Root Water Content Research Articles

Screening the Olive Tree Phyllosphere: Search and Find Potential Antagonists Against Pseudomonas savastanoi pv. savastanoi.

Olive knot (OK) is a widespread bacterial disease, caused by Pseudomonas savastanoi pv. savastanoi (Pss), which currently has not effective control methods. The use of naturally occurring microbial antagonists, such as bacteria, as biocontrol agents could be a strategy to manage this disease. The objective of this work was to select bacteria from olive tree phyllosphere able to antagonize Pss using in vitro and in planta experiments. The elucidation of their modes of action and the potential relationship between antagonism and bacteria origin has been investigated, as well. To this end, 60 bacterial isolates obtained from the surface and inner tissues of different organs (leaves, twigs, and knots), from two olive cultivars of varying susceptibilities to OK, were screened for their in vitro antagonistic effect against Pss. A total of 27 bacterial strains were able to significantly inhibit Pss growth, being this effect linked to bacteria origin. Strains from OK-susceptible cultivar and colonizing the surface of plant tissues showed the strongest antagonistic potential. The antagonistic activity was potentially due to the production of volatile compounds, siderophores and lytic enzymes. Bacillus amyloliquefaciens P41 was the most effective antagonistic strain and their capacity to control OK disease was subsequently assayed using in planta experiments. This strain significantly reduces OK disease severity (43.7%), knots weight (55.4%) and population size of Pss (26.8%), while increasing the shoot dry weight (55.0%) and root water content (39.6%) of Pss-infected olive plantlets. Bacterial isolates characterized in this study, in particular B. amyloliquefaciens P41, may be considered as promising biocontrol candidates for controlling OK disease.

Effect of using harvesting residues as a nursery media on seedling weight in Brutian pine (Pinus brutia Ten.)

Effects of harvesting residues (needle, bark and branch) on fresh and dry weights of two-year bare root seedlings originated from a seed stand and a seed orchard were examined in Brutian pine (Pinus brutia Ten.) to contribute nursery practices of the species and to estimate utilization possibility of the residues. Averages of seedling fresh and dry weights were 9.24 g and 3.36 g, respectively in polled treatments and origins. Results of analysis of variance showed significant differences (p≤0.05) among the treatments and between seed sources for the fresh and dry weights. Total averages of water content were 61.20% in root, 64.69% in stem and 63.75% in fresh weight of full seedling. Seed orchard seedlings had higher water content in root, stem and full seedling than seed stand seedlings opposite to fresh and dry weights. Averages of water content ranged from 60.39% (control treatment) to 65.94% (bark treatment) in full seedling of polled treatments and seed sources.

Coinoculação do amendoim (Arachis hypogaea L.) com Bradyrhizobium e Azospirillum promove maior tolerância à seca

O uso de rizobactérias promotoras de crescimento pode ser uma estratégia de manejo para amenizar os efeitos da deficiência hídrica no crescimento e no desenvolvimento das plantas por modificar o metabolismo fisiológico e promover maior tolerância à seca. Este estudo teve como objetivo investigar os efeitos da inoculação das sementes com Bradyrhizobium japonicum e Azospirillum brasilense de forma isolada e combinada no crescimento e na indução da tolerância das plantas de amendoim (Arachis hypogaea L., cv. RUNNER IAC 886) à restrição hídrica. O delineamento experimental adotado foi o de blocos ao acaso em esquema fatorial 3 × 4, constituídos por três níveis de irrigação [100% da capacidade de retenção de água do solo (controle), 50% do controle (estresse moderado) e 25% do controle (estresse severo)] e por quatro tratamentos de inoculação [controle (sem inoculação), inoculação com B. japonicum, inoculação com A. brasilense e coinoculação das sementes com B. japonicum e A. brasilense, com quatro repetições. A restrição hídrica foi imposta no início do aparecimento do ginóforo, aos 40 dias após a emergência das plantas, por um período de 18 dias. As plantas expostas as condições de restrição hídrica severa tiveram redução de a altura da planta (32%), área foliar (44%), volume radicular (47%), matéria seca da parte aérea (35%) e na matéria seca das raízes (37%) quando comparadas às plantas em condições controle. A inoculação com B. japonicum e A. brasilense de forma isolada ou combinada melhorou a integridade da membrana plasmática em 7% e reduziu em 8% as perdas de água das folhas de amendoim expostas à deficiência hídrica. A inoculação com A. brasilense de forma isolada ou combinada com B. japonicum resultou em maior altura de planta (21%) e maior matéria seca das raízes (23%) quando comparado as plantas não inoculadas sob condições de restrição hídrica severa. Nossos resultados sugerem que inoculação com B. japonicum e A. brasilense de forma isolada ou combinada pode amenizar os efeitos adversos da deficiência hídrica, mantendo o crescimento e o acúmulo de matéria seca das plantas quando expostas à restrição hídrica. Portanto, o uso destas rizobactérias na cultura do amendoim pode ser uma alternativa de manejo em condições de cultivo sujeitas a ocorrência de deficiência hídrica por conferir maior tolerância das plantas à seca.

Physiological and Biochemical Responses to Salt Stress of Alfalfa Populations Selected for Salinity Tolerance and Grown in Symbiosis with Salt-Tolerant Rhizobium

Alfalfa and its rhizobial symbiont are sensitive to salinity. We compared the physiological responses of alfalfa populations inoculated with a salt-tolerant rhizobium strain, exposed to five NaCl concentrations (0, 20, 40, 80, or 160 mM NaCl). Two initial cultivars, Halo (H-TS0) and Bridgeview (B-TS0), and two populations obtained after three cycles of recurrent selection for salt tolerance (H-TS3 and B-TS3) were compared. Biomass, relative water content, carbohydrates, and amino acids concentrations in leaves and nodules were measured. The higher yield of TS3-populations than initial cultivars under salt stress showed the effectiveness of our selection method to improve salinity tolerance. Higher relative root water content in TS3 populations suggests that root osmotic adjustment is one of the mechanisms of salt tolerance. Higher concentrations of sucrose, pinitol, and amino acid in leaves and nodules under salt stress contributed to the osmotic adjustment in alfalfa. Cultivars differed in their response to recurrent selection: under a 160 mM NaCl-stress, aromatic amino acids and branched-chain amino acids (BCAAs) increased in nodules of B-ST3 as compared with B-TS0, while these accumulations were not observed in H-TS3. BCAAs are known to control bacteroid development and their accumulation under severe stress could have contributed to the high nodulation of B-TS3.

Partitioning of dry matter and minerals in Kenyan common guava under salt stress: implications for selection of adapted accessions for saline soils

ABSTRACTCommon guava (Psidium guajava L.) is valued for its fruit, which is a source of vitamins, minerals, and natural antioxidants. However, guava production faces salinity challenges globally. Salinity through sodium chloride (NaCl) – 0 mM (control), 10/20 mM (low), 20/40 mM (medium), and 40/80 mM (high) – supplied through a standard Hoagland nutrient solution to 10 genetically diverse guava accessions from Kenya was investigated. Leaf number and dry matter (DM) were significantly reduced at the medium and high salinity levels while root DM remained similar. Root water content increased with rising salinity levels, whereas leaf water content was significantly reduced at the high NaCl level. A decrease in the leaf potassium/sodium (K/Na) and calcium/sodium (Ca/Na) ratios with increasing salinity was observed, possibly due to the high accumulation of Na rather than to the replacement of K and Ca. Leaf phosphorus (P) and sulphur (S) decreased with increasing salinity. Leaf boron (B) and iron (Fe) were significantly reduced only at the high salinity level. Differences among the accessions relative to the accumulation of Na were observed and positively correlated with the DM. Thus, the ability to maintain more DM under salt stress could serve as an indicator for salinity tolerance in Kenyan guava.

Effect of salinity stress on plant growth and root yield of carrot

This study was carried out at Horticulture Farm of Bangladesh Agricultural University, Mymensingh to evaluate the effects of different levels of NaCl salinity on plant growth and root yield of two carrot varieties during the period from November, 2016 to February, 2017. Four levels of NaCl salt concentration viz., 0 (Control), 50, 100 and 150 mM and two varieties of carrot namely Shundori and Kuruda were used for this pot experiment. The two-factor experiment was laid out in randomized complete block design with three replications. The yield and yield components varied significantly between two carrot varieties and intensity of salt concentration. The maximum plant height (33.92 cm), length of leaves (14.51 cm), fresh weight of leaves (9.62 g), percent dry matter content of leaves (21.25 %), length of root (9.05 cm), diameter (11.24 cm), dry matter content of roots (18.18 %) were produced by Shundori. On the other hand, maximum water content of leaves (80.89 %), water content of roots (84.57 %) and weight of roots (10.76 g) were exhibited by Kuruda. Most of the studied parameters showed decreasing trends with the highest level of salinity (200 mM NaCl) producing lowest weight of roots (3.93 g). In case of combined effects of variety and salt concentrations, Kuruda with control condition produced maximum weight of roots (20.62 g) while the minimum weight of roots (3.53 g) was obtained by the combination of Kuruda with the highest level of salt concentration (200 mM NaCl). The result of the experiment revealed that the salinity stress significantly reduced all studied parameters at 100 mM and 150 mM as compared to control and 50 mM NaCl. Therefore, it can be concluded that the variety of Kuruda was found as relatively salt tolerant than Shundori.
 Progressive Agriculture 30 (3): 263-274, 2019

Screening of drought resistance indices and evaluation of drought resistance in cotton (Gossypium hirsutum L.)

Sixteen cotton cultivars widely planted in China were sowed under five different drought concentrations (0, 2.5, 5, 7.5, and 10%) using PEG6000 to screen the indices of drought resistance identification and explore the drought resistance of different cotton cultivars. Eighteen physiological indices including root, stem, and leaf water contents (RWC, SWC, and LWC), net photosynthetic rate (Pn), the maximum photochemical quantum yield (Fv/Fm), the actual photochemical quantum yield (ϕPSII), non-photochemical quenching coefficient (NPQ), leaf water potential (LWP), osmotic potential (ψs), leaf relative conductivity (REC), leaf proline content (Pro), leaf and root soluble protein contents (LSPC and RSPC), leaf and root malondialdehyde (MDA) contents (LMDA and RMDA), root superoxide dismutase, peroxidase, and catalase activities (RSOD, RPOD, and RCAT) were measured. Results indicated the 18 physiological indices can be converted into five or six independent comprehensive indices by principal component analysis, and nine typical indices (Fv/Fm, SWC, LWP, Pro, LMDA, RSPC, RMDA, RSOD, and RCAT) screened out by a stepwise regression method could be utilized to evaluate the drought resistance. Moreover, the 16 cotton cultivars were divided into four types: drought sensitive, drought weak sensitive, moderate drought resistant, and drought resistant types. The resistance ability of two selected cotton cultivars (drought resistant cultivar, Dexiamian 1; drought sensitive cultivar, Yuzaomian 9110) with contrasting drought sensitivities were further verified by pot experiment. Results showed that the responses of final cotton biomass, yield, and yield composition to drought were significantly different between the two cultivars. In conclusion, drought resistant cultivar Dexiamian 1 and drought sensitive cultivar Yuzaomian 9110 were screened through hydroponics experiment, which can be used as ideal experimental materials to study the mechanism of different cotton cultivars with contrasting drought sensitivities in response to drought stress.

Effects of Drought Stress on Growth and Accumulation of Proline in Five Rice Varieties (Oryza Sativa L.)

A pot experiment was conducted to study the effect of drought stress on growth and accumulation of proline in five rice varieties namely BRRI dhan-30, BRRI dhan-32, BRRI dhan-34, BRRI dhan-38 and BRRI dhan-56 and to characterize them on the basis of their behavior of drought tolerance. Drought stress caused the decrease of growth like root length, shoot length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, the ratio of root-shoot length. Among the rice varieties, BRRI dhan-56 showed the lowest decrease of growth of plant. BRRI dhan-56 showed the least decrease of water content in both root and shoot. On the other hand, the accumulation of proline was increased in five rice varieties under stress. BRRI dhan-56 showed the highest (3.7- folds) increase in the accumulation of proline in leaf under stress. This study suggests that BRRI dhan-56 may possess drought tolerance characteristics while BRRI dhan-30, BRRI dhan-32, BRRI dhan-34 and BRRI dhan-38 may be drought sensitive based on their growth and proline accumulation behavior.
 Asiat. Soc. Bangladesh, Sci. 45(2): 241-247, December 2019

Screening for Salt and Water Stress Tolerance in Fir (Abies alba) Populations

Drought periods are becoming more frequent and intense, due to the effects of climate change, threatening natural habitats worldwide, including European forests. Forest trees can also be affected by high soil salinity, because of the common practice of de-icing of mountain roads with NaCl in winter. We have evaluated the responses to salt and water stress of silver fir (Abies alba), an important forest species for which very limited information is available. One-year-old fir seedlings, with origin in seven different locations in Romania, were subjected to salt (watering with NaCl solutions of increasing concentrations) and water deficit (complete withholding of irrigation) treatments in the greenhouse. After one month, plant material was harvested and different morphological parameters were determined in the stressed and control plants. Both stress treatments inhibited growth of fir seedlings from all seven provenances, although quantitative differences in the responses to stress were observed between populations. Growth inhibition was established by the relative reduction – as compared to the non-stressed controls - in several parameters, such as stem elongation, root length, number of needles, or fresh weight and water content of roots and needles. Statistical multivariate analysis of the results suggested that seedlings from Valea Morii (population 6) were the most tolerant to both, water deficit and high (300 mM NaCl) salt concentrations. These results support the possibility to screen a large number of individuals from different populations, at the seedling stage, to select Abies alba genotypes with enhanced drought and/or salinity tolerance.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Dissection of Phenotypic and Genetic Variation of Drought-Related Traits in Diverse Chinese Wheat Landraces.

Variations in 16 seedling traits under normal and drought conditions were investigated. Extremely resistant and sensitive accessions were identified for future analyses. Under normal and drought conditions, 57 and 29 QTL were identified, respectively. A total of 77 candidate genes were identified, and four were validated by qRT-PCR. Drought is one of the most important abiotic stressors affecting wheat (Triticum aestivum L.) production. To improve wheat yield, a better understanding of the genetic control of traits governing drought resistance is paramount. Here, using 645 wheat landraces, we evaluated 16 seedling traits related to root and shoot growth and water content under normal and drought (induced by polyethylene glycol) conditions. Extremely resistant and sensitive accessions were identified for future drought-resistance breeding and further genetic analyses. A genome-wide association study was performed for the 16 traits using 52,118 diversity arrays technology sequencing (DArT-seq) markers. A total of 57 quantitative trait loci (QTL) were detected for seven traits under normal conditions, whereas 29 QTL were detected for eight traits under drought conditions. On the basis of these markers, we identified 56 candidate genes for six seedling traits under normal conditions, and 21 candidate genes for seven seedling traits under drought conditions. Four candidate genes were validated under normal and drought conditions using quantitative reverse transcription polymerase chain reaction (qRT-PCR) data. The co-localization of the flowering date and drought-related traits indicates that the regulatory networks of flowering may also respond to drought stress or are associated with the correlated responses of these traits. The phenotypic and genetic elucidation of drought-related traits will assist future gene discovery efforts and provide a basis for breeding drought-resistant wheat cultivars.

Comparison of Cold Resistance between Aboveground and Underground of Sedum aizoon L. Seedling with Sprout under Low Temperature

The difference of cold resistance between aboveground and underground parts was compared by measuring the growth and cold-resistance physiology of dormancy-released Sedum aizoon L. seedling with sprout at -5, 0 and 5 degrees Celsius respectively. The results showed that with the decreasing temperature, the plant height and root length all showed a downward trend, and the plant height decreased more than root length. The aboveground fresh weight showed an upward trend, while the underground fresh weight showed a downward first and then upward trend. The relative electrical conductivity (REC), tissue water content, total soluble sugar and free proline content all showed an upward trend, while malondialdehyde (MDA) content showed a downward trend in leaves. The content of soluble protein showed a downward first and then upward trend in leaves. The changing trend of roots was the same as leaves in REC, total soluble sugar and soluble protein content, but the REC of roots increased less than leaves. There was no significant change in tissue water content, free proline and MDA content in roots. At the same low temperature, roots were all higher than leaves in the content of total soluble sugar and soluble protein, while the tissue water content and MDA content were the contrary. In conclusion, the cold resistance of the underground part was stronger than aboveground part in Sedum aizoon L. seedling with sprout.

Is there coordination of leaf and fine root traits at local scales? A test in temperate forest swamps.

Examining the coordination of leaf and fine root traits not only aids a better understanding of plant ecological strategies from a whole‐plant perspective, but also helps improve the prediction of belowground properties from aboveground traits. The relationships between leaf and fine root traits have been extensively explored at global and regional scales, but remain unclear at local scales. Here, we measured six pairs of analogous leaf and fine root traits related to resource economy and organ size for coexisting dominant and subordinate vascular plants at three successional stages of temperate forest swamps in Lingfeng National Nature Reserve in the Greater Hinggan Mountains, NE China. Leaf and fine root traits related to resource acquisition (e.g., specific leaf area [SLA], leaf N, leaf P, root water content, and root P) decreased with succession. Overall, we found strong linear relationships between leaf dry matter content (LDMC) and root water content, and between leaf and root C, N, and P concentrations, but only weak correlations were observed between leaf area and root diameter, and between SLA and specific root length (SRL). The strong relationships between LDMC and root water content and between leaf and root C, N, and P held at the early and late stages, but disappeared at the middle stage. Besides, C and P of leaves were significantly correlated with those of roots for woody plants, while strong linkages existed between LDMC and root water content and between leaf N and root N for herbaceous species. These results provided evidence for the existence of strong coordination between leaf and root traits at the local scale. Meanwhile, the leaf–root trait relationships could be modulated by successional stage and growth form, indicating the complexity of coordination of aboveground and belowground traits at the local scale.

Plant root growth affects FDR soil moisture sensor calibration

To acquire accurate volumetric water content (VWC) measurements from horticultural substrates using dielectric sensors, a substrate-specific calibration is critical. Calibrations typically are conducted with a substrate without plants, but water in the root system may affect soil moisture sensor readings. We investigated the effect of root growth on the measured VWC. Lettuce seedlings (Lactuca sativa L. ‘Joek Chi Ma’) were grown in 10 cm round containers (440 mL) filled with soilless substrate. Four EC-5 soil moisture sensors (Decagon Devices Inc., Pullman, WA, USA) were used to determine the effect of root system size on sensor calibration over an eight week period. Both calibration coefficients (slope and intercept) decreased (P < 0.001) with increasing root system size. The actual VWC at 8 weeks after transplanting (WAT) was 9% lower at 65% VWC compared to the estimated VWC from the substrate-only calibration. Multiple regression models indicated that various root size indicators (WAT, root fresh weight, root dry weight, and root water content) all had a negative effect on the estimation of VWC. The effect of root system size on estimated VWC may be tolerable in production, but should be considered in research applications. Careful interpretation is needed when using FDR soil moisture sensors to monitor substrate VWC in the presence of a growing root system.

The effect of biochar on the physiological, morphological and anatomical characteristics of mung bean roots after exposure to salt stress

To investigate the changes in the anatomical and physiological characteristics of mung bean roots in response to biochar treatment during salt stress, a pot experiment was conducted. Mung bean plants were subjected to three biochar concentrations (0, 50 and 100 g kg-1 soil) and three salinity treatments (0, 5 and 10 dSm-1 NaCl). Salinity decreased root growth, vascular cylinder (VC) and cortical parenchyma (CP) areas, affecting the VC/CP ratio, shoot dry weight, the relative water content (RWC) of roots and leaves, and the root indole-3-acetic acid (IAA) content. It increased specific root length, the shoot/root ratio and root abscisic acid (ABA), and 1-aminocyclopropane-1-carboxylic acid (ACC) contents. Plant growth, RWC, the shoot/root ratio, specific root length, total root area, VC and CP areas, and the IAA/ABA and IAA/ACC ratios were increased by biochar under saline media. Biochar improved xylem structure, the plant growth regulator IAA, and decreased stress hormones, ABA and ACC, which accelerate plant senescence, consequently increasing mung bean growth under salt stress.

Evaluation of wheat varieties to salt stress (NaCl) for seed germination and early seedling growth under laboratory conditions

Abstract Salinity tolerance during germination and early seedling growth was evaluated of four wheat varieties under four salinity (NaCl) levels that included Control (distilled water) 0, 9, 12 and 16 dSm-1. The seeds of four wheat varieties including Imdad-2005, Mahran-89, TJ-83 and TD-1 were sown under various NaCl levels in Petri dishes. The trial was performed at Seed Testing Laboratory, Department of Agronomy, Sindh Agriculture University, Tandojam Pakistan, following completely randomized design with three replications. The results showed that different salt stress (NaCl) levels had significant effects on germination (%), shoot and root length (cm), shoot and root water content (%), shoot and root fresh weight (g) and shoot and root dry weight (g) of wheat varieties. Among varieties, Imdad-2005 showed tolerance against salt stress for all parameters as compared to other varieties. The Imdad-2005 produced maximum mean germination (93.7%), shoot and root length (14.8 cm and 9.3 cm), shoot and root RWC (80.1 % and 86.2%), shoot and root fresh weight (2.3 g and 1.5 g) and heaviest shoot and root dry weight (0.28 g and 0.13 g). However, for NaCl levels, maximum germination (96.2 %), shoot and root length (15.5 cm, 10.7 cm), shoot and root water content (86.4 %, 87.0%), shoot and root fresh weight (2.3 and 1.5 g) and highest shoot and root dry weight (0.28 g and 0.13 g) was noted at control, where seeds were on sown by using distilled water. Keywords: Germination; NaCl Tolerance; Seedling growth; Salinity levels; Wheat (Triticum aestivum L.) http://dx.doi.org/10.19045/bspab.2018.700223

Salicylic acid but not jasmonic acid improved canola root response to salinity stress

We evaluated the effect of foliar sprays of 1 mM salicylic acid and 0.5 mM jasmonic acid on root growth of canola (Brassica napus, Cultivar: Ocapi) under different levels of salt stress (0, 40, 70, 100 mM NaCl) as a practical means to reduce water-stress. Salinity decreased the primary and lateral root length and weight, root diameter, density, shoot dry weight, shoot/root ratio and root water content, but increased the Root length/ Root weight ratio. Jasmonic acid increased the lateral root growth, but reduced the primary root growth and shoot dry weight and did not alter the root water content under different levels of salt stress. Salicylic acid had no effect on lateral root growth, but increased the primary root length, weight, diameter and root density in plants. These enhancements by salicylic acid increased the water content in root tissues and caused considerable improvement in canola growth.

Comparative growth and physiological responses of tetraploid and hexaploid species of wheat to flooding stress

Present study is aimed to comparatively investigate the response of two ploidy levels of wheat including a tetraploid (Triticum turgidum L.) and a hexaploid (Triticum aestivum L.) wheat to different durations of flooding stress. Wheat seedlings were exposed to flooding stress for 0, 3, 6 and 9 days. Results showed that all flooding treatments significantly decreased the shoot and root length, and chlorophyll content of both species of wheat. The decrease in chlorophyll content of tetraploid wheat was more than that of hexaploid one. In both species, ADH activity of root was significantly increased under flooding stress, where the increase was more in hexaploid wheat. Flooding stress did not significantly affect root and shoot water content, root porosity, and shoot protein content of any wheat species. Tetraploid and hexaploid wheat used different mechanisms for better tolerance of flooding condition, where tetraploid wheat increased the proline content but in hexaploid wheat, an increase in soluble sugar content was observed.

Multivariate statistical analyses for studying kenaf germination, growth, and fiber production under salinity constraint

It is due to the lack of renewable fiber sources for industrial purposes that the need for finding available and alternative material has become imperative. Kenaf (Hibiscus cannabinus L.), a fast-growing industrial crop, would be a potential solution for valorizing salinized lands and/or soils irrigated with saline water. With the aim of selecting and valorizing salt-tolerant species with high fiber yields and industrial values, we launched the assessment of the performance of kenaf culture (var. Guangdong 743-2) under salinity constraints. Germination and vegetative stages were considered in the present study to better evaluate the whole life cycle of the species. Several NaCl concentrations (0, 3, 6, 9, 12, and 15 g L-1) were applied to seeds cultivated in petri dishes and to 4-month-old plants growing in hydroponics. Germination rates (germination capacity and coefficient of velocity), growth characteristics (biomass production and relative growth rate), physiological parameters (ionic content and water status), and fiber yields (neutral detergent fiber, acid detergent fiber, and acid detergent lignin) were evaluated to better understand the salt stress and toxic effects on germination, growth, and fiber yield. Multivariate analyses were used to identify the major characteristics pertaining to salinity tolerance. The obtained results have shown that kenaf variety Guangdong 743-2 is able to germinate and grow under high salinity levels (up to 15 g L-1 NaCl), deploying several mechanisms of adaptation. Kenaf could withstand salt stress by germinating smoothly, preserving root and stem biomass, maintaining relative growth rate, stabilizing root water content, producing new leaves while sacrificing older ones, and behaving as a halophyte species through the inclusion of toxic ions within the aerial part, most probably compartmentalized inside vacuoles to ultimately keep its fiber yields unchanged.

Effects of root dehydration on biomechanical properties of woody roots of Ulex europaeus

AimsEffects of root water status on root tensile strength and Young’s modulus were studied in relation to root reinforcement of slopes.MethodsBiomechanical properties of woody roots, Ulex europaeus, were tested during progressive dehydration and after thirty-day moisture equilibration in soil with contrasting water contents. Root diameter, water content and water loss were recorded and root water potential versus water content relation was investigated. Tensile stresses induced by root contraction upon dehydration were measured.ResultsRoot tensile strength and Young’s modulus increased abruptly when root water content dropped below 0.5 g g−1. The strength increase was due to root radial and axial contraction induced by root water potential drop. Diameter decrease and strength gain were the largest for thin roots because of the relatively larger evaporative surface per volume of thin roots. Largely negative water potentials in dry soil induced root drying, affecting root biomechanical properties.ConclusionRoot water status is a factor that can cause (inappropriately) high strength values and the large variability reported in literature for thin roots. Therefore, all root diameter classes should have consistent moisture for fair comparison. Testing fully hydrated roots should be the routine protocol, given that slope instability occurs after heavy rainfall.

Influence of Different Encapsulation Types of Arbuscular Mycorrhizal Fungi on Physiological Adaptation and Growth Promotion of Maize (Zea mays L.) Subjected to Water Deficit

Under drought environment, arbuscular mycorrhizal fungi (AMF) can serve as a long-term biofertilizer to sustain the water and nutrient availability for the host plants. A study was conducted to check the effect of AMF and the encapsulations of the AMF and an organic fertilizer (Fer) with alginate (Al-FA) and agar-agar (Ag-FA) on maize (Zea mays L.) in response to water deficit conditions. The maximum quantum efficiency of PS II (Fv/Fm) of the maize inoculated with Al-FA and Ag-FA under the water deficit was recorded to be 0.70 and 0.50, respectively. Shoot and root water content of the Al-FA plants were found to be maintained under the water deficit and were better than Ag-FA. Besides, phosphorus content in the root tissues of the Al-FA plants grown under the water deficit stress was 1.56-folds greater than in the Ag-FA plants, thereby promoting the photosynthetic abilities and plant height in the former case. The study indicated that the Al-FA type of encapsulation may perform better than the Ag-FA in case of maize plants, leading to its better development under water limited conditions.