The Fcu controlling-element system in maize

Summary The relationship between the Fcu controlling-element system and the spotted-dilute R system was investigated. The Fcu controlling-element system consists of the receptor element allele r-cu and the regulatory element Fcu. The equivalent components of the spotted-dilute R system are respectively R-r#2 (or R-r#2 Dil) and Spf. The R-r#2 allele of the latter system was shown to be responsive (mutable) to Fcu, provided that it has had an uninterrupted association with Dil or Dpf as evidenced by the color variegation of the aleurone tissue. The reverse test, in which the r-cu allele of the Fcu controlling element system was tested for its response to Spf, proved negative. This was surprising in view of the relationship and specificity between systems. The possibility was considered that maize controlling elements may have different sizes as is known for bacterial insertion sequences. —The variable dilute pigmenting capacity of the r-cu allele also was studied. A given level of r-cu-induced pigmentation, despite the wide range in pigmentation expression, was found to be generally non-heritable, as based on a test of correspondence between parent and progeny.Journal Paper No. J-9204 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1884Now with Funk's Seeds, Casalmorano (Cremona), Italy     

Fitting multiple trajectories simultaneously to a model of inducible enzyme synthesis

The iterative scheme described by Milstein [6] is used to estimate the rate constants of a model describing an inducible enzyme system. The model was formulated by Heinmets [5], and was mathematically analyzed by Roth and Roth [9] using Bellman's quasilinearization technique. The method used in this article makes use of multiple trajectories of the system to obtain a set of parameters which fit the data of all trajectories simultaneously. A comparison of the numerical results is presented. The data used in the calculations were generated in a similar way to that of Roth and Roth. However, we introduce into each datum 5% noise from a random number generator uniformly distributed [0,1].     

β-Carotene, vitamin C and vitamin E content of the marine microalga Dunaliella tertiolecta cultured with different nitrogen sources

Variations in the β-carotene, vitamin C and vitamin E content of D. tertiolecta have been shown to result from the nitrogen source used in the culture medium. Differences of 101%, 38% and 69% have been found in β-carotene, ascorbic acid and tocopherol content in mg/g of dry matter, respectively, and differences of 147%, 63% and 37% occurred in β-carotene, vitamin C and E concentrations in mg/litre of culture, respectively. Considering the β-carotene, vitamin C and vitamin E content in mg/g of chlorophyll a, maximum variations occurred in β-carotene content, with differences of 145% among the different nitrogen sources. Maximum β-carotene and vitamin C values were found in urea cultures, whereas urea cultures showed the minimum values for vitamin E.     

Heteronarce rierai,a new narkid ray from Mozambique,western Indian ocean

Heteronarce rierai sp. nov. is described on the basis of six specimens, one male and five females, caught in the waters off Mozambique (western Indian Ocean). Total lengths range from 257 to 296 mm. The new species is distinguished from the three other species of the genusHeteronarce by its narrower disc width (29.6% of TL in male, and 33.0 to 39.2% of TL in females), shorter disc length (32.7% of TL in male, and 34.4 to 40.6% of TL in females), and its longer interdorsal distance (10.1 to 11.7% of TL).     

Fine-root biomass and soil properties in a semideciduous and a lower montane rain forest in Panama

The distribution of root biomass and physical and chemical properties of the soils were studied in a semideciduous and in a lower montane rain forest in Panama. Roots and soil samples were taken by means of soil cores (25 cm deep) and divided into five, 5-cm deep sections. Soils were wet-sieved to retrieve the roots that were classified in four diameter classes: very fine roots (<1 mm), fine roots (1–2 mm), medium roots (2–5 mm) and coarse roots (5–50 mm). Soil samples were analyzed for organic carbon, total nitrogen, available phosphorus, exchangeable bases, cation exchange capacity, pH, aluminium and exchangeable acidity. Total root biomass measured with the soil corer (roots <50 mm in diameter) was not different between the forests (9.45 t ha^-1), while biomass of very fine roots was larger in the mountains (2.00 t ha^-1) than in the lowlands (1.44 t ha^-1). The soils in the semideciduous forest were low in available phosphorus, while in the mountains, soils had low pH, high exchangeable aluminium and exchangeable acidity, and low concentration of exchangeable bases. Phosphorus was in high concentration only in the first 5 cm of the soil. In both forests, there was an exponential reduction of root biomass with increasing depth, and most of the variation in the vertical distribution of roots less than 2 mm in diameter was explained by the concentration of nitrogen in the soils. The results of this study support the hypothesis that a large root biomass in montane forests is related to nutrients in low concentration and diluted in organic soils with high CEC and low bulk density, and that fine root biomass in tropical forests in inversely related to calcium availability but not a phosphorus as has been suggested for other forests.     

Dark inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase in legumes: A biosystematic study

2-carboxyarabinitol 1-phosphate (CA 1-P) is a naturally occurring inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Members of the Fabaceae exhibit a particularly wide range in the extent of CA 1-P accumulation during darkness and include Phaseolus vulgaris, whose dark/light regulation of Rubisco activity is principally achieved by synthesis/degradation of CA 1-P. An extensive survey of the degree of dark inhibition of Rubisco was undertaken for the subfamily Papilionoideae to elucidate evolutionary patterns in the occurrence of this regulatory mechanism. Seventy-five species from 21 tribes were examined. Dark inhibition of Rubisco was found in ancestral tribes such as the Sophoreae, but was substantially reduced or absent in representative species of three more recently evolved tribes, Cicereae, Hedysareae and Vicieae. We conclude that regulation of Rubisco by CA 1-P is neither of recent origin nor of restricted distribution among the Papilionoideae. On the contrary, it becomes lost or less pronounced only in a minority of the more evolutionarily advanced species in this important subfamily.     

Conditions for selective degradation of lignin by the fungus Ganoderma australis

Summary The white-rot fungus Ganoderma australis selectively degrades lignin in the ecosystem palo podrido. Using conditions that simulate those of palo podrido in the laboratory, it was found that low nitrogen content and low O₂ tension stimulate the productio of manganese peroxidase and lignin degradation, and depress cellulose degradation and cellulase production. The inverse is found at high nitrogen concentration and high O₂ tension. This agrees with previous results indicating that low O₂ tension and low nitrogen stimulate selective lignin degradation by this fungus. Correspondence to: J. Eyzaguirre     

The chronostratigraphic position of the Camping Francas section(Neogene of Tarragona,Spain)

The presence of Cirsotrema (s.s.) pumiceum (BROCCHI) and Chlamys (Manupecten) pesfelis (LINNE) in the section of Camping Francás (Province of Tarragona, Spain) suggests that the age of the deposits be changed from the upper Miocene (Tortonian) to the Pliocene. The change is of particular significance as the site is one of the classic localities of Pectinidae of the Neogene in North East Spain, and is type locality of Pecten (Flabellipecten) constisulcatus ALMERA & BOFILL.