Orange Seedlings Research Articles

Response of three citrus genotypes used as rootstocks grown under boron excess conditions

In citrus, the effects of an excess of boron (B) are conditioned by the type of rootstock. In the present work, the morphological, physiological and biochemical responses of seedlings from three citrus genotypes, commonly used as rootstocks in citriculture. In particular, Citrange Carrizo (CC), Citrus macrophylla (CM) and sour orange (SO) seedlings were treated with an excess of B (10 mg L−1) in the nutrient solution in order to determine the relative tolerance and to understand the possible mechanisms that make a rootstock more tolerant than the others. To assess these responses, different parameters were measured in plants, such as vegetative growth, B concentration in leaves, stems and roots, gas exchange and chlorophyll fluorescence, the concentration of osmolytes and the activity of enzymes related to the antioxidant system. The results showed, according to the growth parameters, that the SO rootstock was the most tolerant to an excess of B; while CC was the most sensitive. This result was due to the fact that SO plants accumulated less B in leaves, as its roots have a great capacity of restricting the uptake and transport of B towards the aerial part. Moreover, SO is suggested to diminish B toxicity risk through its antioxidant system, since it presented high activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD), as well as high accumulation of quaternary ammonium compounds (QACs).

Mycorrhiza-induced change in root hair growth is associated with IAA accumulation and expression of EXPs in trifoliate orange under two P levels

Abstract Root hair growth can be regulated by substrate nutrient levels, phytohormones, and arbuscular mycorrhizal (AM) fungi. However, the information about effects of AM fungi and substrate phosphorus (P) levels on root hair features is scarce. This study evaluated the effect of an AM fungus, Funneliformis mosseae, on root hair morphology, root indole-3-acetic acid (IAA) level, indole-3-acetic acid oxidase (IAAO) activity, and expressions of auxin-related genes and expansins (EXPs) in trifoliate orange (Poncirus trifoliata) seedlings under 0.1 mM (P0.1) and 1.0 mM (P1) P levels for 16 weeks. AM seedlings showed better root colonization under P0.1 than under P1. Under P0.1 and P1, mycorrhizal seedlings recorded higher concentrations of P and IAA and lower IAAO activity in roots than non-mycorrhizal seedlings. Root hair density was significantly higher in AM seedlings under P0.1 but dramatically lower under P1 than non-AM seedlings. Root hair length and diameter of AM seedlings were significantly increased under P1 only, relative to non-AM seedlings. Indole-3-pyruvate monooxygenase (PtYUC2) and auxin transporter-like protein 3 (PtLAX3) expressions in roots were significantly up-regulated by mycorrhizal treatment under both P0.1 and P1. The transcript levels of root auxin efflux carrier component 2 and 8 (PtPIN2 and PtPIN8) were dramatically down-regulated by mycorrhizal inoculation, irrespective of P levels. Root PtEXPB2, PtEXPA2, and PtEXPA4 expressions were notably up-regulated by mycorrhiza under P0.1 but down-regulated under P1. These results indicated that mycorrhiza-induced changes in root hair growth is closely related with up-regulated expressions of EXPs and simultaneous IAA accumulation in roots.

Exogenous Carbon Magnifies Mycorrhizal Effects on Growth Behaviour and Sucrose Metabolism in Trifoliate Orange

Arbuscular mycorrhizas (AMs) need the carbohydrates from host plants for its growth, whereas it is not clear whether exogenous carbon affects mycorrhizal roles. A two-chambered rootbox was divided into root + hyphae chamber and hyphae chamber (free of roots) by 37-μm nylon mesh, in which trifoliate orange (Poncirus trifoliata) seedlings and Funneliformis mosseae were applied into root + hyphae chamber, and exogenous 40 mmol/L fructose, glucose and sucrose was applied to hyphae chamber. Application of exogenous sugars dramatically elevated root mycorrhizal colonization. Sole arbuscular mycorrhizal fungi (AMF) inoculation significantly promoted plant growth and root morphology than non-AMF treatment. Mycorrhiza-improved plant growth and root modification could be enlarged by exogenous carbon, especially fructose. Exogenous carbon markedly increased root fructose, glucose and sucrose accumulation in mycorrhizal plants, especially sucrose. Exogenous fructose significantly reduced leaf and root sucrose synthase (SS) activity in synthesis direction and increased them in cleavage direction in AMF seedlings. Exogenous glucose and sucrose heavily elevated root SS activity of mycorrhizal seedlings in synthesis and cleavage direction and reduced leaf SS activity in synthesis direction. Leaf acid invertase (AI) and neutral invertase (NI) activities of mycorrhizal seedlings were decreased by exogenous carbon, except sucrose in NI. Exogenous fructose significantly increased root AI and NI activity in mycorrhizal plants. These results implied that mycorrhizal inoculation represented positive effects on plant growth, root morphology, and sucrose metabolism of trifoliate orange, which could be magnified further by exogenous carbon, especially fructose.

Enhancement of Drought Tolerance in Trifoliate Orange by Mycorrhiza: Changes in Root Sucrose and Proline Metabolisms

Sucrose and proline metabolisms are often associated with drought tolerance of plants. This study was conducted to investigate the effects of two arbuscular mycorrhizal fungi (AMF) species (Funneliformis mosseae and Paraglomus occultum) on root biomass, lateral root number, root sucrose and proline metabolisms in trifoliate orange (Poncirus trifoliata) seedlings under well-watered (WW) or drought stress (DS). All the AMF treatments significantly increased root dry weight, taproot length, and the number of lateral roots in 1st, 2nd, and 3rd class under WW and DS. Mycorrhizal seedlings conferred considerably higher fructose and glucose concentrations but lower sucrose accumulation, regardless of soil water status. Under DS, F. mosseae treatment significantly increased root sucrose synthase (SS, degradative direction) and sucrose phosphate synthase (SPS) activity but deceased root acid invertase (AI) and neutral invertase (NI) activity, and P. occultum inoculation markedly increased root AI, NI, SS, and SPS activities. AMF treatments led to a lower proline accumulation in roots, in company with lower activities of Δ1-pyrroline-5-carboxylate synthetase (P5CS), δ-ornithine aminotransferase (OAT), Δ1-pyrroline-5-carboxylate reductase (P5CR), and proline dehydrogenase (ProDH) in roots. It appears that the AM symbiosis induced greater root development and sucrose and proline metabolisms to adapt DS.

Production efficiency and quality in seedlings of the ‘Pera’ orange interstocked with nucellar plantlet tissue

Production of interstocked seedlings of the ‘Pera’ orange can be achieved through inarching of a rootstock on nucellar seedlings, with the subsequent grafting of a new scion. By this process, the interstocked seedling can be obtained in less time, but production efficiency is low, and no data on quality standards are available. The aim of this study was to evaluate the quality, time and production efficiency of ‘Pera’ orange (PO) seedlings interstocked with two types of nucellar plantlet tissue, using the ‘Flying Dragon’ trifoliate as rootstock. The experimental design was of randomised blocks, with four treatments, six replications and ten plants per plot. For the technique employed, nucellar plantlets of the ‘Seleta’ orange (SO) or Rangpur Lime (RL) were selected, followed by inarching with ‘Flying Dragon’ rootstock (FD) and budding with scions of the ‘Pera’ orange. The treatments consisted of different interstock combinations, PO/SO/FD and PO/RL/FD, and of non-interstock seedling combinations, PO/RL and SO/FD. Seedlings of the ‘Pera’ orange produced with interstocks of nucellar plantlets of the Rangpur Lime give seedling architecture of better quality. The interstocked seedlings were obtained 17 months after sowing the FD, with standards of physical quality similar to those required for commercial production, and with a production efficiency greater than 80%. When grown alone, FD requires more time to reach a sufficient diameter for grafting, delaying the production of seedlings.

Development and Characterization of Needle‐type Ion‐selective Microsensors for in situ Determination of Foliar Uptake of Zn2+ in Citrus Plants

AbstractFor over a decade, the incidence of Huanglongbing (HLB) has grown at an alarming rate, affecting citrus crops worldwide. Current methods of nutrient therapy have little to no effect in alleviating symptoms of HLB, and scarce research has been put forth towards non‐destructive tools for monitoring zinc transport in citrus plants. Here, we have developed and characterized a solid contact micro‐ion‐selective electrode (SC‐μ‐ISE) for the determination of zinc transport in sour orange seedlings using a non‐invasive microelectrode ion flux estimation (MIFE) technique. The SC‐μ‐ISE displayed a 26.05±0.13 mV decade−1 Nernstian response and a LOD of (3.96±2.09)×10−7 M. Results showed a significant Zn2+ uptake in the leaves and roots of sour orange seedlings when bulk concentrations were higher than 5.99 mM. Above this concentration, a linear relationship between flux and bulk Zn2+ concentration was observed. This relationship suggests passive diffusion may be a key mechanism for Zn transport into plants. Overall, this study is the first to use a Zn2+ SC‐μ‐ISE for the determination of ion transport processes in plants. This novel tool can be used to further knowledge the effect of nutrient therapy and disease progression on HLB infected citrus plants.

Arbuscular Mycorrhizal Fungus Enhances Lateral Root Formation in Poncirus trifoliata (L.) as Revealed by RNA-Seq Analysis

Arbuscular mycorrhizal fungi (AMF) establish symbiosis with most terrestrial plants, and greatly regulate lateral root (LR) formation. Phosphorus (P), sugar, and plant hormones are proposed being involved in this regulation, however, no global evidence regarding these factors is available so far, especially in woody plants. In this study, we inoculated trifoliate orange seedlings (Poncirus trifoliata L. Raf) with an AMF isolate, Rhizophagus irregularis BGC JX04B. After 4 months of growth, LR formation was characterized, and sugar contents in roots were determined. RNA-Seq analysis was performed to obtain the transcriptomes of LR root tips from non-mycorrhizal and mycorrhizal seedlings. Quantitative real time PCR (qRT-PCR) of selected genes was also conducted for validation. The results showed that AMF significantly increased LR number, as well as plant biomass and shoot P concentration. The contents of glucose and fructose in primary root, and sucrose content in LR were also increased. A total of 909 differentially expressed genes (DEGs) were identified in response to AMF inoculation, and qRT-PCR validated the transcriptomic data. The numbers of DEGs related to P, sugar, and plant hormones were 31, 32, and 25, respectively. For P metabolism, the most up-regulated DEGs mainly encoded phosphate transporter, and the most down-regulated DEGs encoded acid phosphatase. For sugar metabolism, the most up-regulated DEGs encoded polygalacturonase and chitinase. For plant hormones, the most up-regulated DEGs were related to auxin signaling, and the most down-regulated DEGs were related to ethylene signaling. PLS-SEM analysis indicates that P metabolism was the most important pathway by which AMF regulates LR formation in this study. These data reveal the changes of genome-wide gene expression in responses to AMF inoculation in trifoliate orange and provide a solid basis for the future identification and characterization of key genes involved in LR formation induced by AMF.

Quantitative estimation of water uptake by mycorrhizal extraradical hyphae in citrus under drought stress

Abstract Mycorrhizal hyphae have the functioning on water absorption from soil, while the information regarding hyphal water absorption rate is not fully known. In this study, 37-μm nylon meshes were positioned in a pot bottom to allow mycorrhizal extraradical hyphae, but not roots, to pass through the mesh. The whole pot was placed in a beaker, where distilled water was supplied, reaching a 0.5-cm air gap between the pot bottom and water surface of the beaker. Citrus rootstock, trifoliate orange (Poncirus trifoliata) seedlings of pots were inoculated with Funneliformis mosseae and Paraglomus occultum and also exposed to well-watered (WW) and drought stress (DS). The 71-days soil DS significantly inhibited root mycorrhizal colonization and hyphal length in soil and mesh, regardless of mycorrhizal fungal species. The hyphal water absorption rate was 0.607–1.973 mg H2O/h/mm for F. mosseae and 0.126–0.963 mg H2O/h/mm for P. occultum, respectively. The DS treatment significantly elevated hyphal water absorption rate by 2.3–6.6 times. The increase of leaf water potential by mycorrhization was higher under DS than under WW. Our results provide a quantitative estimation of water absorption rate by mycorrhizal extraradical hyphae and also suggest more important water contribution of hyphae to the host plant under DS than under WW.

Nitric Oxide Accelerates Mycorrhizal Effects on Plant Growth and Root Development of Trifoliate Orange

Arbuscular mycorrhizal fungi (AMF) actively colonize plant roots and thus enhance plant growth through different mechanisms. In the present study, trifoliate orange (Poncirus trifoliata) seedlings inoculated with Diversispora versiformis were subjected to 0 and 0.2 mmol/L sodium nitroprusside (SNP, a nitric oxide donor) treatments. After eight weeks, exogenous SNP considerably increased root mycorrhizal colonization by 25%, showing a positive stimulating effect of NO on mycorrhizal formation. Mycorrhizal inoculation significantly increased plant growth performance (height, stem diameter, leaf number and shoot and root dry weight) and root traits (length, projected area, surface area, volume and number of 2nd and 3rd order lateral roots) than non-mycorrhizal treatment and NO (exogenous SNP treatment) heavily strengthened the mycorrhizal effects. Moreover, NO and mycorrhization induced more fine root (0-0.5 cm) formation. There was an opposite changed trend in root sucrose and leaf and root glucose contents by SNP in AMF versus non-AMF seedlings. All these results implied that NO plays important roles in mycorrhizal formation and development and also accelerates mycorrhizal effects on plant growth and root development of trifoliate orange.

Environmental conditions for Diaphorina citri Kuwayama (Hemiptera: Liviidae) take‐off

AbstractEnvironmental factors that influence flight activity of Diaphorina citri Kuwayama (Hemiptera: Liviidae) may have implications for Huanglongbing spread and management. In this work, four studies were conducted to evaluate the effect of environmental conditions on D. citri take‐off. In the first, insects were transferred to sweet orange seedlings and confined inside an acrylic cage to verify the take‐off periodicity and the effect of environmental factors on this process. In the second, take‐off temperature threshold was estimated by recording the number of insects that initiated flight from a platform when subjected to gradual temperature increases from 15 to 39°C. In the other studies, we evaluated the effect of different photoperiods and temperature regimes (third study) and of constant temperatures (fourth study) on the propensity for D. citri flight. Insects were confined in clear plastic bottle cages with tubes of 50 ml placed on the cab, to collect emerged adults that initiated flights. Results showed that a small portion of the tested population (maximum 10%) tends to take off from plants and this behaviour is more prevalent in the afternoon (14:00–16:00 h), coinciding with daytimes of lower humidity and higher thermal amplitude. Adults that were submitted to lower temperatures (18°C) and short light periods (10 h) showed less propensity to flight. In contrast, at constant 27°C, the insects were more prone to flight, and this result was confirmed when individuals were submitted to increases in temperature, indicating that 27.14°C is the take‐off temperature threshold of D. citri. Results show that temperature plays an important role in the flight activity of D. citri and suggest that control measures of the insect may be more effective in the morning and in temperatures below 27°C, when the probability to take off from a host is lower.

Physiological and Transcriptional Changes of Three Citrus Rootstock Seedlings under Iron Deficiency

Iron is an essential micronutrient for plants, and plants have evolved adaptive mechanisms to improve iron acquisition from soils. Grafting on iron deficiency-tolerant rootstock is an effective strategy to prevent iron deficiency-chlorosis in fruit-tree crops. To determine the mechanisms underlying iron uptake in iron deficiency, two iron deficiency-tolerant citrus rootstocks, Zhique (ZQ) and Xiangcheng (XC), as well as iron deficiency-sensitive rootstock trifoliate orange (TO) seedlings were studied. Plants were grown in hydroponics system for 100 days, having 50 μM iron (control) and 0 μM iron (iron deficiency) nutrient solution. Under iron deficiency, more obvious visual symptoms of iron chlorosis were observed in the leaves of TO, whereas slight symptoms were observed in ZQ and XC. This was further supported by the lower chlorophyll concentration in the leaves of TO than in leaves of ZQ and XC. Ferrous iron showed no differences among the three citrus rootstock roots, whereas ferrous iron was significantly higher in leaves of ZQ and XC than TO. The specific iron absorption rate and leaf iron proportion were significantly higher in ZQ and XC than in TO, suggesting the iron deficiency tolerance can be explained by increased iron uptake in roots of ZQ and XC, allowed by subsequent translocation to shoots. In transcriptome analysis, 29, 298, and 500 differentially expressed genes (DEGs) in response to iron deficiency were identified in ZQ, XC, and TO, respectively (Fold change ≥ 2 and Probability ≥ 0.8 were used as thresholds to identify DEGs). A Gene Ontology analysis suggested that several genotype-specific biological processes are involved in response to iron deficiency. Genes associated with cell wall biosynthesis, ethylene and abscisic acid signal transduction pathways were involved in iron deficiency responses in citrus rootstocks. The results of this study provide a basis for future analyses of the physiological and molecular mechanisms of the tolerance of different citrus rootstocks to iron deficiency.

Mycorrhiza and Common Mycorrhizal Network Regulate the Production of Signal Substances in Trifoliate Orange (Poncirus trifoliata)

Common mycorrhizal networks (CMNs) connecting two or more neighbouring plants are confirmed to transfer signals, whereas little information about CMNs effects on the signal substances production is known. In this study, a two-chambered rootbox separated by 37 µm nylon mesh was used to establish donor and receptor chambers. Two chambers both were planted with trifoliate orange (Poncirus trifoliata) and then only donor chamber inoculated with Diversispora versiformis, Paraglomus occultum and Rhizoglomus intraradices. The roots of the donor and receptor plants both were mycorrhizated suggesting that CMNs were established between donor and receptor seedlings. Moreover, the AMF association dramatically increased plant height, stem diameter, leaf numbers, and shoot and root biomass in both the donor and receptor seedlings. The AMF inoculation in the donor plants and the subsequent mycorrhizal colonization by CMNs in the receptor plants significantly increased root calmodulin (CaM) and salicylic acid (SA) concentrations, while considerably decreased root nitric oxide (NO) and jasmonic acid (JA) concentrations. This was accompanied by down-regulated expression of three JA synthetic genes (PtLOX, PtAOS and PtAOC), regardless of donor and receptor seedlings. These results thus suggest that CMNs between trifoliate orange seedlings manifestly promote plant growth and affect the production of signal substances.

Root colonization by host-specific rhizobacteria alters indigenous root endophyte and rhizosphere soil bacterial communities and promotes the growth of mandarin orange

We assessed whether colonization of mandarin orange roots by host-specific plant growth promoting rhizobacteria (PGPR) can influence the composition of root endophyte, rhizosphere and non-rhizosphere bacterial communities and plant growth. The ability to colonize root by four host-specific PGPR, namely Enterobacter hormaechei RCE1, Enterobacter asburiae RCE2, Enterobacter ludwigii RCE5 and Klebsiella pneumoniae RCE7, was tested in axenically grown mandarin orange seedlings. The combined results of scanning and transmission electron microscopic images showed that PGPR inoculants successfully colonised on surface and within root tissues of axenic mandarin orange seedlings. The effect of root inoculation of 90 days old mandarin orange seedlings grown in natural soil with RCE1, RCE2, RCE5 and RCE7 either individually or as a consortium was evaluated in terms of plant biomass yield at 90, 180 and 360 days of post inoculation (dpi). Inoculation thus enhanced plant biomass yield over the uninoculated control. NMDS and hierarchical clustering of PCR DGGE fingerprints indicated that both the PGPR inoculation and plant age affected bacterial communities in root tissues and rhizosphere soils. Based on sequencing, the majority of the root endophyte and rhizosphere PCR-DGGE bands were from gammaproteobacteria, and the other were from Firmicutes and Deinococcus-Thermus. In conclusion, host-specific PGPR successfully colonized mandarin orange root tissue and rhizosphere soil and enhanced plant growth.

Alleviation of drought stress by mycorrhizas is related to increased root H2O2 efflux in trifoliate orange

The Non-invasive Micro-test Technique (NMT) is used to measure dynamic changes of specific ions/molecules non-invasively, but information about hydrogen peroxide (H2O2) fluxes in different classes of roots by mycorrhiza is scarce in terms of NMT. Effects of Funneliformis mosseae on plant growth, H2O2, superoxide radical (O2·−), malondialdehyde (MDA) concentrations, and H2O2 fluxes in the taproot (TR) and lateral roots (LRs) of trifoliate orange seedlings under well-watered (WW) and drought stress (DS) conditions were studied. DS strongly inhibited mycorrhizal colonization in the TR and LRs, whereas mycorrhizal inoculation significantly promoted plant growth and biomass production. H2O2, O2·−, and MDA concentrations in leaves and roots were dramatically lower in mycorrhizal seedlings than in non-mycorrhizal seedlings under DS. Compared with non-mycorrhizal seedlings, mycorrhizal seedlings had relatively higher net root H2O2 effluxes in the TR and LRs especially under WW, as well as significantly higher total root H2O2 effluxes in the TR and LRs under WW and DS. Total root H2O2 effluxes were significantly positively correlated with root colonization but negatively with root H2O2 and MDA concentrations. It suggested that mycorrhizas induces more H2O2 effluxes of the TR and LRs, thus, alleviating oxidative damage of DS in the host plant.

Mycorrhizal trifoliate orange has greater root adaptation of morphology and phytohormones in response to drought stress

Plant roots are the first parts of plants to face drought stress (DS), and thus root modification is important for plants to adapt to drought. We hypothesized that the roots of arbuscular mycorrhizal (AM) plants exhibit better adaptation in terms of morphology and phytohormones under DS. Trifoliate orange seedlings inoculated with Diversispora versiformis were subjected to well-watered (WW) and DS conditions for 6 weeks. AM seedlings exhibited better growth performance and significantly greater number of 1st, 2nd, and 3rd order lateral roots, root length, area, average diameter, volume, tips, forks, and crossings than non-AM seedlings under both WW and DS conditions. AM fungal inoculation considerably increased root hair density under both WW and DS and root hair length under DS, while dramatically decreased root hair length under WW but there was no change in root hair diameter. AM plants had greater concentrations of indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin in roots, which were significantly correlated with changes in root morphology. These results support the hypothesis that AM plants show superior adaptation in root morphology under DS that is potentially associated with indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin levels.

Mycorrhizal Effects on Growth and Root Morphology are Associated with Changes in Chlorophyll and Carbohydrates in Trifoliate Orange Seedlings

Mycorrhizal Effects on Growth and Root Morphology are Associated with Changes in Chlorophyll and Carbohydrates in Trifoliate Orange Seedlings

Effects of nursery shading on plant growth, chlorophyll content and PSII in ‘Lane Late’ navel orange seedlings

Effects of nursery shading on plant growth, chlorophyll content and PSII in ‘Lane Late’ navel orange seedlings

Systematicness of glomalin in roots and mycorrhizosphere of a split-root trifoliate orange

Understanding the behavior of mycorrhiza-originated glomalin, either of plant or soil origin, is anticipated to facilitate better opportunities of modulating antioxidants and carbon distribution in plants. In this study, trifoliate orange seedlings with half of roots were colonized by Acaulospora scrobiculata and Funneliformis mosseae in a split-root rootbox. Mycorrhizal inoculation showed a significantly higher plant biomass of trifoliate orange, regardless of mycorrhizal species. Glomalin-related root protein showed a systematic increase in non-mycorrhiza-inoculated chamber under inoculation with A. scrobiculata and F. mosseae than under non-mycorrhizal inoculation. Similar increase was also observed in easily extractable glomalin-related soil protein and total glomalin-related soil protein as a result of F. mosseae colonization only. Mean weight diameter and soil organic carbon were significantly higher under mycorrhization than non-mycorrhization, irrespective of mycorrhized or non-mycorrhized chamber. Mycorrhizal inoculation stimulated an increase in soil protease activity in the mycorrhized chamber, without any distinctive change in the non-mycorrhized chamber. These results, hence, suggested that mycorrhization conferred a systematic increase in glomalin synthesis in roots and soils, collectively, aiding in better aggregate stability and soil carbon sequestration.

Effect of soaking seeds Citrusaurantium and Citrus limonumat different concentrations of licorice extract on the percentage of germination and growth of seedlings

This research was conducted under Lath house canopy of a nursery circumstances, Baghdad University for season 2013 in order to study the effect of soak lemon seeds sour orange with different levels of licorice concentrations extract (0, 0.5, 2.5 and 4.5 g/l) for 24 hours in the percentage of germination and some recipes vegetative growth of seedlings .the results outweigh the bitter orange seedlings and focus soak for licorice extract 4.5 g / l significant superiority in most of the traits plant height, leaf number, root length, stem diameter, amounting to 31.077 cm, 14.46 paper / plant, 25.35 cm, 0.52 mm respectively, which showed significant differences for the treatment of comparison which gave lower values. Clear that the licorice extract biological effect similar to the effect of Al Gibberellin at germination lemon seeds, sour orange.

Arbuscular mycorrhizas improve plant growth and soil structure in trifoliate orange under salt stress

ABSTRACTArbuscular mycorrhizal fungi (AMF) as a biostimulant enhance salt tolerance in plants, while the informations regarding AMF-induced changes in soil structure are only available to a limited degree. In this study, trifoliate orange (Poncirus trifoliata) seedlings were inoculated with Diversispora versiformis under 100 mM NaCl for 85 days. The salt stress considerably inhibited mycorrhizal colonization by 26%, compared with non-salt stress. Mycorrhizal inoculation significantly increased plant height, stem diameter, leaf number, shoot biomass, and root biomass, length, surface area, and volume in comparison to non-mycorrhizal inoculation under salt stress or non-salt stress. Mycorrhization induced significantly higher production of easily extractable glomalin-related soil protein (EE-GRSP), and total glomalin-related soil protein (T-GRSP), higher percentage of water-stable aggregates (WSAs) in 0.25–0.50, 0.50–1.00, and 1.00–2.00 mm size, and lower in 2.00–4.00 mm size, regardless of non-salt stress or salt stress. Mycorrhizal soils represented higher aggregate stability (in terms of mean weight diameter) under salt and non-salt stress, which was related with root colonization, root surface area, root volume, EE-GRSP, and T-GRSP. The better soil structure by mycorrhization provided higher leaf water potential under salt stress. It suggests that mycorrhizas had a positive contribution to improve plant growth and soil structure, thereby enhancing salt tolerance.