Types, Amounts, and Possible Functions of Compounds Released into the Rhizosphere by Soil-Grown Plants

Uren, N. C.

doi:10.1201/9781420005585.ch1

Cited by 220 publications

(209 citation statements)

References 128 publications

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“…Although root exudates predominantly consist of carbon compounds, exudates can also contain significant amounts of N, which become available in the rhizosphere and can be used by microorganisms or recaptured by the plants (Bertin et al, 2003;Uren, 2007).…”

Section: Discussionmentioning

confidence: 99%

Soil nitrogen dynamics after Brachiaria desiccation

Castoldi

Reis

Pivetta

et al. 2013

Rev. Bras. Ciênc. Solo

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SUMMARYBrachiaria species, particularly B. humidicola, can synthesize and release compounds from their roots that inhibit nitrification, which can lead to changes in soil nitrogen (N) dynamics, mainly in N-poor soils. This may be important in croplivestock integration systems, where brachiarias are grown together with or in rotation with grain crops. The objective of the present study was to determine whether this holds true in N-rich environments and if other Brachiaria species have the same effect. The soil N dynamics were evaluated after the desiccation of the species B. brizantha, B. decumbens, B. humidicola, and B. ruziziensis, which are widely cultivated in Brazil. The plants were grown in pots with a dystroferric Red Latosol in a greenhouse. Sixty days after sowing, the plants were desiccated using glyphosate herbicide. The plants and soil were analyzed on the day of desiccation and 7, 14, 21 and 28 days after desiccation. The rhizosphere soil of the grasses contained higher levels of organic matter, total N and ammonium than the non-rhizosphere soil. The pH was lowest in the rhizosphere of B. humidicola, which may indicate that this species inhibits the nitrification process. However, variations in the soil ammonium and nitrate levels were not sufficient to confirm the suppressive effect of B. humidicola. The same was observed for B. brizantha, B. decumbens and B. ruziziensis, thereby demonstrating that, where N is abundant, none of the brachiarias studied has a significant effect on the nitrification process in soil.Index terms: Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola, Brachiaria ruziziensis, nitrification, rhizosphere.( RESUMO: DINÂMICA DO NITROGÊNIO NO SOLO APÓS A DESSECAÇÃO DE BRACHIARIASEspécies do gênero Brachiaria, particularmente a B. humidicola, podem sintetizar e liberar de suas raízes compostos que inibem o processo de nitrificação, o que pode provocar alterações na dinâmica do nitrogênio (N) no solo, principalmente em solos com baixa disponibilidade de N. Isso pode ser importante em sistemas com integração lavoura-pecuária, em que a forrageira é cultivada junto ou em rotação com culturas graníferas. Neste estudo, objetivou-se determinar se isso ocorre também em ambiente mais rico em N e se outras espécies de Brachiaria têm o mesmo efeito. Para tal, avaliou-se a dinâmica do N no solo após a dessecação de B. brizantha, B. decumbens, B. humidicola e B. ruziziensis, espécies amplamente cultivadas no Brasil. As plantas foram cultivadas em vasos com um Latossolo Vermelho distroférrico, em casa de vegetação. Sessenta dias após a semeadura, as plantas foram dessecadas com aplicação do herbicida glifosato. Foram realizadas análises de planta e solo, na data da dessecação e aos 7, 14, 21 e 28 dias após a dessecação. Os maiores teores de matéria orgânica, N-total e amônio foram encontrados no solo rizosférico das plantas. A rizosfera da B. humidicola apresentou ainda o menor valor de pH, o que poderia estar associado ao efeito supressivo dessa espécie no processo de nitrificaç...

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Section: Discussionmentioning

confidence: 99%

Soil nitrogen dynamics after Brachiaria desiccation

Castoldi

Reis

Pivetta

et al. 2013

Rev. Bras. Ciênc. Solo

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“…The composition of root exudates depends on plant species and cultivar, developmental stage, plant growth substrate, and stress factors (Uren 2000). Analysis of tomato, cucumber and sweet pepper root exudates from plants grown under gnotobiotic conditions on rock wool showed that the exudates contained higher total amounts of organic acids than of sugars.…”

Section: Root Exudates Influence Soil Microbial Communitiesmentioning

confidence: 99%

Impact of root exudates and plant defense signaling on bacterial communities in the rhizosphere. A review

Doornbos

Loon

Bakker

2011

Agron. Sustain. Dev.

583

313

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Despite significant advances in crop protection, plant diseases cause a 20% yield loss in food and cash crops worldwide. Therefore, interactions between plants and pathogens have been studied in great detail. In contrast, the interplay between plants and non-pathogenic microorganisms has received scant attention, and differential responses of plants to pathogenic and non-pathogenic microorganisms are as yet not well understood. Plants affect their rhizosphere microbial communities that can contain beneficial, neutral and pathogenic elements. Interactions between the different elements of these communities have been studied in relation to biological control of plant pathogens. One of the mechanisms of disease control is induced systemic resistance (ISR). Studies on biological control of plant diseases have focused on ISR the last decade, because ISR is effective against a wide range of pathogens and thus offers serious potential for practical applications in crop protection. Such applications may however affect microbial communities associated with plant roots and interfere with the functioning of the root microbiota. Here, we review the possible impact of plant defense signaling on bacterial communities in the rhizosphere. To better assess implications of shifts in the rhizosphere microflora we first review effects of root exudates on soil microbial communities. Current knowledge on inducible defense signaling in plants is discussed in the context of recognition and systemic responses to pathogenic and beneficial microorganisms. Finally, the as yet limited knowledge on effects of plant defense on rhizosphere microbial communities is reviewed and we discuss future directions of research that will contribute to unravel the molecular interplay of plants and their beneficial microflora.

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“…These compounds (especially phenolic compounds) affect the growth and development of plants and microorganism. Root exudates also contain higher molecular weight compounds such as flavonoids, fatty acids, steroids, tannins, vitamins, alkaloids, enzymes and growth regulators, involved in primary and secondary plant metabolic processes (Fan et al, 1997;Uren, 2000). Therefore, root exudates play a key role in resource competition by soil metabolic process, microbial population and altering soil chemistry.…”

Section: Introductionmentioning

confidence: 99%

Pepper-Garlic Intercropping System Improves Soil Biology and Nutrient Status in Plastic Tunnel

Khan¹,

Cheng²,

Khan³

et al. 2015

IJAB

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A two year (2009)(2010)(2011) experiment was conducted to investigate effect of pepper-garlic intercropping system on soil biology and nutrient profile in plastic tunnel to overcome continuous monocropping obstacles. During first year's trial, garlic cloves of four cultivars (G026, G025, and G087 for the harvest of bulbs) were intercropped between two rows of pepper seedlings (cv. Golden Pepper) on each bed. Similarly, garlic bulb (cv G064 for the harvest of green seedlings) was sandwiched between two rows of pepper seedlings. During 2 nd year, the pepper crop was transplanted on the same beds already having garlic in the field of previous crop, following the same geometry. Sole pepper was grown as control. Both crops received uniform fertilization and irrigation as per requirements of pepper. Results revealed that concentration of soil bacteria and actinomycetes was higher respectively after one month of garlic intercropping during both the years of study as compared to the sole pepper; however, fungal population exhibited a diminishing trend. Soil protective enzyme activity (invertase, urease, and alkaline phosphatase) also showed dynamic changes after the intercropping of garlic. The principal soil nutrients (NPK) attained higher levels in pepper-garlic co-growth treatments as compared to the sole pepper The intercropping with green garlic (cv. G064) resulted highest nutrient levels suggesting that the effect might be cultivar specific. It was concluded that the intercropping of pepper with garlic enhances the soil fertility by changing nutrient levels, enzymatic activity and the soil microbial population. Overall, the pepper-garlic intercropping model provides a cost effective and eco-friendly organic farming system for vegetable growers.

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Types, Amounts, and Possible Functions of Compounds Released into the Rhizosphere by Soil-Grown Plants

Cited by 220 publications

References 128 publications

Soil nitrogen dynamics after Brachiaria desiccation

Soil nitrogen dynamics after Brachiaria desiccation

Impact of root exudates and plant defense signaling on bacterial communities in the rhizosphere. A review

Pepper-Garlic Intercropping System Improves Soil Biology and Nutrient Status in Plastic Tunnel

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