Ranges of critical temperature and water potential values for the germination of species worldwide: Contribution to a seed trait database

Germination is the first essential stage in crop and food production, as well as for the establishment of trees and regeneration of wild species. Temperature and water potential are the primary environmental factors that control germination in all species, and affect both the rate and final percentage germination. A comprehensive description of intra- and inter-variations between groups of species (perennials and annuals, trees, grasses, crops and wild species) helps understand where these species are currently able to grow on earth and will be in the future. By collecting germination trait data on 243 species from the literature and unpublished data, we provide a wide spectrum of species’ seed germination traits, in the form of a set of parameter values describing germination responses to variations in temperature and water potential. Major differences in germination traits were seen to depend on the climatic conditions where the species grow or originated, with species able to germinate on ice and others unable to germinate below 18 °C. By contrast, within the different plant groups, similar ranges of threshold values were found, linked to the species geo-climatic origin. Crops however germinate faster, their range of threshold temperatures and water potential values is wider, and some crops have higher optimum and maximum temperatures as well as lower water potential threshold values. This is likely the result of human selection for rapid germination and for species able to grow in the wide range of environmental conditions where agriculture was developed. Our analyses revealed correlation between traits: negative correlations appeared between germination speed and temperature thresholds, and between temperature and water potential thresholds. The collected data also form a valuable database, enabling plant establishment to be better taken into account in modeling and simulation studies of vegetation boundaries (wild or cultivated) under changing land-use and climate

Selecting the best candidates for resurrecting extinct-in-the-wild plants from herbaria

Resurrecting extinct species is a fascinating and challenging idea for scientists and the general public. Whereas some theoretical progress has been made for animals, the resurrection of extinct plants (de-extinction sensu lato) is a relatively recently discussed topic. In this context, the term ‘de-extinction’ is used sensu lato to refer to the resurrection of ‘extinct in the wild’ species from seeds or tissues preserved in herbaria, as we acknowledge the current impossibility of knowing a priori whether a herbarium seed is alive and can germinate. In plants, this could be achieved by germinating or in vitro tissue-culturing old diaspores such as seeds or spores available in herbarium specimens. This paper reports the first list of plant de-extinction candidates based on the actual availability of seeds in herbarium specimens of globally extinct plants. We reviewed globally extinct seed plants using online resources and additional literature on national red lists, resulting in a list of 361 extinct taxa. We then proposed a method of prioritizing candidates for seed-plant de-extinction from diaspores found in herbarium specimens and complemented this with a phylogenetic approach to identify species that may maximize evolutionarily distinct features. Finally, combining data on seed storage behaviour and longevity, as well as specimen age in the novel ‘best de-extinction candidate’ score (DEXSCO), we identified 556 herbarium specimens belonging to 161 extinct species with available seeds. We expect that this list of de-extinction candidates and the novel approach to rank them will boost research efforts towards the first-ever plant de-extinction

Mouse Chromosome 11

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46996/1/335_2004_Article_BF00648429.pd

Seed controlled deterioration of three interspecific elephant grass × pearl millet hybrids Deterioração controlada de sementes de três híbridos interespecíficos de capim-elefante × milheto

In order to allow using seeds from three interspecific elephant grass &#215;pearl millet hybrids (Original, Cutting and Grazing-types) to set pasture fields, it became necessary to analyze their performances in relation to storage conditions and controlled deterioration. Five moisture content levels and three storage temperatures (40, 50 and 65°C) have been tested for each hybrid. Seed sub samples for each moisture content and storage temperature combination were sealed in laminated aluminum foil packages and stored at those temperatures until complete survival curves have been obtained. The recurrent selection increased seed initial quality (Ki) for grazing-type population (lower and more tillered plants); however inverse results were observed for cutting-type population (higher and less tillered plants). Viability equation constants estimated for Cutting-type, Original and Grazing-type hybrids are: K E = 8.417, 7.735 and 8.285; Cw = 5.037, 4.658 and 4.522; C H = 0.02309, 0.01969 and 0.03655; C Q = 0.000436; 0.000403 and 0.000300, respectively. The viability equation constants for the hybrids are K E = 8.033; Cw = 4.662; C H = 0.02544; C Q = 0.000386. Through the equations, it is feasible to estimate the germination percentage of a seed lot after different storage conditions.<br>Para facilitar o uso de sementes de três híbridos interespecíficos de capim-elefante &#215; milheto (Original, Corte e Pastoreio) para a formação de pastagens, tornou-se necessário analisar o seu comportamento em diversas condições de armazenamento e deterioração controlada. Foram testados para cada híbrido cinco graus de umidade e três temperaturas (40, 50 e 65°C). Em cada combinação de umidade e temperatura, as sementes foram embaladas em papel-alumínio multifoliado e semeadas periodicamente, permanecendo nas estufas até a obtenção de curvas completas de deterioração. A seleção recorrente aumentou a qualidade inicial (Ki) na população de pastoreio (plantas mais baixas e mais perfilhadas) e o inverso ocorreu na população de corte (plantas mais altas e menos perfilhadas). As constantes obtidas para os híbridos Corte, Paraíso e Pastoreio são: K E = 8,417; 7,735 e 8,285; Cw = 5,037; 4,658 e 4,522; C H = 0,02309; 0,01969 e 0,03655; C Q = 0,000436; 0,000403 e 0,000300, respectivamente. Foi possível obter uma equação única de viabilidade para os híbridos, com constantes iguais a: K E = 8,033; Cw = 4,662; C H = 0,02544; C Q = 0,000386. Essa equação possibilita estimar a porcentagem de germinação de um lote de sementes após o armazenamento em diversas condições de temperatura e umidade

Prediction of cottonseed longevity

The objective of this work was to determine the viability equation constants for cottonseed and to detect the occurrence and depletion of hardseededness. Three seedlots of Brazilian cultivars IAC-19 and IAC-20 were tested, using 12 moisture content levels, ranging from 2.2 to 21.7% and three storage temperatures, 40, 50 and 65 degrees C. Seed moisture content level was reached from the initial value (around 8.8%) either by rehydration, in a closed container, or by drying in desiccators containing silica gel, both at 20 degrees C. Twelve seed subsamples for each moisture content/temperature treatment were sealed in laminated aluminium-foil packets and stored in incubators at those temperatures, until complete survival curves were obtained. Seed equilibrium relative humidity was recorded. Hardseededness was detected at moisture content levels below 6% and its releasing was achieved either naturally, during storage period, or artificially through seed coat removal. The viability equation quantified the response of seed longevity to storage environment well with K-E = 9.240, C-W = 5.190, C-H = 0.03965 and C-Q = 0.000426. The lower limit estimated for application of this equation at 65 degrees C was 3.6% moisture content