Pollen transfer and patterns of reproductive success in pure and mixed populations of nectariferous Platanthera bifolia and P. chlorantha (Orchidaceae)

Plant species evolution is driven by many factors that have different roles in space and time. Using different field and laboratory methods, we studied reproductive patterns and their determinants in pure and mixed P. bifolia and P. chlorantha populations in different habitats. We also considered the probability of hybridisation between these two species and the role of intra-population processes in maintaining species integrity. Generally, we found a high level of reproductive success in both Platantherans. In both species, male (MRS) and female (FRS) reproductive success depended on floral display, and male reproductive success additionally on population structure. The flower traits were only weakly related to reproductive success. Moths' assemblages varied spatially and temporally, and their diversity and numbers were correlated with MRS in the year, when their abundance was markedly lower. Analysis of patterns of pollen transfer showed that pollen was transported up to 25 m (average 8.2 ± 4.83 m) and showed gene exchange between these two Platanthera species. The germination level of both species was significantly lower than seed viability, although P. bifolia seed germinated with higher frequency than P. chlorantha seeds. We noted differences in viability and germination of seeds developed as an effect of experimental interspecies crossings and those developed from natural pollination. The presence of intermediate ecotypes together with observations of spontaneous interspecies crosses in the field and viability of seeds produced in interspecies crossing suggest that both pre- and postzygotic reproductive barriers are not complete and do not prevent hybrid production.

Seed Viability Test: A Semi-Throughput Method to Screen Oilseeds for Biodiesel Production

Biofuels offer a solution to combat climate change and secure energy surplus. Among the various sources for biodiesel production, the seed of oilseed crops is primary raw material. The biodiesel industry demands a supply of good quality oil so that it can reduce processing costs and price of biodiesel. In general, the oils with low free fatty acid contents are considered as good quality oil and for which the quality of the oil should be analyzed in seed lot for biodiesel production. Currently, oil quality testing is done to the oil extracted from seed lot using sophisticated instruments. However, the analysis of oil seed lot is not tested, which forms the basic materials for oil extraction. Therefore, analysis of the quality of raw materials (seed lot in this case) is mandatory for assessing oil quality.Till now, there is no standard method available for screening the quality of the oilseed before biodiesel production. The free fatty acid (FFA) content of the oil is the critical factor for biodiesel production. In seeds, the FFA content of oil is directly associated with seed viability. In this chapter, an easy-to-perform protocol is presented for determining the seed viability potential, which is having a significant positive association with FFA content of the seed.

The effects of high oxygen partial pressure on vegetable Allium seeds with a short shelf-life

Storage at an elevated partial pressure of oxygen and classical artificial ageing cause a rapid loss of seed viability of short-lived vegetable seeds. Prolonging seed longevity during storage is of major importance for gene banks and the horticultural industry. Slowing down biochemical deterioration, including oxygen-dependent deterioration caused by oxidative processes can boost longevity. This can be affected by the seed structure and the oxygen permeability of seed coat layers. Classical artificial seed ageing assays are used to estimate seed 'shelf-life' by mimicking seed ageing via incubating seeds at elevated temperature and elevated relative humidity (causing elevated equilibrium seed moisture content). In this study, we show that seed lots of vegetable Allium species are short-lived both during dry storage for several months and in seed ageing assays at elevated seed moisture levels. Micromorphological analysis of the Allium cepa x Allium fistulosum salad onion seed identified intact seed coat and endosperm layers. Allium seeds equilibrated at 70% relative humidity were used to investigate seed ageing at tenfold elevated partial pressure of oxygen (high pO₂) at room temperature (22 ºC) in comparison to classical artificial ageing at elevated temperature (42 ºC). Our results reveal that 30 days high pO₂ treatment causes a rapid loss of seed viability which quantitatively corresponded to the seed viability loss observed by ~ 7 days classical artificial ageing. A similar number of normal seedlings develop from the germinating (viable) proportion of seeds in the population. Many long-lived seeds first exhibit a seed vigour loss, evident from a reduced germination speed, preceding the loss in seed viability. In contrast to this, seed ageing of our short-lived Allium vegetable seems to be characterised by a rapid loss in seed viability.

Chemical composition and in vitro biological activities of cardoon (Cynara cardunculus L. var. altilis DC.) seeds as influenced by viability

Cardoon is a multi-purpose crop for several industries. In this study, cardoon seeds were separated according to the viability and characterized for their chemical composition and bioactivities. Viable seeds contained higher levels of α-tocopherol (6.7 mg/100 g), lipids (23.11 g/100 g, manly oleic and linoleic acids), and free sugars (5.4 g/100 g) than the unviable ones. The hydroethanolic extract of viable seeds presented a higher concentration of phenolic compounds, namely 5-O-caffeoylquinic (8.0 mg/g) and 3,5-O-dicaffeoylquinic (43.9 mg/g) acids, and greater in vitro antioxidant activity. Both extracts showed antibacterial properties, but the best results were achieved with unviable seeds. The extracts had similar antifungal activity but did not reveal anti-inflammatory capacity or cytotoxicity to the tested cell lines. Therefore, while viable seeds contained antioxidant phytochemicals and an energy and carbon source for germination, unavailable seeds stood out for their potential to be used in the development of bio-based antibacterial ingredients.

Origin-dependence of variation in seed morphology, mineral composition and germination percentage in Gynandropsis gynandra (L.) Briq. accessions from Africa and Asia

BACKGROUND

Spider plant [Gynandropsis gynandra (L.) Briq.], an economically promising African leafy vegetable, characterized for leaf yield components and nutritive quality, exhibits poor seed germination that hinders a wider expansion of the crop in urban and periurban horticultural systems. So far, there is little information pertaining to seed morphological traits and mineral elements content that may be associated with higher seed germination. This research investigated the hypothesis that spider plants from different geographical areas exhibited differences in seed mineral composition, morphological traits, and germination capacity. To this end, twenty-nine accessions of Gynandropsis gynandra from West and East-Southern Africa, and Asia were screened for variation in seed size (area, perimeter, length, width), 10-seed weight, mean germination time, germination percentage and mineral content variations. The scanning electron microscopy (SEM), light microscopy and energy dispersive spectroscopy (EDS) solution were used to study seed morphology and mineral composition.

RESULTS

We show for the first time the external and internal structure of the seeds of Gynandropsis gynandra and measured eight mineral elements, including carbon (C), oxygen (O), magnesium (Mg), aluminium (Al), phosphorus (P), sulphur (S), potassium (K) and calcium (Ca). The accessions differed significantly (p < 0.001) with respect to seed size (area, perimeter, length, width), 10-seed weight, mean germination time and germination percentage. The hierarchical cluster analysis based on fourteen variables grouped the accessions into three distinct clusters, partially dependent on their geographical origin. Asian accessions exhibited smaller seeds and recorded higher values in terms of germination percentage. West African accessions had bigger seeds but with lower germination percentage. Variation in minerals such as potassium, carbon, and calcium content showed different patterns according to geographical origins.

CONCLUSION

Smaller seeds in G. gynandra exhibited better germination capacity. The Asian germplasm is a potential source of cultivars with a higher germination percentage for improving seed quality in the species.

Germination niches and seed persistence of tropical epiphytic orchids in an urban landscape

Urbanisation has contributed to significant biodiversity loss, yet, urban areas can facilitate biodiversity conservation. For instance, there is evidence of urban trees supporting natural establishments of orchids, the most species-rich plant family on Earth. However, the germination niches-which include both suitable biophysical conditions and orchid mycorrhizal fungus/fungi (OMF)-are not sufficiently known for most species, especially tropical epiphytic orchids. The fate of their dispersed seeds is poorly understood as well. We conducted fungal baiting and seed sowing experiments, next-generation sequencing, generalised linear models, and seed viability tests to detect and identify potential OMF, investigate biophysical factors that influenced OMF availability and orchid germination, and assess seed longevity. Ceratobasidiaceae- and Serendipitaceae-associated OMF were successfully detected in three of four orchid species. In general, orchid species and humus presence had significant effects on OMF availability. Orchid species and temperature were predictive of germination. Post-experiment viability tests revealed that one orchid species, Grammatophyllum speciosum Blume, may produce long-lived seeds. The results suggest that urban trees can support OMF and orchid germination, but both processes are limited by biophysical factors. This study also indicates the possibility of seed persistence among epiphytic species. As orchid germination niches are complex and tend to be unique to individual species, we do not encourage generalisations. In contrast, species-specific information can help formulate useful recommendations towards conservation.

A cell-wall protein SRPP provides physiological integrity to the Arabidopsis seed

Seed and root hair protective protein (SRPP) is expressed in seeds and root hairs, localized in the cell wall, and involved in cell wall integrity. We analyzed a loss-of-function mutant of SRPP, focusing on siliques and seeds. The srpp-1 plants generated dark brown shrunken seeds at a high rate. The germination rate of these defect seeds of srpp-1 was less than 6%, although apparently normal srpp-1 seeds germinated at a rate of 83%. The production ratio of severe phenotypic seeds was dependent on the growth conditions. When the srpp-1 plants were cultivated at low humidity, the defect ratio was 73%, which was significantly higher than that at normal humidity. Defects of the silique and seeds could be detected on day 7 after pollination and the apical region of the siliques displayed a severe phenotype at a high frequency. Complementation with an SRPP gene under the control of promoters specific to the embryo, seed coat, or valve (carpel) partially rescued the phenotype, and complementation using the SRPP promoter fully rescued the phenotype. Furthermore, overexpression of SRPP enhanced the thermotolerance. After the treatment of seeds at 50 °C for 2 h, the germination rate of the seeds from overexpression with the 35S promoter increased to levels twice that of the wild-type seeds. Under the same conditions, no srpp-1 seeds germinated. These results indicate that SRPP is essential for the production of normal viable seeds in siliques under stress conditions. It is possible that modification of the SRPP gene improves seed integrity.

Conservation of genetic resources for five traditional crops from Jazan, SW Saudi Arabia, at the KACST Gene-Bank

The conservation of five traditional crops is an important aspect of achieving national food security. In the present study, we aimed to collect and conserve germplasm of five local crops from the Jazan region of southwestern Saudi Arabia: Sorghum: Sorghum bicolor (L.) Moench); Barley (Hordeum vulgare L.) Millet (Pennisetum glaucum (L.) R. Br.); Sesame (Sesamum indicum L.) and Guar (Cyamopsis tetragonoloba (L.) Taub). Forty-one seed accessions of these five crops were collected and tested to determine seed moisture content (MC%) and quality as indicators of their potential to survive during long-term dry storage at −18 °C (i.e. ex-situ conservation of genetic resources). Seed viability was assessed using germination tests, the tetrazolium chloride (TZ) test and X-ray imaging. Seeds of the five crops had very low MC% and high viability (fully developed embryos and germination >91%), indicating that they were of good quality and had high potential for long-term survival in gene banks. The genetic resources of these crops (seeds) have now been preserved at the gene-bank of King Abdulaziz City for Science and Technology (KACST-BGB), Riyadh, Saudi Arabia.

Seed bank and growth comparisons of native (Virgilia divaricata) and invasive alien (Acacia mearnsii and A. melanoxylon) plants: implications for conservation

Background

Invasive alien plants with long-lived dormant seed banks and fast growth rates are difficult to manage. Acacia mearnsii and Acacia melanoxylon are two such invaders in the southern Cape of South Africa which occasionally co-occur with a native, ecologically analogous species, Virgilia divaricata. We compared the performance of these three species to determine potential for the native species to be used in management of the invasives.

Methods

We compared the study species in terms of (i) soil seed bank densities, their vertical distribution, and the viability of seeds underneath the canopies of mature trees; (ii) seedling growth from planted seeds over a period of three months; and (iii) growth rates of saplings over a period of 10 months in stands that have naturally regenerated in the field (these stands were dominated by A. mearnsii) and where saplings have been exposed to varying levels of competition from surrounding saplings.

Results

Seed bank densities differed significantly among species but not among soil depth classes. Acacia mearnsii had the highest seed bank densities (mean of 7,596 seeds m⁻²), followed by V. divaricata (938 seeds m⁻²) and A. melanoxylon (274 seeds m⁻²). Seed viability was high (87–91%) in all three study species and did not differ significantly among species or soil depth classes. As seedlings, V. divaricata significantly outgrew A. mearnsii in terms of height, root and shoot dry mass, and root:shoot ratio. Relative growth (the relationship between growth in height and initial height) was negative in the seedlings of both species. Trends during the sapling stage were opposite to those during the seedling stage; A. mearnsii (but not A. melanoxylon) saplings significantly outgrew V. divaricata saplings in height, while relative growth rates were positive in all species. Sapling growth of all species was furthermore uninfluenced by the collective biomass of surrounding competitors.

Discussion

Our findings suggest that amongst the measures considered, A. mearnsii’s success as an invader is primarily attributable to its large seed banks, and secondly to its vigorous growth in height as saplings. However, the superior growth performance of V. divaricata seedlings and no apparent negative effect of competition from the acacias on sapling growth show promise for its use in integrated management of the acacias.

Aldo-ketoreductase 1 (AKR1) improves seed longevity in tobacco and rice by detoxifying reactive cytotoxic compounds generated during ageing

BACKGROUND

Maintenance of seed viability is an important factor for seedling vigour and plant establishment. Lipid peroxidation mediated reactive carbonyl compounds (RCC's) and non-enzymatic modifications of proteins through Maillard and Amadori products reduce seed viability and seedling vigour.

RESULTS

In this study, the relevance of RCCs on genotypic variation in rice seed viability and overexpression of an aldo-ketoreductase (AKR1) enzyme that detoxify cytotoxic compounds to improve seed viability and vigour was studied. Physiological and biochemical approaches were integrated to quantify the variation in seed viability and seedling vigour in rice genotypes after exposing to ageing treatment. AKR1 was overexpressed in a susceptible rice genotype and tobacco to study the relevance of reduced RCC's on seed viability and seedling vigour. The glycation and lipid peroxidation compounds accumulated after accelerated ageing treatments in rice genotypes. The accumulation of malondialdehyde, methyl glyoxal, Maillard and Amadori products affected the seed viability and germination as they showed a significant negative relationship. The transgenic rice and tobacco seeds expressing AKR1 showed lower levels of cytotoxic compounds and glycation products that resulted in improved seed viability and seedling vigour in rice and tobacco.

CONCLUSIONS

The study demonstrates that, reactive cytotoxic compounds affect the seed viability during storage. Detoxification of reactive cytotoxic compounds by Aldo-keto reductases is one of the mechanisms to improve the seed longevity during storage.

Seed viability of five wild Saudi Arabian species by germination and X-ray tests

Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.

Determination of seed viability of eight wild Saudi Arabian species by germination and X-ray tests

Our purpose was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of eight wild species (Salvia spinosa, Salvia aegyptiaca, Ochradenus baccatus, Ochradenus arabicus, Suaeda aegyptiaca, Suaeda vermiculata, Prosopisfarcta and Panicumturgidum) from Saudi Arabia. Several days were required to determine viability of all eight species via germination tests, while immediate results on filled/viable seeds were obtained with the X-ray test. Seeds of all the species, except Sa.aegyptiaca, showed high viability in both the germination (98–70% at 25/15 °C, 93–66% at 35/25 °C) and X-ray (100–75%) test. Furthermore, there was general agreement between the germination (10% at 25/15 °C and 8% at 35/25 °C) and X-ray (5%) tests that seed viability of Sa.aegyptiaca was very low, and X-ray analysis revealed that this was due to poor embryo development. Seeds of P.farcta have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (98% at 25/15 °C and 93% at 35/25 °C) and X-ray (98%) test. Most of the nongerminated seeds of the eight species except those of Sa.aegyptiaca were alive as judged by the tetrazolium test (TZ). Thus, for the eight species examined, the X-ray test was a good and rapid predictor of seed viability.

Effects of origin, seasons and storage under different temperatures on germination of Senecio vulgaris (Asteraceae) seeds

Invasive plants colonize new environments, become pests and cause biodiversity loss, economic loss and health damage. Senecio vulgaris L. (Common groundsel, Asteraceae), a widely distributing cosmopolitan weed in the temperate area, is reported with large populations in the north–eastern and south–western part, but not in southern, central, or north-western parts of China. We studied the germination behavior of S. vulgaris to explain the distribution and the biological invasion of this species in China. We used seeds originating from six native and six invasive populations to conduct germination experiments in a climate chamber and under outdoor condition. When incubated in a climate chamber (15 °C), seeds from the majority of the populations showed >90% germination percentage (GP) and the GP was equal for seeds with a native and invasive origin. The mean germination time (MGT) was significantly different among the populations. Under outdoor conditions, significant effects of origin, storage conditions (stored at 4 °C or ambient room temperature, ca. 27 °C) and seasons (in summer or autumn) were observed on the GP while the MGT was only affected by the season. In autumn, the GP (38.6%) was higher and the MGT was slightly longer than that in summer. In autumn, seeds stored at 4 °C showed higher GP than those stored at ambient room temperature (ca.27 °C), and seeds from invasive populations revealed higher GP than those from native populations. The results implied that the high temperature in summer has a negative impact on the germination and might cause viability loss or secondary dormancy to S. vulgaris seeds. Our study offers a clue to exploring what factor limits the distribution of S. vulgaris in China by explaining why, in the cities in South-East China and central China such as Wuhan, S. vulgaris cannot establish natural and viable populations.

Vermiremediation of toxic jute mill waste employing Metaphire posthuma

India has a giant jute-producing basket which produces considerable quantity of toxic jute mill waste (JMW). Conversely, report on usability potential of JMW is rather scanty. The present study illustrates the efficiency of vermicomposting in bioconversion of JMW for agricultural use. Various combinations of JMW, cow dung, and vegetable waste were fed to Metaphire posthuma in vermireactors. Rapid increment of earthworm count, body weight, and cocoon production was evidenced. Total organic carbon and pH reduction was noteworthy, but N, P, and K availability, formation of stable humic acid C, fulvic acid C, and microbial biomass C substantially increased due to vermicomposting. FTIR spectroscopy confirmed a higher stability of vermicomposted JMW over the composted product. A significant decline in heavy metal concentration (Cr, Pb, Fe, and Zn) in the vermicomposted JMW further establishes the potential of vermicomposting with M. posthuma in successful conversion of the toxic JMW into valuable product.

Study on disinfestation of pulses using microwave technique

Mortality of the pulse beetle (Callosobruchus chinensis L.) exposed, continuously, to microwave radiation (2450 MHz) was evaluated as a function of exposure time and percent power level, at adult stages. The microwave exposure time to attain 100% insect mortality at 100 %, 80%, 60%, 40%, and 20% power levels for Chickpea, Pigeon Pea and Green Gram was optimized. Effect of optimized microwave exposure time on viability, germination, cooking and milling characteristics of Chickpea, Pigeon Pea and Green Gram was also evaluated. Adult stage study was characterized by a distinct dose-exposure curve. The mortality curve was following third degree polynomial equation. The seed viability and germination of Chickpea, Pigeon Pea and Green Gram was affected by microwave exposure time and power level. It was observed that as the power level is decreasing the germination and viability of all the pulses are increasing. The effect on cooking and milling characteristics are not affected by microwave exposure time and power level. The insects in the mobile state were observed to move towards the surface from inside the nutrient medium during microwave exposure. They also curled up and in some cases aggregation was observed.