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61.
Philip G. Oguntunde 《Plant and Soil》2005,278(1-2):371-383
Cassava (Manihot esculenta Crantz), a perennial woody shrub, is known to be highly productive under favourable conditions and produce reasonably well
under adverse conditions where other crops fail. Using constant heat sap flow sensors, sap flow density (F
d
) of cassava was monitored for 10 days in December 2002. Sap flow was highly correlated (R
2
=0.72, P<0.05) to incoming solar radiation (R
s) than to other climatic factors. Using cross-correlation analysis, no time shift was detected between F
d
and solar radiation, whereas vapour pressure deficit (VPD) lags F
d
by 110 min. Solar radiation and VPD together explained 83% of diurnal variation in sap flow. Whole-plant transpiration ranged
from 0.8 to 1.2 mm day−1 and daily canopy conductance (g
c), computed based on the inverted Penman–Monteith model, varied between 0.7 and 2.1 mm s−1 (mean = 1.4 ± 0.5 mm s−1). For the measurement period, characterized by high evaporative demand coupled with low available soil water, transpiration
accounted for 21% of the available energy and was only able to meet 24% of the atmospheric water demand. Average decoupling
factor (Ω) of 0.05±0.02 estimated suggested that a 10% change in g
c may lead to more than 9% change in transpiration which further supports the notion that stomata play significant role in
regulating cassava water use compared to other known mechanisms. Beyond light saturation (R
s
>300 W m−2) and at higher VPD (>1.0 kPa), wind effects on the canopy transpiration under water stress condition were low, while VPD
explains 94% of the observed variance in daily canopy conductance. 相似文献
62.
Soil and climate are major constituents of the French notion of Terroir. This concept implies that there is a strong relationship
between the composition of the grape, the characteristics of the wine and the territory of production. To study this link,
a new method of characterization of the Terroir, including geological and pedological factors, was investigated. It uses a
field model based on depth and clay content of soil, together with the degree of weathering of the parent rock. Consequently,
for every type of parent rock belonging to a given geologic stage, there are a series of soils that show different stages
of pedological evolution. According to the model, three kinds of soils are distinguished with regards to the weathering intensity
of the parent rock, that are named weakly weathered rock (WWR), moderately weathered rock (MWR) and strongly weathered rock
(SWR). By hypothesis, each soil type is considered as a homogeneous unit for vine production from the viewpoint of ecophysiological
factors. Each terroir unit defined by this method is called a Basic Terroir Unit (BTU). To validate this hypothesis, experimental
plots planted with Chenin and Cabernet Franc vines were studied over three consecutive seasons (2000–2002), in the Anjou vineyard
(Loire Valley – France). The major BTUs developed on the two most important geological systems of Anjou (Brioverian and Ordovician–Devonian),
were studied. Results showed that the berries of vines cultivated in WWR were significantly smaller, richer in sugars and
anthocyanins and had a Total Phenolic Index higher than those of the vines cultivated in SWR. They also had a lower titratable
acidity. Cabernet Franc vines cultivated in MWR had berries with sugar and anthocyanin contents but also total phenolics very
close to those of WWR. With Chenin vines there was a good relationship between the global pool of free aromas of berries and
the BTU type. The study showed significant relationships between the quality of grapes and the measured values of several
ecophysiological variables such as the water supply regime or the timing of budburst. 相似文献
63.
Sacramento Doralice Rodrigues Coelho Rosalie Reed Rodrigues Wigg Márcia Dutra Toledo Luna Linhares Luiz Fernando de Matos dos Santos Marta Gonçalves Azevedo Soares Semêdo Luzia Teixeira de Ribeiro da Silva Antonio Jorge 《World journal of microbiology & biotechnology》2004,20(3):225-229
A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial
activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions,
obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic
fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type
1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
64.
Rise and demise of cold-climate Picea abies forest in Sweden 总被引:1,自引:0,他引:1
LEIF KULLMAN 《The New phytologist》1996,134(2):243-256
65.
Twenty-five study sites were established along a 57-km-long transect in order to estimate the impact of an oil refinery, mainly
emitting sulphur dioxide (24000 t yr−1), on forest soil (F/H-horizon) chemistry and microbiology. The study demonstrated the existence of a pollution gradient which
was best represented by the logarithm of the concentration of vanadium in the analyzed F/H soil layer. Of the soil microbial
characteristics measured, including length of fungal hyphae, soil respiration, microbial biomass C and N, and percentage mass
loss of Scots pine (Pinus sylvestris) needle litter, only fungal hyphal length was suppressed by the pollution load. No reduction in basic cations (Ca, Mg, K,
and Na) in the F/H-horizon, or enrichment of soluble aluminum in the F/H-horizon of the Scots pine forest could be detected
to result from the deposition. 相似文献
66.
Nadia Benaouag Michel Sardin Jazia Arrar Fatiha Bentahar 《Soil & Sediment Contamination》2018,27(5):408-425
The transient transport of naphthalene through low organic matter content soil columns was investigated in different water-saturation and flow conditions. Some parameters were tested as flow rate, column height, and water saturation conditions. The soil was a clayed sandy soil from the Algerian coast near Boumerdes. The organic carbon content was 0.13% and the main mineral components were quartz (88%), clays minerals (7%) and calcite (3%). The height of the packing of the soil column (5.1 cm in diameter) varied from 15 to 40 cm. Simultaneous step injections of inert tracer (calcium chloride) and naphthalene at 10 mg L?1 were performed. Tracer and naphthalene breakthrough curves (BTCs) were measured continuously by conductimetry and UV – 220 nm, respectively. The BTCs were simulated using the classical mixing cells in series with exchange model (MCE). In unsaturated conditions the comparison of the mean residence time of tracer BTCs with the geometrical pore volume gave us access to average water saturation along the column as a function of height. The higher the soil bed was, the higher the mean water saturation. The comparison of naphthalene distribution coefficients (Kd) in different flow conditions with the theoretical value from the Karickhoff law showed that in saturated conditions the obtained value was close to the theoretical one. In unsaturated conditions, the measured naphthalene Kd's were much lower than the theoretical value and correlated to the water saturation. 相似文献
67.
68.
69.
Karachi is one of the most populated urban agglomerations in the world. No categorical study has yet discussed the geochemical baseline concentrations of metals in the urban soil of Karachi. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of different heavy metals. Geochemical baseline concentrations of heavy metals were estimated using the cumulative frequency distribution (CDF) curves. The estimated baseline concentrations of Pb, Cr, Cu, Zn and Fe were 56.23, 12.9, 36.31, 123.03 and 11,776 mg kg−1, respectively. The pollution status of heavy metals in urban soils was evaluated using different quantitative indices (enrichment factor–EF, Geo-accumulation Index–Igeo, and pollution index–PI). Enrichments factors of the selected heavy metals determined by using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. The urban soils of Karachi were found to have a moderate to moderately severe enrichment with Pb, whereas Cr and Cu has moderate and Zn has minor enrichment. Igeo results indicated moderate soil contamination by Pb at some of the sampling locations. PI for Pb, Cr, Cu and Zn was found in the range of 0.04–3.42, 0.19–1.55, 0.27–2.45 and 0.32–1.57, respectively. Large variations in PI values of Pb revealed that soil in those areas of the city which are influenced by intensive anthropogenic activities have exceptionally high concentrations of Pb. The findings of this study would contribute to the environmental database of the soil of the region and would also facilitate both at the local and the international scales, in a more accurate global environmental monitoring, which will eventually facilitate the development of management and remediation strategies for heavy metal contaminated urban soil. 相似文献
70.
The biological activities of a sterile red fungus (SRF) capable of plant growth promotion and suppression of take-all disease
were investigated in soils collected from Lancelin, Newdegate and Mt. Barker regions of Western Australia. Further, the effects
of three wheat cultivars and the presence of two isolates ofStreptomyces on the biological activities of the SRF were tested using the Lancelin soil. The biological activities of the SRF were greatest
in the Lancelin and Newdegate (wheat field) soils and with the wheat cultivar Gutha. In in vitro studies the soil streptomycetes
tested showed either a significant increase in the exudate production by the SRF, which had antifungal and growth promoting
properties, or an inhibition of growth of the fungus. Streptomycete A63 which stimulated the exudate production by the SRF
in vitro, however, did not enhance disease protection in vivo. On the other hand, protection from root rot by the SRF in vivo
was reduced in the presence of the streptomycete isolate Ax which is capable of inhibiting the growth of the SRF in vitro. 相似文献