Spread Of Germination Research Articles

Are the Alien Species of Melastomataceae and Bombacoideae a Potential Risk for Brazilian Cerrado?

The cultivation of species in urban areas for landscaping or consumption has increased in cities surrounded by Cerrado, putting in risk the local flora. Thus, the objective of this paper was to describe seed germination and seedling emergence of five urban cultivated species of Melastomataceae and Bombacoideae and compare them with Cerrado native species to evaluate if they offer any risk to local vegetation. The seeds were collected in the urban area of Uberlandia, within the Brazilian Cerrado. We calculated germination and emergence measurements and compared them to literature data. Seeds of Bombax ceiba and Pachira aquatica had a germination and emergence pattern similar to other Bombacoideae. Tibouchina pulchra and Tibouchina granulosa also had a similar pattern to other Melastomataceae, with low germinability. In contrast, seed germination of Heterotis rotundifolia, an invasive African species, was similar to Clidemia hirta, also known as invasive, including the higher spreading of germination through time, a common character of invasive plants. Seed germination of H. rotundifolia was more similar to Cerrado species with dormant seeds, showing high germinability and germination spread through time. These features added to its fast-growing due to its decumbent herbaceous habit that forms dense mats could offer risks to local species. Thus, it is being recommended that its populations be monitored.

Effect of seed scarification on germination parameters in hairy indigo(Indigofera astragalina)

Two seed lots, freshly harvested and one year old seed of hairy indigo (Indigofera astragalina DC) were used in the present study. Non scarified seed was used as control. Germination test of scarified and non scarified seed lots were conducted at 25 and 30°C in the dark, between the paper (BP). First observation was recorded after 24 hr and subsequent observations were recorded at 12 hr interval up to 120 hours and afterwards at 1 day interval up to 20 days. Analysis of variance indicates that germination percentage was significantly higher in the scarified seed (93.0 and 94.5%) as compared to non scarified seed (1.5 and 4.0%) in fresh and one year old seed lot, respectively. Difference was not significant between fresh (1.5 and 2.0%) and one year old seed (3.0 and 4.0%), at 25 and 30°C temperature. In scarified seed 93.5% germination achieved within 10 days, while in non scarified seed germination was only 1.5% even after 20 days. The time spread of germination was more in non scarified (17 and 6 day) than in the scarified seed (4.5 and 4 day) in fresh and one year old seed, respectively. The lower mean germination time indicates faster germination as taken by scarified seed (61–49.8 hours) while it was 296–116 hours in the non-scarified seed in fresh and one year old seed, respectively. Higher germination index was observed in scarified seed (161.8 and 136), which denotes higher percentage and rate of germination as compared in non scarified seed (6.5 and 24.3) in the fresh and one year old seed, respectively. Germination rate index was also very high (39.0 and 47.8% day−1) in scarified seed, while it was very low (0.2 and 0.7% day−1) in the non scarified seed in the fresh and one year old seed, respectively.

Long-term softening of surface and buried hard seeds of yellow serradella grown in a range of environments

A 3-year field experiment was conducted to investigate seed softening in yellow serradella (Ornithopus compressus L.) in a low rainfall Mediterranean environment at Merredin, Western Australia. The study examined seeds of 4 accessions of serradella from separate growing sites (Pindar, Merredin, and Badgingarra), and included the effect of pod burial (only for accessions grown at Merredin). Pods were placed on the soil surface in December 1992 and sampled in March, June, and October for the next 3 years. Burial treatments (2 and 6 cm beneath the surface) commenced in June 1993 after pods had been on the soil surface for one summer. Samples were collected in June for the next 2 years. Softening of seeds over the first summer in the field was compared with that obtained in the laboratory with 16 weeks at a diurnally alternating temperature of 60/15ºC. Few seeds of any accession softened (generally <6%) at the soil surface during the first summer but the rate of softening increased over the next 2 years. The highest annual rate of softening was about 55% in the third year in accessions GEH72-1A and GEH72-2A. Accession of serradella hadmore influence on pattern of seed softening than site at which seeds were produced. Burial of pods at 2 cm markedly accelerated seed softening in all strains, particularly GEH72-1A and cv. Madeira, in which over 95% of hard seeds softened during the first year of burial. Softening at 6 cm was similar to that at the soil surface. Shallow burial of pods, as would occur during cereal cropping in one year,could improve regeneration of serradella, but reduce the longevity of its seed bank. Laboratory treatment at 60/15ºC generally over-estimated field softening during the first summer.The spread of germination in time in laboratory tests differed between accessions and was much wider in GEH72-2A than in others, extending up to 35 days. Such behaviour could provide insurance against total seedling loss following false breaks of season.

Bet-Hedging Germination of Desert Annuals: Beyond the First Year

Prolonged seed dormancy in desert annuals is thought to be an adaptation to environmental uncertainty. Germination spread over several years could reduce the year-to-year variation in the fitness of a genotype. Previous work has demonstrated that, for a number of species, not all viable seeds germinate under one set of conditions in the first year, but the subsequent fate of the dormant seeds has not been tested. In this study, germination experiments were performed on seeds of six species of winter annuals from Portal, Arizona. Seeds that do not germinate under good conditions in the first year germinate under the same conditions in subsequent years. However, germination fractions in the first 2 yr are not equal fractions of remaining viable seeds, which is the theoretical optimal behavior, and the germination distributions differ greatly among species. Germination under good conditions following a year of bad conditions for germination also differs among species. Germination behavior is age-dependent, and germination trials conducted on seeds of unknown ages from soil samples may give misleading results. These results indicate that seed dormancy acts as a form of bet hedging but that selection for an optimal distribution of germination across years may be weak.

DNA synthesis in osmoprimed leek (Allium porrumL.) seeds and evidence for repair and replication

AbstractOsmopriming of leek seeds (Allium porrumL.) in PEG 6000 solution (−10 bars) at 15°C for 14 days leads to reductions in both the spread of germination and mean time to germination, especially in low-vigour seed lots.In vivomethyl [3H]-thymidine pulse-labelling studies have demonstrated constant and low levels of DNA synthesis in leek embryo tissue during the osmopriming treatment. DNA synthesis during osmopriming was not inhibited by aphidicolin, an inhibitor of nuclear DNA replication. Replicative and repair-type DNA synthesis was investigated using BND-cellulose chromatography and these studies revealed that about 30% of the DNA synthesis after 1 day of priming was of a repair-type. DNA repair-type synthesis contributed to approximately 20% of the [3H]thymidine incorporated into DNA during the rest of the priming period in embryo tissue from both high-vigour and low-vigour seed lots. After 1 day of germination following priming, enhanced levels of both replicative and repair-type DNA synthesis were demonstrated. The replicative type of DNA synthesis detected in leek embyros during the priming period was not inhibited by aphidicolin and appears to represent a significant level of mitochondrial DNA synthesis. DNA synthesis could be detected in both nuclei and mitochondria of leek embryo tissue during the osmopriming treatment in the absence of any detectable cell division.

The effects of ripening and drying of carrot seed (Daucus carota) crops on germination

SUMMARYCarrot seeds taken from the parent plant were capable of germinating before the stage when maximum seed dry weight was reached but even after this stage, when the seed moisture content had fallen below 20%, improvement in seed germination characteristics continued. In the latter stages of seed growth losses by shedding were 12–20 kg/ha/day. For low density crops (10 plants/m2) the yield of viable seed was at a maximum in crops whose seed was harvested with a moisture content of between 20 and 40% but no consistent relationship could be established for high density crops (80 plants/m2).There were no effects of umbel order or plant density on mean germination time or spread of germination. At any early harvest, percentage germination was highest for primary‐umbel‐seeds and seeds from low density crops but the differences between the seed origins diminished with later harvests.Drying the seeds on the umbels improved the percentage germination, reduced the mean germination time and the spread of germination particularly at the early harvests compared with seeds removed from the umbels and germinated immediately without drying.

Germination studies with “hardened” vegetable seed

Abstract “Hardening” tomato, carrot, and radish seed by means of a 2% solution of potassium nitrate, or by means of three wetting and drying cycles had no effect on final germination percentage; but hardening reduced the time to 50% germination and reduced the spread of germination at 20°c both in vitro and in simulated field conditions. Similar in vitro results were obtained at 6–8°c, except that final germination percentage of untreated tomato and radish seed was significantly lower than treated seed.

Environmental variation in the long term pattern of germination from hard seeds of Lupinus varius

The long-term field germination pattern from hard seeds of sandplain lupin varied between sites. At Perth, where environmental conditions are almost ideal for the species, the hard seeds formed at the end of a growing season soften and germinate over the following five years. Some 15-20 per cent softened each summer and germinated with the following autumn rains. At Chapman, some 300 miles north of Perth in a drier more marginal environment for the species, all the hard seeds softened and germinated within two years. This wide site variation in the spread of germination from hard seeds is ascribed to environmental differences during the growing and dry seasons.