

“…There are at least two possible explanations, the most obvious that mycorrhizas have higher concentrations of phosphate than adjacent uncolonized roots, and that these induce localized root branching (Jackson, 1983). The second possibility is that either the presence of mycorrhiza or an increased concentration of P i within a root influences plant hormone concentrations (Allen et al, 1980(Allen et al, , 1982Baas & Kuiper, 1989 ;Dannenberg et al, 1992 ;Dru$ ge & Scho$ nbeck, 1992) causing root proliferation (Atkinson et al, 1994). Neither of these possible mechanisms was examined.…”

“…Establishment of AM usually results in a decline in root mass (Hayman & Mosse, 1971 ;Kothari et al, 1990 ;Mosse & Hayman, 1971 ;Crush, 1974 ;Baas & Lambers, 1988) and density of colonized roots might be less than that of adjacent non-mycorrhizal root, within a root system partly colonized by AM fungi. Alternatively, root density might increase with an increase in concentration of root P i associated with colonization.…”