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The new edition of Seeds contains new information on many topics discussed in the first edition, such as fruit/seed heteromorphism, breaking of physical dormancy and effects of inbreeding depression on germination.

This paper examines four key mechanisms of the seed size/number trade-off (SSNT) models to assess their relevance to a general understanding of plant community structure. Mechanism 1 is that large seeds have a greater probability of winning in competition against smaller seeds. I provide interspecific experimental evidence that there is a competitive hierarchy among seedlings based on seed size. Mechanism 2 is that a trade-off exists between the number and size of seeds produced for a given reproductive allocation. Negative correlations between seed size and number were found consistently across a range of species from a range of habitats, from published literature. Mechanism 3, that seedling-seedling competition is an important influence on species composition, was found to exist potentially in a range of environments, including annual-dominated, post-fire and gap-dynamic communities. However, there is little quantitative evidence available and this is likely to be a restrictive mechanism. Mechanism 4, that small seeds are superior colonists due to their greater number, was tested in a field experiment in a calcareous grassland community. No supporting evidence was found, suggesting that the SSNT is not an important determinant of structure in this community. Thus two of the four mechanisms can be considered to hold true generally, while the third mechanism may be valid in particular environments. The fourth mechanism did not apply in the community tested, but could be tested in a wider range of communities.

▪ Abstract  The plant hormone abscisic acid (ABA) plays a major role in seed maturation and germination, as well as in adaptation to abiotic environmental stresses. ABA promotes stomatal closure by rapidly altering ion fluxes in guard cells. Other ABA actions involve modifications of gene expression, and the analysis of ABA-responsive promoters has revealed a diversity of potential cis-acting regulatory elements. The nature of the ABA receptor(s) remains unknown. In contrast, combined biophysical, genetic, and molecular approaches have led to considerable progress in the characterization of more downstream signaling elements. In particular, substantial evidence points to the importance of reversible protein phosphorylation and modifications of cytosolic calcium levels and pH as intermediates in ABA signal transduction. Exciting advances are being made in reassembling individual components into minimal ABA signaling cascades at the single-cell level.

How Hawaiʻi became the epicenter of the biotech seed industry, and how a resistance movement arose to confront the industry's power.Hawaiʻi is a primary site for development of herbicide-resistant corn seed and, until recently, was host to more experimental field trials of genetically engineered crops than anywhere else in the world.

This study investigated the effect of high temperature and drought (during grain-filling) on the quality and components yield of five winter wheat varieties. Drought and drought + heat were found to have a much greater influence on the yield and quality than heat stress alone. Averaged over the varieties, the yield losses were 57% after drought, 76% after drought + heat, and only 31% after heat stresses. The reductions in the unextractable polymeric protein fraction and glutenin-to-gliadin ratio indicated a poorer grain yield quality, despite the higher protein content. Quality deterioration was observed after drought or drought + heat, while high temperatures alone resulted in no change or in a better ratio of protein components. A significant negative correlation was observed between starch granule size and relative protein content after drought.

The rationale of this study is to compare the levels of different antioxidants present in commercially important tomato cultivars of India, specifically developed to grow in high altitude and plain regions. Major antioxidant components like lycopene, ascorbic acid, phenolics, and quenching capacity of free radicals were analysed in different fractions of tomato fruit, i.e., skin, pulp, and seed fractions. Significant differences in antioxidant components were observed among the fractions of the different cultivars studied. Lycopene content was found to be more in high altitude cultivars (‘Sindhu’ and ‘Shalimar’); however, ascorbic acid and phenolic content were found to be higher in plain region cultivars (‘PKM1’ and ‘CO3’). To evaluate the antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays were performed. High altitude cultivars showed 10–15% higher DPPH free radical scavenging activity and 20–30% increase in FRAP than the plain region cultivars. Among the different fruit fractions analysed, skin showed the highest level of antioxidants levels and free radical scavenging activities in all the cultivars tested. The difference in the antioxidants level and activity may be attributed to the genetic variability of the cultivars.

Many seeds carry endophytes, which ensure good chances of seedling colonization. In this work, we have studied the seed-borne bacterial flora of rice varieties cultivated in the northeast of Argentina. Surface-sterilized husked seeds of the rice cultivars CT6919, El Paso 144, CAMBA, and IRGA 417 contained an average of 5×10∨6 CFU/g of mesophilic and copiotrophic bacteria. Microbiological, physiological, and molecular characterization of a set of 39 fast-growing isolates from the CT6919 seeds revealed an important diversity of seed-borne mesophiles and potential plant probiotic activities, including diazotrophy and antagonism of fungal pathogens. In fact, the seed-borne bacterial flora protected the rice seedlings against Curvularia sp. infection. The root colonization pattern of 2 Pantoea isolates from the seeds was studied by fluorescence microscopy of the inoculated axenic rice seedlings. Both isolates strongly colonized the site of emergence of the lateral roots and lenticels, which may represent the entry sites for endophytic spreading. These findings suggest that rice plants allow grain colonization by bacterial species that may act as natural biofertilizers and bioprotectives early from seed germination.

The testa of higher plant seeds protects the embryo against adverse environmental conditions. Its role is assumed mainly by controlling germination through dormancy imposition and by limiting the detrimental activity of physical and biological agents during seed storage. To analyze the function of the testa in the model plant Arabidopsis, we compared mutants affected in testa pigmentation and/or structure for dormancy, germination, and storability. The seeds of most mutants exhibited reduced dormancy. Moreover, unlike wild-type testas, mutant testas were permeable to tetrazolium salts. These altered dormancy and tetrazolium uptake properties were related to defects in the pigmentation of the endothelium and its neighboring crushed parenchymatic layers, as determined by vanillin staining and microscopic observations. Structural aberrations such as missing layers or a modified epidermal layer in specific mutants also affected dormancy levels and permeability to tetrazolium. Both structural and pigmentation mutants deteriorated faster than the wild types during natural aging at room temperature, with structural mutants being the most strongly affected.

In most developing countries, good quality seed is hard to obtain and farmers struggle to save seed from one year to the next. Instead, they increasingly turn to public or private enterprises that multiply, store and distribute seed. African Seed Enterprises takes a people-centred look at the companies, public agencies and family farms that are taking on this role and making a difference to food security across Africa. Case studies are arranged by country, and each chapter includes a profile of the agricultural and policy environment that surrounds these enterprises and affects their development. Each case is unique and presents its own set of lessons, and as a whole, this wide range of experiences is a rich source of data and ideas for future enterprise, offering valuable insights for policy makers, academics and non-governmental organizations throughout the world.

In a greenhouse experiment, seedling survival of two oak species (Quercus rugosa and Q. laurina) was greatly affected by the excision of cotyledons 1 mo after germination, with a greater impact on Q. laurina. The effect of seed size was also significant for both species, with a positive correlation between seed mass and survival and growth. The effect of cotyledon excision on seedling growth persisted throughout the first growing season in Q. rugosa and was not analyzed for Q. laurina due to the low number of seedlings that survived cotyledon excision. Seed size significantly affected seedling height, diameter, leaf area, and biomass at 6 mo. Seed size and cotyledon retention affected the ability of Q. rugosa to recover from herbivory, as both factors had a significant effect on relative growth rates after aerial biomass removal. The results show that seedlings originating from large seeds can better endure loss of cotyledons and aerial biomass and thus are better equipped to confront stress early in their lives