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31.
A field study with barley was conducted in 1984 and 1985 to provide data on uptake rates of N, P, K and Mg and their variation as the growing season progressed. Two varieties were grown: Galt in 1984 and Otal in 1985. Soil fertility was maintained at or near optimum conditions. Samples were obtained approximately every 10 days for shoot dry weight, nutrient content and root length measurements. The approximate method (Williams, 1948) traditionally used for calculating uptake rates was found to be invalid for most of the nutrients studied. The method used for measuring uptake rates was the functional approach proposed by Hunt (1973). Inflow,i.e. uptake rate per unit root length, of plant nutrients, decreased with time. However, maximum uptake rates measured in kg ha–1d–1 occurred at about 50 days from sowing because of increasing root length density with time. Inflow or uptake rates were low in 1985 because of moisture deficiency, and grain yield (0.89 t ha–1) was severely depressed. This study demonstrated that Hunt's method is superior and more advantageous than the traditional, approximate method. 相似文献
32.
The level of vesicular-arbuscular mycorrhizal (VAM) infection in the roots of Leucaena grown in a sand-soil mixture in the
greenhouse increased rapidly with time and reached a peak value of 84% at 30 days from planting. The pattern of immobile nutrient
uptake and accumulation closely paralleled that of the development of infection, particularly during the first 10–30 days
after planting. Significant changes in dry matter yield were also observed only after a significant portion of the root length
was colonized byGlomus aggregatum. The development of VAM infection was not accompanied by growth depression at any of the sampling periods. However, VAM roots
had very high levels of Cu which was not translocated to shoots. It is hypothesized that such a diversion of Cu by the endophyte
from the host could cause growth depression under conditions where the soil volume is supplied with sub-optimal levels of
Cu.
Contribution from the Hawaii Institute of Tropical Agriculture and Human Resources Series No. 3186. 相似文献
33.
34.
35.
ROGER T. KOIDE 《The New phytologist》1991,117(3):365-386
36.
Phosphorus availability under alley cropping and mulched and unmulched sole cropping systems in Costa Rica 总被引:3,自引:0,他引:3
Phosphorus availability was measured in soils under five cropping systems: alley cropping with Erythrina poeppigiana, alley cropping with Gliricidia sepium, sole cropping with Erythrina poeppigiana mulch applied, sole cropping with Gliricidia sepium mulch applied, sole cropping with no mulch. The following parameters were measured: 1) plant-available soil P assessed by P uptake of maize and bean bioassay plants; 2) phosphate desorbable by anion exchange resin; 3) adsorption of added P into isotopically exchangeable and non-exchangeable pools.In the bioassay, P uptake of beans declined in the order: mulched sole-cropped>unmulched sole-cropped>alley-cropped soils. For maize the relative uptake was: mulched sole-cropped>unmulched sole-cropped = alley-cropped soils. These results suggest trees had not incorporated a significant quantity of P into the system after seven years and, probably, there was a decrease in available soil P due to the sequestration of P in the tree biomass. Potentially resin-desorbable P was higher in alley-cropped and mulched sole-cropped soils than in unmulched sole-cropped soils. The adsorption and desorption of added P into and from exchangeable and non-exchangeable pools did not differ between alley-cropped and unmulched sole-cropped soils.Crop yield and crop N, P and K uptake were all higher in the alley crops than in the unmulched sole crop. The supply of P to the crop under alley cropping seems to be dependent on P cycled and released from the mulch. The P cycle in alley cropping appears to be self-sustaining at least under conditions of moderate P fertiliser input. 相似文献
37.
The degree of intergradation between two species of Sulawesi macaques,Macaca tonkeana andM. hecki, was studied by examining the diagnostic external characteristics of more than 100 monkeys kept as pets by natives. Two possible
hybrid monkeys were found and both originated from the borderland between the two species, located in the most proximal region
of the northern peninsula of Sulawesi. The previously postulated wide area of integradation between the two species at the
possible contact zone was, however, not recognized, and typical examples oftonkeana orhecki were found to be present on the two sides of a narrow “hybrid” zone which was defined by direct observations. Furthermore,
despite considerable individual variations, we were able to allocate most monkeys to one or other of the species. Each of
ten external characteristics of the members of both species more or less encompassed the individual variations, but may undergo
changes with the development of the monkeys. The mechanisms of reproduction of hybrid monkeys and the maintenance of differences
between the species are discussed. 相似文献
38.
Kunio Watanabe Shuichi Matsumura Tsuyoshi Watanabe Yuzuru Hamada 《Primates; journal of primatology》1991,32(3):385-389
Morphological observations of pet and wild monkeys were made in the area that was inferred to be the borderland betweenMacaca tonkeana andM. ochreata in Sulawesi. Almost all individual monkeys could be classified into one of two species by their external characteristics.
The possible borderland was estimated to extend from the La River in the east and to around Karaena River in the west. These
two species may make contact in the forest in the western area of the borderland. Some external characteristics exhibited
wide individual variations in the two species. Some monkeys originating from the borderland showed external characteristics
that were intermediate between those of the two species. The possible intergradation between these two species is discussed
in terms of the morphological variations found in the two species. 相似文献
39.
A fertilization experiment was carried out in 3 mesotrophic fens to investigate whether plant growth in these systems is controlled by the availability of N, P or K. The fens are located in an area with high N inputs from precipitation. They are annually mown in the summer to prevent succession to woodland. Above-ground plant biomass increased significantly upon N fertilization in the two mid-succession fens studied. In the late-succession fen that had been mown for at least 60 years, however, plant biomass increased significantly upon P fertilization. The mowing regime depletes the P pool in the soil, while it keeps N inputs and outputs in balance. A long-term shift occurs from limitation of plant production by N toward limitation by P. Hence, mowing is a suitable management tool to conserve the mesothrophic character of the fens. 相似文献
40.
Rhizome dynamics and resource storage in Phragmites australis 总被引:6,自引:1,他引:5
Wilhelm Granéli Stefan E. B. Weisner Mark D. Sytsma 《Wetlands Ecology and Management》1992,1(4):239-247
Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands.Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (< 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m–2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June.Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (> 1000 g m–2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites.The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that reloading of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management.Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves. 相似文献