Below-ground plant-soil interactions affecting adaptations of rice to iron toxicity

Iron toxicity is a major constraint to rice production, particularly in highly-weathered soils of inland valleys in sub-Saharan Africa where the rice area is rapidly expanding. Although there is wide variation in tolerance in the rice germplasm, progress in introgressing tolerance traits into high-yielding germplasm has been slow owing to the complexity of tolerance mechanisms and large genotype by environment effects. We review current understanding of tolerance mechanisms, particularly those involving below-ground plant-soil interactions, which to date have been less studied than above-ground mechanisms. We cover processes in the rhizosphere linked to exclusion of toxic ferrous iron by oxidation, and resulting effects on the mobility of nutrient ions. We also cover the molecular physiology of below-ground processes controlling Fe retention in roots and root-shoot transport, and also plant Fe sensing. We conclude that future breeding programs should be based on well-characterised molecular markers for tolerance traits. To successfully identify such markers, the complex tolerance response should be broken down into its components based on understanding of tolerance mechanisms, and tailored screening methods developed for individual mechanisms.

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Below‐ground plant–soil interactions affecting adaptations of rice to iron toxicity

Plant Cell & Environment ◽

10.1111/pce.14199 ◽

2021 ◽

Author(s):

Guy J.D. Kirk ◽

Hanna R. Manwaring ◽

Yoshiaki Ueda ◽

Vimal K. Semwal ◽

Matthias Wissuwa

Keyword(s):

Iron Toxicity ◽

Plant Soil ◽

Below Ground ◽

Plant Soil Interactions

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Plant and soil nitrogen in oligotrophic boreal forest habitats with varying moss depths: does exclusion of large grazers matter?

Oecologia ◽

10.1007/s00442-021-04957-0 ◽

2021 ◽

Author(s):

Maria Väisänen ◽

Maria Tuomi ◽

Hannah Bailey ◽

Jeffrey M. Welker

Keyword(s):

Boreal Forest ◽

Vascular Plant ◽

Soil N ◽

Inorganic N ◽

N Dynamics ◽

N Content ◽

Feather Moss ◽

Foliar N ◽

Plant Soil ◽

Plant Soil Interactions

AbstractThe boreal forest consists of drier sunlit and moister-shaded habitats with varying moss abundance. Mosses control vascular plant–soil interactions, yet they all can also be altered by grazers. We determined how 2 decades of reindeer (Rangifer tarandus) exclusion affect feather moss (Pleurozium schreberi) depth, and the accompanying soil N dynamics (total and dissolvable inorganic N, δ15N), plant foliar N, and stable isotopes (δ15N, δ13C) in two contrasting habitats of an oligotrophic Scots pine forest. The study species were pine seedling (Pinus sylvestris L.), bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), and feather moss. Moss carpet was deeper in shaded than sunlit habitats and increased with grazer exclusion. Humus N content increased in the shade as did humus δ15N, which also increased due to exclusion in the sunlit habitats. Exclusion increased inorganic N concentration in the mineral soil. These soil responses were correlated with moss depth. Foliar chemistry varied due to habitat depending on species identity. Pine seedlings showed higher foliar N content and lower foliar δ15N in the shaded than in the sunlit habitats, while bilberry had both higher foliar N and δ15N in the shade. Thus, foliar δ15N values of co-existing species diverged in the shade indicating enhanced N partitioning. We conclude that despite strong grazing-induced shifts in mosses and subtler shifts in soil N, the N dynamics of vascular vegetation remain unchanged. These indicate that plant–soil interactions are resistant to shifts in grazing intensity, a pattern that appears to be common across boreal oligotrophic forests.

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Wetland eco-engineering: measuring and modeling feedbacks of oxidation processes between plants and clay-rich material

Biogeosciences ◽

10.5194/bg-13-4945-2016 ◽

2016 ◽

Vol 13 (17) ◽

pp. 4945-4957 ◽

Cited By ~ 6

Author(s):

Rémon Saaltink ◽

Stefan C. Dekker ◽

Jasper Griffioen ◽

Martin J. Wassen

Keyword(s):

Plant Growth ◽

Feedback Loop ◽

Pyrite Oxidation ◽

Iron Toxicity ◽

Biogeochemical Processes ◽

Engineering Project ◽

Feedback Mechanisms ◽

Plant Soil ◽

Water Composition ◽

Rich Material

Abstract. Interest is growing in using soft sediment as a foundation in eco-engineering projects. Wetland construction in the Dutch lake Markermeer is an example: here, dredging some of the clay-rich lake-bed sediment and using it to construct wetland will soon begin. Natural processes will be utilized during and after construction to accelerate ecosystem development. Knowing that plants can eco-engineer their environment via positive or negative biogeochemical plant–soil feedbacks, we conducted a 6-month greenhouse experiment to identify the key biogeochemical processes in the mud when Phragmites australis is used as an eco-engineering species. We applied inverse biogeochemical modeling to link observed changes in pore water composition to biogeochemical processes. Two months after transplantation we observed reduced plant growth and shriveling and yellowing of foliage. The N : P ratios of the plant tissue were low, and these were affected not by hampered uptake of N but by enhanced uptake of P. Subsequent analyses revealed high Fe concentrations in the leaves and roots. Sulfate concentrations rose drastically in our experiment due to pyrite oxidation; as reduction of sulfate will decouple Fe-P in reducing conditions, we argue that plant-induced iron toxicity hampered plant growth, forming a negative feedback loop, while simultaneously there was a positive feedback loop, as iron toxicity promotes P mobilization as a result of reduced conditions through root death, thereby stimulating plant growth and regeneration. Given these two feedback mechanisms, we propose the use of Fe-tolerant species rather than species that thrive in N-limited conditions. The results presented in this study demonstrate the importance of studying the biogeochemical properties of the situated sediment and the feedback mechanisms between plant and soil prior to finalizing the design of the eco-engineering project.

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