Amount Of Viable Seeds Research Articles

Extinction risk of Zamia inermis: a demographic study in its single natural population

Demographic studies of endemic and threatened plant species are essential for establishing effective conservation strategies. This paper aims to determine the structure and dynamics of the only natural population reported for Zamia inermis. All individuals were mapped to determine the spatial structure and patterns of association between categories and sexes. Matrix analysis were conducted to determine the population dynamics based on three on-site visits. The population is distributed randomly, although seedlings were found to be aggregated at all scales, juveniles are aggregated in smaller radii up to 4.5 m and males at radii above 3.5 m. Seedlings and juveniles are associated with males over greater radii of 3 m, the dependence of adults from earlier categories and females is less than 1.5 m. The population growth rate confirms that the population is in decline (λ = 0.963 ± 0.011). Although few juveniles were identified and no seedling survival was observed in the field, also the amount of viable seeds per female cone is low. However, inhabitants of the region are cultivating the species by germinating seeds in backyard nurseries with 92 of 954 seeds reaching the juvenile category to date. It is clear that the population has lost its regenerative potential and is simply holding on to persistence of adults, this implies a great risk to the species. Ex situ propagation is encouraged.

Genetic variability, population size and reproduction potential in Ligularia sibirica (L.) populations in Estonia

Ligularia sibirica (L.) Cass. (Asteraceae) is a EU Habitats Directive Annex II plant species that has suffered a lot from human-caused major changes in quality and availability of habitats in Estonia. The aim of this study was to find out if the observed decline in population size is reflected in the amount of genetic variation and fertility in remnant populations of this species. AFLP technique was used for that purpose. Genetic diversity within populations was assessed as the percentage of polymorphic loci in a given population and average gene diversity over loci. The degree of genetic differentiation among populations and genetic differentiation between pairs of populations was estimated. The amount of viable seeds per flower stem was compared among populations and between years (2007 and 2008). Average genetic diversity over loci and proportion of polymorphic loci in L. sibirica populations were significantly correlated with population size, suggesting the action of genetic drift and/or inbreeding. No correlation was found between genetic and geographic distances. Natural barriers like forests may have been efficiently preventing seed migration even between geographically closer populations. Results of this study suggest that genetic erosion could be partially responsible for the lower fitness in smaller populations of this species.

Diallel cross analysis of seed germination traits in sugar beet

A diallel cross design, involving six diploid O-type lines and their cytoplasmic male sterile (CMS) equivalents was used to examine the genetic control of characters determining seed viability and vigor of seed and seedling in sugar beet. Six characters including percentage of germination, seedling establishment, weight of 1000 germs, seedling vigor, speed of germination, and monogermity were analyzed. Additive genetic effects were shown to be highly important for all characters and significant dominance effects were found for the percentage of germination and seedling establishment, weight of 1000 germs, and rate of monogerm seeds produced by multigerm plants. There were significant reciprocal variations for most characters, indicating that maternal effects and differences of self-incompatibility mechanisms may influence the expression of some characteristics related to the amount of viable seeds produced in plant. Variance of genotypes for seedling vigor and speed of germination was nonsignificant, indicating that both characters are mainly affected by environmental factors. The relative importance of heritability estimates and the ratio of GCA, SCA, and environmental variances to phenotypic variances were calculated for all the traits examined. It is suggested that seed traits are as important as root quality traits for the development of sugar beet varieties.