Plant growth regulator induced phytochemical and antioxidant variations in micropropagated and acclimatized Eucomis autumnalis subspecies autumnalis (Asparagaceae)

Eucomis species is a valuable plant with both medicinal and horticultural potential. The current study evaluated the role of plant growth regulator (PGR) on growth, phytochemicals, and antioxidant activity in Eucomis autumnalis subspecies autumnalis. Five cytokinins including topolins and benzyladenine (BA) at 2 µM in combination with varying (0–15 µM) concentrations of naphthalene acetic acid (NAA) were tested. In vitro regenerants were acclimatized in the greenhouse for 4 months. Highest number of shoots (9 shoots/explant) was observed with 15 µM NAA alone or when combined with BA. Acclimatized plants derived from the 15 µM NAA treatment had the highest number of roots, largest leaf area and biggest bulbs. While applied PGRs increased the iridoids and condensed tannins in the in vitro regenerants, total phenolics and flavonoids were higher in the PGR-free treatment. Among the in vitro regenerants, 5 µM NAA and 2 µM BA treatments produced the best antioxidant activity in the DPPH (55 %) and beta-carotene (88 %) test systems, respectively. A remarkable carry-over effect of the PGR was conspicuous in the phytochemical levels and antioxidant activity of the 4-month-old plants. In addition to the optimized micropropagation protocols, the current findings present a promising potential for manipulating the type and concentration of applied PGRs to improve phytochemical production and hence medicinal value in E. autumnalis subspecies autumnalis.     

Effect of vermicompost leachate in <Emphasis Type="Italic">Ceratotheca triloba</Emphasis> under nutrient deficiency

Ceratotheca triloba (Bernh.) Hook.f. commonly known as an African foxglove is an indigenous plant which occurs in most parts of South Africa. The species is commonly consumed as a leafy vegetable and utilized for its medicinal properties. Although the high nutritional value of the species and medicinal properties are well documented, information related to critical aspect of cultivation is currently limited. Therefore, this study aimed to evaluate the effect of vermicompost leachate (VCL) on growth, nutritional, phytochemical, and antioxidant levels in C. triloba at different growth stages under nutrient-deficient conditions. After in vitro germination, seedlings were grown in the greenhouse for 2 and 4 months under nitrogen (–N); phosphorus (–P); and potassium (–K) deficiency conditions, and were treated with VCL. Vermicompost leachate did not improve the growth of C. triloba plants under the nutrient-deficient conditions. Although –N-deficient plants with or without VCL caused a decline in growth parameters, they significantly enhanced phytochemicals in 2-month-old plants. In most cases, the application of VCL to –P- and –K-deficient plants improved the photosynthetic pigments, protein, and phenolic, as well as flavonoid accumulation. Harvesting time was also found to play a crucial role in the accumulation of evaluated parameters in nutrient-deprived plants. From these findings, it can be deduced that VCL has a potential to minimize the effect of nutrient deficiency especially under –P and –K deficiency in C. triloba plants.     

Seaweed-Derived Biostimulant (Kelpak<Superscript>®</Superscript>) Influences Endogenous Cytokinins and Bioactive Compounds in Hydroponically Grown <Emphasis Type="Italic">Eucomis autumnalis</Emphasis>

The effect of a seaweed-derived biostimulant (Kelpak^® at 1, 2.5 and 5 % dilution; v/v) on the growth, endogenous cytokinin (CK) and phytochemical content in Eucomis autumnalis (Mill.) Chitt. under hydroponic conditions was evaluated. After 4 months, the stimulatory effect of Kelpak^® treatments was more noticeable in the underground organs than in the aerial organs. Total endogenous CK was also higher in plants treated with Kelpak^® (c.a. 1000–1200 pmol g^?1 DW) compared to control plants (860 pmol g^?1 DW). Isoprenoid CKs (which mainly accumulated in the aerial organs) were more dominant than aromatic-type CKs across all the treatments. A total of 11 bioactive chemicals (8 phenolic acids and 3 flavonoids) and eucomic acid known for their diverse biological activities were quantified in the samples. The most abundant compound was p-coumaric acid (6.5 µg g^?1 DW) and it was approximately sevenfold higher in 2.5 % Kelpak^®-treated plants than in the control. It was also noteworthy that syringic acid only occurred in the underground organs of 5 % Kelpak^®-treated plants. Eucomic acid which is a major bioactive compound in E. autumnalis was significantly enhanced in Kelpak^® treatments, and the leaves accounted for more than 70 % of the overall content. Thus, Kelpak^® elicited a significant influence on the growth, endogenous CK and phytochemical content in E. autumnalis. These findings provide additional evidence of the enormous potential of Kelpak^® as a useful biostimulant with practical applications in various agricultural endeavours.     

Analysis of the effect of plant growth regulators and organic elicitors on antibacterial activity of <Emphasis Type="Italic">Eucomis autumnalis</Emphasis> and <Emphasis Type="Italic">Drimia robusta</Emphasis> ex vitro-grown biomass

The effects of plant growth regulators (PGRs) and organic elicitors (OEs) on in vitro propagation of Eucomis autumnalis was established. Three-year-old ex vitro grown plants from organogenesis of E. autumnalis and somatic embryogenesis (previously reported protocol) of Drimia robusta were investigated for antibacterial activity. In vitro propagation from leaf explants of E. autumnalis was established using different PGRs and OE treatments for mass propagation, biomass production and bioactivity analysis to supplement the use of wild plant material. Prolific shoots (16.0?±?0.94 shoots per explant) were obtained with MS (Murashige and Skoog in Physiol Plant 15:473–497, 1962) medium containing 100 mg l^?1 haemoglobin (HB), 10 µM benzyladenine (BA) and 2 µM naphthaleneacetic acid (NAA). The shoots were rooted effectively with a combination of 2.5 µM indole-3-acetic acid and 5.0 µM indole-3-butyric acid. The plantlets were successfully acclimatized in a vermiculite-soil mixture (1:1 v/v) in the greenhouse. Three-year-old ex vitro-grown E. autumnalis and D. robusta plants derived via organogenesis and somatic embryogenesis respectively exhibited antibacterial activity and varied with PGR and OE treatments, plant parts and bacteria. The leaves of E. autumnalis ex vitro-derived from a combination of HB, BA and NAA followed by the individual treatments of BA and HB gave the best antibacterial activities (<?1 mg ml^?1: minimum inhibitory concentration from 0.098 to 0.78 mg ml^?1) against all tested pathogenic bacteria (Bacillus subtilis, Enterococcus faecalis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa). The bulbs of D. robusta ex vitro-derived from solid culture with 10 µM picloram, 1 µM thidiazuron and 20 µM glutamine exhibited good antibacterial activity against E. faecalis, M. luteus and S. aureus when compared with other treatments and mother plants. The ex vitro-grown E. autumnalis and D. robusta biomass produced with PGRs along with OE treatments confirmed a good potent bioresource and can be used as antibacterial agents. The in vitro plant regeneration of E. autumnalis and D. robusta protocols and ex vitro plants could be used for conservation strategies, bioactivity and traditional medicinal use.     

Regulation of growth,nutritive, phytochemical and antioxidant potential of cultivated <Emphasis Type="Italic">Drimiopsis maculata</Emphasis> in response to biostimulant (vermicompost leachate,VCL) application

The effect of vermicompost leachate (VCL, low-cost biostimulant) on the growth, elemental (macro and micro-nutrients) and phytochemical content as well as the antioxidant potential of Drimiopsis maculata was evaluated. Three dilutions (1:5; 1:10 and 1:20) of VCL were tested and the cultivation lasted for 3 months. In addition to the recorded growth parameters, dried and ground plant materials (leaves and bulbs) were evaluated for nutrients, phenolic acids and antioxidant capacity. Vermicompost leachate application enhanced the growth of D. maculata, particularly, the leaves (VCL 1:10) and bulbs (VCL 1:20) which were significantly bigger than the controls. Apart from the concentration of phosphorus which was significantly lower in the leaves of VCL (1:20)-treated plants, the quantity of all four macro-nutrients analysed were similar with and without VCL. Similar observations were also demonstrated in the majority of quantified micro-nutrients in D. maculata. Relative to the control, VCL-treated plants had higher concentrations of the 10 phenolic acids quantified in the leaves. However, the majority of the quantified phenolic acids were not significantly enhanced in bulbs. Antioxidant activity of D. maculata extracts was generally higher in leaves than in the bulbs. The leaf extract from VCL (1:10 and 1:20)-treated plants exhibited lower oxygen radical absorbance capacity (ORAC) when compared to the control. However, bulbs from VCL (1:5) treatment had significantly higher ORAC than the control. From a conservational perspective, the current findings provided insight on viable approaches useful for mitigating challenges associated with over-harvesting of highly utilized but slow-growing plant species.     

Assessment of the preventive effect of vermicompost on salinity resistance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L^??1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na⁺ concentrations, and decreased K⁺ concentrations. Salt stress decreased stomatal conductance (g_s), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (F_v/F_m), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and g_s, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na⁺ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K⁺/Na⁺ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g^??1 FW) and the highest sugar content in roots (9.2 µmol g^??1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.     

Effect of a novel aromatic cytokinin derivative on phytochemical levels and antioxidant potential in greenhouse grown Merwilla plumbea

In an attempt to elucidate the carry-over effect of cytokinins (CKs) on phytochemical and antioxidant activity of acclimatized plants, tissue culture-derived Merwilla plumbea supplemented with three CK types at four (0.25, 0.5, 1 and 2 µM) concentrations were grown for 6 months ex vitro. Phenolic acids including the hydroxybenzoic and hydroxycinnamic acid derivatives in M. plumbea were quantified using ultra performance liquid chromatography while the antioxidant activity was evaluated using oxygen radical absorbance capacity (ORAC). Different concentrations of gallic acid, protocatechuic acid, p-hydroxybenzoic acid and salicylic acid were observed with all the treatments with the exception of non-treated plants. Most phytochemicals (for example, gallic acid, ferulic acid protocatechuic acid and caffeic acid) were highest in plants obtained from 0.25 µM meta-topolin riboside (mTR). Likewise, plants derived from 2 µM mTR had the highest ORAC (684 µmol g^?1 trolox equivalents) activity. Bearing in mind that therapeutic effects of medicinal plants are often associated to their phytochemical content, the current results are an indication on how the intricate in vitro environment (CK type and concentration in this case) affects the growth and general physiology of micropropagated plants especially after acclimatization.     

Importance of mineral nutrition for photosynthesis and growth of Quercus petraea, Fagus sylvatica and Acer pseudoplatanus planted under Norway spruce canopy

The aim of this study was to combine data on photosynthetic performance, growth and mineral nutrition of Quercus petraea, Fagus sylvatica and Acer pseudoplatanus growing six years under a Norway spruce canopy. Three years old saplings were planted on several adjoining plots from the forest edge up to 35 m inside the spruce forest on nutrient poor dystric cambisols. Growth parameters, photosynthetic capacity and leaf nutrition were repeatedly measured on 11 to 13 selected plants for each species every year from 1996 to 2001. The general performance of the plants growing along the light gradient from forest edge into the closed canopy decreased in the order F. sylvatica, Q. petraea and A. pseudoplatanus. The photosynthetic performance of Acer declined from the second year onwards as consequence of low nutrient supply. The plants had in most cases higher leaf nitrogen concentration in shade. This increase going along with declining light input was the best in Quercus and was found in Acer leaves only in the second year after the planting. The growth parameters of all investigated plants were not correlated to the light environment within the range of canopy gap fraction between 0.05 and 0.62. However, the total leaf area as well as nutrient amounts in the foliage were good predictors for total plant height and plant diameter at root collar of Fagus and Quercus, but failed in most cases for Acer. These results emphasise the important role of nutrient acquisition for young broadleaves introduced in Norway spruce stands and underline the different requirements for nutrient supply at the species level.     

Genome sizes of Eucomis L’Hér. (Hyacinthaceae) and a description of the new species Eucomis grimshawii G.D.Duncan & Zonneveld

Nuclear genome size, as measured by flow cytometry with propidium iodide, was used to investigate the relationships within the genus Eucomis L’Hér. (Hyacinthaceae). Most species of Eucomis have the same basic chromosome number, x = 15. However, the somatic DNA 2C-value (2C) is shown to range from 21 to 31 pg for the diploids. The largest genome contains roughly 10¹⁰ more base pairs than the smallest. Genome sizes are evaluated here in combination with available morphological and geographical data. Therefore, the taxonomy proposed here is not based on genome size alone. The genus Eucomis, as here determined, has 12 species. These can be divided into two groups: mainly dwarf diploid species and large-sized, tetraploid species. A small diploid plant, Eucomis (autumnalis subsp.) amaryllidifolia, is restored to species status, as a diploid subspecies seems incongruent with an allotetraploid Eucomis autumnalis. Moreover, as a diploid it is separated reproductively from the allotetraploid E. autumnalis. A new diploid species that has the lowest C value, E. grimshawii, is described here. On the basis of DNA content and other morphological characters, possible parents are suggested for all tetraploid species. Nuclear DNA content as measured by using flow cytometry may conveniently be used to produce systematic data. It is applicable even in dormant bulbs or sterile plants for the monitoring of the trade in bulbous species.     

Effect of cadmium on growth and micronutrient distribution in wild garlic (Tulbaghia violacea)

Tulbaghia violacea Harv. (Alliaceae) is one of the few medicinal plants that is also frequently used as a leafy vegetable. Application of cadmium (Cd) at 2 and 5 mg/L to T. violacea plants of various sizes (small 8–10 g, medium 16–20 g, large 80–95 g) elicited a difference in growth response, Cd accumulation and micronutrient distribution. Application of Cd up to 5 mg/L had no significant effect on growth parameters of large-sized plants while leaf length and fresh weight of leaves of the medium-sized plants decreased with application of Cd at 2 mg/L, and 5 mg/L. Cadmium significantly decreased the number of leaves in small-sized plants. Small plants accumulated more Cd in the leaves than medium or large-sized plants. Application of Cd at 2 and 5 mg/L lowered the leaf Cu, Fe, Mo and Zn contents in small and medium-sized plants but had no effect on the micronutrients in large-sized plants. This study indicates that T. violacea has the ability to accumulate Cd. In addition, plant size plays an important role with regards to Cd accumulation and elemental distribution. The results presented in this study include the first report on the nutritional status of T. violacea leaves.     

Influence of culture age on the phytochemical content and pharmacological activities of five Scenedesmus strains

Five axenic Scenedesmus strains (MACC-411, MACC-422, MACC-493, MACC-720, and MACC-727) were cultured and harvested after 5 and 10 days in culture. Using colorimetric methods, the concentrations of total phenolic, condensed tannin, and iridoids in 50 % methanol extracts from both 5- and 10-day-old cultures were quantified. Different solvent extracts from the strains were also tested for antioxidant, acetylcholinesterase inhibitory (AChEI), and antimicrobial activities using various in vitro test systems. Phenolic content was highest (3.6?±?0.42 mg GAE g^?1 DW) in 10-day-old MACC-727. This was approximately fourfold and significantly higher than in the 5-day-old cultures of MACC-727. Among the tested Scenedesmus strains, 5-day-old MACC-411 had the highest iridoid content (3.4?±?0.3 mg HE g^?1 DW), and this was significantly higher than the level detected in the 10-day-old MACC-411. Scenedesmus strains showed better antioxidant potential in the β-carotene–linoleic acid model compared to the DPPH free radical scavenging assay. The AChEI activity (IC₅₀?μg mL^?1) in all strains (besides MACC-422) was higher in 10-day-old cultures compared to the 5-day-old cultures. Although a broad-spectrum of antibacterial activity was observed, the tested microalgae strains demonstrated varying degrees of antimicrobial potential depending on the harvest time, strain-type, and extracting solvent. Thus, the Scenedesmus strain and time of harvest played a significant role in determining their phytochemical content and resultant pharmacological activity. The promising bioactivity in the tested Scenedesmus strains indicates their potential as possible sources of novel/alternative antioxidants and AChE inhibitors.     

Modulation in growth,photosynthetic efficiency,activity of antioxidants and mineral ions by foliar application of glycinebetaine on pea (Pisum sativum L.) under salt stress

A pot experiment was carried out to explore the role of glycinebetaine (GB) as foliar spray foliar on two pea (Pisum sativum L.) varieties (Pea 09 and Meteor Fsd) under saline and non-saline conditions. Thirty-two-day-old plants were subjected to two levels 0 and 150 mM of NaCl stress. Salt treatment was applied in full strength Hoagland’s nutrient solution. Three levels 0, 5 and 10 mM of GB were applied as foliar treatment on 34-day-old pea plants. After 2 weeks of foliar treatment with GB data for various growth and physiochemical attributes were recorded. Rooting-medium applied salt (150 mM NaCl) stress decreased growth, photosynthesis, chlorophyll, chlorophyll fluorescence and soluble protein contents, while increasing the activities of enzymatic (POD and CAT) and non-enzymatic (ascorbic acid and total phenolics) antioxidant enzymes. Foliar application of GB decreased root and shoot Na⁺ under saline conditions, while increasing shoot dry matter, root length, root fresh weight, stomatal conductance (g _s), contents of seed ascorbic acid, leaf phenolics, and root and shoot Ca²⁺ contents. Of three GB (0, 5, 10 mM) levels, 10 mM proved to be more effective in mitigating the adverse effects of salinity stress. Overall, variety Pea 09 showed better performance in comparison to those of var. Meteor Fsd under both normal and salinity stress conditions. GB-induced modulation of seed ascorbic acid, leaf phenolics, g _s, and root Ca²⁺ values might have contributed to the increased plant biomass, reduction of oxidative stress, increased osmotic adjustment and better photosynthetic performance of pea plants under salt stress.     

Boron excess affects photosynthesis and antioxidant apparatus of greenhouse Cucurbita pepo and Cucumis sativus

This study aimed to evaluate the behavior of zucchini (Cucurbita pepo L.) and cucumber (Cucumis sativus L.) under boron (B) excess. Plants were grown under greenhouse conditions in a sandy soil–peat mixture using a nutrient solution containing 0.2 (control), 10 and 20 mg L^?1 B. Visible symptoms were quantified and leaf B accumulation, gas exchanges, chlorophyll (Chl) a fluorescence, malondialdehyde by-products and antioxidants were investigated 20 days after the beginning of the treatments. Boron toxicity induced oxidative load and leaf necrotic burns coupled with the reduction of leaf growth and biomass accumulation in both species. Boron excess resulted in a decrease of Chl a/b ratio, potential (F_v/F_m) and actual (Φ_PSII) PSII quantum efficiency, photosynthetic rate (Pn), stomatal conductance (g_s), and transpiration (E) as well. A general stimulation of the antioxidant enzymes ascorbate peroxidase, catalase and superoxide dismutase was observed, and a significant increase in the oxidized form of ascorbate and glutathione was evidenced for treated plants of both species. A difference between the two species was observed: C. pepo appeared to be more sensitive to B stress being damaged at all B concentration. C. sativus grown at 10 mg L^?1 B in nutrient solution showed some down-regulated mechanisms, i.e. increase in Chl b content and a good photochemical PSII efficiency as well as a higher amount of constitutive antioxidant molecules, that, however, are not sufficient to contrast the negative effects of B.     

Does Inoculation with Glomus mosseae Improve Salt Tolerance in Pepper Plants?

A pot experiment was conducted to determine the effects of Glomus mosseae inoculation on growth and some biochemical activities in roots and shoots of pepper (Capsicum annuum L. cv. Zhongjiao 105) plants subjected to four levels of NaCl [0 (control), 25 (low), 50 (medium), and 100 (high) mM] for 30 days, after 30 days of establishment under non-saline conditions. In mycorrhizal (M) plants, root colonization varied from 48 to 16 %. M plants had higher root and shoot dry weight and leaf area compared with non-mycorrhizal (NM) plants. Under salinity stress, M plants accumulated higher amounts of leaf photosynthetic pigments as well as soluble sugar, soluble protein, and total free amino acids in roots and shoots than those of NM plants. In contrast, the accumulation of proline was less intense in M plants than NM plants. Salt stress induced oxidative stress by increasing malondialdehyde (MDA) content; however, the extent of oxidative damage in M plants was less compared with NM plants due to G. mosseae-enhanced activity of superoxide dismutase (SOD) and peroxidase (POD). We concluded that inoculation with G. mosseae improved growth performance and enhanced salt tolerance of pepper plants via improving photosynthetic pigments and the accumulation of organic solutes (except proline), reducing oxidative stress, and enhancing antioxidant activities of the SOD-POD system.     

Seed priming improves the emergence potential,growth and antioxidant system of Moringa oleifera under saline conditions

Moringa oleifera is a multipurpose plant which is now being promoted as a fodder crop. The present study was conducted to induce the tolerance in moringa plants to emerge and grow under saline conditions. For this, moringa seeds were primed with aerated water (hydropriming) and moringa leaf extract (MLE) for 12 and 24 h and studied for its emergence, potential growth behaviour, mineral composition, chlorophyll contents and antioxidant activities in comparison with unprimed seeds to investigate the physiological changes in moringa plants under saline conditions. The seeds were sown in plastic pots filled with acid washed sand at four salinity levels (3, 6, 10, 14 dS m^?1) in a completely randomized design with three replications. It was found that salinity >6 dS m^?1 reduced the emergence, growth and vigour of moringa plants but hydropriming (12 h) enhanced moringa emergence at 10 dS m^?1 followed by MLE priming (12 h). Maximum aboveground biomass and photosynthetic pigments were recorded when the seeds were hydroprimed (12 h) but maximum root length and number of roots were found in MLE primed (12 h) moringa plants. Significant decrease in K⁺:Na⁺ ratio with increasing salinity levels resulted in low K⁺ and Mg²⁺ uptake and Na⁺ toxicity in moringa leaves which resulted in reduced chlorophyll contents at 14 dS m^?1 but a significant increase in chlorophyll a and b contents and total phenolics were found in hydroprimed seeds (12 h) while the antioxidant activities of superoxide dismutase, peroxidase and catalas were improved by MLE priming (12 h). This study concludes that moringa emergence and growth performance can be improved by hydropriming under saline conditions.     

Cytotaxonomy of autumnal flowering species of Hyacinthaceae from Algeria

Cytotaxonomic investigations of the autumn-flowering squills, Prospero autumnale (L.) Speta ≡ Scilla autumnalis L., Prospero obtusifolium (Poir.) Speta ≡ Scilla obtusifolia Poir., Barnardia numidica (Poir.) Speta ≡ Scilla numidica Poir., and Hyacinthoides lingulata (Poir.) Rothm. ≡ Scilla lingulata Poir. were performed in 20 populations from northern Algeria located between Tipasa and La Vieille Calle. Various chromosome numbers were found, including a new cytotype, 2n = 8, for the flora of Algeria, concerning plants identified as Prospero obtusifolium (Poir.) Speta [including P. fallax (Steinh.) Speta = S. autumnalis L. ssp. fallax (Steinh.) Batt.]. The numbers 2n = 14, 28, and 42 correspond, respectively, to diploid, tetraploid, and hexaploid levels of P. autumnale s.l. [including P. pulchellum (Munby) Speta ≡ Scilla pulchella Munby = S. autumnalis var. pulchella (Munby) Batt.], with x = 7. The cytotypes of Barnardia numidica (Poir.) Speta with 2n = 18 and Hyacinthoides lingulata (Poir.) Rothm. with 2n = 16 chromosomes were confirmed.     

Garden-waste-vermicompost leachate alleviates salinity stress in tomato seedlings by mobilizing salt tolerance mechanisms

The incidence of salinity-induced plant stress as a result of natural and anthropogenic factors in arid and semi-arid agricultural lands is great. In South Africa alone, 9 % of irrigated agricultural land is salt-affected. Commercial fertilizers used for improving soil nutrient levels are costly and affect the quality, lifespan and sustainability of soil and water resources. Organic farming practices are based on cost-effective and environmentally-aware management systems. Vermicompost leachate (VCL) is a vermicompost-derived liquid product that has become recognised as a suitable soil amendment product. Commercial tomato (Lycopersicon esculentum Mill var. Heinz-1370) seedlings were subjected to sodium chloride (NaCl) concentrations of 0, 25, 50 and 100 mM and were treated with 1:10 (v/v) WizzardWorms VCL prepared in Hoagland’s nutrient solution under greenhouse conditions. Morphological characters of VCL-treated tomato seedlings showed improved root growth and stimulated overall aboveground growth with significantly higher numbers of leaves, greater stem thickness and increased leaf area, even at a high NaCl-tested concentration (100 mM). The accumulation of compatible solutes such as proline and total soluble sugars indicate an induced salt tolerance or adaptive mechanism in VCL-treated tomato seedlings. The current investigation demonstrates the potential of an organic liquid to maximise tomato productivity by improving seedling growth performance under salt stress conditions.     

The toxicity of cerium nitrate to Elodea canadensis: subcellular distribution,chemical forms and physiological effects

The rare earth elements are increasingly being used as trace supplements in different fields. In this study, subcellular distribution, the chemical forms and toxicity of cerium (Ce) were evaluated for Elodea canadensis. The effect of Ce (5–20 mg L^?1) applied for 7 days was assessed by measuring changes in the nutrient elements, photosynthetic pigments, malondialdehyde and antioxidant systems. Ce accumulation was greatest in the cell walls, followed by the organelles and the soluble fraction. Ce levels were higher in cellulose and pectin than in other biomacromolecules. The toxic effects caused by Ce were shown by a reduction in photosynthetic pigments, disruption of nutrient elements, and increases in MDA content. E. canadensis shows Ce-induced oxidative stress by modulating antioxidant enzymes, such as guaiacol peroxidase and catalase. Elevated Ce levels may represent a potential risk for aquatic ecosystems.     

In vivo control of Mycosphaerella pinodes on pea leaves by a crude bulb extract of Eucomis autumnalis

We previously reported on the in vitro antifungal activity of a crude whole plant extract from Eucomis autumnalis against seven economically important plant pathogenic fungi. A crude extract of the bulb showed similar in vitro mycelial growth inhibition of the same plant pathogenic fungi as well as that of an eighth fungus, Mycosphaerella pinodes, the cause of black spot or Ascochyta blight, in peas. Subsequently, fourth internode leaves were removed from 4 wk old pea plants, placed on moist filter paper in Petri dishes and inoculated with an M. pinodes spore suspension before and after treatment with the extract. The control of Ascochyta blight by different concentrations of the crude E. autumnalis extract was followed in vivo by leaf symptoms over a 6 day period at 20°C in a growth cabinet. The crude extract prevented M. pinodes spore infection of the leaves when the leaves were inoculated with spores both before or after treatment with the extract, confirming complete inhibition of spore germination. The crude E. autumnalis extract showed no phytotoxic reaction on the leaves even at the highest concentration applied.     

紫娇花挥发油成分的GC-MS分析及抗氧化能力测定

采用水蒸气蒸馏法和固相微萃取法提取紫娇花不同部位的挥发油,结合气相色谱—质谱(GC-MS)与计算机检索联用技术对其化学成分进行分析和鉴定,用面积归一化法测定各组分的相对含量,并对该挥发油清除DPPH·自由基能力和总抗氧化能力进行了研究。结果表明:紫娇花挥发油具有成分及相对含量差异大、成分较简单、化合物种类以含硫化合物为主的特点。两种方法在紫娇花不同部位挥发油中共检测出了16种化学成分,以硫醚类和含硫烃类化合物为主,相对含量占总成分在80%以上,其中Disulfide,bis(2-sulfhydrylethyl)-含量最高,其余许多成分还具有一定的药用价值。两种方法所得到的挥发油化学成分具有一定的差异性,固相微萃取法对醇类、醛类和酯类物质提取效果较好,而水蒸气蒸馏法对含硫烃类、硫醚类和萜类的提取效果更好。实验条件下紫娇花挥发油清除DPPH·自由基的IC_(50)为17.46 mg·mL~(-1),清除率可达54.86%;紫娇花挥发油在相同条件下较L-抗坏血酸具有更强的总抗氧化力。该研究结果为进一步开发利用该植物资源提供了理论依据。