Marnie E. Light

Isolation of the major germination cue from plant-derived smoke

A highly active, heat stable, long lasting compound, 3- methyl-2H-furo[2,3-c]pyran-2-one (1), that stimulates seed germination was isolated from plant-derived smoke water using bioactivity-guided fractionation. The identification of this natural molecule, the major germination cue from smoke, should now rapidly lead to a more comprehensive understanding of the role of smoke as a promoter of seed germination.

Anti-inflammatory, anticholinesterase, antioxidant and phytochemical properties of medicinal plants used for pain-related ailments in South Africa.

ETHNOPHARMACOLOGICAL RELEVANCE Extracts of seven South African medicinal plants used traditionally for the treatment of pain-related ailments were evaluated. AIMS OF THE STUDY The study was aimed at evaluating medicinal and therapeutic potentials of the investigated traditional medicinal plants. Plant extracts were evaluated for anti-inflammatory activity and other pharmacological properties such as anticholinesterase and antioxidant activities. Phytochemical analysis of total phenolic contents, condensed tannins, gallotannins and flavonoids in the aqueous methanol extracts of the medicinal plants were also carried out. MATERIALS AND METHODS The evaluation of anti-inflammatory activity of 50% methanol (50% MeOH), petroleum ether (PE), dichloromethane (DCM) and ethanol (EtOH) plant extracts was done against cyclooxygenase-1 and -2 (COX-1 and COX-2) enzymes. 50% MeOH, PE, DCM and EtOH extracts were tested for acetylcholinesterase (AChE) inhibition, while 50% MeOH extracts were tested for 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity and ferric-reducing power in the antioxidant assays. Total phenolic compounds, condensed tannins, gallotannins and flavonoids were quantitatively determined using spectrophotometric methods. RESULTS At the screening assay concentration (0.25 microg/microl), 13 extracts showed good COX-1 inhibitory activity (>50%), while good activity was observed in 15 extracts against COX-2 enzyme. All the extracts of Crinum moorei (bulbs) showed good inhibition against both COX-1 and COX-2 enzymes. Though not significantly different (P=0.05), the highest COX-1 percentage inhibition (100%) was shown by Aloe ferox leaf PE and Colocasia antiquorum tuber DCM extracts, while Colocasia antiquorum tuber PE extract exhibited the highest (92.7%) percentage inhibition against COX-2. Crinum moorei bulb DCM extract showed the lowest EC(50) value (2.9 microg/ml) in the AChE assay. In addition, good to moderate bioactivities were observed in some extracts of Aloe ferox (leaves), Crinum moorei (bulbs) and Pycnostachys reticulata (leaves) in all the assays. The presence and/or amounts of phenolic compounds varied with plant species. CONCLUSION The results obtained in this study validate the use of the investigated medicinal plants in South African traditional medicine for pain-related ailments.

The potential of smoke in seed technology

Smoke is an important factor involved in fire and postfire germination cues. The role of smoke in stimulating germination was first highlighted in South Africa in a study on Audouinia capitata , a threatened fynbos species. Further studies on South African fynbos, Californian chaparral and Australian species have illustrated the widespread ability of smoke to promote germination of many species from fire-prone areas. However, smoke-stimulated germination is not limited to species from fire-prone habitats, and a variety of species from fire-free habitats also respond positively. Smoke and aqueous smoke extracts can potentially be used for a variety of applications related to seed technology. These include uses in horticulture, agriculture, ecological management and rehabilitation of disturbed areas.

Butenolides from Plant-Derived Smoke: Natural Plant-Growth Regulators with Antagonistic Actions on Seed Germination

Smoke plays an intriguing role in promoting the germination of seeds of many species following a fire. Recently, a bicyclic compound containing a condensed butenolide moiety, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), was reported as a potent germination promoter from plant-derived smoke. In this study, a related butenolide, 3,4,5-trimethylfuran-2(5H)-one (2), which inhibits germination and significantly reduces the effect of 1 when applied simultaneously, was also isolated from plant-derived smoke. The interaction of these compounds with opposing actions on seed germination may have important ecological implications in a post-fire environment and could be useful molecules for understanding the events involved in breaking seed dormancy and promoting seed germination.

In vitro antimicrobial, anthelmintic and cyclooxygenase-inhibitory activities and phytochemical analysis of Leucosidea sericea

ETHNOPHARMACOLOGICAL RELEVANCE Leucosidea sericea is used as a vermifuge and in the treatment of ophthalmia by various tribes in southern African countries. AIM OF THE STUDY The study aimed at screening leaves and stems of Leucosidea sericea for pharmacological activity and validating the plants traditional use. A general phytochemical screening was also carried out. MATERIALS AND METHODS Petroleum ether (PE), dichloromethane (DCM), ethanol (EtOH) and water extracts of the plant parts were investigated for antimicrobial, anthelmintic and cyclooxygenase (COX) inhibitory activities. Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and Candida albicans were used for the antimicrobial evaluation. Caenorhabditis elegans was used for the anthelmintic assay using the microdilution technique. Cyclooxygenase-1 and -2 (COX-1 and -2) were used to evaluate the anti-inflammatory potential of the plant extracts. Phytochemical analysis for phenolic compounds, including gallotannins, condensed tannins and flavonoids was done using 50% methanol extracts of the leaves and stems employing spectrophotometric methods. RESULTS The leaf extracts exhibited broad spectrum antibacterial activity ranging from 0.025 to 6.25mg/ml. The most noteworthy minimum inhibitory concentration (MIC) of 0.025 mg/ml was exhibited by PE and DCM leaf extracts against Bacillus subtilis and Staphylococcus aureus, respectively. In the anthelmintic assay, the best minimum lethal concentration (MLC) value of 0.26 mg/ml was observed for the DCM and EtOH leaf extracts. Both leaf and stem organic solvent extracts exhibited high to moderate inhibition against COX-1 and -2 at a screening concentration of 250 microg/ml. At lower concentrations, the extracts displayed a dose-dependent inhibition, with the lowest IC(50) values of 0.06 microg/ml (COX-1) and 12.66 microg/ml (COX-2) exhibited by the PE extract of the leaves. Generally, the leaf extracts exhibited better pharmacological activities and contained higher amounts of phenolic compounds than the stem extracts. Alkaloids and saponins were only detected in the leaf and stem extracts, respectively. CONCLUSION The reported results support the local use of Leucosidea sericea against eye infections and as a vermifuge. The pharmacological activities exhibited by the leaf extracts are probably due to their higher phenolic levels.

The fire ephemeral Tersonia cyathiflora (Gyrostemonaceae) germinates in response to smoke but not the butenolide 3-methyl-2H-furo[2,3-c]pyran-2-one.

BACKGROUND AND AIMS Tersonia cyathiflora (Gyrostemonaceae) is a fire ephemeral with an obligate requirement for smoke to germinate. Whether it is stimulated to germinate by 3-methyl-2H-furo[2,3-c]pyran-2-one (karrikinolide, KAR(1)), the butenolide isolated from smoke that stimulates the germination of many other smoke-responsive species, is tested. METHODS Seeds of T. cyathiflora were buried in autumn following collection and were exhumed 1 year later, as this alleviates dormancy and enables seeds to germinate in response to smoke-water. Exhumed seeds were tested with smoke-water and KAR(1). Fresh preparations of these solutions were again tested on seeds exhumed 2 months later under a broader range of conditions. They were also tested on Grevillea eriostachya (Proteaceae) and Stylidium affine (Stylidiaceae) to confirm the activity of KAR(1). KEY RESULTS T. cyathiflora seeds germinated in response to smoke-water but not to KAR(1). In contrast, G. eriostachya and S. affine germinated in response to both smoke-water and KAR(1). CONCLUSIONS Although many smoke-responsive seeds germinate in the presence of KAR(1), this does not apply universally. This suggests that other chemical(s) in smoke-water may play an important role in stimulating the germination of certain species.

Smoke-water-induced changes of expression pattern in Grand Rapids lettuce achenes.

Aerosol smoke and smoke-water can break dormancy and promote seed germination of many plant species. In this study we investigated changes in gene expression after imbibition of light-sensitive Lactuca sativa L. cv. ‘Grand Rapids’ achenes with dilute smoke-water compared to water control samples kept in the dark or continuous light, using the fluorescent differential display technique. Although no difference was detected in the smoke-water versus water control samples germinated in light, smoke-water treatment resulted in the differential display of several expressed sequence tags (ESTs) when compared to water control samples kept in the dark. The most pronounced fragments isolated correspond to known genes related to germination, with functions in cell wall expansion, regulation of translation, the cell division cycle, carbohydrate metabolism and abscisic acid (ABA) regulation. Real-time polymerase chain reaction (PCR) validation revealed that the transcript abundance of the genes, HVA22 , short-chain dehydrogenase/reductase and late embryogenesis abundant protein, are upregulated after smoke treatment when compared to control achenes kept in the light. The results indicate that smoke has a dual effect. On the one hand, the smoke can induce genes that may be linked to ABA action, whereas, on the other hand, it elicits a faster germination rate by inducing a similar pattern in gene expression as light treatment. Smoke effects could be manifested mainly through the induction of the cell division cycle, cell wall extension and storage mobilization.

Do fire-related cues, including smoke-water, karrikinolide, glyceronitrile and nitrate, stimulate the germination of 17 Anigozanthos taxa and Blancoa canescens (Haemodoraceae)?

Many species in fire-prone environments germinate after fire including most taxa in the genus Anigozanthos Labill. Following preliminary studies with Anigozanthos manglesii D.Don subsp. manglesii, the response of several Anigozanthos taxa to germination stimulants relating to the post-fire environment including smoke, karrikinolide (KAR1, 3-methyl-2H-furo[2,3-c]pyran-2-one) and nitrate were compared in seed when freshly collected and after a period of burial. Following after-ripening, the response of seed to water, smoke-water, KAR1 and glyceronitrile (2,3-dihydroxypropanenitrile) was examined. Seed of 16 Anigozanthos taxa, and the related monotypic genus Blancoa Lindl., were highly dormant at maturity. Investigations of eight Anigozanthos taxa and B. canescens indicated that these taxa had morphophysiological dormancy. Following a period of either 3- to 4 months or 1 year of burial and exhumation in autumn, many taxa remained dormant. However, dormancy was alleviated and smoke-water stimulated some germination of A. manglesii subsp. manglesii, A. flavidus DC., A. viridis Endl. subsp. viridis, and A. viridis Endl. subsp. Cataby (S.D. Hopper 1786). Nitrate also stimulated germination of A. flavidus in the light. Following 3–3.5 years of laboratory after-ripening, 13 of the 17 Anigozanthos taxa examined were smoke-responsive. When testing individual smoke-derived compounds these taxa germinated in response to glyceronitrile and not KAR1. In contrast, smoke-responsive B. canescens seed responded to KAR1 and not glyceronitrile. These findings suggest a phylogenetic link between responsiveness to different chemicals in smoke in this family that may shed light on the evolutionary development of these smoke responses.

Positive effect of smoke-derived butenolide priming on melon seedling emergence and growth

Abstract A smoke-derived butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one, has previously been shown to improve seedling vigour. The aim of this study is to examine the effect of hydropriming and butenolide priming treatments on seedling emergence and growth under different sowing depths at 20 and 25°C in two melon (Cucumis melo L.) seed lots of high and low quality. Seeds are subjected to hydropriming (21 h at 25°C) and butenolide priming (10−7 M, 21 h at 25°C) and sown at a depth of 4 or 8 cm in peat moss (field capacity, 64% water by mass). In general, seedlings from butenolide-primed and hydroprimed seeds are superior to those of the control. At 20°C, the effect of butenolide priming is more pronounced than that of hydropriming and the control, particularly for the seeds sown at a depth of 8 cm. Butenolide priming has a ‘repair-inducing’ effect and enhances the low-quality seeds more than those of the high-quality seed lot, an effect which is more obvious at 20°C than 25°C. It can be concluded that butenolide priming may be a useful tool to enhance melon seedling performance under low temperature sowing conditions.

Effect on nursery and field performance of Pinus patula seedlings after inoculation with Fusarium circinatum

Fusarium circinatum is an important fungal pathogen of Pinus species. In South Africa, it is the most significant pathogen of Pinus patula seedlings in forestry nurseries where it presents a substantial constraint to productivity and can continue to cause mortality in-field for up to two years after establishment. This study describes the results from two trials where P. patula seedlings were inoculated with F. circinatum to determine the impact of the pathogen on nursery and field performance. Seedlings were also subjected to water stress treatments to ascertain whether this would trigger the onset of disease symptoms. Inoculum load and timing of inoculation had significant effects on seedling survival in both the nursery and field. High inoculum concentrations caused greater levels of mortality and, where seedlings were inoculated at a young age, they showed higher levels of susceptibility to F. circinatum. Temporary water-stress in the nursery produced smaller plants and improved in-field survival, but this treatment did not trigger higher mortality in inoculated treatments. On the other hand, transplant stress was a major contributor to the higher levels of mortality observed in inoculated treatments. Overall, these studies confirmed that infection in the nursery leads to the disease problems observed during early plant establishment in the field.