Smoke-saturated Water and Karrikinolide Modulate Germination,Growth, Photosynthesis and Nutritional Values of Carrot (Daucus carota L.)

Plant-derived smoke is a positive regulator of seed germination and growth with regard to many plant species. Of the several compounds present in plant-derived smoke, karrikinolide or KAR₁ (3-methyl-2H-furo[2,3-c]pyran-2-one) is considered to be the major active growth-promoting compound. To test the efficacy of smoke-saturated water (SSW) and KAR₁ on carrot (Daucus carota L.), two separate pot experiments were simultaneously conducted in the same environmental conditions. SSW and KAR₁ treatments were applied to the plants in the form of aqueous solutions of variable concentrations. Prior to sowing, seeds were soaked in the solutions of SSW (25.8 µg L⁻¹_, 51.6 µg L⁻¹,103.2 µg L⁻¹ and 258.0 µg L⁻¹) and KAR₁ (0.015 µg L⁻¹, 0.150 µg L⁻¹, 1.501 µg L⁻¹ and 15.013 µg L⁻¹). Percent seed germination, vegetative growth, photosynthesis and nutritional values were the major parameters through which the plant response to the applied treatments was investigated. The results obtained indicated a significant improvement in all the plant attributes studied. In general, SSW (51.6 µg L⁻¹) and KAR₁ (1.501 µg L⁻¹) proved optimum treatments for most the parameters. As compared to the control, 51.6 µg L⁻¹ of SSW and 1.501 µg L⁻¹ of KAR₁ increased the percent seed germination by 58.0% and 54.4%, respectively. Over the control, the values of plant height and net photosynthetic rate were enhanced by 33.9% and 40.9%, respectively, due to 51.6 µg L⁻¹ of SSW, while the values of these parameters were increased by 25.2% and 34.0%, respectively, due to 1.501 µg L⁻¹ of KAR₁. In comparison with the control, treatment 51.6 µg L⁻¹ of SSW increased the contents of β-carotene and ascorbic acid by 32.7% and 37.9%, respectively, while the treatment 1.501 µg L⁻¹ M of KAR₁ enhanced these contents by 42.0% and 48.4%, respectively. This study provides an insight into an affordable and feasible method of crop improvement.

     

Highly efficient regeneration and medicinal component determination of Phellodendron chinense Schneid

Phellodendron chinense Schneid is an important Chinese herb with berberine and phellodendrine in stems and leaves, but with little information available on in vitro culture of this species. Disinfection of explants in 75% alcohol for 45 s, sterilization in 0.1% HgCl₂ for 20 min, and submersion in 1.0 mol L⁻¹ gibberellin3 (GA₃) solution for 24 h was the optimal condition for seed germination. Murashige and Skoog’s (MS) medium supplemented with 2.0 mg L⁻¹ 6-benzylaminopurine (6-BA) in combination with 1.5 mg L⁻¹ 1-naphthylacetic acid (NAA) was optimal for callus induction. MS medium supplemented with 2.0 mg L⁻¹ 6-BA was the appropriate medium for induction of adventitious shoots, and 1/2MS medium supplemented with 2.0 mg L⁻¹ indole-3-butytric acid (IBA) and 0.5% active carbon was the optimal medium for root induction. The 15-d survival rate of regenerated plantlets after transplanting to basins containing perlite and peat moss (1:4) was greater than 80%, and the berberine and phellodendrine accumulation was lower in callus compared with regenerated plantlets. The establishment of highly efficient regeneration system provides technical support for genetic breeding of Phellodendron chinense Schneid.

     

Extracts of the Brown Alga Dictyota dichotoma (Hudson) J.V. Lamouroux Alleviate Salt Stress in Rice (Oryza sativa L.) During Germination

Algal extracts provide a safe regime for enhancing crop productivity under stressful conditions. The present study evaluated the efficiency of aqueous and ethanolic extracts of the brown alga Dictyota dichotoma in alleviation of salt stress on germination of rice seeds. Firstly, seeds were germinated using the aqueous extract of D. dichotoma at concentrations of 0, 5, 10, 20, and 50 g L⁻¹, prepared either at room temperature (RTE) or by boiling (BLE). The % germination of rice increased from 84% in non-treated seeds to 100% when treated with 20 g L⁻¹ BLE, although this treatment caused reduced uniformity of germination. Embryo growth was maximum at 20 g L⁻¹ of both extracts with superiority of BLE over RTE. In the second experiment, the effect of 20 g L⁻¹ aqueous and ethanolic extracts relative to a balanced nutrient supply on germination of seeds treated with 0, 40, 90, and 170 mM NaCl was investigated. Salinity reduced % germination with delayed onset but high uniformity of germination, whereas algal amendments counterbalanced the effect of salinity to a greater extent relative to the nutrient supply. Upon withdrawal of salt stress, seeds promptly recovered, with more efficient recovery of seeds exposed to 170 mM than from 90 mM NaCl. The lower recovery of salt-treated seeds compared with the control seed germination suggests that rice suffered from the toxic ion effect of salinity on embryo rather than from the osmotic effect. Extracts of D. dichotoma can enhance and also alleviate salinity stress on rice seed germination.

     

Effects of Plant Growth Regulators on Seed Filling,Endogenous Hormone Contents and Maize Production in Semiarid Regions

In this study, we determined whether the application of uniconazole alone or combined with ethephon could enhance the seed-filling rates in maize by regulating the endogenous hormone contents. Uniconazole was applied to the foliage at concentrations of 0 (CK), 25 (U₂₅), 50 (U₅₀) and 75 (U₇₅) mg L⁻¹ at the 12-leaf stage. In addition, uniconazole was applied to the foliage at the 12-leaf stage and ethephon at 10 days after silking stage at concentrations of 0 (CK), 25 mg L⁻¹ uniconazole + 100 mg L⁻¹ ethephon (U₂₅ + E₁₀₀), 50 mg L⁻¹ uniconazole + 200 mg L⁻¹ ethephon (U₅₀ + E₂₀₀) and 75 mg L⁻¹ uniconazole + 300 mg L⁻¹ ethephon (U₇₅ + E₃₀₀). Uniconazole applied alone or in combination with ethephon significantly improved ear characters and grain yield. Uniconazole applied alone or combination with ethephon significantly improved the dry matter accumulation in seeds and seed-filling rates. Uniconazole significantly increased the abscisic acid (ABA) and zeatin (Z) + zeatin riboside (ZR) contents of seeds, but reduced the gibberellic acid (GA) contents. The application of uniconazole combined with ethephon decreased the ABA, Z + ZR and GA contents in seeds. The ABA and Z + ZR contents were significantly positively correlated, whereas the GA content was negatively correlated with the maximum seed weight, maximum seed-filling rate and mean seed-filling rate. The application of uniconazole alone significantly improved the seed-filling rates in maize by regulating the endogenous hormone contents. Thus, we conclude that uniconazole application at 50 mg L⁻¹ in the 12-leaf stage can enhance the maize production.

     

Influence of linear alkylbenzene sulfonate and ethanol on the degradation kinetics of domestic sewage in co-digestion with commercial laundry wastewater

The influence of ethanol on the degradation kinetics of linear alkyl benzene sulfonate (LAS) and organic matter was investigated using batch experiments with different initial LAS concentrations (8.3 mg L⁻¹ to 66.9 mg L⁻¹) and biomass immobilized on sand. Data were fitted with a substrate inhibition model. Concentrations of 2.4 mg LAS L⁻¹ and 18.9 mg LAS L⁻¹ (without and with ethanol) provided the maximum LAS utilization rate by the biomass (S_bm). For LAS degradation, ethanol addition favored a lower decrease in the specific substrate utilization rate (r_obs), even at the LAS concentration usually reported as inhibitory (> 14.4 mg L⁻¹). For organic matter degradation, r_obs was higher with ethanol. Higher biomass differentiation was observed at higher LAS concentrations. With ethanol, microbial selection occurred at LAS concentrations near S_bm. At higher LAS concentrations, the dominance and diversity values did not change significantly with ethanol, whereas without ethanol, their behaviors were irregular.

     

Synergistic effect of cytokinins and auxins enables mass clonal multiplication of drumstick tree (Moringa oleifera Lam.): a wonder

The synergistic effect of plant growth regulators on axillary bud proliferation for mass clonal multiplication of Moringa oleifera Lam. (vern. drumstick) has been assessed for the first time. Treatment of decoated seeds with 1% (w/v) Bavistin for 60 min, 0.33% (w/v) streptocycline for 30 min, and 0.1% (w/v) HgCl₂ for 3.5 min resulted in complete removal of the surface contaminants. Maximum seed germination (89.13%) was obtained on quarter-strength Murashige & Skoog (MS) medium. Culture of nodal segments on MS + 6-benzyladenine (BA) at 3 mg L⁻¹ resulted in multiple shoot proliferation with ~ 18 shoots per explant. All combinations of indole-3-acetic acid (IAA) + kinetin (Kn) resulted in elongated shoots, while only lower concentrations of BA (0.5 mg L⁻¹), along with IAA (0.5 to 2 mg L⁻¹), or Kn (0.5 to 5 mg L⁻¹), showed significant synergy in the shoot morphogenesis. In addition, the maximum (100%) rooting efficiency was attained on half-strength MS medium supplemented with different concentrations of IAA and indole-3-butyric acid (IBA). The rooted plants were successfully established in the greenhouse for acclimatization. Clonality of the raised plants was assessed using 15 random primers of Operon® technologies (OPT and OPF series), and eight primers resulted in significant amplification with distinct, identical, and reproducible bands that confirmed clonality of the micropropagated plants. The present study provides a comprehensive analysis of the synergistic effect of plant growth regulators (PGRs) on in vitro shoot regeneration and proliferation for clonal mass multiplication disease-free plantlets, which can be utilized to maximize the yield of healthy and genetically identical plants of drumstick tree, which is considered to be a miracle multipurpose tree.

     

Comparative study on seed germination characteristics of two species of Australia saltbush under salt stress

In order to examine the response characteristics and possible reasons of Atriplex lentiformis and Atriplex undulata under salt stress at stage of seed germination, the seeds were treated with different concentrations of NaCl (0, 50, 100, 200 and 300 mmol⋅L⁻¹), 20 mmol⋅L⁻¹ LiCl or mannitol whose iso-osmotic concentrations corresponding to 200 mmol⋅L⁻¹ NaCl. The results showed that the germination rate of two species of saltbush was depressed with the increase of NaCl concentration, and A. lentiformis showed greater salt tolerance compared with A. undulata. After removal of salt stress, the final germination ratio of A. lentiformis was over 93%, while that of A. undulata was only 56%. Evans blue staining revealed that 200 mmol⋅L⁻¹ NaCl did not damage membrane permeability of A. lentiformis seed embryos, but significantly increased the membrane permeability of A. undulata seed embryos and caused irreversible damage to them, especially radicles. The results on water uptake indicated that the inhibition of NaCl on seed germination was mainly due to osmotic stress instead of ionic toxicity, and A. lentiformis exhibited higher salt tolerance due to its greater resistance to osmotic stress.     

Somatic embryogenesis to overcome low seed viability and conserve wild banana (Ensete superbum (Roxb.) Cheesman)

The seed viability, ex vitro germination, and percentage of in vitro zygotic embryo germination were found to be very low in Ensete superbum (Roxb.) Cheesman. Only 33.33% of seeds were viable, and the ex vitro germination percentage was only 5%, while the percentage of in vitro zygotic embryo germination was 33%. Somatic embryogenesis experiments produced competent callus on Murashige and Skoog (MS) medium supplemented with 2.5 mg L⁻¹ 2,4-D and 3 mg L⁻¹ BAP from inflorescence explants. The embryogenic callus produced the maximum number of somatic embryos on MS basal medium kept in a dark chamber for 15 wk. Half-strength MS medium supplemented with 500 mg L⁻¹ glutamine was optimal for somatic embryo germination and development of plantlets. Regenerated plants had 80 to 90% survival rate. Therefore, somatic embryogenesis can be considered as an efficient method to overcome a drastic reduction in population and to achieve germplasm conservation.

     

Effects of heavy metals on aerobic denitrification by strain Pseudomonas stutzeri PCN-1

Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67∼6.67 mg L⁻¹ h⁻¹), higher nitrite accumulation (47.3∼99.8 mg L⁻¹), and higher N₂O emission ratios (5∼283 mg L⁻¹/mg L⁻¹). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0∼0.05 mg L⁻¹) was found, and the absence of Cu resulted in massive N₂O emission due to poor synthesis of N₂O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5∼2.5 mg L⁻¹) > Cu(II) (0.5∼5 mg L⁻¹) > Ni(II) (2∼10 mg L⁻¹) > Zn(II) (25∼50 mg L⁻¹). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ≈ cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.

     

Implication of storage conditions on luminescence response from Photobacterium phosphoreum in free and immobilized form

Bioluminescent bacteria in the form of a cell suspension for on-site hazard analysis are not suitable as in vivo luminescence in free cells fluctuates and may lead to erroneous results. Furthermore, the culture broth cannot be stored for long durations to continue sensing analytes as the luminescence ceases over time. Factors that affect luminescence response include growth dynamism, and ambient environmental conditions. The present study investigated the effect of storage conditions such as temperature (25 ± 2°C, room temperature; 4°C; and −20°C) and ambient aqueous environment (M1: sucrose, 1.02 M; M2, bioluminescent media [tryptone, 10 g L⁻¹; NaCl, 28.5 g L⁻¹; MgCl₂.7H₂O, 4.5 g L⁻¹; CaCl₂, 0.5 g L⁻¹; KCl 0.5 g L⁻¹; yeast extract, 1 g L⁻¹; H₂O, 1 L]; M3, bioluminescent media and 95% glycerol, 1:1 ratio) on the luminescence emission from the calcium alginate-immobilized Photobacterium phosphoreum (S_b) against the cells in free suspension for an extended period. The results indicated that both the parameters that were undertaken markedly affected the luminescence. In the study, S_b showed an enhanced luminescence emission than the control up to 18.5-fold and for a prolonged period which can be efficiently utilized for rapid biosensing of hazardous materials.     

Biostimulants Derived from Moroccan Seaweeds: Seed Germination Metabolomics and Growth Promotion of Tomato Plant

Polysaccharides extracted from seaweeds can function as plant biostimulants. The aim of this study was to assess the effects of Polysaccharide Enriched Extracts (PEEs) obtained from 17 Moroccan seaweeds, on tomato seed germination and plant growth. Three concentrations (0.02, 0.05 and 0.1 mg mL⁻¹) of PEEs were applied to tomato seeds to evaluate their effect on 3 germination parameters: germination percentage (GP), germination speed (GS) and mean germination time (MGT). Metabolomic analysis by GC–MS was subsequently performed on seedlings. In the second experiment, four PEEs concentrations (0.02, 0.05, 0.1 and 0.2 mg mL⁻¹) were used as foliar spray or as soil application to tomato plants. Their growth parameters (number of leaves, shoot length, fresh and dry weight of stem and roots) and biochemical parameters (chlorophyll a and b) were measured. Results indicated a significant increase of GP and GS associated with a significant reduction of MGT of tomato seeds treated with 0.02 mg mL⁻¹ of PEEs obtained from Gigartina sp., Gigartina pistillata, Chondracanthus acicularis, Gelidium crinale, Schizymenia dubyi, Cystoseira. foeniculacea and Fucus spiralis. Similar results were also obtained by application of higher PEEs concentration (0.1 mg mL⁻¹) extracted from Ulva rigida, Codium tomentosum, Codium decorticatum and Bifurcaria bifurcata. Metabolomic analysis on seedlings detected the presence of some metabolites which could possibly be involved in seed germination enhancement or inhibition. The results of the second experiment showed that the same PEEs cited above at the same concentrations enhanced plant dry weight and chlorophyll a content except Gigartina sp., C. foeniculacea and C. decorticatum. Furthermore, soil application of PEEs was more effective in improving plant growth parameters than foliar application. The study shows the potential of PEEs from Moroccan seaweed to be used as biostimulants for a sustainable agriculture.

     

Impact of hypoxia conditions on the Mnemiopsis leidyi A. Agassiz, 1865 bioluminescence

The findings of the study on the impact of hypoxia on the glow of the Black Sea ctenophore Mnemiopsis leidyi A. Agassiz, 1865 of three size groups (20–30, 30–45, and 45–60 mm) were obtained under experimental conditions. Peculiarities of ctenophore bioluminescence were studied during mechanical and chemical stimulation under the conditions of normoxia (at an oxygen concentration of 5.6–6.7 mg O₂ L⁻¹), moderate hypoxia (2.5–2.8 mg O₂ L⁻¹), and acute hypoxia (1.2–1.5 mg O₂ L⁻¹). An increase in the amplitude and energy of luminescence of the ctenophores mechanically and chemically stimulated was observed at an oxygen concentration of 1.2–1.5 mg O₂ L⁻¹ (acute hypoxia) in two size groups in the lobate form (30–45 and 45–60 mm). The inhibition of amplitude, energy, and duration of the signal was registered in M. leidyi ctenophores at the transitional stage from larva to the lobate form under conditions of acute hypoxia. It was noted that in normoxia, the values of the amplitude and energy of the bioluminescent signal of M. leidyi increase along with a size growth of an individual. This phenomenon was observed both during mechanical and chemical stimulations. Under conditions of acute hypoxia, this trend was mainly preserved. The universality of the relation between the bioluminescence of the organisms and their bioenergetics is obvious. The bioluminescent system of ctenophores has the role of an antioxidant system and is engaged in the neutralization of reactive oxygen species (ROS), that is the process during which photons are emitted. The response of the bioluminescent system to a decrease in oxygen concentration can be associated with an increase in the production of ROS that provides high values of the ctenophore luminescence under hypoxic conditions.     

Flow injection chemiluminescence determination of acetochlor and cartap-HCl in freshwater samples using an acidic KMnO4–rhodamine-B reaction system

A flow injection (FI) methodology using the acidic potassium permanganate (KMnO₄)–rhodamine-B (Rh-B) reaction with chemiluminescence (CL) detection was established to determine acetochlor and cartap-HCl pesticides in freshwater samples. Experimental parameters were optimized, and Chelex-100 cationic exchanger mini column and solid-phase extraction (SPE) were used as phase separation techniques. Linear calibration curves were observed for the standard solutions of acetochlor and cartap-HCl over the ranges 0.005–2.0 mg L⁻¹ [y = 1155.8x + 57.551, R² = 0.9999 (n = 8)] and 0.005–1.0 mg L⁻¹ [y = 979.76x + 14.491, R² = 0.9998 (n = 8)] with LODs and LOQs of 7.5 × 10⁻⁴ and 8.0 × 10⁻⁴ mg L⁻¹ (3σ blank) and 2.5 × 10⁻³ and 2.7 × 10⁻³ mg L⁻¹ (10σ blank), respectively, with an injection throughput of 140 h⁻¹. These methods were used to estimate acetochlor and cartap-HCl with or without the SPE procedure, respectively, in spiked freshwater samples. Results obtained were not significantly different at a 95% confidence level to those of other reported methods. Recoveries for acetochlor and cartap-HCl were obtained over the ranges 93–112% (RSD = 1.9–3.6%) and 98–109% (RSD = 1.7–3.8%), respectively. The most probable CL reaction mechanism was explored.     

Timing of exposure to ozone affects reproductive sensitivity and compensatory ability in Brassica campestris

It is well established that exposure to ozone (O₃) may impair vegetative growth and reproductive development in plants, although the consequences for yield depend on the effectiveness of the compensatory processes induced. This study examined the effects of exposing the terminal inflorescence of Brassica campestris L. to 100 ppb O₃ for 6 h d⁻¹ on four consecutive days during early flowering while the vegetative organs received charcoal-filtered air. The ordered predictability of development in B. campestris is ideal for studies of the impact of abiotic stress factors such as O₃ on reproductive development and seed production. Effects on reproductive development and seed yield characteristics were determined for floral sites exposed at different developmental stages. Flower and pod numbers on the terminal raceme were unaffected by exposure, but effects on pod length varied depending on the developmental stage of floral sites during exposure. Increased ovule abortion and precocious seed germination in the pods of O₃-treated plants reduced mature seed number pod⁻¹. Although the individual weight of mature seeds was slightly greater in O₃-treated plants, seed yield pod⁻¹ and seed yield plant⁻¹ were reduced due to the lower seed number pod⁻¹. Seed from O₃-treated plants germinated more rapidly than control seed irrespective of the stage of floral development during exposure. The results show that exposure to realistic O₃ episodes during the early stages of flowering significantly reduced seed yield without impairing the vigour of the seeds produced. The physiological origins of these effects are discussed.     

Effect of different CO2 concentrations on biomass,pigment content,and lipid production of the marine diatom Thalassiosira pseudonana

The marine diatom Thalassiosira pseudonana grown under air (0.04% CO₂) and 1 and 5% CO₂ concentrations was evaluated to determine its potential for CO₂ mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO₂ showed higher growth rates (1.14 and 1.29 div day⁻¹, respectively) and biomass productivities (44 and 48 mg_AFDWL⁻¹ day⁻¹) than air grown cultures (with 1.13 div day⁻¹ and 26 mg_AFDWL⁻¹ day⁻¹). The increase of CO₂ resulted in higher cell volume and pigment content per cell of T. pseudonana. Interestingly, lipid content doubled when air was enriched with 1–5% CO₂. Moreover, the analysis of the fatty acid composition of T. pseudonana revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO₂ levels. These results suggested that T. pseudonana seems to be an ideal candidate for biodiesel production using flue gases.

     

Determination of pioglitazone hydrochloride by flow injection chemiluminescence tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex system

A novel flow injection-chemiluminescence (FI–CL) approach is proposed for the assay of pioglitazone hydrochloride (PG-HCl) based on its enhancing influence on the tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex (Ru(bipy)₃²⁺-DPA) CL system in sulfuric acid medium. The possible CL reaction mechanism is discussed with CL and ultraviolet (UV) spectra. The optimum experimental conditions were found as: Ru(bipy)₃²⁺, 5.0 × 10⁻⁵ M; sulfuric acid, 1.0 × 10⁻³ M; diperiodatoargentate(III) (DPA), 1.0 × 10⁻⁴ M; potassium hydroxide, 1.0 × 10⁻³ M; flow rate 4.0 ml min⁻¹ for each flow stream and sample loop volume, 180 μl. The CL intensity of PG-HCl was linear in the range of 1.0 × 10⁻³ to 5.0 mg L⁻¹ (R² = 0.9998, n = 10) with limit of detection [LOD, signal-to-noise ratio (S/N) = 3] of 2.2 × 10⁻⁴ mg L⁻¹, limit of quantification (LOQ, S/N = 10) of 6.7 × 10⁻⁴ mg L⁻¹, relative standard deviation (RSD) of 1.0 to 3.3% and sampling rate of 106 h⁻¹. The methodology was satisfactorily used to quantify PG-HCl in pharmaceutical tablets with recoveries ranging from 93.17 to 102.77 and RSD from 1.9 to 2.8%.     

Seed development and germination ecophysiology of the invasive tree <Emphasis Type="Italic">Prunus serotina</Emphasis> (Rosaceae) in a temperate forest in Western Europe

Seed development, dormancy and germination of the American invasive tree species, Prunus serotina, are described for plants growing in a large forest in Belgium. Seeds of P. serotina were collected following anthesis in the first week of July and thereafter at fortnightly intervals. Seed dormancy, temperature requirements for germination and the soil seed bank were investigated. At maturation (about 105 days after anthesis), seed moisture content had decreased to around 13.7%, and 44% of the seeds had attained the capacity to germinate. Mature seeds of P. serotina exhibited physiological dormancy, germinating only after a long cold, moist stratification period. Highest germination percentage occurred in seeds treated with gibberellic acid (GA₃), at 10°C. We found no evidence that P. serotina forms a persistent seed bank but noticed a persistent seedling bank in the field.     

Antioxidant activity of in vitro plantlets and callus cultures of Randia echinocarpa,a medicinal plant from northwestern Mexico

Randia echinocarpa, an endemic plant to Northwest Mexico, is used as food and in traditional medicine, and several of its biological activities have been demonstrated (antioxidant, antimutagenic, antidiabetic, and immunomodulatory). Plant tissue culture is a safe and scalable system for plant propagation and production of bioactive compounds. Therefore, this study aims to establish protocols for seed germination and callus culture of R. echinocarpa and to evaluate the antioxidant activity of methanol extracts (ME) of plantlets and calli via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) methods. Seeds were cultured in media with different concentrations of Murashige and Skoog (MS) salts and sucrose, and a higher germination rate and plantlet growth was observed in half-strength MS medium with 15 g L⁻¹ of sucrose. Calli were obtained from cotyledon and hypocotyl explants cultured in MS media with different concentrations of benzyl aminopurine (BAP) and indole-3-acetic acid (IAA). All treatments induced callus formation in 100% of explants; however, the medium containing 1 mg L⁻¹ BAP + 1 mg L⁻¹ IAA was selected because it produced calli with higher biomass and friable texture. The ME of cotyledons showed the highest antioxidant activity values (μmol Trolox per 100 g dry weight) in DPPH (345.5) and ABTS (1166.4) assays, whereas the ME of calli from hypocotyls showed a higher antioxidant activity than the ME of calli from cotyledons in both antioxidant assays. The tissue culture protocols established here will be useful for R. echinocarpa germplasm conservation and propagation, as well as for the production of bioactive compounds.

     

Germination studies on three critically endangered endemic angiosperm species of the Kashmir Himalaya,India

The critically endangered and perennial alpine endemic angiosperms, namely, Aquilegia nivalis, Lagotis cashmeriana and Meconopsis latifolia inhabit such habitats in the Kashmir Himalaya that are characterised by short growing season and heavy snow cover for about 3–4 months during winter season. The seeds of these species under natural conditions experience a long period of pre-chilling during winter prior to their germination in following spring season. Taking cue from such a requirement, present study investigated the effect of chilling and exogenous application of growth hormones, NO₃ ⁻ and NH₄ ⁺ on total percent germination of otherwise deep-dormant seeds of these species, under alternate light/dark and continuous dark light regimes. Prolonged pre-chilling followed by treatment of seeds with different doses of GA₃ had a pronounced stimulatory effect on the total germination percentage in all the three species. In fact, highest germination percentage in A. nivalis was recorded only when pre-chilled seeds were treated with 1.5 mM GA₃ under alternate light/dark conditions. Likewise, germination of pre-chilled seeds of L. cashmeriana with ruptured seed coats was improved when treated with various concentrations of GA₃. Seed germination in M. latifolia was also favourably influenced by treatment of pre-chilled seeds with GA₃ or nitrogen applied either as NO₃ ⁻ or as NH₄ ⁺ under alternate light/dark conditions. Treatment of seeds with kinetin (6-furfuryl-aminopurine) had no significant influence on germination percentage in any of the three species. Thus, prolonged chilling of seeds followed by their treatment with GA₃ under alternate light/dark conditions are the requirements necessary for seed germination in these species.     

Morphological and functional seed traits of the wild medicinal plant Dioscorea strydomiana,the most threatened yam in the world

• Morphological and functional seed traits have important roles in characterising the species regeneration niche and help to understand the reproductive biology of rare and threatened plants, which can thus support appropriate plant conservation measures.
• Seed morphometric and dispersal kinetics of the critically endangered Dioscorea strydomiana were measured and compared with those of four other Dioscorea species, and seed germination response under constant temperatures (5–35 °C) was compared with that of the congeneric and widespread D. sylvatica.
• Seed mass of D. strydomiana (ca. 14 mg) was twice that of D. sylvatica, but similar to or smaller than the other species examined. Seeds of D. strydomiana have the lowest speed of descent and lowest variability in most of the morphological traits considered, suggesting lower phenotypic plasticity but higher variance in the wing‐loading value. Seeds of D. strydomiana reached maximum germination at 15 °C (ca. 47%), which decreased slightly to ca. 37% at 25 °C and was completely inhibited at 35 °C. D. sylvatica seeds started to germinate at 10 °C (ca. 3%), reached 75–80% germination at 15–20 °C and maximum (ca. 90%) at 25–30 °C. Base temperatures for germination (T_b) were 9.3 and 5.7 °C, for D. strydomiana and D. sylvatica, respectively. Due to the higher germination percentages of D. sylvatica, ceiling and optimum temperatures could also be modelled for this species, suggesting higher sensitivity to high temperature for seeds of D. strydomiana.
• The detected poor seed lot quality of D. strydomiana suggests difficulties in reproduction from seed, highlighting the need for further investigation and conservation actions for this threatened yam species.