Dynamics of organic acid occurrence under flooding stress in the rhizosphere of three plant species from the water fluctuation zone of the Three Gorges Reservoir, P.R. China

Abstract

The effects of flooding on rhizospheric organic acid concentrations of three abundant flooding tolerant plant species (Alternanthera philoxeroides Mart., Arundinella anomala Steud., Salix variegata Franch.) from the water fluctuation zone of the Three Gorges Reservoir (TGR, Yangtze River) were investigated. Soil solution samples of eight low molecular weight organic acids were obtained from rhizotrons using micro suction cups during 3 weeks of waterlogging, after 6 weeks flooding and after a 1 week recovery. To estimate the contribution of water temperature and microbial community, plants in sterile glass bead substrate and original Yangtze sediment were submerged in laboratory at +10°, +20°and +30°C. Waterlogged plants did seldom express a significantly different pattern of rhizospheric organic acid (OA) composition compared to control plants. Flooding caused no burst of organic acid concentration in soil solution: All species express a silencing strategy. Average OA levels were higher in A. anomala rhizosphere than in the other two species, but increased again after resurfacing in all species. Temperature had a stronger influence in sediment than in sterile setup. In contrast to field measurements, succinate, malate and citrate were detected in the sterile setup. Microbial contribution appeared to have great influence on increasing OA occurrence.

Flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone of the Three Gorges Reservoir, China

“…Seasonal water level fluctuation has created a reservoir fluctuation zone, which refers to all geomorphological features that fall into the elevation ranges between the base and peak levels (Bao et al, 2015a). The reservoir fluctuation zone, commonly also referred to as water-level fluctuation zone (Schreiber et al, 2011;Ye et al, 2011), littoral zone (Li et al, 2011a;Yuan et al, 2013), transitional area, drawdown zone Su et al, 2012), or disturbance zone (Bao et al, 2015a), represents a unique artificial landscape that was originally composed of terrestrial uplands with diverse land use and which was transformed to a transitional area undergoing seasonal flooding and exposure. This zone differs substantially from well-recognized natural riparian zones in unmanaged river systems (Table 1).…”

Monitoring rhizospheric pH, oxygen, and organic acid dynamics in two short‐time flooded plant species

“…Soil microbial communities were present, since almost no ox, suc, mal, or cit was found in soil-solution samples. These exudates are known to be utilized quickly by soil microbiota, and indeed the study species exuded them in a sterile experiment in glass-bead substrate (Schreiber et al, 2011).…”

“…Plant-available cations were determined by AAS after NH 4 -acetate extraction and found to be in a low range (K 2.5, Mn 0.7, Mg 2.8, Fe 4.4, Ca 6.3 mg kg -1 , cf. also Schreiber et al, 2011). Nitrate (< 5 mgkg -1 ), ammonia (< 1.2 mg kg -1 ), and phosphate (< 2 mg kg -1 ) were detected by a Spectroquant test kit (Merck).…”

Investigation of small-scale processes in the rhizosphere of Lupinus albus using micro push-pull tests

“…In the 1990s, small-scale soil-solution investigations started with the miniaturization of sampling probes, which enabled non-destructive in situ observation of soil-solution chemistry (Göttlein et al 1996;Vetterlein et al 1993). Later, micro-suction cups were used successfully in conjunction with rhizoboxes that allow observation of root-system development through a transparent front plate and thus permitted the targeted sampling of soil solution adjacent to roots (Dessureault-Rompré et al 2006Dieffenbach et al 1997;Göttlein et al 1999;Puschenreiter et al 2005;Schreiber et al 2011). This allowed the determination of solute concentrations in the rhizosphere at high spatial and temporal resolution and provided information about small-scale heterogeneities with respect to solute concentrations.…”