Direct somatic embryogenesis from axes of mature peanut embryos

Summary Plant regeneration via somatic embryogenesis was obtained in peanut (Arachis hypogaea L.) from axes of mature zygotic embryos. The area of greatest embryogenic activity was a 2-mm region adjacent to and encircling the epicotyl. Somatic embryogenesis was evaluated on Murashige and Skoog media supplemented with a variety of auxin treatments. Maximum production occurred on medium supplemented with 3 mg · liter⁻¹ 4-amino-3,5,6-trichloropicolinic acid. Explant cultures were transferred to half-strength medium supplemented with 1 mg · liter⁻¹ gibberellic acid for somatic embryo germination and early plantlet growth. Plantlets, transferred to soil, were placed in a greenhouse and grown to maturity.     

Optimization of biotin and thiamine requirements for somatic embryogenesis of date palm (Phoenix dactylifera L.)

Summary This study was conducted to examine the effect of biotin and thiamine concentrations on callus growth and somatic embryogenesis of date palm (Phoenix dactylifera L.). Embryogenic callus derived from offshoot tip explants was cultured on hormone-free MS medium containing biotin at 0, 0.1, 1, or 2 mg l⁻¹ combined with thiamine at 0.1, 0.5, 2, or 5 mg l⁻¹. Embryogenic callus weight, number of resultant embryos, and embryo length were significantly influenced by thiamine and biotin concentration. The optimum callus growth treatment consisted of 0.5 mg l⁻¹ thiamine and 2 mg l⁻¹ biotin. This treatment also gave the highest number of embryos. Embryo elongation was greatest at 0.5 or 2 mg l⁻¹ thiamine combined with 1 mg l⁻¹ biotin. Embryos from all treatments germinated and regenerants exhibited normal growth in soil. This study provides an insight into the importance of optimizing various culture medium components to overcome in vitro recalcitrace of date palm.     

Within-tree spatial variation in the leaf monoterpenes of Sequoia sempervirens

Location within a tree was analyzed as a source of variation in Sequoia sempervirens leaf monoterpenes. No differences were found for quantitative composition or total yield/dry wt among lower, middle and upper canopy positions. The awlshaped, spirally arranged leaves of vigorous upper shoots showed small quantitative compositional differences, but not differences in total yield. The intermediate leaf form of young sprouts had the most different monoterpene quantitative composition and about three times the total yield of the above two leaf forms. Analysis of a clonal ring of 17 adult trees resulted in coefficients of variation similar to those for samples collected from different canopy levels of the same shoot. Results revealed the sources and magnitudes of experimental error in comparative studies of this species' leaf monoterpenes, and did not support the concept that somatic mutation provides an important source of variation in a large, long-lived organism such as coast redwood.     

Seasonal growth of Atlantic cod: effects of temperature, feeding and reproduction

Growth of 2659 Atlantic cod Gadus morhua aged 4 to 9 years examined in Placentia Bay, Newfoundland, peaked in most cases in June and was at a minimum in October or November. Water temperature, partial fullness index ( I _P) and gonado‐somatic index ( I _G) explained between 31 and 52% of the monthly variability in growth. Temperature and I _P of capelin Mallotus villosus had significant effects on growth of all age groups and explained most of the variance for ages 6–8 and 4–5 years, respectively. The I _P of large invertebrates (ages 4 to 7 years), sandlance ( Ammodytes sp. age 6 years) and demersal fishes (age 9 years) had age‐specific effects in the model. Overall, amphipods, decapods and echinoderms dominated the Atlantic cod diet in most seasons, but fish consumption by Atlantic cod was high in June and July, particularly on capelin. The rapid increase in somatic mass during June and July occurred despite cold water temperatures ( < 3° C at 50 m) and moderate to high gonado‐somatic index. The findings of this study suggest that when food was not a limiting factor, growth tended to increase even when Atlantic cod occupied colder waters, but when food was limiting, the opposite may have occured.     

Sex-specific somatic–otolith growth relationship in two Gadidae

Otolith and somatic mass of two Gadidae ( Merlangius merlangus and Trisopterus minutus ) were compared in order to analyse the sex-specific relationship between otolith and somatic growth at age. In the present study, otolith mass appeared a reliable indicator of age in both species. Otolith growth reflected somatic growth, but the relationship between these characters varied and differed between species and sexes.     

Seasonal and interannual variation in the energetic condition of adult male Atlantic sharpnose shark Rhizoprionodon terraenovae in the northern Gulf of Mexico

One hundred and thirty Atlantic sharpnose shark Rhizoprionodon terraenovae livers were collected from April 1999 to October 2001 from inshore waters of the Mississippi Sound to investigate seasonal and inter‐annual variation in their energetic condition. A decline in the hepato‐somatic index ( I _H) was observed from 1999 to 2001. In addition, I _H, liver specific energy content and total energy content were lowest during the summer and highest during the spring and autumn, while liver water content was highest during the summer and lowest during the spring and autumn.     

Neutral mutations and repetitive DNA

We have previously shown that computer simulations of processes that generate selectively advantageous changes together with random duplications and deletions give rise to genomes with many different genes embedded in a large amount of dispensable DNA sequence. We now explore the consequences of neutral changes on the evolution of genomes. We follow the consequences of sequence divergences that are neutral when they occur in dispensable sequences or extra copies of genes present in multigene families. We find that when divergence occurs at about the same frequency as duplication/deletion events, genomes carry repetitive sequences in proportion to their size. Inspection of the genomes as they evolved showed that multigene families were generated by relatively recent duplications of single genes and so would be expected to be highly homogeneous.     

Analysis of mitochondrial DNA from somatic hybrid cell lines of Saccharum officinarum (sugarcane) and Pennisetum americanum (pearl millet)

Mitochondrial DNA (mtDNA) from cell suspension cultures of two intergeneric somatic hybrids of Pennisetum americanum (pearl millet) + Saccharum officinarum (sugarcane) was examined by restriction endonuclease digestion and hybridization with sorghum mtDNA cosmids. The mtDNA of one somatic hybrid was indistinguishable from that of pearl millet, while the second exhibited a combination of parental mtDNAs, suggesting mitochondrial fusion. Several novel, possibly recombinant, mtDNA restriction fragments were detected in this hybrid, which may have resulted from intergenmic recombination.Florida Agriculture Experiment Station Journal Series No: 8090.