Kosala Ranathunge

Role of roots in adaptation of soil-indifferent Proteaceae to calcareous soils in south-western Australia

Publisher: Oxford University Press (OUP)

Date: 11-11-2021

DOI: 10.1093/JXB/ERAA515

Abstract: Very few of the & Proteaceae species in south-western Australia cope with the high calcium (Ca) levels in young, calcareous soils (soil indifferent) most are Ca sensitive and occur on nutrient-impoverished, acidic soils (calcifuge). We assessed possible control points for Ca transport across roots of two soil-indifferent (Hakea prostrata and Banksia prionotes) and two calcifuge (H. incrassata and B. menziesii) Proteaceae. Using quantitative X-ray microanalysis, we investigated cell-specific elemental Ca concentrations at two positions behind the apex in relation to development of apoplastic barriers in roots of plants grown in nutrient solution with low or high Ca supply. In H. prostrata, Ca accumulated in outer cortical cells at 20 mm behind the apex, but [Ca] was low in other cell types. In H. incrassata, [Ca] was low in all cells. Accumulation of Ca in roots of H. prostrata corresponded to development of apoplastic barriers in the endodermis. We found similar [Ca] profiles in roots and similar [Ca] in leaves of two contrasting Banksia species. Soil-indifferent Hakea and Banksia species show different strategies to inhabit calcareous soils: H. prostrata intercepts Ca in roots, reducing transport to shoots, whereas B. prionotes allocates Ca to specific leaf cells.

Water permeability and reflection coefficient of the outer part of young rice roots are differently affected by closure of water channels (aquaporins) or blockage of apoplastic pores

Publisher: Oxford University Press (OUP)

Date: 22-01-2004

DOI: 10.1093/JXB/ERH041

Composite transport model and water and solute transport across plant roots

Publisher: Frontiers Media SA

Date: 16-02-2018

DOI: 10.3389/FPLS.2018.00193

Overexpression of the CC-type glutaredoxin, OsGRX6 affects hormone and nitrogen status in rice plants

Publisher: Frontiers Media SA

Date: 03-11-2015

DOI: 10.3389/FPLS.2015.00934

Control of water uptake by rice (Oryza sativa L.): role of the outer part of the root

Publisher: Springer Science and Business Media LLC

Date: 05-03-2003

DOI: 10.1007/S00425-003-0984-9

Abstract: A new pressure-perfusion technique was used to measure hydraulic and osmotic properties of the outer part of roots (OPR) of 30-day-old rice plants (lowland cultivar: IR64, and upland cultivar: Azucena). The OPR comprised rhizodermis, exodermis, sclerenchyma and one cortical cell layer. The technique involved perfusion of aerenchyma of segments from two different root zones (20-50 mm and 50-100 mm from the tip) at precise rates using aerated nutrient solution. The hydraulic conductivity of the OPR (Lp(OPR)=1.2x10(-6) m s(-1) MPa(-1)) was larger by a factor of 30 than the overall hydraulic conductivity (Lp(r)=4x10(-8) m s(-1) MPa(-1)) as measured by pressure chamber and root pressure probe. Low reflection coefficients were obtained for mannitol and NaCl for the OPR (sigma(sOPR)=0.14 and 0.09, respectively). The diffusional water permeability ( P(dOPR)) estimated from isobaric flow of heavy water was smaller by three orders of magnitude than the hydraulic conductivity (Lp(OPR)/ P(fOPR)). Although detailed root anatomy showed well-defined Casparian bands and suberin lamellae in the exodermis, the findings strongly indicate a predominantly apoplastic water flow in the OPR. The Lp(OPR) of heat-killed root segments increased by a factor of only 2, which is in line with the conclusion of a dominating apoplastic water flow. The hydraulic resistance of the OPR was not limiting the passage of water across the root cylinder. Estimations of the hydraulic properties of aerenchyma suggested that the endodermis was rate-limiting the water flow, although the aerenchyma may contribute to the overall resistance. The resistance of the aerenchyma was relatively low, because mono-layered cortical septa crossing the aerenchyma ('spokes') short-circuited the air space between the stele and the OPR. Spokes form hydraulic bridges that act like wicks. Low diffusional water permeabilities of the OPR suggest that radial oxygen losses from aerenchyma to medium are also low. It is concluded that in rice roots, water uptake and oxygen retention are optimized in such a way that hydraulic water flow can be kept high in the presence of a low efflux of oxygen which is diffusional in nature.

Metabolic adaptations leading to lignification in wheat roots under salinity stress

Publisher: Cold Spring Harbor Laboratory

Date: 08-06-2023

DOI: 10.1101/2023.06.08.544172

Abstract: Analysis of salinity tolerance processes in wheat has focused on salt exclusion from shoots while root phenotypes have received limited attention. Here we consider the varying phenotypic response of four bread wheat varieties that differ in their type and degree of salt tolerance and consider in detail their molecular responses to salinity and changes in root cell wall lignification. These varieties were Westonia introgressed with Nax1 and Nax2 root sodium transporters ( HKT1 -A ) that reduce Na + accumulation in leaves, as well as the ‘tissue tolerant’ Portugese landrace Mocho de Espiga Branca that has a mutation in the homologous gene HKT1 -D and has high Na + concentration in leaves. These three varieties were compared with the more salt-sensitive cultivar Gladius. Through the use of root structural analysis, ion concentrations, as well as differential proteomics and targeted metabolomics we provide an integrated view of the wheat root response to salinity. We show different metabolic re-arrangements in energy conversion, primary metabolic machinery and phenylpropanoid pathway leading to monolignol production in a genotype and genotype by treatment dependent manner that alters the extent and localisation of root lignification which correlated with an improved capacity of wheat roots to cope better under salinity stress.

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

Publisher: Springer Science and Business Media LLC

Date: 30-09-2017

DOI: 10.1007/S11104-017-3427-2

Functional and chemical comparison of apoplastic barriers to radial oxygen loss in roots of rice (Oryza sativa L.) grown in aerated or deoxygenated solution

Publisher: Oxford University Press (OUP)

Date: 05-2009

DOI: 10.1093/JXB/ERP089

Abstract: Radial oxygen loss (ROL) and root porosity of rice (Oryza sativa L.) plants grown in either aerated or deoxygenated (stagnant) conditions were combined for the first time with extensive histochemical and biochemical studies of the apoplastic barriers in the roots' peripheral cell layers. Growth in stagnant solution significantly affected structural and, consequently, the physiological features of rice roots. It increased adventitious root porosity by about 20% and decreased the ROL towards the base to zero at a distance of 40 mm from the apex. By contrast, roots of plants grown in aerated solutions revealed the highest rates of ROL at 30 mm from the apex. Differences in the ROL pattern along the root were related to histochemical studies, which showed an early development of Casparian bands and suberin lamellae in the exodermis, and lignified sclerenchyma cells in roots of plants grown in deoxygenated solution. In agreement with anatomical studies, absolute contents of suberin and lignin in the outer part of the roots (OPR) were higher in plants grown in deoxygenated solution. Regardless of growth conditions, the levels of suberin and lignin increased along the roots towards the base. It is concluded that radial oxygen loss can be effectively restricted by the formation of a suberized exodermis and/or lignified sclerenchyma in the OPR. However, the relative contribution of suberin and lignin in the formation of a tight barrier is unclear. Knowing the permeability coefficient across OPR for roots of plants grown in both conditions will allow a more precise understanding of the mechanisms controlling ROL.

Soybean root suberin

Publisher: Oxford University Press (OUP)

Date: 06-04-2007

DOI: 10.1104/PP.106.091090

Abstract: Soybean (Glycine max L. Merr.) is a versatile and important agronomic crop grown worldwide. Each year millions of dollars of potential yield revenues are lost due to a root rot disease caused by the oomycete Phytophthora sojae (Kaufmann & Gerdemann). Since the root is the primary site of infection by this organism, we undertook an examination of the physicochemical barriers in soybean root, namely, the suberized walls of the epidermis and endodermis, to establish whether or not preformed suberin (i.e. naturally present in noninfected plants) could have a role in partial resistance to P. sojae. Herein we describe the anatomical distribution and chemical composition of soybean root suberin as well as its relationship to partial resistance to P. sojae. Soybean roots contain a state I endodermis (Casparian bands only) within the first 80 mm of the root tip, and a state II endodermis (Casparian bands and some cells with suberin lamellae) in more proximal regions. A state III endodermis (with thick, cellulosic, tertiary walls) was not present within the 200-mm-long roots examined. An exodermis was also absent, but some walls of the epidermal and neighboring cortical cells were suberized. Chemically, soybean root suberin resembles a typical suberin, and consists of waxes, fatty acids, ω-hydroxy acids, α,ω-diacids, primary alcohols, and guaiacyl- and syringyl-substituted phenolics. Total suberin analysis of isolated soybean epidermis/outer cortex and endodermis tissues demonstrated (1) significantly higher amounts in the endodermis compared to the epidermis/outer cortex, (2) increased amounts in the endodermis as the root matured from state I to state II, (3) increased amounts in the epidermis/outer cortex along the axis of the root, and (4) significantly higher amounts in tissues isolated from a cultivar (‘Conrad’) with a high degree of partial resistance to P. sojae compared with a susceptible line (OX760-6). This latter correlation was extended by an analysis of nine independent and 32 recombinant inbred lines (derived from a ‘Conrad’ × OX760-6 cross) ranging in partial resistance to P. sojae: Strong negative correlations (−0.89 and −0.72, respectively) were observed between the amount of the aliphatic component of root suberin and plant mortality in P. sojae-infested fields.

Strong host specificity of a root hemi-parasite (Santalum acuminatum) limits its local distribution: beggars can be choosers

Publisher: Springer Science and Business Media LLC

Date: 09-02-2019

DOI: 10.1007/S11104-019-03966-6

Using activated charcoal to remove substances interfering with the colorimetric assay of inorganic phosphate in plant extracts

Publisher: Springer Science and Business Media LLC

Date: 05-11-2021

DOI: 10.1007/S11104-021-05195-2

Abstract: Organic substances in leaves of several southwest Australian native species interfere with sensitive colorimetric assays and prevent quantification of inorganic phosphate concentration ([Pi]). We aimed to develop a reproducible routine procedure for treating leaf extracts with activated charcoal (AC) to remove interfering substances, allowing the determination of [Pi] by the malachite green spectrophotometric assay. Leaf extracts of native plants from southwest Australia in 1% ( v / v ) acetic acid were treated with 10 mg mL −1 acid-washed AC for removal of interfering substances. Standard solutions (0 to 18 μM Pi) with and without AC treatment were compared to quantify Pi loss. A spiking and recovery test was performed to validate the AC treatment. Leaf extracts treated with AC exhibited distinguishable absorbance peaks for the malachite green-orthophosphate complex between 630 and 650 nm, as opposed to untreated s les. The Pi-adsorption by AC represented a relatively larger fraction of [Pi] in solutions at 0–4 μM Pi range and stabilised at higher [Pi] when maximum adsorption capacity of AC reached at 11.7 μg Pi g −1 AC. The Pi recovery after AC treatment in spiked s les ranged between 100 and 111%. The AC treatment successfully removed interfering substances from s les but caused Pi loss. Thus, quantification of [Pi] in AC-treated extracts requires s le [Pi] ≥ 6 μM Pi and the use of AC-treated standards. The error of the AC treatment was minor compared with environmental variability of leaf [Pi]. The AC treatment was a reproducible time- and cost-effective method to remove interfering substances from leaf extracts.

Soybean root suberin and partial resistance to root rot caused by Phytophthora sojae

Publisher: Scientific Societies

Date: 11-2008

DOI: 10.1094/PHYTO-98-11-1179

Abstract: Phytophthora sojae is the causal agent of root and stem rot of soybean (Glycine max). Various cultivars with partial resistance to the pathogen have been developed to mitigate this damage. Herein, two contrasting genotypes, the cultivar Conrad (with strong partial resistance) and the line OX760-6 (with weak partial resistance), were compared regarding their amounts of preformed and induced suberin components, and to early events during the P. sojae infection process. To colonize the root, hyphae grew through the suberized middle lamellae between epidermal cells. This took 2 to 3 h longer in Conrad than in OX760-6, giving Conrad plants more time to establish their chemical defenses. Subsequent growth of hyphae through the endodermis was also delayed in Conrad. This cultivar had more preformed aliphatic suberin than the line OX760-6 and was induced to form more aliphatic suberin several days prior to that of OX760-6. However, the induced suberin was formed subsequent to the initial infection process. Eventually, the amount of induced suberin (measured 8 days postinoculation) was the same in both genotypes. Preformed root epidermal suberin provides a target for selection and development of new soybean cultivars with higher levels of expression of partial resistance to P. sojae.

Strategies to acquire and use phosphorus in phosphorus-impoverished and fire-prone environments

Publisher: Springer Science and Business Media LLC

Date: 19-05-2022

DOI: 10.1007/S11104-022-05464-8

Abstract: Unveiling the ersity of plant strategies to acquire and use phosphorus (P) is crucial to understand factors promoting their coexistence in hyper erse P-impoverished communities within fire-prone landscapes such as in cerrado (South America), fynbos (South Africa) and kwongan (Australia). We explore the ersity of P-acquisition strategies, highlighting one that has received little attention: acquisition of P following fires that temporarily enrich soil with P. This strategy is expressed by fire ephemerals as well as fast-resprouting perennial shrubs. A plant’s leaf manganese concentration ([Mn]) provides significant clues on P-acquisition strategies. High leaf [Mn] indicates carboxylate-releasing P-acquisition strategies, but other exudates may play the same role as carboxylates in P acquisition. Intermediate leaf [Mn] suggests facilitation of P acquisition by P-mobilising neighbours, through release of carboxylates or functionally similar compounds. Very low leaf [Mn] indicates that carboxylates play no immediate role in P acquisition. Release of phosphatases also represents a P-mining strategy, mobilising organic P. Some species may express multiple strategies, depending on time since germination or since fire, or on position in the landscape. In severely P-impoverished landscapes, photosynthetic P-use efficiency converges among species. Efficient species exhibit rapid rates of photosynthesis at low leaf P concentrations. A high P-remobilisation efficiency from senescing organs is another way to use P efficiently, as is extended longevity of plant organs. Many P-acquisition strategies coexist in P-impoverished landscapes, but P-use strategies tend to converge. Common strategies of which we know little are those expressed by ephemeral or perennial species that are the first to respond after a fire. We surmise that carboxylate-releasing P-mobilising strategies are far more widespread than envisaged so far, and likely expressed by species that accumulate metals, exemplified by Mn, metalloids, such as selenium, fluorine, in the form of fluoroacetate, or silicon. Some carboxylate-releasing strategies are likely important to consider when restoring sites in bio erse regions as well as in cropping systems on P-impoverished or strongly P-sorbing soils, because some species may only be able to establish themselves next to neighbours that mobilise P.

A new precipitation technique provides evidence for the permeability of Casparian bands to ions in young roots of corn (Zea mays L.) and rice (Oryza sativa L.)

Publisher: Wiley

Date: 26-08-2005

DOI: 10.1111/J.1365-3040.2005.01391.X

Mutation in Wilted Dwarf and Lethal 1 (WDL1) causes abnormal cuticle formation and rapid water loss in rice

Publisher: Springer Science and Business Media LLC

Date: 30-06-2010

DOI: 10.1007/S11103-010-9656-X

Abstract: Epidermal cell layers play important roles in plant defenses against various environmental stresses. Here we report the identification of a cuticle membrane mutant, wilted dwarf and lethal 1 (wdl1), from a rice T-DNA insertional population. The mutant is dwarf and die at seedling stage due to increased rates of water loss. Stomatal cells and pavement cells are smaller in the mutant, suggesting that WDL1 affects epidermal cell differentiation. T-DNA was inserted into a gene that encodes a protein belonging to the SGNH subfamily, within the GDSL lipase superfamily. The WDL1-sGFP signal coincided with the RFP signal driven by AtBIP-mRFP, indicating that WDL1 is an ER protein. SEM analyses showed that their leaves have a disorganized crystal wax layer. Cross-sectioning reveals loose packing of the cuticle and irregular thickness of cell wall. Detailed analyses of the epicuticular wax showed no significant changes either in the total amount and amounts of each monomer or in the levels of lipid polymers, including cutin and other covalently bound lipids, attached to the cell wall. We propose that WDL1 is involved in cutin organization, affecting depolymerizable components.

Suberin research in the genomics era—New interest for an old polymer

Publisher: Elsevier BV

Date: 03-2011

DOI: 10.1016/J.PLANTSCI.2010.11.003

Abstract: Suberin is an apoplastic biopolymer with tissue-specific deposition in the cell walls of the endo- and exodermis of roots, of periderms including wound periderm and other border tissues. Suberised cell walls contain both polyaliphatic and polyaromatic domains which are supposedly cross-linked. The predominant aliphatic components are ω-hydroxyacids, α,ω-diacids, fatty acids and primary alcohols, whereas hydroxycinnamic acids, especially ferulic acid, are the main components of the polyaromatic domain. Although the monomeric composition of suberin has been known for decades, its biosynthesis and deposition has mainly been a subject of speculation. Only recently, significant progress elucidating suberin biosynthesis has been achieved using molecular genetic approaches, especially in the model species Arabidopsis. In parallel, the long-standing hypothesis that suberin functions as an apoplastic barrier has been corroborated by sophisticated, quantitative physiological studies in the past decade. These studies demonstrated that suberised cell walls could act as barriers, minimising the movement of water and nutrients, restricting pathogen invasion and impeding toxic gas diffusion. In addition, suberised cell walls provide a barrier to radial oxygen loss from roots to the anaerobic root substrate in wetland plants. The recent onset of multidisciplinary approaches combining genetic, analytical and physiological studies has begun to deliver further insights into the physiological importance of suberin depositions in plants.

The carboxylate‐releasing phosphorus‐mobilizing strategy can be proxied by foliar manganese concentration in a large set of chickpea germplasm under low phosphorus supply

Publisher: Wiley

Date: 14-05-2018

DOI: 10.1111/NPH.15200

Abstract: Root foraging and root physiology such as exudation of carboxylates into the rhizosphere are important strategies for plant phosphorus (P) acquisition. We used 100 chickpea (Cicer arietinum) genotypes with erse genetic backgrounds to study the relative roles of root morphology and physiology in P acquisition. Plants were grown in pots in a low-P sterilized river sand supplied with 10 μg P g

Apoplastic water transport in roots

Publisher: Springer Netherlands

Date: 2007

DOI: 10.1007/978-1-4020-5843-1_9

Stagnant deoxygenated growth enhances root suberization and lignifications, but differentially affects water and NaCl permeabilities in rice (Oryza sativa L.) roots

Publisher: Wiley

Date: 21-04-2011

DOI: 10.1111/J.1365-3040.2011.02318.X

Abstract: It has been shown that rice roots grown in a stagnant medium develop a tight barrier to radial oxygen loss (ROL), whereas aerated roots do not. This study investigated whether the induction of a barrier to ROL affects water and solute permeabilities. Growth in stagnant medium markedly reduced the root growth rate relative to aerated conditions. Histochemical studies revealed an early deposition of Casparian bands (CBs) and suberin lamellae (SL) in both the endodermis (EN) and exodermis, and accelerated lignification of stagnant roots. The absolute amounts of suberin, lignin and esterified aromatics (coumaric and ferulic acid) in these barriers were significantly higher in stagnant roots. However, correlative permeability studies revealed that early deposition of barriers in stagnant roots failed to reduce hydraulic conductivity (Lp(r) ) below those of aerated roots. In contrast to Lp(r) , the NaCl permeability (P(sr) ) of stagnant roots was markedly lower than that of aerated roots, as indicated by an increased reflection coefficient (σ(sr) ). In stagnant roots, P(sr) decreased by 60%, while σ(sr) increased by 55%. The stagnant medium differentially affected the Lp(r) and P(sr) of roots, which can be explained in terms of the physical properties of the molecules used and the size of the pores in the apoplast.

Suberized transport barriers in Arabidopsis, barley and rice roots: From the model plant to crop species

Publisher: Elsevier BV

Date: 08-2018

DOI: 10.1016/J.JPLPH.2018.02.002

Abstract: Water is the most important prerequisite for life and plays a major role during uptake and transport of nutrients. Roots are the plant organs that take up the major part of water, from the surrounding soil. Water uptake is related to the root system architecture, root growth, age and species dependent complex developmental changes in the anatomical structures. The latter is mainly attributed to the deposition of suberized barriers in certain layers of cell walls, such as endo- and exodermis. With respect to water permeability, changes in the suberization of roots are most relevant. Water transport or hydraulic conductivity of roots (Lp

Edaphic niche characterization of four Proteaceae reveals unique calcicole physiology linked to hyper‐endemism of Grevillea thelemanniana

Publisher: Wiley

Date: 25-08-2020

DOI: 10.1111/NPH.16833

Abstract: Endemism and rarity have long intrigued scientists. We focused on a rare endemic and critically‐endangered species in a global bio ersity hotspot, Grevillea thelemanniana (Proteaceae). We carried out plant and soil analyses of four Proteaceae, including G. thelemanniana , and combined these with glasshouse studies. The analyses related to hydrology and plant water relations as well as soil nutrient concentrations and plant nutrition, with an emphasis on sodium (Na) and calcium (Ca). The local hydrology and matching plant traits related to water relations partially accounted for the distribution of the four Proteaceae. What determined the rarity of G. thelemanniana , however, was its accumulation of Ca. Despite much higher total Ca concentrations in the leaves of the rare G. thelemanniana than in the common Proteaceae, very few Ca crystals were detected in epidermal or mesophyll cells. Instead of crystals, G. thelemanniana epidermal cell vacuoles contained exceptionally high concentrations of noncrystalline Ca. Calcium ameliorated the negative effects of Na on the very salt‐sensitive G. thelemanniana . Most importantly, G. thelemanniana required high concentrations of Ca to balance a massively accumulated feeding‐deterrent carboxylate, trans ‐aconitate. This is the first ex le of a calcicole species accumulating and using Ca to balance accumulation of an antimetabolite.

Delayed leaf greening involves a major shift in the expression of cytosolic and mitochondrial ribosomes to plastid ribosomes in the highly phosphorus-use-efficient Hakea prostrata (Proteaceae)

Publisher: Springer Science and Business Media LLC

Date: 27-09-2023

DOI: 10.1007/S11104-023-06275-1

The composite water and solute transport of barley (Hordeum vulgare) roots: effect of suberized barriers

Publisher: Oxford University Press (OUP)

Date: 08-01-2017

DOI: 10.1093/AOB/MCW252

The chemical composition of suberin in apoplastic barriers affects radial hydraulic conductivity differently in the roots of rice (Oryza sativa L. cv. IR64) and corn (Zea mays L. cv. Helix)

Publisher: Oxford University Press (OUP)

Date: 04-04-2005

DOI: 10.1093/JXB/ERI144

Abstract: Apoplastic transport barriers in the roots of rice (Oryza sativa L. cv. IR64) and corn (Zea mays L. cv. Helix) were isolated enzymatically. Following chemical degradation (monomerization, derivatization), the amounts of aliphatic and aromatic suberin monomers were analysed quantitatively by gas chromatography and mass spectrometry. In corn, suberin was determined for isolated endodermal (ECW) and rhizo-hypodermal (RHCW) cell walls. In rice, the strong lignification of the central cylinder (CC), did not allow the isolation of endodermal cell walls. Similarly, exodermal walls could not be separated from the rhizodermal and sclerenchyma cell layers. Suberin analyses of ECW and RHCW of rice, thus, refer to either the entire CC or to the entire outer part of the root (OPR), the latter lacking the inner cortical cell layer. In both species, aromatic suberin was mainly composed of coumaric and ferulic acids. Aliphatic suberin monomers released from rice and corn belonged to five substance classes: primary fatty acids, primary alcohols, diacids, omega-hydroxy fatty acids, and 2-hydroxy fatty acids, with omega-hydroxy fatty acids being the most prominent substance class. Qualitative composition of aliphatic suberin of rice was different from that of corn (i) it was much less erse, and (ii) besides monomers with chain lengths of C(16), a second maximum of C(28) was evident. In corn, C(24) monomers represented the most prominent class of chain lengths. When suberin quantities were related to surface areas of the respective tissues of interest (hypodermis and/or exodermis and endodermis), exodermal cell walls of rice contained, on average, six-times more aliphatic suberin than those of corn. In endodermal cell walls, amounts were 34 times greater in rice than in corn. Significantly higher amounts of suberin detected in the apoplastic barriers of rice corresponded with a substantially lower root hydraulic conductivity (Lp(r)) compared with corn, when water flow was driven by hydrostatic pressure gradients across the apoplast. As the OPR of rice is highly porous and permeable to water, it is argued that this holds true only for the endodermis. The results imply that some caution is required when discussing the role of suberin in terms of an efficient transport barrier for water. The simple view that only the quantity of suberin present is important, may not hold. A more detailed consideration of both the chemical nature of suberins and of the microstructure of deposits is required, i.e. how suberins impregnate wall pores.

A cool spot in a biodiversity hotspot: why do tall Eucalyptus forests in Southwest Australia exhibit low diversity?

Publisher: Springer Science and Business Media LLC

Date: 07-2022

DOI: 10.1007/S11104-022-05559-2

Abstract: Southwest Australia is a bio ersity hotspot, with greatest plant species ersity on the most severely phosphorus (P)-impoverished soils. Here, non-mycorrhizal species with highly-effective carboxylate-releasing P-acquisition strategies coexist with mycorrhizal species that are less effective at accessing P on these soils. Non-mycorrhizal carboxylate-releasing species facilitate P acquisition of mycorrhizal neighbours that are better defended against pathogens. In the Southwest Australian Bio ersity Hotspot, there are also ‘cool spots’ of low- ersity tall mycorrhizal Eucalyptus communities on P-impoverished soils. These Eucalyptus trees obviously do not require facilitation of their P acquisition by carboxylate-releasing neighbours, because these are only a minor component of the low- ersity communities. We hypothesised that in low- ersity tall Eucalyptus forests, mycorrhizal species release carboxylates to acquire P. Thus, they would not depend on facilitation, and must be strong competitors. However, because they would not depend on external mycorrhizal hyphae to acquire P, they would also not be able to access soil organic nitrogen (N), for which they would need external hyphae. Since carboxylates not only mobilise P, but also manganese (Mn), we used leaf Mn concentrations ([Mn]) in the natural habitat to proxy rhizosphere carboxylates. To verify this proxy, we also measured carboxylate exudation of targeted species with high leaf [Mn] using seedlings grown in low-P nutrient solutions. Using these complementary approaches, we confirmed our hypothesis that dominant Eucalyptus species in ‘cool spots’ release carboxylates. Since mineralisation of organic N is associated with fractionation of N, enriching organic N with 15 N while nitrate is depleted in 15 N, we measured the stable N isotope composition of leaf material. The results show that dominant Eucalyptus species did not access organic N, despite being ectomycorrhizal. The low ersity of tall Eucalyptus forests in southwest Australia can be explained by dominant mycorrhizal species exhibiting a carboxylate-releasing strategy. The tall eucalypts are therefore strong competitors that do not require facilitation, but also do not access organic N.

RCN1/OsABCG5, an ATP‐binding cassette (ABC) transporter, is required for hypodermal suberization of roots in rice (Oryza sativa)

Publisher: Wiley

Date: 13-08-2014

DOI: 10.1111/TPJ.12614

Abstract: Suberin is a complex polymer composed of aliphatic and phenolic compounds. It is a constituent of apoplastic plant interfaces. In many plant species, including rice (Oryza sativa), the hypodermis in the outer part of roots forms a suberized cell wall (the Casparian strip and/or suberin lamellae), which inhibits the flow of water and ions and protects against pathogens. To date, there is no genetic evidence that suberin forms an apoplastic transport barrier in the hypodermis. We discovered that a rice reduced culm number1 (rcn1) mutant could not develop roots longer than 100 mm in waterlogged soil. The mutated gene encoded an ATP-binding cassette (ABC) transporter named RCN1/OsABCG5. RCN1/OsABCG5 gene expression in the wild type was increased in most hypodermal and some endodermal roots cells under stagnant deoxygenated conditions. A GFP-RCN1/OsABCG5 fusion protein localized at the plasma membrane of the wild type. Under stagnant deoxygenated conditions, well suberized hypodermis developed in wild types but not in rcn1 mutants. Under stagnant deoxygenated conditions, apoplastic tracers (periodic acid and berberine) were blocked at the hypodermis in the wild type but not in rcn1, indicating that the apoplastic barrier in the mutant was impaired. The amount of the major aliphatic suberin monomers originating from C(28) and C(30) fatty acids or ω-OH fatty acids was much lower in rcn1 than in the wild type. These findings suggest that RCN1/OsABCG5 has a role in the suberization of the hypodermis of rice roots, which contributes to formation of the apoplastic barrier.

Nitrate-uptake restraint in Banksia spp. (Proteaceae) and Melaleuca spp. (Myrtaceae) from a severely phosphorus-impoverished environment

Publisher: Springer Science and Business Media LLC

Date: 20-05-2022

DOI: 10.1007/S11104-022-05477-3

Abstract: South-western Australia has some of the most phosphorus (P)-impoverished soils in the world. Hakea prostrata (Proteaceae) has nitrate (NO 3 − )-uptake restraint, associated with its high P-use efficiency. This research explores how common this trait is in other Proteaceae and in co-occurring plant species in south-western Australia. Banksia attenuata (Proteaceae), B. telmatiaea (Proteaceae), Melaleuca seriata (Myrtaceae) and M. rhaphiophylla (Myrtaceae) were grown with no NO 3 − , Medium (500 µM) NO 3 − or High (2500 µM) NO 3 − treatments with no other source of nitrogen (N). Plants were harvested after treatments. Leaf nitrate and phosphate concentrations were determined, as well as biomass, total N and total P concentrations of leaves, stems and roots separately. Banksia attenuata , B. telmatiaea and M. seriata had similar total N content when supplied with High NO 3 − as they did when supplied with Medium NO 3 − . All four species had the same low leaf NO 3 − -N concentration in High and Medium NO 3 − treatments, no more than 6% of leaf total N. All species had similar leaf NO 3 − concentrations as those of plants growing in their natural habitat where the available soil nitrate concentration was much lower. These results are in sharp contrast with plants that are typically studied, for ex le Arabidopsis thaliana . All four species exhibited NO 3 − -uptake restraint to different degrees. Nitrate-uptake restraint appears a convergent trait common to many species that evolved in severely P-impoverished landscapes, allowing them to be more P-efficient.

The Rice R2R3-MYB Transcription Factor OsMYB55 Is Involved in the Tolerance to High Temperature and Modulates Amino Acid Metabolism

Publisher: Public Library of Science (PLoS)

Date: 14-12-2012

DOI: 10.1371/JOURNAL.PONE.0052030

AMT1;1 transgenic rice plants with enhanced NH4 permeability show superior growth and higher yield under optimal and suboptimal NH4 conditions

Publisher: Oxford University Press (OUP)

Date: 13-01-2014

DOI: 10.1093/JXB/ERT458

Delayed greening in phosphorus-efficient Hakea prostrata (Proteaceae) is a photoprotective and nutrient-saving strategy

Publisher: CSIRO Publishing

Date: 2021

DOI: 10.1071/FP19285

Abstract: Hakea prostrata R.Br. (Proteaceae) shows a ‘delayed greening’ strategy of leaf development characterised by reddish young leaves that become green as they mature. This trait may contribute to efficient use of phosphorus (P) during leaf development by first investing P in the development of leaf structure followed by maturation of the photosynthetic machinery. In this study, we investigated the properties of delayed greening in a highly P-efficient species to enhance our understanding of the ecological significance of this trait as a nutrient-saving and photoprotective strategy. In glasshouse-grown plants, we assessed foliar pigments, fatty acids and nutrient composition across five leaf developmental stages. Young leaves had higher concentrations of anthocyanin, P, nitrogen (N), copper (Cu), xanthophyll-cycle pigments and saturated fatty acids than mature leaves. As leaves developed, the concentration of anthocyanins decreased, whereas that of chlorophyll and the double bond index of fatty acids increased. In mature leaves, ~60% of the fatty acids was α-linolenic acid (C18:3 n-3). Mature leaves also had higher concentrations of aluminium (Al), calcium (Ca) and manganese (Mn) than young leaves. We conclude that delayed greening in H. prostrata is a strategy that saves P as well as N and Cu through sequential allocation of these resources, first to cell production and structural development, and then to supplement chloroplast development. This strategy also protects young leaves against photodamage and oxidative stress during leaf expansion under high-light conditions.

Root apoplastic barriers block Na+ transport to shoots in rice (Oryza sativa L.)

Publisher: Oxford University Press (OUP)

Date: 09-05-2011

DOI: 10.1093/JXB/ERR135

Water and solute permeabilities of Arabidopsis roots in relation to the amount and composition of aliphatic suberin

Publisher: Oxford University Press (OUP)

Date: 03-2011

DOI: 10.1093/JXB/ERQ389

Populus × canescens root suberization in reaction to osmotic and salt stress is limited to the developing younger root tip region

Publisher: Wiley

Date: 09-2022

DOI: 10.1111/PPL.13765

Abstract: Populus is a valuable and fast‐growing tree species commonly cultivated for economic and scientific purposes. But most of the poplar species are sensitive to drought and salt stress. Thus, we compared the physiological effects of osmotic stress (PEG8000) and salt treatment (NaCl) on poplar roots to identify potential strategies for future breeding or genetic engineering approaches. We investigated root anatomy using epifluorescence microscopy, changes in root suberin composition and amount using gas chromatography, transcriptional reprogramming using RNA sequencing, and modifications of root transport physiology using a pressure chamber. Poplar roots reacted to the imposed stress conditions, especially in the developing younger root tip region, with remarkable differences between both types of stress. Overall, the increase in suberin content was surprisingly small, but the expression of key suberin biosynthesis genes was strongly induced. Significant reductions of the radial water transport in roots were only observed for the osmotic and not the hydrostatic hydraulic conductivity. Our data indicate that the genetic enhancement of root suberization processes in poplar might be a promising target to convey increased tolerance, especially against toxic sodium chloride.

Seminal roots of wild and cultivated barley differentially respond to osmotic stress in gene expression, suberization, and hydraulic conductivity

Publisher: Wiley

Date: 24-11-2019

DOI: 10.1111/PCE.13675

Abstract: Wild barley, Hordeum vulgare spp. spontaneum, has a wider genetic ersity than its cultivated progeny, Hordeum vulgare spp. vulgare. Osmotic stress leads to a series of different responses in wild barley seminal roots, ranging from no changes in suberization to enhanced endodermal suberization of certain zones and the formation of a suberized exodermis, which was not observed in the modern cultivars studied so far. Further, as a response to osmotic stress, the hydraulic conductivity of roots was not affected in wild barley, but it was 2.5-fold reduced in cultivated barley. In both subspecies, osmotic adjustment by increasing proline concentration and decreasing osmotic potential in roots was observed. RNA-sequencing indicated that the regulation of suberin biosynthesis and water transport via aquaporins were different between wild and cultivated barley. These results indicate that wild barley uses different strategies to cope with osmotic stress compared with cultivated barley. Thus, it seems that wild barley is better adapted to cope with osmotic stress by maintaining a significantly higher hydraulic conductivity of roots during water deficit.

Ammonium-induced architectural and anatomical changes with altered suberin and lignin levels significantly change water and solute permeabilities of rice (Oryza sativa L.) roots

Publisher: Springer Science and Business Media LLC

Date: 18-09-2015

DOI: 10.1007/S00425-015-2406-1

Abstract: Non-optimal ammonium levels significantly alter root architecture, anatomy and root permeabilities for water and nutrient ions. Higher ammonium levels induced strong apoplastic barriers whereas it was opposite for lower levels. Application of nitrogen fertilizer increases crop productivity. However, non-optimal applications can have negative effects on plant growth and development. In this study, we investigated how different levels of ammonium (NH4 (+)) [low (30 or 100 μM) or optimum (300 μM) or high (1000 or 3000 μM)] affect physio-chemical properties of 1-month-old, hydroponically grown rice roots. Different NH4 (+) treatments markedly altered the root architecture and anatomy. Plants grown in low NH4 (+) had the longest roots with a weak deposition of suberised and lignified apoplastic barriers, and it was opposite for plants grown in high NH4 (+). The relative expression levels of selected suberin and lignin biosynthesis candidate genes, determined using qRT-PCR, were lowest in the roots from low NH4 (+), whereas, they were highest for those grown in high NH4 (+). This was reflected by the suberin and lignin contents, and was significantly lower in roots from low NH4 (+) resulting in greater hydraulic conductivity (Lp r) and solute permeability (P sr) than roots from optimum NH4 (+). In contrast, roots grown at high NH4 (+) had markedly greater suberin and lignin contents, which were reflected by strong barriers. These barriers significantly decreased the P sr of roots but failed to reduce the Lp r below those of roots grown in optimum NH4 (+), which can be explained in terms of the physical properties of the molecules used and the size of pores in the apoplast. It is concluded that, in rice, non-optimal NH4 (+) levels differentially affected root properties including Lp r and P sr to successfully adapt to the changing root environment.

Altered Expression of OsNLA1 Modulates Pi Accumulation in Rice (Oryza sativa L.) Plants

Publisher: Frontiers Media SA

Date: 02-06-2017

DOI: 10.3389/FPLS.2017.00928

The intersection of nitrogen nutrition and water use in plants: new paths toward improved crop productivity

Publisher: Oxford University Press (OUP)

Date: 06-02-2020

DOI: 10.1093/JXB/ERAA049

Abstract: Water and nitrogen availability limit crop productivity globally more than most other environmental factors. Plant availability of macronutrients such as nitrate is, to a large extent, regulated by the amount of water available in the soil, and, during drought episodes, crops can become simultaneously water and nitrogen limited. In this review, we explore the intricate relationship between water and nitrogen transport in plants, from transpiration-driven mass flow in the soil to uptake by roots via membrane transporters and channels and transport to aerial organs. We discuss the roles of root architecture and of suberized hydrophobic root barriers governing apoplastic water and nitrogen movement into the vascular system. We also highlight the need to identify the signalling cascades regulating water and nitrogen transport, as well as the need for targeted physiological analyses of plant traits influencing water and nitrogen uptake. We further advocate for incorporation of new phenotyping technologies, breeding strategies, and agronomic practices to improve crop yield in water- and nitrogen-limited production systems.

Overexpression of ANAC046 Promotes Suberin Biosynthesis in Roots of Arabidopsis thaliana

Publisher: MDPI AG

Date: 04-12-2019

DOI: 10.3390/IJMS20246117

Abstract: NAC (NAM (no apical meristem), ATAF1/2, and CUC2 (cup-shaped cotyledon)) proteins are one of the largest families of plant-specific transcription factors, and this family is present in a wide range of land plants. Here, we have investigated the role of ANAC046 in the regulation of suberin biosynthesis and deposition in Arabidopsis. Subcellular localization and transcriptional activity assays showed that ANAC046 localizes in the nucleus, where it functions as a transcription activator. Analysis of the PANAC046:GUS lines revealed that ANAC046 is mainly expressed in the root endodermis and periderm, and is also induced in leaves by wounding. The transgenic lines overexpressing ANAC046 exhibited defective surfaces on the aerial plant parts compared to the wild-type (WT) as characterized by increased permeability for Toluidine blue stain and greater chlorophyll leaching. Quantitative RT-PCR analysis showed that the expression of suberin biosynthesis genes was significantly higher in the roots and leaves of overexpression lines compared to the WT. The biochemical analysis of leaf cuticular waxes showed that the overexpression lines accumulated 30% more waxes than the WT. Concurrently, overexpression lines also deposited almost twice the amount of suberin content in their roots compared with the WT. Taken together, these results showed that ANAC046 is an important transcription factor that promotes suberin biosynthesis in Arabidopsis thaliana roots.

Leaf phosphorus allocation to chemical fractions and its seasonal variation in south-western Australia is a species-dependent trait

Publisher: Elsevier BV

Date: 11-2023

DOI: 10.1016/J.SCITOTENV.2023.166395

Wax Crystal-Sparse Leaf1 encodes a beta-ketoacyl CoA synthase involved in biosynthesis of cuticular waxes on rice leaf

Publisher: Springer Science and Business Media LLC

Date: 24-06-2008

DOI: 10.1007/S00425-008-0770-9

Osmotic stress enhances suberization of apoplastic barriers in barley seminal roots: analysis of chemical, transcriptomic and physiological responses

Publisher: Wiley

Date: 28-07-2018

DOI: 10.1111/NPH.15351

Defective Pollen WallIs Required for Anther and Microspore Development in Rice and Encodes a Fatty Acyl Carrier Protein Reductase    

Publisher: Oxford University Press (OUP)

Date: 06-2011

DOI: 10.1105/TPC.111.087528

Abstract: Aliphatic alcohols naturally exist in many organisms as important cellular components however, their roles in extracellular polymer biosynthesis are poorly defined. We report here the isolation and characterization of a rice (Oryza sativa) male-sterile mutant, defective pollen wall (dpw), which displays defective anther development and degenerated pollen grains with an irregular exine. Chemical analysis revealed that dpw anthers had a dramatic reduction in cutin monomers and an altered composition of cuticular wax, as well as soluble fatty acids and alcohols. Using map-based cloning, we identified the DPW gene, which is expressed in both tapetal cells and microspores during anther development. Biochemical analysis of the recombinant DPW enzyme shows that it is a novel fatty acid reductase that produces 1-hexadecanol and exhibits & -fold higher specificity for palmiltoyl-acyl carrier protein than for C16:0 CoA substrates. DPW was predominantly targeted to plastids mediated by its N-terminal transit peptide. Moreover, we demonstrate that the monocot DPW from rice complements the dicot Arabidopsis thaliana male sterile2 (ms2) mutant and is the probable ortholog of MS2. These data suggest that DPWs participate in a conserved step in primary fatty alcohol synthesis for anther cuticle and pollen sporopollenin biosynthesis in monocots and dicots.

Blockage of apoplastic bypass-flow of water in rice roots by insoluble salt precipitates analogous to a Pfeffer cell

Publisher: Wiley

Date: 15-11-2005

DOI: 10.1111/J.1365-3040.2004.01245.X

Apoplastic barriers effectively block oxygen permeability across outer cell layers of rice roots under deoxygenated conditions: Roles of apoplastic pores and of respiration

Publisher: Wiley

Date: 18-09-2009

DOI: 10.1111/J.1469-8137.2009.03021.X

Abstract: *Despite the importance of the barrier to oxygen losses of the roots of hygrophytes growing in wet environments devoid of oxygen, there are few data available on permeability coefficients for O(2) across outer root cell layers (P(OPR)) and how they may change in response to low O(2). *A gas perfusion technique was used to measure the P(OPR) of rice (Oryza sativa) plants grown in either aerated or deoxygenated solution. The contributions of the apoplast and of living cells to the overall P(OPR) were characterized either by blocking apoplastic pores with precipitates of brown Cu(2)[Fe(CN)(6)] or by killing cells with 0.1 N HCl. *Compared with that of plants from aerated hydroponics, the P(OPR) of plants grown in deoxygenated medium was smaller by an order of magnitude. Precipitates resulting from CuSO(4)/K(4)[Fe(CN)(6)] treatment only formed in plants grown in aerated solution, where they reduced the P(OPR) by 5-20%. Killing of root segments with HCl increased P(OPR) in plants grown in both conditions by 20-55%. *The results indicated that apoplastic barriers effectively restricted radial O(2) loss. The relative role of the respiratory O(2) consumption of root peripheral layers increased as P(OPR) decreased.

Facilitation of phosphorus acquisition by Banksia attenuata allows Adenanthos cygnorum (Proteaceae) to extend its range into severely phosphorus-impoverished habitats

Publisher: Springer Science and Business Media LLC

Date: 21-02-2023

DOI: 10.1007/S11104-023-05935-6

Abstract: In extremely low-phosphorus (P) environments, most Proteaceae exude carboxylates from cluster roots. These carboxylates mobilise inorganic P which leads to a relatively high leaf manganese concentration ([Mn]). However, we found that Adenanthos cygnorum (Proteaceae) in a low-P habitat did not invariably have a high leaf [Mn] in south-western Australia. We aimed to explore how A. cygnorum acquires P in severely P-impoverished habitats. We determined soil P concentrations and leaf [Mn] of A. cygnorum growing within 1 m and more than 10 m away from other large Proteaceae. We also grew plants in a glasshouse to determine its root carboxylate exudation and rhizosheath phosphatase activity. Adenanthos cygnorum did not produce functional cluster roots. It depended on carboxylates released by a P-mobilising neighbour, Banksia attenuata (Proteaceae), to acquire P when growing in severely P-impoverished soil ( 8 mg P kg − 1 dry soil). In slightly less P-impoverished soil ( 11 mg P kg − 1 dry soil), phosphatases released by A. cygnorum hydrolysed sufficient organic P that was relatively mobile. The reliance on facilitation of P acquisition in A cygnorum depended strongly on location. We demonstrated the exudation of phosphatases, which mobilise inorganic P this P was adequate for growth when there was sufficient organic P in soil. Facilitation of P acquisition by B. attenuata allowed A. cygnorum to extend its range into severely P-impoverished habitats where it cannot exist without facilitation. This knowledge provides a better understanding of the ersity of P-acquisition strategies in severely P-impoverished environments.

ABCG Transporters Are Required for Suberin and Pollen Wall Extracellular Barriers inArabidopsis   

Publisher: Oxford University Press (OUP)

Date: 09-2014

DOI: 10.1105/TPC.114.129049

Abstract: Effective regulation of water balance in plants requires localized extracellular barriers that control water and solute movement. We describe a clade of five Arabidopsis thaliana ABCG half-transporters that are required for synthesis of an effective suberin barrier in roots and seed coats (ABCG2, ABCG6, and ABCG20) and for synthesis of an intact pollen wall (ABCG1 and ABCG16). Seed coats of abcg2 abcg6 abcg20 triple mutant plants had increased permeability to tetrazolium red and decreased suberin content. The root system of triple mutant plants was more permeable to water and salts in a zone complementary to that affected by the Casparian strip. Suberin of mutant roots and seed coats had distorted lamellar structure and reduced proportions of aliphatic components. Root wax from the mutant was deficient in alkylhydroxycinnamate esters. These mutant plants also had few lateral roots and precocious secondary growth in primary roots. abcg1 abcg16 double mutants defective in the other two members of the clade had pollen with defects in the nexine layer of the tapetum-derived exine pollen wall and in the pollen-derived intine layer. Mutant pollen collapsed at the time of anther desiccation. These mutants reveal transport requirements for barrier synthesis as well as physiological and developmental consequences of barrier deficiency.

Phosphorus fractions in leaves

Publisher: Wiley

Date: 02-12-2023

DOI: 10.1111/NPH.18588

Abstract: Leaf phosphorus (P) comprises four major fractions: inorganic phosphate (P i ), nucleic acids, phospholipids, P‐containing metabolites and a residual fraction. In this review paper, we investigated whether allocation of P fractions varies among groups of terrestrial vascular plants, and is indicative of a species' strategy to use P efficiently. We found that as leaf total P concentration increases, the P i fraction increases the most, without a plateau, while other fractions plateau. Variability of the concentrations of leaf P fractions is greatest among families species(family) regions plant life forms. The percentage of total P allocated to nucleic acid‐P (20–35%) and lipid‐P (14–34%) varies less among families/species. High photosynthetic P‐use efficiency is associated with low concentrations of all P fractions, and preferential allocation of P to metabolite‐P and mesophyll cells. Sequential resorption of P from senescing leaves starts with P i , followed by metabolite‐P, and then other organic P fractions. Allocation of P to leaf P fractions varies with season. Leaf phytate concentrations vary considerably among species, associated with variation in photosynthesis and defence. Plasticity of P allocation to its fractions is important for acclimation to low soil P availability, and species‐specific P allocation is needed for co‐occurrence with other species.

University Of Waterloo Faculty Of Science

Location: Canada

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University Of Peradeniya Faculty Of Agriculture

Location: Sri Lanka

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University Of Guelph

Location: Canada

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University Of Bayreuth

Location: Germany

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University Of Western Australia

Location: Australia

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Rheinische Friedrich-Wilhelms-Universität Bonn

Location: Germany

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Max Planck Institute For Plant Breeding, Cologne, Germany

Location: Germany

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Discovery Projects - Grant ID: DP220100494

Start Date: 07-2022

End Date: 06-2025

Amount: $563,520.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230101190

Start Date: 2023

End Date: 12-2025

Amount: $520,088.00

Funder: Australian Research Council

ARC Future Fellowships - Grant ID: FT170100195

Start Date: 10-2017

End Date: 09-2022

Amount: $757,000.00

Funder: Australian Research Council