Pool sizes of fructans in roots and leaves of mycorrhizal and non‐mycorrhizal barley

Abstract

The effect of arbuscular mycorrhizas on fructan accumulation was studied in barley (Hordeum vulgare) infected with Glomus mosseae. Treatments with and without fertilizer were included in order to distinguish between mere fertilizer effects and the effects of the symbiosis, and plants were harvested at two different time points, 35 and 50 d after planting. Fructan was the major storage carboyhdrate in both leaves and roots. The amounts of fructan were markedly altered in the mycorrhizal plants. In roots of non-fertilized mycorrhizal plants, fructan pools were significantly greater than in the corresponding non-mycorrhizal plants. By contrast, fertilization caused a general decrease in amounts of fructan in roots. The increase of fructan in mycorrhizal roots was correlated with a decrease of invertase activity. In leaves, fructan pools decreased or remained unchanged upon mycorrhizal infection ; fertilization had a similar effect. However, when individual leaves of a plant were compared, intriguing effects of the mycorrhizal symbiosis could be observed. Whereas in non-mycorrhizal plants, the youngest leaves had the highest fructan contents and the oldest leaves the lowest (as previously reported), this gradient was markedly altered in mycorrhizal plants, indicating systemic effects of mycorrhiza on assimilate partitioning in shoots.

Arbuscular mycorrhiza increased the activity of a biotrophic leaf pathogen - is a compensation possible?

“…This suggests that a better filling of long-term storage pools in mycorrhizal plants, efficient utilisation of these during grain filling and unimpaired photosynthesis are factors determining compensation of pathogen attack. Systemic effects of mycorrhiza on assimilate partitioning in shoots of barley plants had been reported by Müller et al (1999) as represented by an altered gradient of fructan content in the youngest and oldest leaves of AM plants.…”

Arbuscular mycorrhizal fungi influence life history traits of a lepidopteran herbivore

“…C and/or P could have positively affected larval performance since plant C concentration is related to the presence and composition of many plant compounds affecting herbivory (e.g. sugar composition, allelochemicals, phagostimulants) (Rosenthal and Berenbaum 1991;Bernays and Chapman 1994;Goverde et al 1999;Müller et al 1999), and since P is an important element for insect growth (Wigglesworth 1984;Schoonhoven et al 1998).…”

“…Plants which are colonised by AMF normally contain more P and micro-nutrients than uncolonised plants and N concentrations vary between mycorrhizal and non-mycorrhizal plants (Table 1). Furthermore, the pool sizes and distribution of non-structural carbohydrates within the plant, and the presence and composition of secondary plant metabolites, some of which might be toxic for herbivores, can also vary between mycorrhizal and non-mycorrhizal plants (Morandi 1996;Vierheilig et al 1998;Müller et al 1999). Some leaf-quality variables which are important for herbivores and which are influenced by AMF are summarised in Table 1.…”

Mycorrhizal mediated feedbacks influence net carbon gain and nutrient uptake in Andropogon gerardii

“…However, it has proven difficult to differentiate whether this increased C gain is a direct effect of fungal colonization or an indirect effect of the enhanced leaf P status that accompanies fungal colonization (Graham, 2000). Explanations for increased sink strength caused by mycorrhizal fungal colonization of roots include rapid utilization of C and its rapid conversion into fungal-specific compounds (Bevage et al, 1975;Losel & Cooper, 1979), increased respiration by the mycorrhizal root system (Pang & Paul, 1980;Snellgrove et al, 1982;Harris et al, 1985), and increased activity of sucrolytic enzymes ( Wright et al, 1998b;Müller et al, 1999).…”