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51.
Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in
mitochondria isolated from rice 9311 (Oryza sativa L). From the thermogenic curves the activity recovery rate constant k and the maximum heat power P
m were obtained. Both were positively correlated to the protein content of rice mitochondria. The corresponding correlation
coefficients were 0.9959 and 0.9950, respectively, indicating that the in vitro metabolic activity of mitochondria can be reliably expressed by these parameters. Addition of La (III) ions in concentrations
ranging from 0 to 130 μg/mL resulted in significantly higher k and P
m values. Concentrations from 140 to 180 μg/mL had the opposite effect. These results are consistent with previous reports
on the effects of rare earth elements on plant growth. We propose that the lanthanum-induced change of mitochondrial metabolic
activity is a possible mechanism by which La (III) ions influence indica rice 9311 growth. 相似文献
52.
Joseph J. O'Brien Steven F. Oberbauer David B. Clark Deborah A. Clark 《Biotropica》2008,40(2):151-159
The relationship between phenology and tree stem diameter increment is largely unexplored in tropical species, especially in wet tropical forests. To explore links between these phenomena, we measured stem diameter increment and phenology of ten canopy tree species from a range of functional types in the Atlantic lowlands of Costa Rica to test for seasonal and interannual patterns. We measured stem diameter increment using band dendrometers and visually assessed leaf and reproductive phenology monthly from 1997 to 2000. We categorized the species into groups based on patterns of leaf exchange and reproduction. Species were either deciduous with synchronous or asynchronous leaf drop, or evergreen with continuous or seasonal leaf flushing. Flowering occurred supra-annually, annually, or continuously. Of the ten species studied, four species, Cecropia insignis, Dipteryx panamensis, Lecythis ampla, and Simarouba amara , had consistent seasonal stem diameter increment patterns in both years. Dipteryx panamensis and L. ampla were deciduous with synchronized leaf drop . Cecropia insignis was evergreen and produced new leaves continuously. Simarouba amara , also evergreen, exchanged leaves over a brief period once a year. We tested whether stem diameter increment was correlated to phenology using logistic regression. Leaflessness significantly explained patterns in stem diameter increment but reproductive phenology did not. Deciduous trees were 2.6–9.3 times more likely to grow less than average the month following leaffall than in months when trees had full crowns. 相似文献
53.
Thomas Martin 《Journal of Mammalian Evolution》2005,12(3-4):405-417
Investigation of the enamel microstructure of 20 isolated rodent incisors from the ?Eocene Santa Rosa local fauna (Peru) yielded exclusively schmelzmuster with multiserial Hunter–Schreger bands (HSB). All three subtypes of multiserialHSB with parallel, acute angular, and rectangular interprismatic matrix (IPM) that were previously reported for caviomorph rodents are present. Two lower incisors with rectangular IPM can be attributed to the Octodontoidea, a caviomorph superfamily exhibiting this highly derived enamel type. The plesiomorphic pauciserial condition that characterizes early Paleogene rodents such as North American Ischyromyoidea (including “Franimorpha”) has not been detected. It is therefore probable that the founder populations of South American Caviomorpha already possessed a derived incisor schmelzmuster with multiserial HSB that is shared with African Thryonomyoidea. Because on the North American continent a possible stem-lineage representative of Caviomorpha with multiserial HSB has never been detected, incisor enamel microstructure supports the hypothesis of an African origin of Caviomorpha from a common ancestor shared with Thryonomyoidea. 相似文献
54.
55.
Jose Luis León-de la Luz José J. Pérez-Navarro Reymundo Domínguez-Cadena 《Brittonia》2002,54(2):72-77
Marina victoriae andM. brevis are newly described species from the southern Baja California peninsula, Mexico. The former is a perennial herb locally abundant
in the eroded hillsides at the foothills of Sierra de la Victoria, where an oak woodland and a dry tropical forest meet. The
latter is an elusive ephemeral inhabiting a narrow strip of land between the mangroves and the desert scrub on an island in
the Gulf of California. These two new species belong to the seriesChrysorrhizae, a group native to the Gulf of California basin. 相似文献
56.
Daniela S. Nitiu 《Aerobiologia》2003,19(2):71-78
The behaviour of Celtis airborne pollenwas studied for a period of three years(1998–2000) in the city of La Plata. The pollengrains were captured with a Lanzoni trap andthe maximum pollination period was observed tooccur during the end of winter and spring inthe three years. The annual values of pollenconcentration varied, and a significantdecrease was observed during 2000. The greatestairborne pollen record was in October with anaverage of 82.3% in relation to its totalconcentration during 1998–2000. Based on theintradiurnal behaviour analysis, it wasobserved that the maximum pollination peakoccurs at 2H when the temperaturereaches its maximum values. Considering thethree sampling years, the meteorologicalvariables that most influenced the processes of pollen emission,dispersion and transportation in the atmospherewere: maximum and minimum temperature andrainfall. 相似文献
57.
CHRISTOPHER M. STOJANOWSKI 《American anthropologist》2005,107(3):417-431
In this article, I consider the effects of Spanish missionization on indigenous identity and biological interaction patterns. Odontometric data were recorded for 26 skeletal samples dating to three time periods: precontact (C.E. 1200–1400), early mission (C.E. 1600–1650), and late mission (C.E. 1650–1700). Population genetic analyses generated estimates of regional genetic variation (FST ) and intersample genetic distances. Genetic variation during the precontact period was limited despite documented linguistic and cultural variation. Variation increased during the early mission period, indicating a decline in between-group interaction despite inclusion within a single colonial sociopolitical framework. During the late mission period, variation declined significantly, indicating a dramatic reduction in between-group variability consistent with genetic drift and gene flow between communities. I discuss these results in terms of archaeological and historical models of postcolonial transformation and suggest an emerging polyethnic community was resident in La Florida preceding the subsequent diaspora caused by burgeoning European military conflict in eastern North America. 相似文献
58.
《Mammalian Biology》2014,79(4):225-229
We studied serum testosterone levels in the endemic Mexican cottontail, Sylvilagus cunicularius, which has been reported to show seasonal breeding. Animals were trapped in the wild and in a field enclosure in the National Park La Malinche in central Mexico over a period of five years. Serum testosterone (T) levels were quantified by ELISA from blood samples. T levels of adult males were lowest around 4 months after the onset of the annual reproductive season and were already high prior to the onset of breeding. As expected, the T levels of adult females were consistently lower than in males, and there were no differences in T level with respect to female reproductive state. There were no detectable sex-specific differences in juveniles and subadults, but there was a marked increase in T levels between juvenile and adult males. Overall, our study clearly reflects and confirms the seasonal breeding strategy of this species, showing high similarities to the much better studied European rabbit. 相似文献
59.
Seasonal patterns in rainforest litterfall: Detecting endogenous and environmental influences from long‐term sampling 下载免费PDF全文
Will Edwards Michael J. Liddell Peter Franks Cassandra Nichols Susan G. W. Laurance 《Austral ecology》2018,43(2):225-235
Tropical rainforests play an important role in the storage and cycling of global terrestrial carbon. In the carbon cycle, net primary productivity of forests is linked to soil respiration through the production and decomposition of forest litter. Climate seasonality appears to influence the production of litter although there is considerable variability within and across forests that makes accurate estimates challenging. We explored the effects of climate seasonality on litterfall dynamics in a lowland humid rainforest over a 7‐year period from 2007 to 2013, including an El Niño/La Niña cycle in 2010/2011. Litterfall was sampled fortnightly in 24 traps of 0.50 m diameter within a 1‐ha forest plot. Total mean litterfall was 10.48 ± 1.32 (±SD, dry weight) Mg ha?1 year?1 and seasonal in distribution. The different components of litterfall were divided into LLeaf (63.5%), LWood (27.7%) and LFF[flowers & fruit] (8.8%), which all demonstrated seasonal dynamics. Peak falls in LLeaf and LWood were highly predictable, coinciding with maximum daily temperatures and 1 and 2 months prior to maximum monthly rainfall. The El Niño/La Niña cycle coincided with elevated local winter temperatures and peak falls of LLeaf and LWood. Importantly, we establish how sampling length and generalized additive models eliminate the requirement for extensive within‐site sampling when the intention is to describe dynamics in litterfall patterns. Further, a greater understanding of seasonal cycles in litterfall allows us to distinguish between endogenous controls and environmental factors, such as El Niño events, which may have significant impacts on biochemical cycles. 相似文献
60.
The genus Dombeya is an important component of tropical forests in west Africa, Madagascar, and the Mascarene islands, but little is known about the reproductive biology of its members. In this study, we quantified gender variation and flower‐size variation in three populations of the dioecious tree Dombeya ciliata, an endemic of La Reunion Island (Indian Ocean). Variation among the three populations was observed for three characters. First, the high elevation population had strict males and females, whereas in the two low elevation populations, males were inconstant, with > 50 percent of the males set a small number of fruit. Second, females showed greater seed production at high elevation. Third, flower‐size dimorphism was greater at high elevation because male flowers were larger than female flowers. 相似文献