Caracterización por contenido de β-carotenos de ocho cultivares de zanahoria (Daucus carota L.) y su relación con el color

El objetivo fue determinar, durante dos años, el contenido de β-caroteno y su relación con el Índice de Color (IC), de ocho cultivares comerciales del tipo 'Flakkee' cultivadas en el INTA La Consulta. El diseño experimental a campo utilizado fue en bloques al azar con 3 repeticiones. Se evaluó β-caroteno (espectrofotometría a 450 nm) y se calculó el IC, mediante captación de imagen digital con PC y escáner, midiendo L, a y b del Sistema CIELAB. Los datos fueron analizados por ACP (análisis de componentes principales), la visualización de la variabilidad, por cartografiado de datos, análisis de varianza, pruebas de diferencia de medias y correlaciones. Los contenidos de β-carotenos y el IC de los cultivares se mantuvieron constantes durante los dos años estudiados, resultando las cultivares Natasha, Flakesse y Colmar las de mayor valor nutricional en cuanto a aporte de β-carotenos. En el rango de valores menores de 18 mg%g de β-carotenos, se observó una correlación positiva significativa en las cultivares Supreme, Spring y Laval. No se encontró una correlación alta lineal entre el IC y el contenido de β-carotenos. El uso del IC resulta adecuado para predecir, en un intervalo de valores, el contenido de β-carotenos en cultivares de zanahoria.

Age model and color measurements of sediment cores from the eastern equatorial Pacific

High-resolution records of glacial-interglacial variations in biogenic carbonate, opal, and detritus (derived from non-destructive core log measurements of density, P-wave velocity and color; r >= 0.9) from 15 sediment sites in the eastern equatorial (sampling resolution is ~1 kyr) clear response to eccentricity and precession forcing. For the Peru Basin, we generate a high-resolution (21 kyr increment) orbitally-based chronology for the last 1.3 Ma. Spectral analysis indicates that the 100 kyr cycle became dominant at roughly 1.2 Ma, 200-300 kyr earlier than reported for other paleoclimatic records. The response to orbital forcing is weaker since the Mid-Brunhes Dissolution Event (at 400 ka). A west-east reconstruction of biogenic sedimentation in the Peru Basin (four cores; 91-85°W) distinguishes equatorial and coastal upwelling systems in the western and eastern sites, respectively. A north-south reconstruction perpendicular to the equatorial upwelling system (11 cores, 11°N-°3S) shows high carbonate contents (>= 50%) between 6°N and 4°S and highly variable opal contents between 2°N and 4°S. Carbonate cycles B-6, B-8, B-10, B-12, B-14, M-2, and M-6 are well developed with B-10 (430 ka) as the most prominent cycle. Carbonate highs during glacials and glacial-interglacial transitions extended up to 400 km north and south compared to interglacial or interglacial^glacial carbonate lows. Our reconstruction thus favors glacial-interglacial expansion and contraction of the equatorial upwelling system rather than shifting north or south. Elevated accumulation rates are documented near the equator from 6°N to 4°S and from 2°N to 4°S for carbonate and opal, respectively. Accumulation rates are higher during glacials and glacial-interglacial transitions in all cores, whereas increased dissolution is concentrated on Peru Basin sediments close to the carbonate compensation depth and occurred during interglacials or interglacial-glacial transitions.

(Table 1) Color, Fe-C-S chemistry and carbonate content from ODP Sites 172-1062 and 172-1063

Reflectance spectra collected during ODP Leg 172 were used in concert with solid phase iron chemistry, carbonate content, and organic carbon content measurements to evaluate the agents responsible for setting the color in sediments. Factor analysis has proved a valuable and rapid technique to detect the local and regional primary factors that influence sediment color. On the western North Atlantic drifts, sediment color is the result of primary mineralogy as well as diagenetic changes. Sediment lightness is controlled by the carbonate content while the hue is primarily due to the presence of hematite and Fe2+/Fe3+ changes in clay minerals. Hematite, most likely derived from the Permo-Carboniferous red beds of the Canadian Maritimes, is differentially preserved at various sites due to differences in reductive diagenesis and dilution by other sedimentary components. Various intensities for diagenesis result from changes in organic carbon content, sedimentation rates, and H2S production via anaerobic methane oxidation. Iron monosulfides occur extensively at all high sedimentation sites especially in glacial periods suggesting increased high terrigenous flux and/or increased reactive iron flux in glacials.

Magnetic susceptibility, XRF and color reflectance data of DSDP Hole 72-516F, cores 113 and 114

Deep marine successions of early Campanian age from DSDP site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession and eccentricity related variations. Elemental abundance ratios point to a similar 5 climatic origin for these variations and exclude a quadripartite structure - as observed in the Mediterranean Neogene - of the precession related cycles as an explanation for the inferred semi-precession cyclicity in MS. However, the semi-precession cycle itself is likely an artifact, reflecting the first harmonic of the precession signal. The sub-Milankovitch variability is best approximated by a ~ 7 kyr cycle as shown by 10 spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession induced variations in insolation between the tropics.