Do water regimes affect iron‐plaque formation and microbial communities in the rhizosphere of paddy rice?

Abstract

Pot experiments were conducted to investigate the effect of soil water regimes on the formation of iron (Fe) plaque on the root surface of rice seedlings (Oryza sativa L.) and on the microbial functional diversity in a paddy soil. The rice seedlings were subjected to three moisture regimes (submergence, 100%, and 60% water-holding capacity [WHC]), and were grown for 5 and 11 weeks. Aerobic lithotrophic Fe(II)-oxidizing (FeOB) and acetate-utilizing Fe(III)-reducing bacteria (FeRB) in the rhizosphere and non-rhizosphere soil were determined at 5 weeks using the most probable number (MPN) method. The carbon substrate use patterns of the microbial communities in the rhizosphere and non-rhizosphere soil samples were determined at 11 weeks using Biolog-GN2 plates. The amount of Fe plaque (per unit dry root weight) was much higher under submerged conditions than at lower soil moisture contents and decreased with plant age. There was a positive correlation between the amount of Fe plaque and phosphorus accumulated in the Fe plaque at both sampling times (r = 0.98 and 0.92, respectively, n = 12). Numbers of FeOB and FeRB in the submerged soil were lower than in aerobic soil, but by two orders of magnitude higher in the rhizosphere than in the bulk soil. On the other hand, the functional diversity of the rhizosphere microbial communities was much higher than that of the non-rhizosphere soil, irrespective of soil water regimes. We conclude that soil flooding results in a decreased number and diversity of Fe-oxidizing/reducing bacteria, while increasing the Fe-plaque formation.

Comparison of soil microbial community catabolic diversity between rhizosphere and bulk soil induced by tillage or residue retention

“…The catabolic functional diversity of microbial communities in the rhizosphere was higher than that of in bulk soil, consistent with the results in paddy rice (Chen et al ,2008), This may be due to the higher (or diversity of) carbon resources in the rhizosphere soil, which is considered as the driving force for microbial density and activity (Bowen & Rovira 1999;Lugtenberg & Dekkers 1999). A gelatinous film on the root surface, which is a primary source of nutrients and energy amongst soil microbes, has been reported in a variety of ecosystems (Salt et al, 1998).…”

Radial oxygen loss has different effects on the accumulation of total mercury and methylmercury in rice

“…It should also be noted that the Fe formation on root surfaces can be influenced by many abiotic factors such as the availability of soil Fe, temperature, pH, CO 2 , soil permeability, etc. (Chen et al 1980;St-Cyr and Crowder 1988), as well as biotic factors, including ROL and rhizosphere bacteria (St-Cyr and Crowder 1989;Chen et al 2008). Mendelssohn et al (1995) reported that ROL is the most important biotic factor controlling Fe plaque formation.…”

Interactive effects of different inorganic As and Se species on their uptake and translocation by rice (Oryza sativa L.) seedlings

“…Rice seedling preparation and culture conditions Rice (O. sativa L.) seeds were surface sterilized in 30 % H 2 O 2 solution for 15 min and thoroughly washed with deionized water (Chen et al 2008). The seeds were germinated in moist perlite.…”