scholarly journals Effects of tree species on root exudation and mineralization of organic acids in a tropical forest

2021 ◽  
Author(s):  
Kazumichi Fujii ◽  
Chie Hayakawa ◽  
Tininsih Sukar
Keyword(s):  
Organic Acids ◽  
Tree Species ◽  
Rhizosphere Soil ◽  
Root Exudation ◽  
Root Surface ◽  
Root Surface Area ◽  
Mature Trees ◽  
Pioneer Trees ◽  
Highly Weathered Soils ◽  
Organic Acid Exudation

<p>Tropical forests can develop by roots foraging nutrients in the highly weathered soils. In rhizosphere, soil volume affected by roots, tree species modify carbon (C) and nutrient cycles directly through root exudation and indirectly through increased microbial activity. We test whether root exudation and rhizosphere C fluxes of organic acids and sugars differ between dominant dipterocarp trees and pioneer trees (Macaranga gigantea). To quantify the C fluxes of organic acids in the rhizosphere soils, we measured in situ root exudation from mature trees, concentrations of monosaccharides and organic acids (acetate, oxalate, malate, and citrate) in the rhizosphere and bulk soil fractions, and mineralization kinetics of <sup>14</sup>C-radiolabelled substrates. Organic acid exudation increases with increasing root surface area. Dipterocarp roots release greater amounts of malate, while monosaccharides are dominant exudates of pioneer trees. Microbial activities of malate mineralization increase in the rhizosphere soil both under dipterocarp and pioneer trees. The greater C fluxes of malate mineralization, compared to root exudation, suggests rhizosphere microbes are another malate producer under dipterocarp trees. Both root exudation composition and rhizosphere microbes increase malate production with increasing phosphorus demands and with increasing soil acidity.</p>

scholarly journals Effects of Tree Species on Root Exudation and Mineralization of Organic Acids in a Tropical Forest

2021 ◽  
Author(s):  
Kazumichi Fujii ◽  
Chie Hayakawa ◽  
Sukarti Ningsih
Keyword(s):  
Organic Acids ◽  
Organic Acid ◽  
Tree Species ◽  
Root Exudation ◽  
Root Surface ◽  
Root Surface Area ◽  
Microbial Activities ◽  
Mature Trees ◽  
Highly Weathered Soils ◽  
Organic Acid Exudation

Abstract Aims Root exudation of organic acids is one of strategies for tropical trees to facilitate nutrient uptake from the highly weathered soils. However, paradoxical relationship remains that root exudation also stimulates microbial activities to consume organic acids in the rhizosphere (root-soil interface). Plant-specific root exudation might shape different rhizosphere carbon (C) cycles between tree species. We test whether root exudation and rhizosphere C fluxes of organic acids and sugars differ between dominant dipterocarp trees and pioneer trees (Macaranga spp.). Methods We measured (1) root exudation from mature trees, (2) soil solution concentrations of organic acids and monosaccharides, and (3) mineralization kinetics of 14C-radiolabelled substrates in the rhizosphere and bulk soils of the Dipterocarp and Macaranga trees. Results Malate was a dominant organic acid exuded from Dipterocarp roots, while monosaccharides were dominant exudates of pioneer Macaranga trees. Malate exudation rates by Dipterocarp roots were greater compared to Macaranga roots. Organic acid exudation increased with increasing root surface area and with decreasing soil pH. Microbial activities of malate mineralization were enhanced in the rhizosphere both under Dipterocarp and Macaranga trees, but the C fluxes of malate mineralization by rhizosphere microbes far exceeded root exudation due to microbial malate production in the rhizosphere of Dipterocarp trees. Conclusion Tree species develop different strategies to increase malate concentration in rhizosphere soil directly through root exudation or indirectly through rhizosphere microbial activities to increase malate production, which is favorable for phosphorus solubilization, aluminum detoxification, and lignin degradation in acidic soils.

Using a novel electrical measurement approach to measure the effects of liming on rooting parameters in German beech forests

2020 ◽  
Author(s):  
Oliver van Straaten ◽  
Jan Čermák ◽  
Larissa Kulp ◽  
Ulrike Talkner
Keyword(s):  
Low Frequency ◽  
Cost Effective ◽  
Electrical Measurement ◽  
Root Surface ◽  
Fine Root Biomass ◽  
Impedance Method ◽  
Root Surface Area ◽  
Beech Forests ◽  
Mature Trees ◽  
Measurement Approach

<p>Hundreds of thousands of hectares have been limed in German forests in the last three decades to mitigate the effects of soil acidification. To understand the long-term impacts of liming on tree rooting behaviour and the implications for soil organic matter, we used a novel electrical approach to quantify rooting parameters of mature beech forests and compared it to the standard monolith excavation approach. At each of the three experiment sites located in northern Germany, we looked at rooting behaviour in limed plots (overall eight tons of lime per hectare applied in the 1980s and 1990s) in comparison to adjacent control plots. First, we used the standard monolith excavation approach to determine fine root biomass at the stand level. With an electrical approach called the “earth impedance method” (EIM) we subsequently estimated tree absorbing root surface area (ARSA; this is the contact area where roots take up nutrients and water). This experimental, non-destructive approach uses a low frequency alternating electric current that flows from the roots to the soil and vice versa, and the electrical impedance (resistivity) is recalculated to estimate ARSA for the sample tree. We measured the ARSA of six mature trees per plot (12 trees per site).</p><p>To summarize the results of the sampling approaches, (1) both root estimation approach measurements were positively correlated, validating the EIM; (2) the ARSA was positively correlated with tree size at each site, further substantiating the rapid and cost effective EIM; (3) however this method is vulnerable to variables that effect electrical conductivity, such as soil moisture and the thickness and makeup of the organic horizons.</p><p>Overall, no significant differences between limed and control plots were detected with either measurement approach, suggesting that despite improved soil pH conditions the tree root systems in limed plots remain relatively constant in size and capacity to take up nutrients and water.</p>

Organic acid exudation associated with aluminium stress tolerance in triticale and wheat

2003 ◽  
Vol 54 (10) ◽  
pp. 979 ◽  
Author(s):  
X. G. Zhang ◽  
R. S. Jessop ◽  
D. Alter
Keyword(s):  
Organic Acids ◽  
Organic Acid ◽  
Stress Tolerance ◽  
High Performance ◽  
Root Exudation ◽  
Enzymatic Assay ◽  
Root Tips ◽  
Al Tolerance ◽  
Al Stress ◽  
Organic Acid Exudation

Three triticale cultivars differing in aluminium (Al) stress response, together with 1 Al-tolerant wheat cultivar (Carazinho) and 1 Al-tolerant wheat line (ET3), were used to investigate the root exudation of organic acids during Al stress. The likely relationship of organic acid exudation with Al tolerance, as assessed by root regrowth in nutrient solutions, was also examined. An enzymatic assay was used to detect malate release from both root tips and the whole root system; high performance liquid chromatography (HPLC) was also used to measure the exudation of organic acids from Al-stressed root tips. The enzymatic assay revealed some associations between Al tolerance and malate efflux from Al-stressed wheat or triticale roots, although Al-tolerant triticale cvv. Tahara and 19th ITSN 70-4 released less malate than the Al-tolerant wheat. HPLC analysis indicated that malate and citrate were not the main exudates related to the different levels of Al tolerance in these triticale cultivars. A yet to be identified organic acid in 19th ITSN 70-4 showed significant concentration differences from 2 other cultivars tested. This study highlighted the importance and necessity of elucidating the biochemical mechanisms involved in Al stress tolerance in triticale and other crops.

scholarly journals Root exudation of low-molecular-mass-organic acids by six tree species alters the dynamics of calcium and magnesium in soil

2016 ◽  
Vol 96 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Tamihisa Ohta ◽  
Tsutom Hiura
Keyword(s):  
Organic Acids ◽  
Molecular Mass ◽  
Tree Species ◽  
Root Exudation ◽  
Oyster Shell ◽  
Exchangeable Cations ◽  
Nutrient Concentrations ◽  
Ca Deficiency ◽  
Exchangeable Ca ◽  
Exudation Rate

Soils in plantations of Cryptomeria japonica in Japan have ∼threefold more exchangeable Ca compared with soils in other types of forest vegetation even in a Ca-poor environment. To explain mechanisms underlying this phenomenon, we determined the effect of root exudation rate of low-molecular-mass organic acids (LMMOAs) on exchangeable cations in soil. We conducted a pot experiment using C. japonica and five dominant tree species in Japan, and measured the root exudation rates of LMMOAs and exchangeable nutrient concentrations in the soils. To estimate whether the root exudation rate of LMMOAs is elevated in response to Ca deficiency, we created variation in Ca availability by adding different amounts of crushed oyster shells. The root exudation rates of LMMOAs were two to five times higher for C. japonica than for other tree species, but did not differ significantly among the different quantities of oyster shell. Exchangeable Ca and Mg were significantly higher in the soils with C. japonica and significantly correlated with the root exudation rate of LMMOAs (R2 > 0.24) at high and moderate quantities of oyster shell. Therefore, variation among species, in terms of root exudation of organic acids, might be one important factor affecting the cation dynamics in soil.

scholarly journals Effects of Ridge Tillage and Straw Mulching on Cultivation the Fresh Faba Beans

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1054
Author(s):  
Bo Li ◽  
Xinyu Chen ◽  
Xiaoxu Shi ◽  
Jian Liu ◽  
Yafeng Wei ◽  
...  
Keyword(s):  
Rice Straw ◽  
Precision Agriculture ◽  
Field Experiments ◽  
Root Length Density ◽  
Root Surface ◽  
High Yield ◽  
Root Surface Area ◽  
Straw Mulching ◽  
Faba Beans ◽  
Ridge Tillage

Ridge tillage is an effective agronomic practice and a miniature precision agriculture; however, its effects on the growth of faba beans (Vicia faba L.) are poorly understood. This study aimed to determine the effect of ridge tillage and straw mulching on the root growth, nutrient accumulation and yield of faba beans. Field experiments were conducted during 2016 and 2017 cropping seasons and comprised four treatments: ridge tillage without any mulching (RT), flat tillage without any mulch (FT), flat tillage with rice straw mulched on the ridge tillage (FTRSM) and ridge tillage with rice straw mulched on the ridge tillage (RTRSM). The RT and RTRSM increased soil temperature and decreased soil humidity and improved soil total nitrogen, total phosphorus, available potassium and organic matter. RT and RTRSM increased the root length density, root surface area, root diameter and root activity of faba beans at flowering and harvest periods. The RT and RTRSM also increased the nitrogen, phosphorus, potassium absorption and the yield of faba beans. These results indicated that ridge tillage and straw mulching affect faba bean growth by improving soil moisture conditions and providing good air permeability and effective soil nutrition supply. This study provides a theoretical basis for the high yield cultivation improvement of faba beans.

scholarly journals El Niño-Southern Oscillation affects the water relations of tree species in the Yucatan Peninsula, Mexico

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jorge Palomo-Kumul ◽  
Mirna Valdez-Hernández ◽  
Gerald A. Islebe ◽  
Manuel J. Cach-Pérez ◽  
José Luis Andrade
Keyword(s):  
Water Potential ◽  
Leaf Area ◽  
Tropical Forests ◽  
Specific Leaf Area ◽  
Tree Species ◽  
Deciduous Species ◽  
Mature Trees ◽  
Seasonally Dry ◽  
Seasonally Dry Tropical Forests ◽  
Dry Tropical Forests

AbstractWe evaluated the effect of ENSO 2015/16 on the water relations of eight tree species in seasonally dry tropical forests of the Yucatan Peninsula, Mexico. The functional traits: wood density, relative water content in wood, xylem water potential and specific leaf area were recorded during the rainy season and compared in three consecutive years: 2015 (pre-ENSO conditions), 2016 (ENSO conditions) and 2017 (post-ENSO conditions). We analyzed tree size on the capacity to respond to water deficit, considering young and mature trees, and if this response is distinctive in species with different leaf patterns in seasonally dry tropical forests distributed along a precipitation gradient (700–1200 mm year−1). These traits showed a strong decrease in all species in response to water stress in 2016, mainly in the driest site. Deciduous species had lower wood density, higher predawn water potential and higher specific leaf area than evergreen species. In all cases, mature trees were more tolerant to drought. In the driest site, there was a significant reduction in water status, regardless of their leaf phenology, indicating that seasonally dry tropical forests are highly vulnerable to ENSO. Vulnerability of deciduous species is intensified in the driest areas and in the youngest trees.

scholarly journals Biological nitrification inhibition in maize—isolation and identification of hydrophobic inhibitors from root exudates

2021 ◽  
Author(s):  
Junnosuke Otaka ◽  
Guntur Venkata Subbarao ◽  
Hiroshi Ono ◽  
Tadashi Yoshihashi
Keyword(s):  
Root Exudation ◽  
Root Systems ◽  
Root Surface ◽  
Maize Root ◽  
Nitrification Inhibition ◽  
Isolation And Identification ◽  
N Losses ◽  
Chemical Structures ◽  
Maize Roots ◽  
Biological Nitrification

AbstractTo control agronomic N losses and reduce environmental pollution, biological nitrification inhibition (BNI) is a promising strategy. BNI is an ecological phenomenon by which certain plants release bioactive compounds that can suppress nitrifying soil microbes. Herein, we report on two hydrophobic BNI compounds released from maize root exudation (1 and 2), together with two BNI compounds inside maize roots (3 and 4). On the basis of a bioassay-guided fractionation method using a recombinant nitrifying bacterium Nitrosomonas europaea, 2,7-dimethoxy-1,4-naphthoquinone (1, ED50 = 2 μM) was identified for the first time from dichloromethane (DCM) wash concentrate of maize root surface and named “zeanone.” The benzoxazinoid 2-hydroxy-4,7-dimethoxy-2H-1,4-benzoxazin-3(4H)-one (HDMBOA, 2, ED50 = 13 μM) was isolated from DCM extract of maize roots, and two analogs of compound 2, 2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (HMBOA, 3, ED50 = 91 μM) and HDMBOA-β-glucoside (4, ED50 = 94 μM), were isolated from methanol extract of maize roots. Their chemical structures (1–4) were determined by extensive spectroscopic methods. The contributions of these four isolated BNI compounds (1–4) to the hydrophobic BNI activity in maize roots were 19%, 20%, 2%, and 4%, respectively. A possible biosynthetic pathway for zeanone (1) is proposed. These results provide insights into the strength of hydrophobic BNI activity released from maize root systems, the chemical identities of the isolated BNIs, and their relative contribution to the BNI activity from maize root systems.

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