PHYSICAL DORMANCY IN SEEDS, WITH SPECIAL REFERENCE TO GERANIACEAE: MORPHO-ANATOMY, DEVELOPMENT, PHYSIOLOGY, BIOMECHANICS AND CLASSIFICATION OF WATER-GAP COMPLEXES

The primary aims of this dissertation were to (1) identify and characterize the water-gap complex in seeds of Geraniaceae, (2) investigate its role in physical dormancy (PY) break and (3) develop a new classification system for water-gap complexes in seeds of angiosperms. The winter annuals Geranium carolinianum and G. dissectum were selected as the main representative species for the study, and seeds of an additional 29 species from the Geraniaceae were used to compare the water-gap complex within the family. A new classification system for water-gap complexes in species with PY was developed by comparing the morpho-anatomical features of PY seeds and fruits of 16 families. The water-gap complex of G. carolinianum was identified as a micropyle-hinged valve gap complex, and only a slight morpho-anatomical variation was observed within the family. Ontogenetic studies of the seed coat of G. carolinianum revealed that the water-gap region of Geraniaceae develops as an entity of the micropyle. The timing of seed germination with the onset of autumn can be explained by PY-breaking processes involving (a) two-temperature-dependent steps in G. carolinianum, and (b) one or two moisture-dependent step(s) along with the inability to germinate under high temperatures in G. dissectum. Step-I and step-II in PY-breaking of G. carolinianum are controlled by chemical and physical processes, respectively. This study indicates the feasibility of applying the developed thermal time model to predict or manipulate sensitivity induction in seeds with two-step PY-breaking processes. The model is the first and the most detailed one yet developed for sensitivity induction in PY-break. Based on the morpho-anatomical features, three basic water-gap complexes (types I, II and III) were identified in species with PY in 16 families. Depending on the number of openings involved in initial imbibition, the water-gap complexes were subdivided into simple and compound. The new classification system enables the understanding of relationships between water-gap complexes of taxonomically unrelated species with PY

Seed Dormancy and Germination Requirements of Two Endemic Palm Species of Sri Lanka

Sri Lankan endemic lowland rain forest palm species Areca concinna and Oncosperma fasciculatum are considered to be threatened due to habitat loss. Seed dormancy and germination behavior of these species are poorly understood. Therefore, the present study was conducted to identify the dormancy, germination requirements and the effect of storage time on dormancy alleviation of these species. Ripe fruits of A. concinna and O. fasciculatum were collected from home-gardens and natural populations. Initial moisture contents of fruits were measured. The effects of different gibberellic acid (GA3) concentrations (0, 250, 500, 1000, 2000, 3000 and 4000 ppm) and the removal of fruit coats and/or operculum on seed germination of both species were tested in vitro. The effects of wet storage (moist coir dust in sealed bags) at 250 C and dry storage (open trays) at ambient room temperature (approx. 29º C) on seed dormancy break and seed viability were tested after 0, 3, 9 and 12 months. Fruit moisture of A. concinna and O. fasciculatum were approximately 15% and 30%, respectively. Intact fruits of A. concinna treated with 500 ppm GA3, showed a significantly higher germination percentage (88%) than 0 ppm (33%) (P<0.05).Intact fruits of O. fasciculatum did not respond to GA3 treatments, with <4% germination. The highest germination percentages were achieved by removing pericarp+mesocarp+endocarp and 1000 ppm GA3 application in A. concinna (89%), and removing pericarp+mesocarp and operculum in O. fasciculatum (36%). Seed viability of fresh A. concinna was 87% and remained high even after 12 months of dry storage while that of O. fasciculatum has declined to 2% from 85% after 6 months of dry storage. Seed germination percentages of intact A. concinna and O. fasciculatum after 12 months of dry storage were 20% and 0% respectively. Seeds of A. concinna stored wet at 25ºC germinated slowly during 12 month period reaching 22%. Seeds of O. fasciculatum showed a similar pattern reaching 36%. It can be concluded that both species exhibit physiological dormancy. O. fasciculatum was identified as recalcitrant while A. concinnaas orthodox. Seed germination of A. concinna can be promoted by removing all fruit coats and GA3 treatment whereas in O. fasciculatum by removing the operculumor storing seeds in moist coir dust for >6 months. These findings will be useful in producing seedlings for restoration of these species.Keywords: Areca, Oncosperma, Orthodox, Physiological dormancy, Recalcitran

Germination, harvesting stage, antioxidant activity and consumer acceptance of ten microgreens

Microgreens which are tender immature seedlings of vegetables and herbs are known for their health beneficial effects. The concept of microgreens is generally less popular in many countries including Sri Lanka. Ten species were tested to obtain data on seed germination, height gain, leaf area expansion, and consumer acceptance. Of these, three species of which the seeds are commonly consumed in Sri Lanka were analyzed for antioxidant activities as seeds, sprouts, and microgreens. Seed germination of most of the species was>75% with the time taken to reach 75% germination (G75) varying from 1 to >14 days. A strong positive correlation between seedling and leaf area was observed (R2=0.8). Lettuce and carrot were found to be the most preferred microgreens followed by green peas, red amaranth and finger millet. For the three selected species where respective seeds, sprouts, and microgreens were compared, higher antioxidant activities were recorded in finger millet seeds and sesame microgreens; IC50 697 μg/mL and IC50 772 μg/mL respectively with the latter recording a high total phenol content (4873 mg/100g dry weight). Green pea microgreens showed higher total phenol content than its seeds and sprouts (1871 mg/100 g dry weight). The information generated will be of value to introduce microgreens to countries where consumers are unfamiliar with this product

Species-specific smoke effects on seed germination of plants from different habitats from Sri Lanka

Smoke and in particular karrikinolide (KAR1), a growth promoting compound found in smoke, have been shown to enhance seed germination in phylogenetically diverse plant families from both fire-prone and fire-free ecosystems. We tested the effects of water saturated with smoke, “smoke water” (SW), and KAR1 on seed germination of 18 native and exotic plant species from different habitats affected by anthropogenic fires in Sri Lanka. Seeds were tested with five concentrations of SW (5 %, 25 %, 50 %, 75 %, 100 %) and those that positively responded were tested with three different concentrations of KAR1 (10 nM, 100 nM and 1 μM). Germination percentage of three native (Flueggea leucopyrus, Maesa indica and Phyllanthus emblica) and two exotic (Chromolaena odorata and Hyptis suaveolens) species was significantly increased by both SW and KAR1 treatments. Seed germination percentage of the exotic species Euphorbia heterophylla was increased by SW treatments only. The time taken for 50 % germination (t50) of C. odorata, M. indica and P. emblica was decreased by both SW and KAR1, whilst t50 of E. heterophylla was decreased by SW only. Species-specific seed germination promotion response to SW and KAR1 was observed in both native and exotic plant species tested in the study confirming that the recruitment ecology of at least some species found in fire prone habitats of Sri Lanka is likely to be influenced by fire management practices

Seed Biology of Ten Common Roadside Sri Lankan Weed Species

Weeds are undesirable in habitats where they grow and cause negative economic and environmental impacts. Understanding in weed seed germination is important to deploy control measures. This study was conducted to evaluate the effect of seed dormancy, smoke, KAR1, salinity and pH on germination of ten common roadside weed species in Sri Lanka. Freshly collected seeds of ten weed species were subjected to five treatments vis, (1) 0 and 500 ppm GA3; (2) Smoke solutions of 0%, 5%, 25%, 50%, 75%, and 100% strength; (3) 0 nM, 10 nM, 100 nM and 1 μM KAR1 solutions; (4) 0 nM, 25 mM, 50 mM, 75 mM, 100 mM, and 200 mM NaCl solutions; and (5) 4,5,6,7,8,9 and 10 pH buffer solutions. All the treatments were applied on 100 seeds (five replicates, 20 seeds each) and incubated at 25° C under 12/12 hrs light/dark for 4 weeks. Final germination percentages were calculated. Seeds of Bidens pilosa, Mikania micrantha, Rivina humilis, Tridax procumbens, and Vernonia cinerea were identified as non-dormant (germination>90%) and seeds of Ageratum conyzoides, Hyptis capitata, Oldenlandia herbacea, Ocimum tenuiflorum and Spilanthes iabadicensis were identified as dormant (germination<65%). GA3 improved germination of S. iabadicensis and KAR1 improved germination of A. conyzoides, H. capitata, O. herbacea, and S. iabadicensis. Smoke water did not improve seed germination of any of the species. Seven species (B. pilosa, M. micrantha, O. herbacea, O. tenuiflorum, R. humilis, and T. procumbens) exhibited a wide range of salinity tolerance (0-75 mM NaCl) with>50% germination. R. humilis exhibited a wide range of pH tolerance (pH 5-8) with >50% germination. Seed dormancy of four species were broken by GA3 and KAR1 treatments indicating physiological seed dormancy (PD). Due to unresponsiveness to dormancy breaking treatments, it can be assumed that seed of O. tenuiflorum possess deep-PD. The study confirmed that responsiveness to KAR1, smoke, salinity and pH is species specific and seed dormancy may lead to the formation of persistent soil weed seed banks. These traits may facilitate the weed seeds to compete with other species and dominate the vegetation.Keywords: Karrikinolide (KAR1), pH, Smoke water, Salinity, Weed specie

Seaweeds as a Source of Functional Proteins

International audienceProtein is one of the major macronutrients essential in human nutrition. Protein sources especially animal sourced proteins are expensive, thus much work has been carried out to explore alternative protein sources. Seaweeds, or macroalgae, are emerging as one of the alternative protein sources. They are rich in protein with an excellent amino acid profile comparable to the other conventional protein sources. Seaweed protein contains bioactive components, such as free amino acids, peptides, lectins, and phycobiliproteins, including phycoerythrin and phycocyanin, among others. Seaweed proteins have been proved for their antihypertensive, antidiabetic, antioxidant, anti-inflammatory, antitumoral, antiviral, antimicrobial, and many other beneficial functional properties. Therefore, seaweed proteins can be a natural alternative source for functional food development. This paper discusses the compositional and nutritional aspects of seaweed protein, protein extraction techniques, functional properties of various seaweed proteins, as well as their safety for new product development and functional food applications

Efficacy and safety of co-trimoxazole in eradication phase of melioidosis; systematic review

Abstract Background Melioidosis is an infectious disease caused by the bacterium Burkholderia pseudomallei. The two stages of melioidosis treatment are the intense intravenous phase and the oral eradication phase. Although co-trimoxazole has been in use for several years, the literature does not demonstrate uniformity of the drug doses, combinations, or durations suitable for the eradication phase of melioidosis. The safety profile of co-trimoxazole was not documented in the literature, nor have systematic studies of its effectiveness been done. This systematic review sought to study on the dose, duration and combination of co-trimoxazole therapy in view of clinical efficacy and safety in the eradication phase of melioidosis. Main body This systematic review included all of the published articles that employed co-trimoxazole in the eradication phase after 1989, including, randomized clinical trials, case–control studies, cohorts, case reports, and case series. Throughout the eradication (maintenance) phase, co-trimoxazole usage was permissible in any dose for any period. A total of 40 results were included in the analysis which contained six clinical trials, one cohort study, one Cochrane review, and thirty-two case series/case reports. Clinical and microbial relapse rates are low when co-trimoxazole is used in single therapy than in combination. There were several adverse events of co-trimoxazole, however, a quantitative analysis was not conducted as the data did not include quantitative values in most studies. Short conclusion The dose of co-trimoxazole, duration of the eradication phase, and other combinations used in the treatment was varying between studies. Compared to combined therapy patients treated with co-trimoxazole alone the mortality and relapse rates were low. The lowest relapse rate and lowest mortality rate occur when using co-trimoxazole 1920 mg twice daily. The duration of therapy varies on the focus of melioidosis and it is ranged from 2 months to one year and minimum treatment duration associated with low relapse rate is 3 months. The use of co-trimoxazole over the maintenance phase of melioidosis is associated with clinical cure but has adverse effects