Senecio Vulgaris Research Articles

PCR-based detection of sunflower white blister rust (Pustula helianthicola C. Rost & Thines) in soil samples and asymptomatic host tissue

Sequencing of partial cox2 (part of the mitochondrial cytochrome-c-oxydase (COX) gene) was performed with samples from the oomycete genus Pustula, the white blister rusts of Asteraceae and related families. Sequence comparison uncovered several single nucleotide polymorphisms (SNPs) between P. spinulosa and host specific strains of Pustula isolated from Senecio vulgaris, Tragopogon pratensis and cultivated sunflower, Helianthus annuus. Based on these differences, specific primers were designed for PCR-based detection of white blister rust strains pathogenic to sunflower. The specificity of the primers was confirmed by cross testing with DNA from various oomycetes occurring in the same locality. The limit of detection for DNA of P. helianthicola was 10 pg. This allowed detection with DNA from single sporangia and single oospores. The PCR-based experiments allowed detection of the presence of sunflower white blister rust in soil samples from fields on which infected plants had been cultivated several months before. Moreover, the molecular tools were successfully applied to trace the pathogen in asymptomatic tissue of infected plants, demonstrating the systemic nature of Pustula on sunflower.

Fraser oat and soil extraction responses to zinc and manganese applied to a soil with historic limestone treatments

Kowalenko, C. G. and Ihnat, M. 2011. Fraser oat and soil extraction responses to zinc and manganese applied to a soil with historic limestone treatments. Can. J. Soil Sci. 91: 647–659. A field trial initiated in 1979 examined the possibility of zinc (Zn) and manganese (Mn) deficiencies when limestone was applied to an acidic (approximately pH 5) soil at Agassiz, British Columbia. The results from an initial phase of the study conducted from 1979 through 1985 with cauliflower as the test crop and foliar Zn and Mn have been reported. This study reports on a follow-up to that study, with a focus on the effect of historic limestone treatments on oats with soil rather than foliar applications of Zn and Mn. Oats was selected for this phase, since it is widely assumed to be sensitive to low Mn contents, and was grown from 1988 through 1990. The limestone treatments were made in 1979, 1981 and 1986 at two rates (9 and 19 Mg ha−1each time). The micronutrient treatments were applied to the soil in each of the 3 yr of oat growth to plots that did not have previous soil micronutrient applications. Quantitative visual measurements showed that limestone applications reduced the vigor of common groundsel (Senecio vulgaris L.) weed when the plot area was being fallowed in 1987. In 1988, nitrogen (N) deficiencies were confirmed by visual observations and soil and plant measurements, especially in the treatment with no limestone applied. Adjustments were made to the amount of N fertilizer applied in 1989 and 1990 to eliminate the complication of N deficiencies to the assessment of the effects of limestone on potential Zn and Mn deficiencies. Visual assessment, and plant and soil measurements confirmed that adequate N had been applied. Visual symptoms, dry matter measurements and nutrient contents in the crop showed that Mn and, to a lesser extent, Zn deficiencies were induced by the historic applications of limestone. The effects were quite small showing that these micronutrients were only marginally deficient. Mehlich-3 solution tended to extract more calcium (Ca) and less Mn and Zn from limestone-treated soil than control soil, similar to the response of the crop, showing the potential of this soil test to predict limestone-induced Mn and Zn deficiencies. Although plant uptake and corresponding soil extractions of Ca, Zn and Mn were consistent with regard to treatment effects, the relationships were weak, but provide sufficient information for using soil measurements to assist designing better follow-up studies. Plant measurements showed unexpected increases of iron (Fe) uptake by the crop with increased limestone application rates, whereas, limestone had the opposite effect on soil extraction of the element. Further work is required to determine why this occurred.

Authentication of Senecio scandens and S. vulgaris based on the comprehensive secondary metabolic patterns gained by UPLC–DAD/ESI-MS

A secondary metabolic pattern using ultra-performance liquid chromatography (UPLC)–DAD/ESI-MS was constructed to gain chemical information for authentication of Senecio scandens (SS) and Senecio vulgaris (SV), the two representative species containing hepatotoxic pyrrolizidine alkaloids (HPAs). The metabolic pattern showed three groups of bioactive constituents: phenolic/aromatic acids, flavonoid glycosides and the HPAs. 47 peaks were identified including 19 phenolic/aromatic acids, 10 flavonoid glycosides and 18 PAs by direct comparison with the available reference compounds or deduced from the UV absorption and their ESI-MS fragmentation patterns. The two species could be authenticated diagnostically by their metabolic profiling of the three chromatographic fingerprints. Although both SS and SV contain PAs as the characteristic constituents, only 2 PAs, adonifoline and adonifoline N-oxide were detected in SS, while other 16 PAs were detected in SV, including the highly toxic senecionine, retrorsine, seneciphylline and their corresponding N-oxides. The concentration of PAs in SV is also higher than that in SS. The number and concentration of the phenolic compounds in SS were higher than in SV. Jacaranone derivatives were only detected in SS and jacaranone ethyl ester was detected as the predominant constituent. In the fingerprint of the n-butanol extracts, 10 quercetin and kaempferol glycosides derivatives were detected. 9 were found in SS and only 2 in SV. PAs, jacaranone derivatives and flavonoid glycosides can serve as the metabolic markers to distinguish the Senecio plants from each other, and provide evidence for their clinical application in the consideration of safety and efficacy.

Host range of Secusio extensa (Lepidoptera: Arctiidae), and potential for biological control of Senecio madagascariensis (Asteraceae)

Secusio extensa (Lepidoptera: Arctiidae) was evaluated as a potential biological control agent for Madagascar fireweed, Senecio madagascariensis (Asteraceae), which has invaded over 400 000 acres of rangeland in the Hawaiian Islands and is toxic to cattle and horses. The moth was introduced from southeastern Madagascar into containment facilities in Hawaii, and host specificity tests were conducted on 71 endemic and naturalized species (52 genera) in 12 tribes of Asteraceae and 17 species of non-Asteraceae including six native shrubs and trees considered key components of Hawaiian ecosystems. No-choice feeding tests indicated that plant species of the tribe Senecioneae were suitable hosts with first instars completing development to adult stage on S. madagascariensis (78.3%), Delairea odorata (66.1%), Senecio vulgaris (57.1%), Crassocephalum crepidioides (41.2%), and at significantly lower rates on Emilia fosbergii (1.8%) and Erechtites hieracifolia (1.3%). A low rate of complete larval development also was observed on sunflower, Helianthus annuus (11.6%), in the tribe Heliantheae. However, sunflower was rejected as a potential host in larval-feeding and adult oviposition choice tests involving the primary host S. madagascariensis as control. Although larvae died as first instars on most test species, incomplete development and low levels of feeding were observed on nine species in the tribes Heliantheae, Cardueae and Lactuceae. Larvae did not feed on any non-Asteraceae tested, including species with similar pyrrolizidene alkaloid chemistry, crops, and six ecologically prominent native species. Because all species of Senecioneae are non-native and weedy in Hawaii, these results indicate that S. extensa is sufficiently host-specific for introduction for biological control. High levels of feeding damage observed on potted plants indicate that S. extensa can severely impact the target fireweed as well as D. odorata, a noxious weed in native Hawaiian forests.

Alien species of plants in aquatic and semiaquatic ecosystems of the Vyatka-Kama Cis-Urals

In the territory of the Vyatka-Kama Cis-Urals, 22 species of alien macrophytes are recorded. They compose 6.5% of the number of known macrophyte species known for the region. Most of them do not play an active role in formation of vegetative communities and constitute a part of aquatic communities as accompanying elements (Amaranthus retroflexus, Chenopodium glaucum, C. rubrum, Xanthium strumarium, Epilobium pseudorubescens, Juncus gerardii, Senecio vulgaris, Typha laxmannii, Mimulus guttatus, Butomus junceus, Scirpus tabernaemontani, and Zannichellia repens). They grow in secondary and open natural ecotones and do not pose a serious threat to aquatic ecosystems in the region because of their low activity in aquatic communities. Among alien species of macrophytes, invasive species are encountered. Some of them (Najas major, Vallisneria spiralis, Phragmites altissimus, Juncus tenuis, and Echinochloa crusgalli) have become a constant part of secondary biotope communities but pose a threat to indigenous macrophyte species only in specific biotopes where ecological conditions differ significantly from normal ones. Other species (Elodea canadensis, Epilobium adenocaulon, Impatiens glandulifera, Mentha longifolia, and Lemna gibba) have successfully naturalized in natural ecosystems or have been penetrating into them. The overwhelming majority of alien macrophyte species within the region are plants which do not refer to aquatic plants: hygrophytes (ten species or 45.5%) and hygromesophytes (three species or 13.6%). Only five species (22.7%) belong to hydrophytes and four species are helophytes (18.2%). Six species of alien macrophytes are characterized by transcontinental (North America) drift, 12 species (54.5%) are characterized by transzonal drift, and four species (18.2%) have been introduced from adjacent natural zones.

ChemInform Abstract: A New Acetophenone Derivative and Other Constituents from Senecio vulgaris

Abstractisolation and structure determination

Plant‐mediated effects of soil invertebrates and summer drought on above‐ground multitrophic interactions

Summary1.We conducted a large‐scale field study to determine how the interactive effects of earthworms (Aporrectodea caliginosa) and summer drought affected plant communities containing barley (Hordeum vulgare), shepherd’s purse (Capsella bursa‐pastoris) and common groundsel (Senecio vulgaris), and how such effects then influenced populations of the aphidRhopalosiphum padiand its parasitoid,Aphidius ervi.2.Total biomass of plant communities decreased by around 25% with summer drought, but was increased by the presence of earthworms by over 11%. The effects of drought and earthworms onH. vulgarediffered in monocultures and mixed plant communities. In monocultures, earthworms had the biggest impact, increasing plant biomass, but drought had the biggest effect in multi‐species communities, causing a decrease in biomass.3.Drought had an extremely negative impact onS. vulgarisshoot and root biomass, but this was ameliorated in the roots when earthworms were present.Capsella bursa‐pastoriswas not significantly affected by drought or earthworms. Drought caused a significant increase in shoot nitrogen concentrations in all plants, includingH. vulgare(from 19.2 to 23.8 mg g−1).4.In total, 35 234 aphids were recorded, of which 3936 were parasitized. Drought conditions reduced aphid abundance by over 50%. The interaction was moderated by earthworms, which caused further declines inR. padipopulations under drought conditions, most notably in monocultures.5.The plant‐mediated effects of drought and earthworms (negative and positive, respectively) onR. padihad cascading effects on the parasitoid,Aphidius ervi, which declined in abundance with reduced numbers ofR. padi. In addition, drought had a negative impact onA. erviabundance beyond its impacts on aphid density, suggesting reduced prey quality as well as quantity.6.Synthesis. This study demonstrated the effect of predicted climate change (i.e. reduced summer rainfall) on plant‐mediated interactions between earthworms and above‐ground multitrophic groups. These effects were seen to differ between monocultures and multi‐species plant communities, suggesting that changes in above‐ground–below‐ground linkages in response to drought may influence plant communities in the future.

Plants growing on contaminated and brownfield sites appropriate for use in Organisation for Economic Co-operation and Development terrestrial plant growth test

The Organisation for Economic Co-operation and Development (OECD) terrestrial plant test is often used for the ecological risk assessment of contaminated land. However, its origins in plant protection product testing mean that the species recommended in the OECD guidelines are unlikely to occur on contaminated land. Six alternative species were tested on contaminated soils from a former Zn smelter and a metal fragmentizer with elevated concentrations of Cd, Cu, Pb, and Zn. The response of the alternative species was compared with that of two species recommended by the OECD: Lolium perenne (perennial ryegrass) and Trifolium pratense (red clover). Urtica dioica (stinging nettle) and Poa annua (annual meadowgrass) had low emergence rates in the control soil and so may be considered unsuitable. Festuca rubra (Chewings fescue), Holcus lanatus (Yorkshire fog), Senecio vulgaris (common groundsel), and Verbascum thapsus (great mullein) offer good alternatives to the OECD species. In particular, H. lanatus and S. vulgaris were more sensitive to the soils with moderate concentrations of Cd, Cu, Pb, and Zn than the OECD species.

A New Acetophenone Derivative and other Constituents from Senecio Vulgaris

A new acetophenone derivative, 5-acetyl-2-(2-hydroxyisopropyl)-7-(3,3-dimethylallyl)-2,3-dihydrobenzofuran, has been isolated from the whole plants of Senecio vulgaris. Its structure was established on the basis of spectroscopic methods.

Maternal Environment Effects on Common Groundsel (Senecio vulgaris) Seed Dormancy

Common groundsel adapts readily to new environments and selection pressures and has been variably described as both a winter and summer annual. We characterized germination response to temperature in seeds from populations occurring at six sites along a 700-km north–south transect (Kentucky to Michigan). Seeds were collected in 2000 and 2002 from randomly selected plants (350 to 400), at each sampling site. Two germination patterns were observed: (1) seeds from the southern locations averaged 80 to 90% germination across the range of 5 to 25 C; and (2) seeds from northern locations had reduced germination when incubation temperatures were close to 5 or 25 C. When seed from all locations were grown in a common environment (14/10-h thermoperiod of 22/18 C), their progeny had a germination response that was similar across the temperature gradient, regardless of original location, suggesting germination of the parent seed was due to maternal environmental effects. In a subsequent experiment, common groundsel was grown in growth chambers with warm long days (22/15 C and 16 h of light), warm short days (8 h of light), cold long days (15/8 C and 16 h of light), and cold short days. Eighty percent of seeds from the warm environments germinated across the range from 5 to 25 C indicating that these maternal conditions had produced nondormant seeds. In contrast, 20% or fewer of the seeds from plants in the cold chambers germinated regardless of temperature, suggesting that dormancy had been induced by the cool maternal environment. Results also indicated that signaling of maternal environment varied with inflorescence development stages, meaning the earlier the inflorescences are exposed to cold conditions, the lower the percent germination in F1seeds. Preventing seed maturation on common groundsel growing under cool conditions may reduce the formation of a persistent seed bank.

Genotype and maternal environment affect belowground interactions between Arabidopsis thaliana and its competitors

Ecological interactions between different species are not fixed, but they may depend, at least to some extent, on the particular genotypes involved as well as on the environmental conditions experienced by previous generations. We used a set of natural genotypes of Arabidopsisthaliana, that previously experienced contrasting nutrient and herbivory conditions, to test for the influences of genetic variation and maternal effects on competitive interactions between Arabidopsis and the weedy annuals Anagallisarvensis and Senecio vulgaris. We used activated carbon to discriminate between resource competition and allelopathy components of plant‐plant interactions. There was a clear competitive hierarchy: Senecio>Arabidopsis>Anagallis. Although we found no evidence for allelopathic potential of Arabidopsis, our results indicate that both Anagallis and Senecio exerted negative (direct or indirect) allelopathic effects on Arabidopsis. There were significant differences among Arabidopsis genotypes in their competitive effects on both neighbor species, as well as in their response to competition. Maternal environments significantly influenced not only the growth and fitness of Arabidopsis itself, but also its competitive effect on Anagallis. We found, however, no evidence that maternal environments affected the competitive effect on Senecio or overall competitive response of Arabidopsis. Generally, resource competition played a greater role than allelopathy, and genotype effects were more important than maternal effects. Our study demonstrates that ecological interactions, such as plant competition, are complex and multi‐layered, and that, in particular, the influence of genetic variation on interactions with other species should not be overlooked.

Is reproductive allocation inSenecio vulgarisplastic?

Several purported cases of plasticity in plant allocation patterns appear to be the effects of size and allometric growth (“apparent plasticity”). To ask whether there is true plasticity (i.e., a change in the allometric trajectory) in reproductive allocation in Senecio vulgaris L., we grew S. vulgaris plants at high and low levels of water, nutrients, and competition, and analyzed the relationship between vegetative and seed biomass. Plant size was the major determinant of reproductive output, accounting for 83% of the variation in log (seed mass). There were also significant effects of the treatments that were not due to size, accounting for an additional 9% of the variation. The treatments affected the allometric coefficient (intercept), not the allometric exponent (slope) of the relationship, reflecting a small but significant shift in the efficiency of conversion of total plant biomass into reproductive biomass. In a second experiment, we grew S. vulgaris plants at three nutrient levels and allowed all individuals to complete their life cycles. Again, nutrient level had a small but significant effect on the allometric coefficient. Plasticity in reproductive allocation exists, but is very limited. The primary effects of the environment on the reproductive output of S. vulgaris occur via plant size.

Weed Community Composition in Tree Fruit Nurseries Treated with Methyl Bromide and Alternative Fumigants

Many agricultural cropping systems have relied on methyl bromide (MeBr) for pest control, including weeds, for decades. Alternative fumigants are being sought worldwide because MeBr has been identified as an ozone-layer depleting substance. Weed communities respond dynamically to alterations in management systems. Thus, transition from MeBr to alternative fumigants may cause shifts in weed communities. This hypothesis was tested in four commercial fruit nurseries in California, USA. Treatments included nonfumigated control, MeBr (98%), iodomethane (50%) + chloropicrin (50%), 1,3-dichloropropene (1,3-D), 1,3-D (61%) + chloropicrin (35%), and 1,3-D (62%) + chloropicrin (35%) applied subsurface. All the fumigants reduced the population of common major weed species and had similar species composition as MeBr. None of the fumigants, including MeBr, controlled species such as Medicago polymorpha, Lotus purshianus, Malva parviflora, Conyza sp., Senecio vulgaris, and Sonchus oleraceus. This study suggested that, fruit nurseries transitioning from MeBr to alternatives may not see an immediate shift in weed communities. However, Additional weed control measures will be required to manage weed species of the Asteraceae, Fabaceae, and Malvaceae family that are not controlled by either MeBr or the alternate fumigants.

HERBIGATION IN A CHERRY ORCHARD – EFFICIENCY OF PENDIMETHALIN

HERBIGATION IN A CHERRY ORCHARD – EFFICIENCY OF PENDIMETHALIN

Tomato infectious chlorosis virus

<i>Tomato infectious chlorosis virus</i>

Palatability to a generalist herbivore, defence and growth of invasive and native Senecio species: testing the evolution of increased competitive ability hypothesis

This paper tests the prediction that introduced plants may become successful invaders because they experience evolutionary changes in growth and defence in their new range [evolution of increased competitive ability hypothesis (EICA)]. Interspecific and intraspecific binary feeding choices were offered to the snail Helix aspersa. The choices were between: (1) plants of the invasive Senecio inaequidens and Senecio pterophorus derived from populations in the introduced range (Europe) and plants of three indigenous species (Senecio jacobea, Senecio vulgaris and Senecio malacitanus) from populations in Europe; (2) plants of the invasive S. inaequidens and S. pterophorus from populations in the introduced range (Europe) and from populations in the native range (South Africa). We did not find a clear pattern of preference for indigenous or alien species of Senecio. However, we found that European invasive populations of S. inaequidens and S. pterophorus were less palatable than South African native populations. Moreover, in contrast to the predictions of the EICA hypothesis, the invasive genotypes of both species also showed a higher total concentration of pyrrolizidine alkaloids, and in the case of S. inaequidens we also found higher growth than in native genotypes. Our results are discussed with respect to the refinement of the EICA hypothesis that takes into account the difference between specialist and generalist herbivores and between qualitative and quantitative defences. We conclude that invasive populations of S. inaequidens and S. pterophorus are less palatable than native populations, suggesting that genetic differentiation associated with founding may occur and contribute to the plants' invasion success by selecting the best-defended genotypes in the introduced range.

Involvement of Bcl-xL degradation and mitochondrial-mediated apoptotic pathway in pyrrolizidine alkaloids-induced apoptosis in hepatocytes

Pyrrolizidine alkaloids (PAs) are natural hepatotoxins with worldwide distribution in more than 6000 high plants including medicinal herbs or teas. The aim of this study is to investigate the signal pathway involved in PAs-induced hepatotoxicity. Our results showed that clivorine, isolated from Ligularia hodgsonii Hook, decreased cell viability and induced apoptosis in L-02 cells and mouse hepatocytes. Western-blot results showed that clivorine induced caspase-3/-9 activation, mitochondrial release of cytochrome c and decreased anti-apoptotic Bcl-xL in a time (8–48 h)- and concentration (1–100 μM)-dependent manner. Furthermore, inhibitors of pan-caspase, caspase-3 and caspase-9 significantly inhibited clivorine-induced apoptosis and rescued clivorine-decreased cell viability. Polyubiquitination of Bcl-xL was detected after incubation with 100 μM clivorine for 40 h in the presence of proteasome specific inhibitor MG132, indicating possible degradation of Bcl-xL protein. Furthermore, pretreatment with MG132 or calpain inhibitor I for 2 h significantly enhanced clivorine-decreased Bcl-xL level and cell viability. All the other tested PAs such as senecionine, isoline and monocrotaline decreased mouse hepatocytes viability in a concentration-dependent manner. Clivorine (10 μM) induced caspase-3 activation and decreased Bcl-xL was also confirmed in mouse hepatocytes. Meanwhile, another PA senecionine isolated from Senecio vulgaris L also induced apoptosis, caspase-3 activation and decreased Bcl-xL in mouse hepatocytes. In conclusion, our results suggest that PAs may share the same hepatotoxic signal pathway, which involves degradation of Bcl-xL protein and thus leading to the activation of mitochondrial-mediated apoptotic pathway.

Seed production and subsequent seed germination of Senecio vulgaris (groundsel) grown alone or in autumn‐sown crops

Summary Senecio vulgaris is a common weed of agriculture in the UK, but is also of food value to invertebrates and birds. Thus, it may be beneficial to retain it within agricultural ecosystems to enhance overall biodiversity. A less intensive approach to weed management requires a sound understanding of weed population dynamics so as to avoid unacceptable population growth. Experiments were carried out in 2003 and 2004 to assess seed production, and subsequent germination, by S. vulgaris growing alone, in winter wheat, or in winter field beans. Plant and seed samples were collected during May and June. There was a strong allometric relationship between capsule number and plant weight, irrespective of the year or the presence of crop competition. Numbers of seeds/capsule varied slightly from 51 to 66 seeds per capsule. Plants growing alone were estimated to produce 8471 to 12 887 seeds per plant, whilst those in wheat only 923 to 2156. Germination tests in Petri dishes in incubators showed that virtually all seeds were viable and germinated under daily alternating light:dark conditions within 10 days. Seeds in continuous dark germinated less readily, reaching only 30% after 21 days. On the basis of this and other published work, it would appear that the retention of S. vulgaris in arable fields will not pose a major threat to the long‐term viability of crop production.

Weed Control and Phytotoxicity Following Preemergence Herbicide Applications to Container-grown Herbaceous Plants

Abstract Effectiveness of five preemergence herbicides was determined for four container-grown ornamental crops. Herbicides tested were Barricade (prodiamine); BroadStar (flumioxazin); Gallery (isoxaben); Scotts Ornamental Weedgrass Control (Scotts OWC) (pendimethalin); and Treflan (trifluralin). Four herbaceous plant species were utilized in this trial, namely, Guizhou sage (Artemisia lactiflora Wall. (Guizhou group)); hopflower oregano (Origanum libanoticum Boiss.); Daghestan sage (Salvia daghestanica Sosn.); and skullcap (Scutellaria resinosa Torr.). The seven weed species evaluated in this trial were annual bluegrass (Poa annua L.); barnyardgrass (Echinochloa crus-galli L.); yellow foxtail grass (Setaria glauca L.); purslane (Portulaca oleracea L.); common groundsel (Senecio vulgaris L.); redroot pigweed (Amaranthus retroflexus L.); and annual sowthistle (Sonchus oleraceus L.). Two controls, one with weeds and one without were also evaluated. The experiment was conducted in two locations: Fort Collins and Grand Junction, Colorado. Weed control levels varied across a range of herbicide treatments and ornamental species. Where differences among herbicides were observed, BroadStar and Treflan tended to be more effective than the other herbicides, while Gallery, Scotts OWC and Barricade, were less effective. Plants treated with Gallery often resulted in decreased dry weights; however, no visual phytotoxicity symptoms were observed with any herbicide treatments. Daghestan sage and skullcap were the crop species most adversely effected.

Emergence Prediction of Common Groundsel (Senecio Vulgaris)

Abstract Common groundsel is an important weed of strawberry and other horticultural crops. Few herbicides are registered for common groundsel control in such crops, and understanding and predicting the timing and extent of common groundsel emergence might facilitate its management. We developed simple emergence models on the basis of soil thermal time and soil hydrothermal time and validate them with the use of field-derived data from Minnesota and Ohio. Soil thermal time did not predict the timing and extent of seedling emergence as well as hydrothermal time. Soil hydrothermal time, adjusted for shading effects caused by straw mulch in strawberry, greatly improved the accuracy of seedling emergence predictions. Although common groundsel generally emerges from sites at or near the soil surface, the hydrothermal model better predicts emergence when using hydrothermal time at 5 cm rather than 0.005 cm, probably because of the volatility of soil temperature and water potential near the soil surface. Nomencl...