Aims: Soil invertebrates have the potential to modify plant responses to drought stress. For example, some functional groups improve soil conditions via resource provision and water retention, potentially alleviating drought stress. This study was designed in order to mechanistically understand the functional roles of soil fauna in ecosystem services. Methods: A pot experiment using tomatoes (Lycopersicon esculentum) was conducted in a greenhouse. This study adopted a complete factorial design that manipulated earthworm (Metaphire guillelmi) abundance and drought stress level. Results: Our results indicate that earthworms promote plant drought resistance under high drought stress, which significantly up-regulated gene expression (NCED, NSY, OPR, AOS and LOX) of abscisic acid and jasmonic acid biosynthesis, promoted the accumulation of abscisic acid and jasmonic acid by 43.2% and 33.6%, up-regulated transcription factor expression, and increased the activities of catalase, peroxidase and superoxide dismutase by 12.9%, 8.4% and 47.3% in tomato shoots, respectively. However, under low drought stress, earthworms up-regulated jasmonic acid synthesis pathway gene expression, but reduced abscisic acid content, and had no significant effect on the expression of transcription factors ABF4 and MYC2 genes or plant antioxidant capacity.
Conclusion:The effects of earthworms on plant resistance depends on drought level. This study confirms the importance of soil invertebrates in plant drought resistance including the potential impact of earthworms on plant hormone synthesis, signal transduction, and antioxidant capacity.
<p>Global biodiversity is being threatened by climate change and human activities. Prior studies have demonstrated the negative concequences of land-use such as conversion of forest into monoculture, while its effects on belowground organisms especially soil invertebrates remain unclear. Earthworms are well-known ecosystem engineers that deliver multiple ecosystem functions including decomposition, carbon sequestration and plant growth. Yet, all of those functions are negatively affected by land-use conversion. Previous studies concerning land-use effects on soil biodiversity were generally conducted at a single site and small spatial scale, how soil biodiversity changes across spatial scales remains poorly understood.</p><p>In current study, earthworms were quantitatively sampled from 41 sites in three land-use types (i.e., farmland, orchard and forest at each site, five replicates) in subtropical region of China. Earthworm species were identified using both morphological and molecular methods. Earthworm density, biomass and body size were recorded. Notably, the species were also classified into different functional guilds. Totally, 84 species (or subspecies) were identified. Generally, local diversity (&#945; diversity) was higher in agricultural lands than in forest lands, however, the opposite was true for regional diversity (&#947; diversity). In addition, the density of earthworm was the lowest in forest, while the biomass and body size were higher in agricultural lands. A higher proportion of endogeic and anecic earthworms were found in farmland and orchard than in forest. The land-use caused changes in soil properties contributed to the difference in earthworm diversity, abundance, biomass and body size.</p><p>In conclusion, we suggest that the impacts of human land-use on soil earthworm assemblage are scale-dependent, and the diversity, abundance, biomass and body size respond differently to land-use. Researches on different scales about land-use effects to soil biodiversity are urgently needed.</p>
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