Naked Seeds Research Articles

Emergence and Persistence of Volunteer Flax in Western Canadian Cropping Systems

Flax (Linum usitatissimum L.) is being evaluated as a platform crop for genetically engineered (GE) novel oils but it must be able to coexist with non‐GE flax without causing market harm. The GE flax volunteers are a potential source of gene flow via pollen and seed. Field experiments in 2005 and 2006 quantified emergence periodicity of volunteer flax in direct seeded and conventionally tilled fields. Germination and emergence rates of naked seeds and seed retained in flax bolls were compared in laboratory and greenhouse trials. Lastly, 20 commercial flax fields were surveyed to quantify population size and persistence of volunteer flax for 3 yr following the flax crop. Volunteer flax emergence ranged from 31 to 4597 plants m−2, the year following flax crops. Emergence was slower in direct seeded fields compared to conventionally tilled with 50% emergence (E50) occurring at 340 and 228 growing degree days (GDD), respectively in 2005 and 297 and 236, respectively in 2006. The E50 occurred after crop emergence and before in‐crop herbicides are normally applied. Greenhouse experiments confirmed that emergence of volunteer flax may be prolonged because seeds retained in flax bolls are protected from germination. In surveyed commercial fields, flax volunteer populations declined rapidly between the first and second year, but continued to emerge in some fields 3 yr following flax production. Field surveys confirmed the relatively slow emergence of volunteer flax, with the highest volunteer flax density observed in the survey period before in‐crop herbicide application. Few flax volunteers set seeds in commercial fields and are, therefore, unlikely to contribute to population persistence. Volunteer flax requires effective control in the year following the crop to reduce the potential for pollen‐ and seed‐mediated gene flow.

The role of the persistent fruit wall in seed water regulation in Raphanus raphanistrum (Brassicaceae)

Dry fruits remain around the seeds at dispersal in a number of species, especially the Brassicaceae. Explanations for this vary, but usually involve mechanisms of innate dormancy. We speculate that, instead, a persistent fruit may give additional protection through control of dehydration, to species growing in arid or Mediterranean environments where water is sporadic. X-rays and weight measurements were used to determine the extent to which Raphanus raphanistrum seeds within mature fruits imbibe water, and germination tests determined the roles of the fruit and seed coat in seed dormancy. Rates of water uptake and desiccation, and seedling emergence were compared with and without the fruit. Finally, germinability of seeds extracted from fruits was determined after various periods of moist conditions followed by a range of dry conditions. Most seeds rapidly take up water within the fruit, but they do not fully imbibe when compared with naked seeds. The seed coat is more important than the dry fruit wall in maintaining seed dormancy. The presence of a dry fruit slows emergence from the soil by up to 6-8 weeks. The fruit slows the rate of desiccation of the seed to a limited extent. The presence of the fruit for a few days during imbibition somehow primes more seeds to germinate than if the fruit is absent; longer moist periods within the pod appear to induce dormancy. The fruit certainly modifies the seed environment as external conditions change between wet and dry, but not to a great extent. The major role seems to be: (a) the physical restriction of imbibition and germination; and (b) the release and then re-imposition of dormancy within the seed. The ecological significance of the results requires more research under field conditions.

Effects of environmental factors on seed germination of Anthyllis barba-jovis L

The influence of the main environmental factors on seed germination of Anthyllis barba-jovis L. were analysed. This work is part of a broader investigation aimed at the reintroduction of this species on Mount Conero, Ancona (central Italy), where it is at present extinct. The seeds were collected from the Gargano headland (southern Adriatic coast). Experimental analyses were carried out to determine: (i) dormancy levels of seeds collected in successive years, and also collected from the soil seed bank; (ii) effects of usual pre-treatments for overriding the physical dormancy of the seeds; (iii) optimal temperature range for maximum germination; (iv) effects of fire on seed germination; and (v) effects of NaCl on germination and on early stages of seedling development. Our results confirm that A. barba-jovis seeds have a physical dormancy due to their teguments, which are water-impermeable. This barrier persists in naked seeds that remain in the soil. Regularly water-drenched seeds show a high germinative ability. The optimal seed germination temperature is 20°C, with germination decreasing progressively at lower temperatures, and falling drastically over 20°C. Fire and high temperatures positively affected germination. The seeds were shown to be strongly resistant to salt stress, thus enabling the plants to colonize a habitat suitable for halophytes.

Adventitious embryo formation derived from zygotic embryos in Cycas revoluta

Numerous adventitious embryos of Cycas revoluta were successfully induced and grown on the mature zygotic embryos in the well-ripe, naked seeds used on Schenk and Hildebrandt (SH) medium supplemented with 3.0% sucrose, 20% coconut milk, 0.6% agar and the growth regulators of 0.20 to 2.00 mg l−1 BAP and 0.00 to 0.20 mg l−1 2,4-D in combination at pH 5.9 42 to 84 days after the beginning of the culture. Maximum proliferation of 88.7±40.5 adventitious embryos per zygotic embryo was obtained on SH basal medium supplemented with 0.20 mg l−1 BAP and 0.02 mg l−1 2,4-D. Root formation was seen on all of the adventitious embryos by continuous culture on the same medium. Each rooted plantlet was isolated individually and then, grew big enough to juvenile stage that had one to three leaves with pinnate leaflets, thick trunk and primary tap root on SH basal medium without any growth regulator 196 days after the beginning of the culture and was ready for acclimatization.

セル成型苗育苗における播種後のミスト潅水処理がホウレンソウの出芽に及ぼす影響

We investigated the effects of the watering level after sowing on the emergence of spinach (‘Active’: primax seeds) in a plug-transplant nursery system. An emergence rate over 90% was obtained by providing about 200ml of water per plug tray (200 cells per tray, 13ml per cell) regardless of the culture soil component. Contradictorily, a low emergency rate was observed after excessive watering. The emergence rate under a consecutive 25°C condition was 70% or less. The rate was improved by 1) watering with 400-600ml per tray, and 2) subjecting trays to 15-20°C (optimal temperatures for germination) for 3 days after sowing. These management methods promoted about 90% emergence rate even if trays were exposed to a 25°C condition from the fourth day onward. The optimal watering level per plug tray for seed emergence under a condition of 19.1°C were, 100-400ml for normal seeds (with pericarp) and presoaked normal seeds, 200ml for primax seeds, and 400-800ml for naked seeds, respectively. In an optimal watering level, about 90% seeds emerged promptly within 10 days.

Seed storage of Avicennia alba Bl.

Seeds of Avicennia alba BI. matured at high moisture content and were sensitive to desiccation: no seeds survived desiccation below 35% moisture content. The effect on survival of a factorial combination of five moist storage treatments (fresh seeds in a polyethylene bag, open with water sprayed over regularly, mixed with sand at 10% moisture content, mixed with moist paddy hulls, or naked seeds mixed with sand at 10% moisture content) and three temperatures (28-30degreesC, 17degreesC and 8-10degreesC) was investigated. In addition, seeds were mixed with sand at 5% moisture content and stored at 17degreesC in order to determine the effect of sand moisture content on seed moisture content and viability during storage. Avicennia alba showed recalcitrant seed storage behaviour, but 75% of the seeds remained viable after four months' moist (45-47% moisture content) storage in 10% moisture content sand at 17degreesC.

Quebra da dormência de sementes de quatro leguminosas arbóreas

Nas sementes de leguminosas é comum a ocorrência de dormência devido à dureza do tegumento. Sementes de bordão-de-velho (Samanea saman (Jacq.) Merr.), angico-de-bezerro (Piptadenia moniliformis Benth.), pau-ferro (Caesalpinia ferrea Mart. ex. Tul.) e sabiá (Mimosa caesalpiniifolia Benth.) foram submetidas aos seguintes tratamentos: escarificação com lixa, água a 80ºC por 1,0; 2,5 e 5,0min; água à temperatura ambiente (12; 24 e 48h); ácido sulfúrico concentrado (1; 5 e 10min) e álcool etílico (5; 10 e 25min), visando a quebra da dormência. De sabiá foram testados os artículos e as sementes nuas. Usou-se o delineamento inteiramente ao acaso, com quatro repetições (50 sementes/repetição). Os tratamentos com ácido sulfúrico resultaram em maiores percentuais de germinação para bordão-de-velho (98,5-99,0%) e para pau-ferro (76,5-89,0%). Para angico-de-bezerro, destacaram-se água a 80ºC durante 1,0 ou 2,5min, e ácido durante 10min (82,5; 74,0 e 87,0% de germinação, respectivamente). Maiores percentagens de germinação foram obtidas nas sementes nuas de sabiá do que nos artículos, destacando-se, com germinação de 73,0 a 93,5%, os tratamentos com água a 80ºC, com ácido 5 e 10min, e com álcool etílico por 5min. Considerando-se o custo e os riscos na utilização do ácido sulfúrico, é preferível, para quebrar a dormência das sementes estudadas, a utilização dos tratamentos com água a 80ºC, ainda que seja necessário aumento na densidade de semeadura.

344 Dormancy Breaking and Germination of Liriope spicata Lour.

There are many ground covers native to Korea. Liriope spicata is very promising for landscaping purposes due to its waxy and dark-green foliage fragrant and pink flowers, as well as fruit. However, seeds harvested during late fall do not germinate at all if they are sown in spring. Thus, series of experiments were conducted to undestand the physiological mechanism of dormancy breaking and germination of Liriope spicata Lour. seeds and to determine the effective methods for enhancing seed germination. Fruit were harvested in October through December. Depulped seeds germinated rapidly, indicating that one or more inhibitors may be present in the pulps of fruit and/or seeds. GA3, NaOCl, NaOH, and H2SO4 treatments and dry cold treatment had no effect on germination, whereas wet, cold seed treatment for at least 30 days promoted germination up to 75% within 15 days. Optimum conditions for germination was continuous dark and 25/20 °C alternate temperature conditions. Extracts from pulps and seeds showed a strong inhibition effects on the germination of lettuce seeds, indicating that germination inhibitors are present in pulp and seeds. Since extracts from naked seeds did not show inhibition, inhibitory substances are thought to be present in pulp and seedcoat. Pulp and seeds were extracted with water and methanol and autoclaved at 115 °C, followed by bioassay experiments. Germination inhibitors were found water soluble and heat stable by series of bioassay experiments. Diluted extracts 4 to 8 times still maintained inhibitory effects. Optimum seed harvesting time was from 22 Nov. to 1 Dec., where seed germination was high without additional seed treatments. Total phenolic compounds and ABA contents of pulp and seeds decreased by wet cold seed treatment. Changes in total phenolic compounds and ABA in from October through December were correlated with germination during the seed development. When contents of total phenolic compounds and ABA were high, seeds did not germinate at all, while low contents resulted in good seed germination.

REHABILITATION OF DEGRADED GRASSLANDS IN NORTH SYRIA: THE USE OF AWASSI SHEEP TO DISPERSE THE SEEDS OF ANNUAL PASTURE LEGUMES

Four experiments were conducted to facilitate the improvement of degraded grasslands in north Syria. The first examined the survival of legume seeds fed to penned Awassi wethers. The second and third observed the germination and establishment of legumes from faecal pellets in the field and in a glasshouse respectively. The fourth explored the possibility of transporting seeds from legume-rich (source) to legume-poor (target) grasslands using commercial flocks on communally-owned land. Seeds of small-seeded clovers passed through sheep in greater numbers (58–72%) than did seeds of larger-seeded species (10–40%). Of the clover seeds Trifolium campestre (seed size 0.45 mg) disintegrated least (72% passage) and T. haussknechtii (seed size 2.68 mg) disintegrated most (10% passage). Recoveries of Medicago noeana and Scorpiurus muricatus seeds were larger than expected on the basis of their seed sizes. Maximum rate of recovery was at 36 h after the seed meal for all species, all seeds were recovered by 120 h and 90% of the recovered seeds were passed in 72 h. Ingestion had little effect on the hardness and viability of most seeds. Experiments 2 and 3 suggested that seeds in pellets germinated and established as successfully as naked seeds. Burial increased establishment, whether in the field or under conditions of low moisture stress in the glasshouse. The small-seeded clovers, T. tomentosum and T. campestre, established most successfully whether from pellets or from naked seeds. About 500 seeds m−2 were successfully transported from the source to the target grassland. About half were Trigonella monspeliaca, a naturally-occurring legume found on both the source and target grasslands. Of the species sown on the source grassland, 115 seeds m−2 of Trifolium campestre (33% of the source seed bank), 62 seeds m−2 of T. tomentosum (27%) and 78 seeds m−2 of T. purpureum (21%) were detected in the target. Few medics were transported (for example, <2% of M. noeana). Apart from Trigonella monspeliaca, Trifolium tomentosum (16 plants m−2) was the most frequent species found in the target grassland in the following April. The results suggest that using sheep is a cheap and practical way of dispersing the seeds of pasture legumes and thereby improving the degraded grasslands of north Syria. They clearly demonstrate the role of small-seeded legumes (<1 mg) in grassland improvement, especially the small-seeded clovers.

Control of fungal growth with sphagnum for cold stratification and germination of tree seeds.

A method for seed germination has been practiced at the Taiwan Forestry Research Institute, Taiwan since 1985 and is worthy of introduction to other users. The method involves germinating seeds in a mixture with moist sphagnum in a polyethylene bag sealed with adequate air inside and placing the bags vertically in trays at required germination conditions. The water content of sphagnum was 85% (fresh weight basis). Since the bags can stand side by side, the space needed for germination is much reduced. Five isolates of Trichoderma viride (fungi), and 5 of actinomycetes were identified as associated with sphagnum. They were also identified as antagonistic to the microorganisms which cause mold development on seeds. The sphagnum medium can provide a germination condition which prevents the spread of mold which has been found to be of common occurrence in seeds requiring prolonged incubation periods in the traditional filter paper germination method of tree seeds. The seed germination rates, however, obtained in different germination media did not respond to the extent of mold contamination. In another experiment, tree seeds embedded in sphagnum medium were found to be significantly better protected from mold development than were naked seeds in the wet storage condition. Therefore sphagnum medium has great advantages for seeds which need a prolonged period of cold stratification.

The role of the seed coat in the light sensivity in Raphanus sativus L. cv. redondo gigante seeds

The role of the seed coat in the light sensitivity of seeds of Raphanus sativus L. cv. redondo gigante was analysed by germination tests of intact and naked seeds. Far-red light caused high inhibition of seed germination, while under white and red lights low inhibition was found. Naked seeds presented no light sensitivity with high percentage germination under light and darkness. However, incubation of naked seeds in -0.6MPa polyethylene glycol solution resulted in light inhibition as observed in intact seeds. The analysis of the seed coat transmitted light indicated that the filtered light presented the same photoequilibrium of phytochrome when compared to the white light, with a decrease of only 33% in the light irradiance which reaches the embryo.

Response of the recalcitrant seeds of Avicennia marina to hydrated storage: events occurring at the root primordia

AbstractThis study was undertaken to test the hypotheses that germinative metabolism of recalcitrant seeds in storage induces a requirement for additional water, which may result in the development of mild water stress, and that a reduction of the rate of this germinative metabolism will increase the storage lifespan of recalcitrant seeds. Studies were undertaken on seeds of Avicennia marina (Forssk.) Vierh. and concentrated on root primordia as these constitute the tissue that undergoes most change during storage. Encapsulating seeds from which the pericarp had been removed (naked seeds) in an alginate gel increased storage lifespan fourfold compared with naked seeds. Measures of metabolic rate such as time to first germination in storage and rate of protein synthesis did not indicate differences between alginate-coated and naked seeds, although ultrastructural observations indicated that both germinative and deteriorative processes were occurring more slowly in the alginate-coated seeds. Measures of water content and water and turgor potentials did not reveal signs of a mild water stress in either treatment. However, the number of seeds visibly contaminated with fungi and the rapidity with which this contamination became apparent were much reduced in alginate-coated seeds. It is suggested that fungal contamination constitutes a major cause of deterioration in stored, hydrated seeds of A. marina (and possibly other recalcitrant seed species) and the main effect of the alginate coating was to reduce the incidence of fungal contamination.

COMBINING ABILITY STUDIES ON OIL CONTENT IN RELATION TO FUZZ GRADES IN COTTON

The seeds of Gossypium are usually fuzzy of different grades. The combining ability on oil content in relation to fuzz grades is reported in this paper. Seven cotton lines differing in fuzz grade from fully fuzz to naked seeds were crossed with the fuzzy varieties: MCU.5, MUC.7, MCU.9 and LRA. 5166 in a 'line x tester' fashion. Seed oil percentage exhibited greater range of variation among hybrids (16.55 to 23.58). The naked seed parent, TCH.89/7 recorded the highest significant oil percentage (23.66) and hybrids involving naked seed parent also recorded significantly higher oil percentage. Heritability (broad sense) was as high as 94.6 per cent though, the genetic advance as percentage of mean was low (8.49%). The GCASCA ratio was also less than unity indicating the preponderance of non-additive gene action for oil content. Significant relationship between the per se performance and gea effects of the parents for oil content was noticed with sparsely fuzzed line TCH.65/8 and naked seed line TCH.89/7. Bot the cross combinations with high sea effects with respect to oil content involved poor conbiners. Correlation studies revealed that seed oil content had a significant and negative correlation co-efficient (-0.34) with fuzz grade and had significant and positive correlation co-efficient (0.34) with single seed kernel weight.

Avian Dispersal of "Mimetic Seeds" of Ormosia lignivalvis by Terrestrial Granivores: Deception or Mutualism?

Several tropical forest legume species producing hard and brightly-colored seeds, which apparently evolved as mimics of fleshy fruit and arillate-seed models, have been presumed to be dispersed by avian frugivores through non-mutualistic interactions involving sensorial deception. Here we examine the interactions between a typical so-called mimetic seed species and its potential dispersers in an Amazonian forest site, and propose that such interactions are best interpreted as mutualistic. Ormosia lignivalvis (Leguminosae : Papilionaceae) is a relatively rare but widespread canopy tree producing naked seeds with a conspicuous, bicolored (scarlet and black) hard seed coat, containing no nutrient rewards to its putative dispersers. Mature seeds are gradually released from dehiscent pods in a piecemeal fashion, during an extended fruiting period of up to 8 months, but may be retained by persistent funicles throughout the year. Intact Ormosia seeds were found in stomach contents of large-bodied terrestrial birds - including one tinamou, one trumpeter, and two cracid species - which appear to be the main dispersers. On the other hand, a total of 185 h of vigils of 5 fruiting tree crowns failed to result in any observed cases of seed removal by arboreal frugivores. Laboratory measurements of seed resistance, elasticity, and hardness showed that Ormosia seeds are extremely hard, and could, therefore, aid in the mechanical breakdown of softer seeds which make up a large proportion of the diet of these terrestrial granivores. We argue that the hard, non-elastic O. lignivalvis seeds, and perhaps a number of other so-called mimetic-seed species, can function as similarly shaped and sized mineral grit universally swallowed by large gallinaceous birds, in that they help to crush and grind the mostly pliable seeds digested by their dispersers. This interaction is thus best described as a mutualism in that (I) Ormosia germination is greatly enhanced by the abrasive gut treatment of avian granivores, and (2) such birds would otherwise find no adequate gizzard grit substitutes in environments conspicuously lacking small pebbles, such as the lowland rainforests of sedimentary river basins of Amazonia.

Seed germination and seedling growth in a wilty mutant of sunflower ( Helianthus annuus L.): Effect of abscisic acid and osmotic potential

The effect of abscisic acid (ABA) on seed germination and seedling growth of w−1, a wilty, ABA-deficient sunflower ( Helianthus annuus L.) mutant, is described in comparison with the control line (W-1). Exogenous ABA inhibited seed germination in both genotypes; however, for some ABA concentrations, whole achenes of w-1 mutant were slightly more inhibited than the wild type; naked seeds of w-1 were significantly less inhibited than the wild type. To investigate the sensitivity to osmotic stress in relation to ABA levels, naked seeds were subjected to different PEG solutions. Mutant seeds showed a higher osmotic resistance, germinating at more negative osmotic potentials; moreover, at low osmotic potentials, germination of w-1 seeds occurred much earlier than control seeds. Growth inhibition experiments indicated that shoot and root growth of w-1 seedlings is less sensitive to ABA with respect to control line. These differences may be related to the ABA deficiency of the w-1 genotype, but we cannot exclude the possibility that the wilty mutant may have a complex alteration of either ABA synthesis and the reception and/or transduction of the hormonal signal.

Effects of seed treatments on the germination of Atriplex nummularia Lindl.

Laboratory experiments were conducted to determine the influence of length of soaking period and water temperature treatments on the germination of Atriplex nummularia. Germination percentages increased significantly (P≤0,01) with increasing soaking period in water with a temperature of 20°C, while there was a tendency for a decrease in germination at the higher water temperature (30°C) treatment. The fruits were almost fully imbibed after 8 days of soaking at both water temperature treatments. Fruits germinated better in pots than in petri dishes, but for naked seeds the opposite was the case. Some of the unexplained findings should be further investigated.

The role of seed coat in early stages of soybean germination

The presence of the seed coat delays the early stages of germination of soybean embryos. This retardation seems to be due to the seed coat acting as a mechanical barrier to seedling. Although entire soybean seeds are insensitive to light, removal of the seed coat induces a light requiring condition. The early germination of naked seeds or isolated embryonic axes is enhanced by darkness. Red light produced a similar effect as white, providing evidence for the effective wavelength of the photo-inhibition. Far-red light acted similarly to darkness in promoting the early germination of the embryos. It is suggested that possibly light may act through phytochrome by the high irradiance system.

A new leaf, Glossopteris duocaudata sp. nov., from the late Permian of Cooyal, New South Wales

A reticulate-veined leaf with conspicuous basal lobes and having a fructification consisting of an elliptic cluster of sessile naked seeds adnately attached to the petiole is described as Glossopteris duocaudata sp. nov. The sterile leaves are somewhat similar to Belemnopteris elongata Lacey, van Dijk & Gordon-Gray from Natal but differ from the three Indian species of Belemnopteris by the manner in which the secondary venation in the basal lobes arises from the intramarginal vein on the inner sides of the lobes.

Polyploidy in gymnosperms.

A discussion in gymnosperms as a group is somewhat meaningless so far as discerning trends or ascertaining general principles. It is now generally recognized (1, 2) that g3niinosperms as a class probably never existed, and that gymnospermy should be regarded as a way of life rather than suggesting that the plants possessing naked seeds are somehow closely related. So before surveying the occurrence of Polyploidy in gymnosperms, it might be appropriate to indicate the kinds and degree of relationships of plants that are loosely included in the group.

Contribution of growth rate and harvest index to grain yield of oats (Avena sativa L.) following selfing and outcrossing of M1 plants

Three populations of oats, each with 790 lines, were derived from CI 7555: (a) one (M population) consisted of M2-derived lines obtained from EMS treatment of naked seeds, (b) one (O population) consisted of F2-derived lines from crosses of M1 with check plants, and (c) one (C population) consisted of check lines.