Effects of drought on non‐mycorrhizal and mycorrhizal maize: changes in the pools of non‐structural carbohydrates, in the activities of invertase and trehalase, and in the pools of amino acids and imino acids

Abstract

To study the response of non-mycorrhizal and mycorrhizal maize plants to drought, the changes in the pools of non-structural carbohydrates and amino acids were analysed in leaves and roots of two maize cvs. Plants well colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) (60 % of root length infected) and comparable non-mycorrhizal plants were subjected to moderate drought stress by reducing the water supply. This stress induced a conspicuous increase in the trehalose pool in the mycorrhizal roots, probably because it was accumulated by the fungal symbiont. Furthermore, glucose and fructose were accumulated in leaves and roots of non-mycorrhizal plants but not in the mycorrhizal ones. Starch disappeared completely from the leaves of both mycorrhizal and non-mycorrhizal plants in response to drought. Activities of soluble acid invertase and trehalase were also measured. Acid invertase activity increased during drought in the leaves of both non-mycorrhizal and mycorrhizal plants whilst in the roots it was unaffected in non-mycorrhizal plants and decreased in the mycorrhizal ones. Without drought stress, trehalase activity was considerably higher in the leaves and roots of mycorrhizal plants than in those of non-mycorrhizal plants. It increased conspicuously during drought, primarily in the leaves of non-mycorrhizal plants. A drought-induced accumulation of amino acids as well as imino acids was found in roots and leaves of both mycorrhizal and non-mycorrhizal plants ; leaves of mycorrhizal plants accumulated more imino acids than those of non-mycorrhizal ones. Our results show that drought stress and the presence of a mycorrhizal fungus have a considerable effect on carbon partitioning, imino acid and amino acid accumulation in maize plants.

Effects of plant growth-promoting rhizobacterium (PGPR) and arbuscular mycorrhizal fungus (AMF) on antioxidant enzyme activities in salt-stressed bean (phaseolus vulgaris l.)

“…In plants exposed to salinity, the total non-structural carbohydrate content in the shoots was reduced significantly compared with plants not exposed to salinity. This could indicate that salinity induces a preferential partitioning of carbohydrates to the roots, as demonstrated by Schellenbaum et al (1998). The decrease in total soluble carbohydrates due to salinity could be related also to limited carbohydrate availability, as a consequence of a decline in photosynthesis (Goicoechea et al 2005).…”

Soil depth: an overriding factor for distribution of arbuscular mycorrhizal fungi

“…Clay has capacity to retain water therefore moisture remains in the soil for more time which might affect the AMF sporulation (Dubey et al, 2008). Schellenbaum et al (1998) suggested that availability of moisture increases the growth of fungal mycelium for root colonization, leading to a decrease on AMF spore germination.…”

Effects of drought, transgenic expression of a fructan synthesizing enzyme and of mycorrhizal symbiosis on growth and soluble carbohydrate pools in tobacco plants

“…Under normal photosynthetic conditions, most of the plant species that establish the symbiosis appear to compensate for the extra carbon demand by the root system (Harris & Paul, 1987). However, when the photosynthetic abilities of the plant are limited, the presence of the fungus in the root system might affect carbohydrate allocation as has been shown in maize in drought (Schellenbaum et al, 1998).…”