Mapping of QTL controlling root hair length in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) under phosphorus deficiency

Suboptimal phosphorus availability is a primary constraint for terrestrial plant growth and crop productivity. Root hairs are subcellular extensions from the root epidermis that play an important role in the uptake of immobile nutrients such as phosphorus by increasing soil exploration. The objective of this study was to identify quantitative trait loci for root hair length and plasticity in response to phosphorus stress in maize. Using a cigar roll culture system in a controlled environment, root traits including root hair length, tap root length, root thickness, and root biomass were evaluated in 169 recombinant inbred lines derived from a cross between B73 and Mo17. These parents have contrasting adaptation to low phosphorus availability in the field. The parents segregated for the length of individual root hairs under low phosphorus. Average root hair length (RHL) of RI lines ranged from 0.6 to 3.5 mm with an average of 2.0 mm under fertile conditions, and RHL was increased from 0% to 185% under phosphorus stress. Using composite interval mapping with a LOD threshold of 3.27, one QTL was associated with RHL plasticity, three QTL with RHL under high fertility, and one QTL with root hair length under low phosphorus. These QTL accounted for 12.7%, 31.9%, and 9.6% of phenotypic variation, respectively. No QTL were detected for taproot thickness and root biomass. Six QTL were associated with 53.1% of the total variation for seed phosphorus in the population. Root biomass plasticity was significantly correlated with RHL induced by low phosphorus, taproot length plasticity, and seed phosphorus reserves. Our results suggest that genetic variation in root hair length and plasticity may be an appropriate target for marker aided selection to improve the phosphorus efficiency of maize.     

Significance of root hairs for plant performance under contrasting field conditions and water deficit

Background and AimsPrevious laboratory studies have suggested selection for root hair traits in future crop breeding to improve resource use efficiency and stress tolerance. However, data on the interplay between root hairs and open-field systems, under contrasting soils and climate conditions, are limited. As such, this study aims to experimentally elucidate some of the impacts that root hairs have on plant performance on a field scale.MethodsA field experiment was set up in Scotland for two consecutive years, under contrasting climate conditions and different soil textures (i.e. clay loam vs. sandy loam). Five barley (Hordeum vulgare) genotypes exhibiting variation in root hair length and density were used in the study. Root hair length, density and rhizosheath weight were measured at several growth stages, as well as shoot biomass, plant water status, shoot phosphorus (P) accumulation and grain yield.Key ResultsMeasurements of root hair density, length and its correlation with rhizosheath weight highlighted trait robustness in the field under variable environmental conditions, although significant variations were found between soil textures as the growing season progressed. Root hairs did not confer a notable advantage to barley under optimal conditions, but under soil water deficit root hairs enhanced plant water status and stress tolerance resulting in a less negative leaf water potential and lower leaf abscisic acid concentration, while promoting shoot P accumulation. Furthermore, the presence of root hairs did not decrease yield under optimal conditions, while root hairs enhanced yield stability under drought.ConclusionsSelecting for beneficial root hair traits can enhance yield stability without diminishing yield potential, overcoming the breeder’s dilemma of trying to simultaneously enhance both productivity and resilience. Therefore, the maintenance or enhancement of root hairs can represent a key trait for breeding the next generation of crops for improved drought tolerance in relation to climate change.     

What are the implications of variation in root hair length on tolerance to phosphorus deficiency in combination with water stress in barley (Hordeum vulgare)?

Background and Aims

Phosphorus commonly limits crop yield and is frequently applied as fertilizer; however, supplies of quality rock phosphate for fertilizer production are diminishing. Plants have evolved many mechanisms to increase their P-fertilizer use efficiency, and an understanding of these traits could result in improved long-term sustainability of agriculture. Here a mutant population is utilized to assess the impact of root hair length on P acquisition and yield under P-deficient conditions alone or when combined with drought.

Methods

Mutants with various root hair phenotypes were grown in the glasshouse in pots filled with soil representing sufficient and deficient P treatments and, in one experiment, a range of water availability was also imposed. Plants were variously harvested at 7 d, 8 weeks and 14 weeks, and variables including root hair length, rhizosheath weight, biomass, P accumulation and yield were measured.

Key Results

The results confirmed the robustness of the root hair phenotypes in soils and their relationship to rhizosheath production. The data demonstrated that root hair length is important for shoot P accumulation and biomass, while only the presence of root hairs is critical for yield. Root hair presence was also critical for tolerance to extreme combined P deficit and drought stress, with genotypes with no root hairs suffering extreme growth retardation in comparison with those with root hairs.

Conclusions

The results suggest that although root hair length is not important for maintaining yield, the presence of root hairs is implicit to sustainable yield of barley under P-deficient conditions and when combined with extreme drought. Root hairs are a trait that should be maintained in future germplasm.     

Rhizosheath formation and involvement in foxtail millet(Setaria italica) root growth under drought stress

The rhizosheath, a layer of soil particles that adheres firmly to the root surface by a combination of root hairs and mucilage, may improve tolerance to drought stress. Setaria italica(L.) P. Beauv.(foxtail millet), a member of the Poaceae family, is an important food and fodder crop in arid regions and forms a larger rhizosheath under drought conditions. Rhizosheath formation under drought conditions has been studied, but the regulation of root hair growth and rhizosheath size in response to soil moisture remains unclear. To address this question, in this study we monitored root hair growth and rhizosheath development in response to a gradual decline in soil moisture. Here, we determined that a soil moisture level of 10%–14%(w/w)stimulated greater rhizosheath production compared to other soil moisture levels. Root hair density and length also increased at this soil moisture level, which was validated by measurement of the expression of root hair-related genes.These findings contribute to our understanding of rhizosheath formation in response to soil water stress.     

OsSNDP1, a Sec14-nodulin domain-containing protein, plays a critical role in root hair elongation in rice

Rice is cultivated in water-logged paddy lands. Thus, rice root hairs on the epidermal layers are exposed to a different redox status of nitrogen species, organic acids, and metal ions than root hairs growing in drained soil. To identify genes that play an important role in root hair growth, a forward genetics approach was used to screen for short-root-hair mutants. A short-root-hair mutant was identified and isolated by using map-based cloning and sequencing. The mutation arose from a single amino acid substitution of OsSNDP1 (Oryza sativa Sec14-nodulin domain protein), which shows high sequence homology with Arabidopsis COW1/AtSFH1 and encodes a phosphatidylinositol transfer protein (PITP). By performing complementation assays with Atsfh1 mutants, we demonstrated that OsSNDP1 is involved in growth of root hairs. Cryo-scanning electron microscopy was utilized to further characterize the effect of the Ossndp1 mutation on root hair morphology. Aberrant morphogenesis was detected in root hair elongation and maturation zones. Many root hairs were branched and showed irregular shapes due to bulged nodes. Many epidermal cells also produced dome-shaped root hairs, which indicated that root hair elongation ceased at an early stage. These studies showed that PITP-mediated phospholipid signaling and metabolism is critical for root hair elongation in rice.     

Uncovering Genes and Ploidy Involved in the High Diversity in Root Hair Density,Length and Response to Local Scarce Phosphate in Arabidopsis thaliana

Plant root hairs increase the root surface to enhance the uptake of sparingly soluble and immobile nutrients, such as the essential nutrient phosphorus, from the soil. Here, root hair traits and the response to scarce local phosphorus concentration were studied in 166 accessions of Arabidopsis thaliana using split plates. Root hair density and length were correlated, but highly variable among accessions. Surprisingly, the well-known increase in root hair density under low phosphorus was mostly restricted to genotypes that had less and shorter root hairs under P sufficient conditions. By contrast, several accessions with dense and long root hairs even had lower hair density or shorter hairs in local scarce phosphorus. Furthermore, accessions with whole-genome duplications developed more dense but phosphorus-insensitive root hairs. The impact of genome duplication on root hair density was confirmed by comparing tetraploid accessions with their diploid ancestors. Genome-wide association mapping identified candidate genes potentially involved in root hair responses tp scarce local phosphate. Knock-out mutants in identified candidate genes (CYR1, At1g32360 and RLP48) were isolated and differences in root hair traits in the mutants were confirmed. The large diversity in root hair traits among accessions and the diverse response when local phosphorus is scarce is a rich resource for further functional analyses.     

CHARACTERIZATION OF THE NUCLEAR DNA OF HORDEUM VULGARE ROOT HAIRS: AMPLIFICATION DISAPPEARS UNDER SALT STRESS

In Hordeum vulgare L., the nucleus of differentiating root hairs contains amplified, extrachromosomal DNA sequences. Cytophotometry shows that the nuclei of trichoblasts and root hairs grown under normal conditions contain up to 50% more DNA than those grown in 200 mM salt. Although the root hairs develop and differentiate under salt stress, amplification of their nuclear DNA is suppressed. From this, we conclude that amplification is not necessary for differentiation at the cellular level. Characterization of the amplified nuclear DNA of the root hair is based on the physical/chemical nature of the DNA. The amplified sequences separate as a satellite band when total nucleic acids are centrifuged on CsCl gradients. Enzyme restriction of the satellite and main bands with Msp I and Hpa II followed by agarose gel electrophoresis shows that the satellite band is not more highly methylated than the main band. Restriction of the root hair DNA with EcoRI reveals repetitive DNA sequences not seen in similarly restricted whole root, leaf or salt-stressed root hair preparations. While these unique, repetitive sequences in the 2–6 kb region of the gel do not hybridize with ribosomal, chloroplast, or mitochondrial DNAs, RNA hybridization shows that some of them are transcribed. We believe that the amplified sequences are extrachromosomal based on their selective degradation during root hair senescence, their separation as a satellite band and their restriction patterns.     

Effect of soil moisture and phosphate level on root hair growth of corn roots

Summary Root hairs have been shown to enhance P uptake by plants growing in low P soil. Little is known of the factors controlling root hair growth. The objective of this study was to investigate the influence of soil moisture and P level on root hair growth of corn (Zea mays L.). The effect of volumetric soil moistures of 22% (M₀), 27% (M₁), and 32% (M₂) and soil (Raub silt loam, Aquic Argiudoll) P levels of, 0.81 (P₀), 12.1 (P₁), 21.6 (P₂), 48.7 (P₃), and 203.3 (P₄) mol P L^–1 initially in the soil solution, on shoot and root growth, P uptake, and root hair growth of corn was studied in a series of pot experiments in a controlled climate chamber. Root hair growth was affected more by soil moisture than soil P. The percentage of total root length with root hairs and the density and length of root hairs on the root sections having root hairs all increased as soil moisture was reduced from M₂ to M₀. No relationship was found between root hair length and soil P. Density of root hairs, however, was found to decrease with an increase in soil P. No correlation was found between root hair growth parameters and plant P content, further suggesting P plays a secondary role to moisture in regulating root hair growth in soils. The increase in root hair growth appears to be a response by the plant to stress as yield and P uptake by corn grown at M₀ were only 0.47 to 0.82, and 0.34 to 0.74, respectively, of that measured at M₁ across the five soil P levels. The increase in root hair growth at M₀, which represents an increase of 2.76 to 4.03 in root surface area, could offset, in part, the reduced rate of root growth, which was the primary reason for reduced P uptake under limited soil moisture conditions.Journal Paper No. 10,066 Purdue Univ. Agric. Exp. Stn., W. Lafayette, IN 47907. Contribution from the Dep. of Agron. This paper was supported in part by a grant from the Tennessee Valley Authority.     

The root epidermis of<Emphasis Type="Italic"> Echium plantagineum</Emphasis> L.: a novel type of pattern based on the distribution of short and long root hairs

The great majority of angiosperm species form a group in which either every cell in the root epidermis produces a root hair, or the cells that produce these hairs are randomly distributed. We describe, for the first time, pattern in the root epidermal cells of a species within this group. The seedling root of Echium plantagineum L. (Boraginaceae) has an epidermis in which almost every cell produces a root hair, but these are of two types, short hairs (up to 200 micro m) and long hairs (>200 micro m), which are in separate cell files, with the cells bearing long hairs usually separated by one or two files of cells bearing short hairs; the epidermal cells with the long root hairs are longer than the epidermal cells with the short root hairs. The long root hairs are initiated and develop earlier than the short root hairs. Transverse sections of the region of the root which contains only developing long root hairs show that the hair cells are located above anticlinal walls between underlying cortical cells. We regard the distribution of root epidermal cells in E. plantagineum as a sub-type of this group. We discuss the possible evolution, from this sub-type, of another group that is characterised by hair cells and non-hair cells occurring in separate files.     

Hair density in the Eurasian otter <Emphasis Type="Italic">Lutra lutra</Emphasis> and the Sea otter <Emphasis Type="Italic">Enhydra lutris</Emphasis>

The hair density of adult Eurasian otters Lutra lutra (Linnaeus, 1758) and sea otters Enhydra lutris (Linnaeus, 1758) was analysed using skin samples taken from frozen carcasses. Lutra lutra exhibited a mean hair density of about 70 000 hairs/cm² (whole body, appendages excepted), the mean individual density ranging from about 60 000 to 80 000 hairs/cm². The dominant hair type were secondary hairs (wool hairs), the hair coat comprising only 1.26% of primary hairs (PH). Secondary hair (SH) density remained constant over the body (appendages excepted), whereas a few variations in PH density were observed. Neither an influence of the sex, nor a seasonal variation of the hair coat was found, moulting seems to be continuous. Enhydra lutris had a hair density between 120 000 and 140 000 hairs/cm², the primary hairs representing less than 1% within the hair coat. Hair density remained quite constant over the regions of the trunk but was lower at the head (about 60 000 hairs/cm² on the cheek). The hair follicles were arranged in specific groups with different bundles of varying size, normally comprising dominant numbers of wool hair (SH) follicles. Invariably there was always a large central primary hair follicle and numerous sebaceous glands between the bundles and principally around the PH follicles. The results are discussed related to possible ecological influences on hair coat density.     

Sodium chloride reduces growth and cytosolic calcium,but does not affect cytosolic pH,in root hairs of Arabidopsis thaliana L

The effects of salinity (NaCl) stress on growth, cytosolic Ca(2+) gradients and cytosolic pH homeostasis of root hairs of Arabidopsis thaliana are assessed here. Neither cytosolic Ca(2+) nor pH at the hair apex were significantly affected by 20 min exposure of up to 90 mM NaCl or of up to 5 mM extracellular Ca(2+). Exposure to increasing NaCl concentrations, up to 90 mM, for 2 d or 6 d reduced hair extension, and this inhibition was relieved by supplemental extracellular Ca(2+). Such extended salinity stress reduced the magnitude of the Ca(2+) gradient in the apical 12 microm of hairs at all NaCl concentrations tested (up to 90 mM), including NaCl concentrations that did not reduce hair extension. The magnitude of the tip-focused gradient was also reduced in root hairs of plants grown with low (0.5 mM) extracellular Ca(2+) when compared to those in 5 mM extracellular Ca(2+), regardless of the presence of NaCl. Up to 90 mM NaCl did not affect cytosolic pH of root hairs in any of the treatments. It is concluded that NaCl inhibition of root hair extension in the long term may operate via alterations in the tip-focused Ca(2+) gradient that regulates root hair growth. However, NaCl-induced alterations in this gradient do not always lead to detectably altered growth kinetics. Short-term signalling events in response to NaCl may operate by a means other than altering Ca(2+) at the root hair apex. Salinity stress in root hairs does not appear to be mediated by effects on cytosolic pH.     

Electron Microscopic Observation of the Azolla-Anabaena azollae Relationship

The structure of Azolla pinnate leaves was examined by means of light and transmission electron microscopy. Emphasis was put on the ultra structural cytology of leaf cavity hairs both in association with Anabaena and in Anabaena-free cultures of Azolla and on the roles of the hair in substance change between the symbionts. The cavity hairs were multicultural and branched. There were numerous mitochondria, plastids, endoplasmic reticular and ribosome’s in the cytoplasm of the hair. A. marked characteristic of the hair was the cell wall ingrowths; There were large electron-transparent area between the in growing cell wall and the plasmolemma. Some vesicles were found in this area. It was suggested that these vesicles as transporters played the role in transporting substances. Electron microscopy revealed that some differences were present between the basal cell and the terminal branched cell of the hairs. In the latter, the cytoplasma, organelles, growing wall and vesicles were richer in the electron-transparent area than in the former This feature of the terminal branched cell showed that the terminal cell of the hair was more active in absorption and/or secretion of metabolites than that of the basal cell. Some hairs were found near the stem apex of Azolla. It was suggested that these hairs functioned in supplying the nitric compounds for the algae living on the stem apex of Azolla. These algae had no ability to fix nitrogen because of lacking heterocyst. In the absence of Anabaena azollae, the leaf cavity hairs were still present in Azolla pinnata. However, a lot of osmiophilic substances can often be seen in the vacuole of this hair.     

Root hair length and rhizosheath mass depend on soil porosity,strength and water content in barley genotypes

Selecting plants with improved root hair growth is a key strategy for improving phosphorus-uptake efficiency in agriculture. While significant inter- and intra-specific variation is reported for root hair length, it is not known whether these phenotypic differences are exhibited under conditions that are known to affect root hair elongation. This work investigates the effect of soil strength, soil water content (SWC) and soil particle size (SPS) on the root hair length of different root hair genotypes of barley. The root hair and rhizosheath development of five root hair genotypes of barley (Hordeum vulgare L.) was compared in soils with penetrometer resistances ranging from 0.03 to 4.45 MPa (dry bulk densities 1.2–1.7 g cm^?3). A “short” (SRH) and “long” root hair (LRH) genotype was selected to further investigate whether differentiation of these genotypes was related to SWC or SPS when grown in washed graded sand. In low-strength soil (<1.43 MPa), root hairs of the LRH genotype were on average 25 % longer than that of the SRH genotype. In high-strength soil, root hair length of the LRH genotype was shorter than that in low-strength soil and did not differ from that of the SRH genotype. Root hairs were shorter in wetter soils or soils with smaller particles, and again SRH and LRH did not differ in hair length. Longer root hairs were generally, but not always, associated with larger rhizosheaths, suggesting that mucilage adhesion was also important. The root hair growth of barley was found to be highly responsive to soil properties and this impacted on the expression of phenotypic differences in root hair length. While root hairs are an important trait for phosphorus acquisition in dense soils, the results highlight the importance of selecting multiple and potentially robust root traits to improve resource acquisition in agricultural systems.     

不同灌溉方式对玉米根毛生长发育的影响

在盆栽条件下,采用分根装置,在光学显微镜和电子显微镜下对均匀灌水、固定部分根区灌水和根系分区交替灌水3种方式下各1/2根区的根毛发育状况进行观察并采样照相,研究不同根区根毛的生长发育特征.结果表明：处理40 d时,固定部分根区灌水条件下,非灌水区的根毛有明显退化脱落现象,退化区所占比例为20.96%,明显大于其他根区;灌水区的根系发黄,有腐烂斑,且根分枝有退化现象,根毛密集区的密集程度不如非灌水区,但根毛退化区所占比例小（15.72%）,退化程度轻.均匀灌水根系的根毛发育状况与固定灌水的灌水区类似.交替灌水条件下,先灌水区和后灌水区根毛密集区的密集程度均较高,根毛退化脱落区分别占9.77%和10.38%,明显小于均匀灌水和固定灌水.说明采用交替灌水方式可促进根系根毛的生长发育,而持续湿润或干燥不利于根系根毛的生长发育.     

Morphological synergism in root hair length,density, initiation and geometry for phosphorus acquisition in Arabidopsis thaliana: A modeling approach

Low phosphorus availability regulates root hair growth in Arabidopsis by (1) increasing root hair length, (2) increasing root hair density, (3) decreasing the distance between the root tip and the point at which root hairs begin to emerge, and (4) increasing the number of epidermal cell files that bear hairs (trichoblasts). The coordinated regulation of these traits by phosphorus availability prompted us to speculate that they are synergistic, that is, that they have greater adaptive value in combination than they do in isolation. In this study, we explored this concept using a geometric model to evaluate the effect of varying root hair length (short, medium, and long), density (0, 24, 48, 72, 96, and 120 root hairs per mm of root length), tip to first root hair distance (0.5, 1, 2, and 4 mm), and number of trichoblast files (8 vs. 12) on phosphorus acquisition efficiency (PAE) in Arabidopsis. SimRoot, a dynamic three-dimensional geometric model of root growth and architecture, was used to simulate the growth of Arabidopsis roots with contrasting root hair parameters at three values of phosphorus diffusion coefficient (D _e=1×10^–7, 1×10^–8, and 1×10^–9 cm² s^–1) over time (20, 40, and 60 h). Depzone, a program that dynamically models nutrient diffusion to roots, was employed to estimate PAE and competition among root hairs. As D _e decreased from 1×10^–7 to 1×10^–9 cm² s^–1, roots with longer root hairs and higher root hair densities had greater PAE than those with shorter and less dense root hairs. At D _e=1×10^–9 cm² s^–1, the PAE of root hairs at any given density was in the order of long hairs > medium length hairs > short hairs, and the maximum PAE occurred at density = 96 hairs mm^–1 for both long and medium length hairs. This was due to greater competition among root hairs when they were short and dense. Competition over time decreased differences in PAE due to density, but the effect of length was maintained, as there was less competition among long hairs than short hairs. At high D _e(1×10^–7 cm² s^–1), competition among root hairs was greatest among long hairs and lowest among short hairs, and competition increased with increasing root hair densities. This led to a decrease in PAE as root hair length and density increased. PAE was also affected by the tip to first root hair distance. At low D _e values, decreasing tip to first root hair distance increased PAE of long hairs more than that of short hairs, whereas at high D _e values, decreasing tip to first root hair distance increased PAE of root hairs at low density but decreased PAE of long hairs at very high density. Our models confirmed the benefits of increasing root hair density by increasing the number of trichoblast files rather than decreasing the trichoblast length. The combined effects of all four root hair traits on phosphorus acquisition was 371% greater than their additive effects, demonstrating substantial morphological synergy. In conclusion, our data support the hypothesis that the responses of root hairs to low phosphorus availability are synergistic, which may account for their coordinated regulation.     

The efficiency of Arabidopsis thaliana (Brassicaceae) root hairs in phosphorus acquisition

Arabidopsis thaliana root hairs grow longer and denser in response to low-phosphorus availability. In addition, plants with the root hair response acquire more phosphorus than mutants that have root hairs that do not respond to phosphorus limiting conditions. The purpose of this experiment was to determine the efficiency of root hairs in phosphorus acquisition at high- and low-phosphorus availability. Root hair growth, root growth, root respiration, plant phosphorus uptake, and plant phosphorus content of 3-wk-old wild-type Arabidopsis (WS) were compared to two root hair mutants (rhd6 and rhd2) under high (54 mmol/m) and low (0.4 mmol/m) phosphorus availability. A cost-benefit analysis was constructed from the measurements to determine root hair efficiency. Under high-phosphorus availability, root hairs did not have an effect on any of the parameters measured. Under low-phosphorus availability, wild-type Arabidopsis had greater total root surface area, shoot biomass, phosphorus per root length, and specific phosphorus uptake. The cost-benefit analysis shows that under low phosphorus, wild-type roots acquire more phosphorus for every unit of carbon respired or unit of phosphorus invested into the roots than the mutants. We conclude that the response of root hairs to low-phosphorus availability is an efficient strategy for phosphorus acquisition.     

Observations on root hair production by lucerne,maize and perennial ryegrass grown in a sandy loam

Summary Root hair production by young plants of lucerne, maize and perennial ryegrass grown in a sandy loam was assessed by examining roots growing at a soil-glass interface. Results are given for the percentage frequency distribution of root hair lengths and the numbers of root hairs produced per mm root. The mean lengths of root hairs observed on lucerne, maize and perennial ryegrass roots were 0.35, 0.90 and 1.12 mm respectively. Lucerne produced an average of 105 root hairs per mm of root, whereas maize produced 161 and perennial ryegrass produced 88. The total length of root hairs per mm length of root was estimated to be 37, 146 and 99 mm for lucerne, maize and perennial ryegrass resp. Letcombe Laboratory     

Biological and environmental degradation of gorilla hair and microsatellite amplification success

Naturally shed hairs are an important source of genetic material for both conservation and forensics but are notoriously poor sources of DNA. DNA degradation in hair roots is caused by apoptosis as part of the cycle of hair growth and by autolysis in decomposing animals. Shed hairs are additionally exposed to degenerative environmental processes. However, genetic studies rarely examine hair root morphologies or refer to root growth phases prior to analysis, and detailed knowledge of the rapidity of DNA degradation amongst shed hairs is lacking. We examined the effects of biological and environmental processes on western lowland gorilla ( Gorilla gorilla gorilla Savage and Wyman) hair roots with respect to morphological characteristics and polymerase chain reaction (PCR) success at eight nuclear loci. Root type frequencies indicate that gorilla body hairs may exhibit a longer telogen phase than human head hairs. All plucked hair root types amplified more efficiently than shed hairs, and only 41% of shed hairs had root types considered suitable for genotyping. Telogen hairs from fresh nests were four-fold more useful for genotyping if the roots were associated with translucent epithelial tissue, and preselection of these root types doubled the overall data-yield to 58%. Nest age correlated with root morphology and PCR success, and PCR success was almost halved after 3 days of exposure. Finally, an association between postmortem interval, root morphology, and PCR success was observed that was consistent with postmortem changes reported in human head hairs.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 281–294.     

Role of manganese in low-pH-induced root hair formation in<Emphasis Type="Italic"> Lactuca sativa</Emphasis> cv. Grand Rapids seedlings

Root hair formation is induced by low pH in lettuce (Lactuca sativa L. cv. Grand Rapids) seedlings cultured in mineral medium. The role of mineral concentrations in this phenomenon was investigated, especially for manganese. When lettuce seedlings were cultured in media that were deficient in calcium (Ca), manganese (Mn), boron (B) or molybdenum (Mo), morphological changes were induced in roots. Deficiency of other nutrients had little effect on root hair formation. Ca or B deficiency inhibited the growth of the main root and the formation of root hairs, regardless of pH. Mn or Mo deficiency increased root hair formation at pH 6 and suppressed main root growth slightly. In contrast, increasing the Mn concentration suppressed low-pH-induced root hair formation. The Mn content of roots grown at pH 4 was only about 15% of that at pH 6. In contrast, the Mo content of roots grown at low pH was about six times that of roots grown at neutral pH. These results suggest that root hair formation induced by low pH is at least partly mediated by decreased Mn uptake in root cells.