The use of image analysis to monitor the germination of seeds of broccoli (Brassica oleracea) and radish (Raphanus sativus)

To study broccoli and radish seed germination under different temperature regimes the germination test has been used to assess final germination percentage, start and rate. This method has been integrated with a computer‐aided image analysis test which is more accurate in monitoring the extent of imbibition phases through the assessment of seed area increase and timing of radicle emergence detected on single seeds. In addition, seed area increase has been used also to establish a close relationship with radicle elongation rate in the time range when ‘visible germination’ is scored by a classical germination test. The results suggest that this image analysis parameter may be considered as a reliable seed imbibition marker to integrate the germination parameters obtained by a germination test.     

Restoration of Araucaria Forest: The Role of Perches, Pioneer Vegetation, and Soil Fertility

The Araucaria forest is Brazil's highly threatened subtropical forest ecosystem that has been disappearing in recent decades. Restoration programs involving this forest type are scarce, and there is a lack of scientific information on how ecological processes such as competition, facilitation, and seed dispersal influence natural forest restoration. This work aims to investigate how use of perches to attract seed dispersers and the influence of pioneer vegetation and soil fertilization could affect the colonization of woody species in a degraded area. An experiment was conducted in an abandoned field where the natural establishment of seeds and seedlings of woody species was monitored under factorial combinations of the following treatments: (1) pioneer vegetation (presence and absence); (2) soil fertility (addition of NPK and control); and (3) perches (presence and absence). Seed and seedling abundance, seed and seedling species richness, and seedling mortality were recorded monthly during 12 months. Seed abundance and species richness were significantly greater in places with perches than in control plots. These results were consistent over the year and more pronounced when the surrounding forest produced a higher amount of fruit. Species richness and abundance of seedlings were significantly greater in places with perches than in control plots, and in places with vegetation than without. Soil fertility did not influence seedling establishment. Facilitation and seed dispersal are important factors affecting the colonization of woody species in this subtropical area. Nutrient availability neither regulates the facilitation process nor influences species replacement during the early stages of Araucaria forest succession.     

Restoring Western (Basalt) Plains grassland. 2. Field emergence, establishment and recruitment following direct seeding

Summary   Both reservation of small remnants and ecological restoration of degraded areas will be crucial if the Victorian Western (Basalt) Plains grassland community is to be conserved in the long term. This study examined the potential of direct seeding as a technique for grassland restoration by recording the initial establishment and subsequent recruitment success of 64 (predominantly perennial) grassland species direct sown onto a constructed site. Forty-three (67%) of the sown species emerged and established during the 2-year study and a further three species were recorded in subsequent years. In the second year, 32 species increased their number either through seedling or vegetative recruitment and 30 species dispersed beyond their original sown plot. Seed size was not correlated with field emergence but life form did influence initial field success for some groups. The finding that many species are able to establish and recruit under the study conditions supports the need for further investigation of direct seeding in the restoration of grassland communities.     

Size-Related Differential Seed Predation in a Heavily Defaunated Neotropical Rain Forest

Hunting and habitat loss represent an increasingly common anthropogenic impact. Available evidence suggests that defaunation is typically differential: medium/large mammals are most affected while small rodents are less affected, or even favored. In heavily impacted areas, such as Los Tuxtlas, the residual mammalian fauna is dominated by small rodents. We tested the expectation that if small rodents will preferentially attack small-seeded species, large-seeded species may escape predation in the absence of medium/large seed predators and that this may affect germination and, possibly, recruitment. Experiments with caged rodents ( Heteromys desmarestianus ) under laboratory conditions showed a preference for smaller seeds. A field experiment involving seeds of contrasting size showed that small, unprotected seeds experienced a predation risk 30-times larger than protected seeds, while the effect of protection was not significant for large seeds. These patterns of predation led to significant differences in germination: protected small-seeded species had a fourfold greater germination than unprotected small-seeded species, while germination was not significantly different between exposed and protected large seeds. The observed contrasts in germination suggest that under heavy defaunation, small-seeded species are likely to be penalized by the overabundance of small rodents, while large-seeded species escape predation. Our results are consistent with the observation of dense seedling carpets dominated by large-seeded species in the understory of Los Tuxtlas. We speculate that the patterns we uncovered may explain, at least partly, the impoverished diversity of the understory vegetation that characterizes heavily defaunated understories and that this has the potential to affect forest regeneration.     

Hunting of Mammals Reduces Seed Removal and Dispersal of the Afrotropical Tree Antrocaryon klaineanum (Anacardiaceae)

Throughout the tropics, mammalian seed dispersers are being driven to local extinction by intense hunting pressure, generating concern not only about the loss of these species, but also about the consequences for the plants they disperse. We compared two rain forest sites in Cameroon—one with heavy hunting pressure and one protected from hunting—to appraise the loss of mammalian seed dispersers and to assess the impact of this loss on seed removal and seed dispersal of Antrocaryon klaineanum (Anacardiaceae), a mammal-dispersed tree. Surveys of arboreal frugivores indicate that three of the five monkey species, as well as chimpanzee and gorilla, have been extirpated from the hunted forest. Diaspore counts underneath A. klaineanum adults (six trees per site) indicate that seed removal is severely reduced in the hunted forest. Finally, genetic maternity exclusion analysis (using 3–7 nuclear microsatellite loci) of maternally inherited endocarp tissue from diaspores collected under the canopies of 12 fruiting "mother" trees (six trees per site) revealed that seed dispersal in the hunted forest is also greatly reduced. In the hunted forest with reduced mammal dispersal agents, only 1 of the 53 assayed endocarps (2%) did not match the mother and was determined to be from a dispersed diaspore. By contrast, in the protected forest, 20 of the 48 assayed endocarps (42%) were from dispersed diaspores. This study provides strong evidence that loss of dispersal agents can lead to reduced seed removal and loss of seed dispersal, disrupting the seed dispersal cycle.     

重金属对油菜种子萌发和胚根生长的影响

分析了Hg2 、Cd2 、Ni2 、Co2 、Zn2 5种重金属离子对油菜种子萌发和胚根伸长的影响,以及金属离子K 、Mg2 和Ca2 与重金属的交互作用。结果表明:(1)重金属对油菜种子萌发的抑制作用依次为Hg2 >Cd2 和Co2 >Ni2 >Zn2 ,而对胚根生长的毒害作用依次为Hg2 >Cd2 >Co2 >Ni2 >Zn2 。(2)萌发率为40%以上时,K 和Ca2 可以提高Ni2 、Zn2 和Co2 胁迫下油菜种子的萌发率,却进一步降低了Hg2 、Cd2 胁迫下种子的萌发;Mg2 可以提高Ni2 、Zn2 、Cd2 和Co2 胁迫下种子的萌发率,但对Hg2 毒害却没有缓解。(3)胚根伸长率达到60%以上时,K 和Mg2 增强了Ni2 、Hg2 、Cd2 和Co2 对胚根生长的抑制,而Ca2 则缓解了Zn2 、Ni2 和Co2 对胚根生长的抑制作用。研究结果对于重金属复合污染土壤中植物种子的萌发和定植具有理论和实践意义。     

Chimpanzee (Pan troglodytes) Seed Dispersal in an Afromontane Forest: Microhabitat Influences on the Postdispersal Fate of Large Seeds1

We examined the postdispersal fate of large seeds (≥5 mm) dispersed by chimpanzees in an afromontane forest to evaluate aspects of the effectiveness of seed dispersal by chimpanzees, Pan troglodytes. We assessed the influence of six microhabitat characteristics on seed persistence and germination in seeds dispersed in chimpanzee feces and “wadges.” A total of 257 fecal samples and 56 wadges were located over a 4‐mo period by tracking a semi‐habituated chimpanzee community on day follows. Forty‐nine (19.1%) of the fecal samples contained large seeds from five different tree species. The majority of fecal samples with seeds contained seeds from the mature forest tree Olea capensis (Oleaceae) (83.7%). Forty‐two wadges (75%) contained seeds from the mature forest tree Syzygium guineense (Myrtaceae). Seeds were monitored at their deposition site for removal and germination up to 49 d following deposition. We collected data on the microhabitat surrounding each fecal and wadge sample. Multivariate analyses indicated that while fecal and wadge samples were not clustered into particular microhabitats, there was little overlap in the microhabitats in which wadges and fecal samples were deposited. Significantly more seeds persisted over 49 d in wadges (67.9%) than in feces (30.3%). Elevation was the only microhabitat variable determined to have a significant influence on seed persistence, whereas slope was determined to have a significant influence on germination.     

Stimulatory effects of sodium and calcium hypochlorite, pre‐chilling and cytokinins on the germination of Cypripedium macranthos seed in vitro

Cypripedium macranthos is a wild orchid that is becoming endangered. Efficient methods for its propagation from seed, which is indispensable for conservation, production and breeding, have not been reported. The effects of sodium and calcium hypochlorite, pre‐chilling and cytokinins on the germination of seeds of Cypripedium macranthos Swartz were examined. The duration of treatment with a solution of hypochlorite prior to sowing was one of the critical factors that affected germination. Approximately 70% of seeds that had been treated with either a solution of NaClO that contained 0.5% available chlorine for 60 min or with one of Ca(ClO)₂ with 3.2% available chlorine for 7 h, germinated after 3 months of culture at 20°C, subsequent to 2 months chilling at 4°C. Chilling seeds at 4°C prior to culture at 20°C was another factor that stimulated germination. Even chilling for 2 weeks had a promotive effect on germination, and chilling for 2 months enhanced it most effectively: the frequency of germination was 67% after 3 months of culture at 20°C. However, the promotive effects of chilling on germination were reduced by holding seeds at 20°C for 3 and 6 weeks prior to chilling treatment. Germination of 58‐70% was achieved by the addition of 1 µ M cytokinin to the medium, while the frequency was only 17% in cytokinin‐free medium. We report a reproducible and efficient method for enhancing seed germination of C. macranthos , which involves treatment with hypochlorite prior to sowing, and the combination of chilling at 4°C prior to germination and exposure to a cytokinin.     

Simultaneous parsimony jackknife analysis of 2538rbcL DNA sequences reveals support for major clades of green plants, land plants, seed plants and flowering plants

The ever-larger data matrices resulting from continuing improvements in DNA sequencing techniques require faster and more efficient methods of phylogenetic analysis. Here we explore a promising new method, parsimony jackknifing, by analyzing a matrix comprising 2538 sequences of the chloroplast generbcL. The sequences included cover a broad taxonomic range, from cyanobacteria to flowering plants. Several parsimony jackknife analyses were performed, both with and without branch-swapping and multiple random addition sequences: 1) including all positions; 2) including only first and second codon positions; 3) including only third positions; and 4) using only transversions. The best resolution was obtained using all positions. Removal of third positions or transitions led to massive loss of resolution, although using only transversions somewhat improved basal resolution. While branch-swapping improved both resolution and the support found for several groups, most of the groups could be recovered by faster simple analyses. Designed to eliminate groups poorly supported by the data, parsimony jackknifing recognizes 1400 groups on the basis of allrbcL positions. These include major taxa such as green plants, land plants, flowering plants, monocots and eudicots. We include appendices of supported angiosperm families, as well as larger groups.