Root Elongation Rate Research Articles

Willow oak (Quercus phellos) seedling roots continue respiration and growth during fall and winter in a soil temperature-dependent manner.

Many greentree reservoirs (GTRs) and other bottomland hardwood forests have experienced a shift in tree species composition away from desired red oaks (Quercus section Lobatae), like willow oak (Quercus phellos L.), due to flood stress mortality. Trees experience flood stress primarily through their root system, so it is surmised that GTR flooding may be occurring before root systems have reduced their activity entering the winter. Because soils buffer seasonal temperature changes, we hypothesized that root activity would respond to the belowground environment, rather than the aboveground environment. To investigate whether cold soil temperatures induce reduced root growth and respiration of willow oak during winter, soil temperatures of container seedlings were either held at 15°C, or transitioned to 10 or 5°C in the late fall. Root elongation was measured in seedlings grown in rhizotron pots by analyzing repeated images of roots during the fall-winter transition period. Root respiration, measured at soil temperature levels, was used as an indicator of root energetic expenses. Also, root respiration was measured at 15°C and 5°C to determine Q10 values to test for acclimation to low soil temperature. Root elongation continued in winter, even after stem elongation stopped in soil temperatures ≥5°C, a condition usually met throughout most of the native range of willow oak. Both root elongation and respiration rates decreased in cooler soil temperatures. However, Q10 values were unaffected by soil temperature treatment. These findings do not support root dormancy or cold acclimation of root respiratory activity but indicate that temperature directly and reversibly affected root respiration rate. Root elongation may have been dependent on photoassimilates produced by green leaves that were retained through much of winter. Overall, our results suggest that willow oak roots may continue a high rate of growth throughout winter, unlike most temperate species measured to date, and that soil temperature has a major influence over their growth and respiration rates.

QTL for the Kinematic Traits That Define the Arabidopsis Root Elongation Zone and Their Relationship to Gravitropism.

Cell expansion in a discrete region called the elongation zone drives root elongation. Analyzing time lapse images can quantify the expansion in kinematic terms as if it were fluid flow. We used horizontal microscopes to collect images from which custom software extracted the length of the elongation zone, the peak relative elemental growth rate (REGR) within it, the axial position of the REGR peak, and the root elongation rate. Automation enabled these kinematic traits to be measured in 1575 Arabidopsis seedlings representing 162 recombinant inbred lines (RILs) derived from a cross of Cvi and Ler ecotypes. We mapped ten quantitative trait loci (QTL), affecting the four kinematic traits. Three QTL affected two or more traits in these vertically oriented seedlings. We compared this genetic architecture with that previously determined for gravitropism using the same RIL population. The major QTL peaks for the kinematic traits did not overlap with the gravitropism QTL. Furthermore, no single kinematic trait correlated with quantitative descriptors of the gravitropism response curve across this population. In addition to mapping QTL for growth zone traits, this study showed that the size and shape of the elongation zone may vary widely without affecting the differential growth induced by gravity.

Evaluation of rapeseed (Brassica napus L.) genotypes for tolerance to PEG (polyethylene glycol) induced drought at germination and early seedling growth

Rapeseed (Brassica napus L.) is an important oilseed crop well adapted to Mediterranean area. However, increasing drought, due to climate change, impairs its growth and development, mainly when this stress occurs early during germination. This study carried out in vitro conditions aimed to investigate the effect of water deficit on seed germination and seedling growth traits in 12 genotypes to select the most drought-tolerant ones. Drought conditions were created using polyethylene glycol 6000 to induce three osmotic potential levels, namely −0.7 MPa for moderate stress, −0.9 MPa for intermediate stress, and −1.1 MPa for severe stress. Germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root-to-shoot ratio (RSR), seedling vigor index (SVI), shoot elongation rate (SER), and root elongation rate (RER) were measured/calculated. ANOVA and PCA were performed to analyze the data gathered. Results showed a significant effect of genotype, drought, and drought × genotype interaction on all studied parameters. Under severe drought conditions, overall values of GP, GR, RL, SL, SER, RER, and SVI decreased by 87.15 %, 53.29 %, 9.33 %, 4.73 %, 78 %, 82 %, and 96 %, respectively, while those of MGT and RSR increased by 56 % and 76 %, respectively, when compared to unstressed conditions. However, the genotypes studied reacted differently to the three levels of water stress. Based on PCA results, RL, RER, and GP proved to be the most discriminating of drought-tolerant genotypes. Overall, higher drought tolerance was associated with higher values in RL, SL, and SVI. Accordingly, the variety ‘Nap10’ and, to a lesser extent, ‘Baraka’ and ‘Nap9’ exhibited higher drought tolerance than the rest of genotypes, which makes them potential cultivars for dry areas. However, further studies in real field conditions are needed to confirm their tolerance to drought occurring at germination as well as during other stages, mainly flowering.

Patch Track Software for Measuring Kinematic Phenotypes of Arabidopsis Roots Demonstrated on Auxin Transport Mutants.

Plant roots elongate when cells produced in the apical meristem enter a transient period of rapid expansion. To measure the dynamic process of root cell expansion in the elongation zone, we captured digital images of growing Arabidopsis roots with horizontal microscopes and analyzed them with a custom image analysis program (PatchTrack) designed to track the growth-driven displacement of many closely spaced image patches. Fitting a flexible logistics equation to patch velocities plotted versus position along the root axis produced the length of the elongation zone (mm), peak relative elemental growth rate (% h-1), the axial position of the peak (mm from the tip), and average root elongation rate (mm h-1). For a wild-type root, the average values of these kinematic traits were 0.52 mm, 23.7% h-1, 0.35 mm, and 0.1 mm h-1, respectively. We used the platform to determine the kinematic phenotypes of auxin transport mutants. The results support a model in which the PIN2 auxin transporter creates an area of expansion-suppressing, supraoptimal auxin concentration that ends 0.1 mm from the quiescent center (QC), and that ABCB4 and ABCB19 auxin transporters maintain expansion-limiting suboptimal auxin levels beginning approximately 0.5 mm from the QC. This study shows that PatchTrack can quantify dynamic root phenotypes in kinematic terms.

Genotypic differences in systemic root responses to mechanical obstacles.

As roots grow through the soil to forage for water and nutrients, they encounter mechanical obstacles such as patches of dense soil and stones that locally impede root growth. Here, we investigated hitherto poorly understood systemic responses of roots to localised root impedance. Seedlings of two wheat genotypes were grown in hydroponics and exposed to impenetrable obstacles constraining the vertical growth of the primary or a single seminal root. We deployed high-resolution in vivo imaging to quantify temporal dynamics of root elongation rate, helical root movement, and root growth direction. The two genotypes exhibited distinctly different patterns of systemic responses to localised root impedance, suggesting different strategies to cope with obstacles, namely stress avoidance and stress tolerance. Shallower growth of unconstrained seminal roots and more pronounced helical movement of unconstrained primary and seminal roots upon localised root impedance characterised the avoidance strategy shown by one genotype. Stress tolerance to localised root impedance, as exhibited by the other genotype, was indicated by relatively fast elongation of primary roots and steeper seminal root growth. These different strategies highlight that the effects of mechanical obstacles on spatiotemporal root growth patterns can differ within species, which may have major implications for resource acquisition and whole-plant growth.

Age-dependent analysis dissects the stepwise control of auxin-mediated lateral root development in rice.

As root elongation rates are different among each individual root, the distance from the root apices does not always reflect the age of root cells. Thus, methods for correcting variations in elongation rates are needed to accurately evaluate the root developmental process. Here, we show that modeling-based age-dependent analysis is effective for dissecting stepwise lateral root (LR) development in rice (Oryza sativa). First, we measured the increases in LR and LR primordium (LRP) numbers, diameters, and lengths in wild type and an auxin-signaling-defective mutant, which has a faster main (crown) root elongation rate caused by the mutation in the gene encoding AUXIN/INDOLE-3-ACETIC ACID protein 13 (IAA13). The longitudinal patterns of these parameters were fitted by the appropriate models and the age-dependent patterns were identified using the root elongation rates. As a result, we found that LR and LRP numbers and lengths were reduced in iaa13. We also found that the duration of the increases in LR and LRP diameters were prolonged in iaa13. Subsequent age-dependent comparisons with gene expression patterns suggest that AUXIN RESPONSE FACTOR11 (ARF11), the homolog of MONOPTEROS (MP)/ARF5 in Arabidopsis (Arabidopsis thaliana), is involved in the initiation and growth of LR(P). Indeed, the arf11 mutant showed a reduction of LR and LRP numbers and lengths. Our results also suggest that PINOID-dependent rootward-to-shootward shift of auxin flux contributes to the increase in LR and LRP diameters. Together, we propose that modeling-based age-dependent analysis is useful for root developmental studies by enabling accurate evaluation of root traits' expression.

Exploring the importance of root architecture plasticity in plant adaptation to environmental constraints

AbstractPlants, as immobile organisms, depend on their roots to access soil resources efficiently and cost‐effectively. To achieve this goal, maximize productivity, and adapt to variable challenging conditions, plants rely on root phenotypic plasticity. This includes changes in root morphology, growth angles, diameter, elongation, branching density, and turnover rate. In simple terms, a plant root system is a dynamic structure that can change its branching structure in response to changes in biotic and abiotic conditions such as water availability, soil mineral nutrient content, soil compaction, salinity, and the formation of symbiotic relationships with other organisms or anchored in the substrate. However, the complexity of these responses and their impact on plant fitness are not well understood. In this paper, we review different aspects of the morphological plasticity of the root system. The results show that root flexibility can greatly support plant adaptation and control the nature of plant–plant interactions within the population. Thus, gaining a comprehensive understanding of root plasticity can lead to improved and sustainable plant production. We discuss the morphological plasticity of plant root systems in response to various biotic and abiotic factors, such as water availability, soil nutrient content, compaction, salinity, plant–plant interactions, and interactions with soil microorganisms. The aspects examined include root morphology, growth angles, diameter, elongation, branching density, and turnover rate. These parameters are crucial in determining how plants adapt to changes in their environment and optimize their growth and productivity.

Contrasting effects of two hydrogels on biomass allocation, needle loss, and root growth of Picea abies seedlings under drought

Adapted management methodologies are required to alleviate increasing and/or more frequent water stress under climate change, enabling successful tree seedling establishment after planting. Hydrogel amendments have been suggested to increase soil water holding capacity, tree seedling growth and survival. However, the effect of a non-uniform addition of hydrogels to tree planting pits as compared to homogenously admixed hydrogels in agricultural soils, as well as effects of hydrogels on woody root system establishment, have been poorly studied.Here we studied the effect of two commercial hydrogels (Polyter and Stockosorb) on the above- and belowground growth of Picea abies seedlings during a ∼ 5-weeks-long drought period. Rhizoboxes with a non-uniform distribution of nutrients and hydrogels were used to monitor root system development in a stratified soil. Biomass allocation, root morphology and root elongation rates were related to evapotranspiration rates. Proximity effects of hydrogels on root traits were determined.Total plant biomass was significantly greater if plants were grown in Polyter-amended soil (+16, 17 %) compared to the Stockosorb and control treatments, respectively. Dead needle mass was significantly greater in Stockosorb than in Polyter (+719 %) and control (+274 %). Root elongation was faster in both hydrogel treatments compared to the control during the first part of the drought period, but subsequently ceased to the order Polyter > control > Stockosorb. Root morphological changes in relation to hydrogels were limited.The better performance of Polyter-amended seedlings was related to a slow water release from the hydrogel, while Stockosorb released the additional soil water content prematurely. The latter might have imposed a “false sense of security”, and the subsequent lack of acclimation responses early in the drought resulted in an even more severe drought stress and a higher needle loss of Stockosorb-amended seedlings as compared to control. However, both hydrogels did not result in preferential growth towards or away from the hydrogel, suggesting that roots did neither sense the hydrogel-bound water nor that secondary compounds hampered root growth. A deeper root system placement and thus potential advantages for drought events at later growth stages were not encountered, asPolyter also had a strong positive effect on root growth in the fertile top soil. As hydrogel amendments may influence root system establishment and seedling vitality differently during drought, further studies are urgently needed before large scale applications to mitigate climate change effects on forest regeneration / restoration can take place.

Perennial grass root system specializes for multiple resource acquisitions with differential elongation and branching patterns.

Roots optimize the acquisition of limited soil resources, but relationships between root forms and functions have often been assumed rather than demonstrated. Furthermore, how root systems co-specialize for multiple resource acquisitions is unclear. Theory suggests that trade-offs exist for the acquisition of different resource types, such as water and certain nutrients. Measurements used to describe the acquisition of different resources should then account for differential root responses within a single system. To demonstrate this, we grew Panicum virgatum in split-root systems that vertically partitioned high water availability from nutrient availability so that root systems must absorb the resources separately to fully meet plant demands. We evaluated root elongation, surface area, and branching, and we characterized traits using an order-based classification scheme. Plants allocated approximately 3/4th of primary root length towards water acquisition, whereas lateral branches were progressively allocated towards nutrients. However, root elongation rates, specific root length, and mass fraction were similar. Our results support the existence of differential root functioning within perennial grasses. Similar responses have been recorded in many plant functional types suggesting a fundamental relationship. Root responses to resource availability can be incorporated into root growth models via maximum root length and branching interval parameters.

Seed Priming Treatments to Improve Heat Stress Tolerance of Garden Pea (Pisum sativum L.)

Heat stress seriously affects the production of cool-season food legume crops such as garden peas. Seed priming is a widely used technique that increases germination and improves plant growth and development, resulting in better field performance and higher yield of crops. In the current study, we investigated three seed priming treatments—hydropriming (dH2O), osmopriming (2.2% w/v CaCl2), and hormopriming (50 mg L−1 salicylic acid—SA)—and their effect on germination, initial seedling development, and physiological traits of two novel garden pea cultivars, under optimal conditions and heat stress. Seed priming with H2O, CaCl2, and SA enhanced garden pea performance under both optimal and stress conditions via significant improvements in germination energy, final germination, mean germination time, mean germination rate, seedling vigor index, shoot length, root length, fresh seedling weight, dry seedling weight, shoot elongation rate, root elongation rate, relative water content, chlorophyll content, and membrane stability index, as compared to control. The highest effect on the examined parameters was achieved by osmopriming and hormopriming in both cultivars, suggesting that these treatments could be used to improve the heat stress tolerance of garden pea, after extensive field trials.

Different effects of gellan gum and agar on change in root elongation in Arabidopsis thaliana by polyploidization: the key role of aluminum.

Agar and gellan gum have been considered to have different effects on polyploidy-dependent growth in plants. We aim to demonstrate that agar and gellan gum differently affect the change in root elongation in Arabidopsis thaliana by polyploidization and examined the physico-chemical parameters in each gelling agent to elucidate key factors that caused the differences. Each polyploid strain was cultured vertically on agar and gellan gum solidified medium under fixed conditions. Root elongation rate was measured during 4-10 days after sowing. As a result, agar promoted root elongation of polyploids more than the gellan gum. Then water potential, gel hardness, and trace elements of each medium were quantified in each medium. Water potential and gel hardness of agar medium were significantly higher than those of gellan gum medium. The decrease in water potential and gel hardness in agar medium, however, did not affect the change in polyploidy-dependent growth. Elemental analysis showed that gellan gum contained more aluminum than agar. Subsequently, the polyploids were grown on agar media with additional aluminum, on which the root elongation in tetraploids and octoploids was significantly suppressed. These results revealed that agar and gellan gum affect the change in growth of root elongation in A. thaliana by polyploidization in different ways and the different effects on change in polyploidy-dependent growth is partially caused by aluminum in the gellan gum, which may be due to cell wall composition of polyploids.

ZmBET5L1 inhibits primary root growth and decreases osmotic stress tolerance by mediating vesicle aggregation and tethering in maize.

Improving osmotic stress tolerance is critical to help crops to thrive and maintain high yields in adverse environments. Here, we characterized a core subunit of the transport protein particle (TRAPP) complex, ZmBET5L1, in maize using knowledge-driven data mining and genome editing. We found that ZmBET5L1 can interact with TRAPP I complex subunits and act as a tethering factor to mediate vesicle aggregation and targeting from the endoplasmic reticulum to the Golgi apparatus. ZmBET5L1 knock-out increased the primary root elongation rate under 20% polyethylene glycol-simulated osmotic stress and the survival rate under drought stress compared to wild-type seedlings. In addition, we found that ZmBET5L1 moderates PIN1 polar localization and auxin flow to maintain normal root growth. ZmBET5L1 knock-out optimized auxin flow to the lateral side of the root and promoted its growth to generate a robust root, which may be related to improved osmotic stress tolerance. Together, these findings demonstrate that ZmBET5L1 inhibits primary root growth and decreases osmotic stress tolerance by regulating vesicle transport and auxin distribution. This study has improved our understanding of the role of tethering factors in response to abiotic stresses and identified desirable variants for breeding osmotic stress tolerance in maize.

Qualitative and quantitative phytochemical screening of Nerium oleander L. extracts associated with toxicity profile

In this study, phytochemical analysis and toxicity profile of leaf and flower extracts of Nerium oleander L. species collected from Giresun province (Turkey) were investigated. In phytochemical analyzes, the cardiac glycoside, alkaloid, saponin and tannin contents of the extracts were analyzed qualitatively and quantitatively. The physiological effects of extracts were determined by examining root elongation, weight gain and germination rates. Biochemical effects were determined by measuring the levels of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT), which are indicators of oxidative stress. Cytotoxic and genotoxic effects were investigated by mitotic index (MI), micronucleus (MN) and chromosomal abnormality (CA) tests. N. oleander leaf and flower extract applications caused significant decreases in the physiological parameters of Allium bulbs. SOD and CAT activity in root tip cells increased significantly after the application of leaf extract compared to the control group. Similar changes were observed in the application of flower extract, but these increases were found to be at a lower level compared to the increases induced by the leaf extract. An increase in MDA levels and a decrease in GSH levels were observed in groups treated with leaf and flower extracts. These changes show that the extracts cause deterioration in antioxidant/oxidant balance. It was determined that the extracts, which caused a decrease in MI rates and an increase in MN and CAs frequencies, showed the most prominent cytotoxic and genotoxic effects at 250 μg/mL doses. These toxic effects were associated with the phytochemical content of the extracts, and it was thought that cardiac glycosides and alkaloids, whose presence were detected in qualitative and quantitative analyzes, may play an important role in toxicity. Studies investigating the therapeutic properties of plants as well as their toxic effects are insufficient, which leads to the fact that plants exhibiting potential toxicity are not well known. Therefore, this study will lead many studies on the toxicity profile of the phytochemical contents of plants. Therefore, this study will draw attention to the investigation of the toxicity profile and phytochemical contents of plants and will lead to similar studies.

Reductive dissolution of iron phosphate modifies rice root morphology in phosphorus-deficient paddy soils

Root morphology reflects plant adaptations to phosphorus (P) deficiency. We hypothesized that changes in rice root morphology reflect P deficiency decrease after ferric iron (Fe(III))-bound phosphate (Fe–P) dissolution in low-redox paddy soils. We developed a novel in-situ32P phosphor-imaging approach under flooding to estimate P uptake by rice roots released from Fe–P dissolution. 32P-labeled ferrihydrite (31 mg P kg−1) was supplied either (1) in polyamide mesh bags (30 μm mesh size) to prevent roots but not microorganisms from direct Fe–P mobilization, or (2) directly mixed with soil to enable roots and microorganisms unrestricted access to the Fe–P. The establishment of low redox conditions (Eh values between −176 and −224 mV) drove the reductive dissolution of Fe–P. Rice root-derived organic acids alone were unable to control Fe–P dissolution, and Fe(III) reduction is predominately a microbially-mediated process. Direct root access to Fe–P raised both the number and mean diameter of crown roots and root tips, and increased P uptake by 149–231%. Crown root elongation rate, 32P activities along roots and root tips were 5–133% higher when roots directly accessed Fe–P compared to Fe–P excluded from roots in mesh bags. Iron accumulation on roots depended on the rice growth stage, but not on their access to Fe–P. Roots’ access to Fe–P increased rice crown roots elongation and branching and increased P accessibility under P deficiency.

Functional groups on wheat (Triticum aestivum) root surface affect aluminium transverse accumulation

Plant root growth is inhibited markedly by aluminium (Al) even at micromolar concentration and Al is mainly accumulated in plant roots outer layer cell walls. But the underlying reason for this asymmetric transverse distribution is unknown. In this study, two wheat (Triticum aestivum L.) genotypes ET8 and ES8 differing in Al resistance were investigated by hydroculture. The Al-tolerant ET8 expressed a higher root elongation rate (RER) than Al-sensitive ES8 under Al stress. Morphological examination showed symptoms such as root surface ruptures were observed in ET8 and ES8, with ES8 being more obvious. The cation exchange capacity (CEC) values of root tips of ES8 under different Al concentrations are higher than those of ET8. The sensitive genotype ES8 accumulated more Al than ET8 in plant apical root tips as well as cell walls. Under 48 h Al exposure, the root cell wall pectin concentration was increased with a higher magnitude in ES8 than in ET8. The functional groups on ET8 and ES8 roots outer layer and inner cells were investigated by Fourier transform infrared spectrometry (FTIR) under Al stress. The FTIR spectra of selected examined areas showed that the characteristic absorption peaks were located at 1692, 2920, and 3380 cm−1. The outer layer cells had stronger peaks than inner cells at wavenumber 1680–1740 cm−1, indicating root outer layer cells contain more carboxyls in both ET8 and ES8. The results demonstrate that Al transverse distribution on plants apical root cross section is likely influenced by functional groups such as negatively charged carboxylic acid.

The Influence of Different Row Spacing and Weed Control Intervals on Weed Infestation and Yield-Related Traits of American (Gossypium hirsutum L.) and Desi (Gossypium arboreum) Cotton

Narrow row spacing has attracted significant attention due to its beneficial impacts on weed management in cotton. This study compared the effects of normal and ultra-narrow row spacing on critical periods of weed control in American (Gossypium hirsutum L.) and ‘Desi’ (Gossypium arboreum) cotton. Two different row spacings (i.e., recommended (75 cm) and ultra-narrow (30 cm)) and three weed control intervals (i.e., weed control at 30, 60 and 90 days after sowing (DAS)) were included in the study. Weedy-check and weed-free treatments were included in the experiment as controls for comparison. ‘Desi’ cotton grown under ultra-narrow spacing recorded the lowest weed density and individual density of Trianthema portulacastarum L., Cyperus rotundus L., Cynodon dactylon L., Echinochloa colona (L.) Link and Digera muricata (L.) Mart. Moreover, ‘Desi’ cotton sown under ultra-narrow spacing with weed-free and weed control at 30 DAS resulted in the highest leaf area index (LAI), leaf area duration (LAD), net assimilation late (NAR), root elongation rate (RER) and root growth rate (RGR) at all sampling dates. Likewise, ‘desi’ cotton sown under recommended row spacing and weed-free conditions produced the highest number of sympodial and monopodial branches, number of flowers and bolls per plant, whereas the highest seed cotton yield of ‘Desi’ cotton was noted under ultra-narrow spacing and weed-free conditions. It is concluded that sowing both cotton types in ultra-narrow row spacing and controlling weeds at 30 DAS will result in lower weed infestation and higher seed cotton yield.

Waterlogging and restricted-below ground aeration on photosynthetic performance and root elongation rate of RRIM 600 and RRIT 251 rubber genotypes (Hevea brasiliensis Mull. Arg.)

Due to extended inundation, waterlogging and restricted below-ground aeration cause inhibition in plant growth performance. This study examined two different rubber clones, RRIM 600 and RRIT 251, for waterlogging and restricted below ground aeration. To evaluate the plant performance under the stress conditions, net photosynthetic rate (PN), maximum quantum yield photosystem II (Fv/Fm) and root elongation rate were observed. RRIM 600 has a higher photosynthetic performance under normal conditions. However, the PN rate and Fv/Fm ratio trend showed that RRIM 600 seems to have difficulties recovering after exposure to restricted-below ground aeration. Although RRIT 251 had a lower tendency of PN rate under normal conditions, the PN rate and Fv/Fm ratio of this clone showed fast recovery. RRIT 251 also performed a higher trend of root elongation rate under both stress conditions than RRIM 600.

Effect of soil contamination with polycyclic aromatic hydrocarbons from drilling waste on germination and growth of lawn grasses

In many studies, grasses were used to increase the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil because they are the most common plant species on the ground level and are quite resistant to contamination with these compounds. One of the main failures in PAH remediation in soil using plant species was the negative impact on germination and seedling growth. The objective of this study was to evaluate grass seed germination and seedling growth affected by drill cuttings to determine the resistance of selected grass species to the impact of PAH and their suitability for an effective phytoremediation of soils contaminated with waste that contain compounds from this group. In the study four grass species: tall fescue (Festuca arundinacea), red fescue (Festuca rubra), perennial ryegrass (Lolium perenne) and common meadow-grass (Poa pratensis). The germination energy of all species decreased as the amount of drill cuttings increased. Among the species studied, the highest germination energy and capacity were found in Lolium perenne (54.1 and 73.2 respectively), and the lowest – in Poa pratensis (16.7 and 23.3 respectively). With an increasing amount of drill cuttings, the root and seedling height were decreased. Festuca arundinacea seedlings were distinctly the highest and had the longest roots (96.7 and 52.7, respectively), while Poa pratensis seedlings showed the significantly slowest seedling and root elongation rate (30.4 and 12.4, respectively). However, the strongest decrease in seedling height and root length compared to the control was observed in Festuca rubra. Based on IC50, the greatest tolerance to the addition of drilling waste to the substrate was found for Festuca arundinacea and Festuca rubra. The conducted investigation indicates that Festuca arundinacea and Lolium perenne are grass species that are least sensitive to drilling waste in the substrate because no significant differences were found in root length and seedling height between the control soil and the soil where a PAH dose of 5% and 10% was applied.

Olive Mill Waste-Based Anaerobic Digestion as a Source of Local Renewable Energy and Nutrients

This study focused on what combination of anaerobic digestion (AD) temperature (ambient, mesophilic, and thermophilic) and olive mill waste (OMW) to dairy manure (DM) ratio mixture delivers the desired renewable energy and digestate qualities when using AD as olive mill waste treatment. OMW is widespread in the local environment in the North Sinai region, Egypt, which causes many environmental hazards if left without proper treatment. Three different mixtures consisting of OMW, dairy manure (DM), and inoculum (IN) were incubated under ambient, mesophilic, and thermophilic conditions for 45 days. The results showed that mixture B (2:1:2, OMW:DM:IN) at 55 °C produced more methane than at 35 °C and ambient temperature by 40% and 252%, respectively. Another aim of this study was to investigate the effects of the different concentrations of the digestate taken from each mixture on faba bean growth. The results showed that the maximum fresh weight values of the shoot system were observed at 10% and 15% for mixture B at ambient temperature. The best concentration value for the highest root elongation rate is a 5% addition of digestate mixture A at 55 °C, compared with other treatments.

Different plant species exhibit contrasting root traits and penetration to variation in soil bulk density of clayey red soil

AbstractHigh bulk density reduces yields in almost every soil and management system worldwide. Using pioneer plants was one of the practical solutions to remediate the adverse effects from high bulk density. The objectives of this research were to investigate the effect of soil bulk density on root traits and penetration of different pioneer plants (rape [Brassica napus L. cv. Huashuang 4]; deep rape [Brassica napus L. cv. Xinan 28]; lucerne [Medicago sativa L. cv. Ladino]; vetiver [Chrysopogon zizanioides L. cv. Wild]) under controlled and field conditions. Replicated field and laboratory studies were conducted in a soil composition of high clay percentage, high oxides content, and low organic matter content. Seedling and matured root traits of four plants under contrasting bulk density in controlled study and field were analyzed. Under controlled situations, soil with a bulk density of 1.4 g cm–3 had thicker roots (higher diameter) than soil with a bulk density of 1.2 g cm–3, whereas soil with a bulk density of 1.6 g cm–3 had reduced root lengths (RL), branch number, root tip angle, and root elongation rate than soil with a bulk density of 1.4 g cm–3. Similar changes of root diameter (RD) and root length density (RLD) with bulk density also appeared in the field. Generally, the penetration ability of plant species displayed in the order of vetiver > lucerne > deep rape > rape. Vetiver showed the highest penetrating ability due to its high RD (0.7 mm in field), percentage of medium roots (20–50%) and RLD, and small root tip angle to ensure penetration through hard layers. The results demonstrated that vetiver will be an effective pioneer plant for red soil management.