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61.
Two experiments were undertaken in southern Greece during 2000–2002 in which turnip-rooted parsley was tested for its suitability for cultivation in comparison with locally grown curly-leafed and plain-leafed forms. Plants were harvested when the foliage was acceptable for marketing, rather than on completion of the vegetative cycle, hence root size was relatively small. In year 1, the foliage development of plain-leafed parsley was significantly higher than that of the other two forms, irrespective of sowing date. In year 2, both plain-leafed and curly-leafed parsley produced more foliage than turnip-rooted parsley in the early sowing (November), but not in subsequent sowings (December and February). During both years, root development was higher in turnip-rooted parsley than in curly-leafed parsley, although in the November and February sowings of year 1 the root weight of both plain-leafed and turnip-rooted forms were similar. In all three types of parsley, foliage yield fell off significantly in the spring sowing (February), and in year 1 there was a considerable decrease in root production as well. In most cultivars, foliage weight was higher when plants were grown from transplanted seedlings rather than by direct sowing, whereas the effect of sowing method on root weight was sowing date dependent. Cultivar differences in the foliage weight of direct sown and transplanted plants were reflected by differences in plant height and, in some cases, by leaf number. It is concluded that although overall turnip-rooted parsley produced rather less foliage than that plain-leafed parsley, this was compensated for by the satisfactory production of roots and therefore turnip-rooted cultivars may constitute a suitable crop for introduction to the Mediterranean region. 相似文献
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Scaevola aemula is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties of S. aemula ‘New Wonder’ in response to photosynthetically active radiation (PAR), carbon dioxide concentration, and leaf temperature. Net CO2 assimilation rate (A) was responsive to CO2, exhibiting a saturation when intercellular CO2 concentration (Ci) was greater than 600 μmol mol−1. Net CO2 assimilation rate and dark respiration rate (Rd) were 23.1 and 2.3 μmol m−2 s−1, respectively, at 25 °C and PAR = 1500 μmol m−2 s−1. Net CO2 assimilation rates were similar at leaf temperatures between 20 and 30 °C but significantly reduced at 15 °C. These gas exchange results were used to test the extendibility of a coupled gas exchange model previously developed for cut-roses. Utilizing the gas exchange data measured at 25 °C leaf temperature, several model parameters were independently determined for S. aemula. Model predictions were then compared with observations at different leaf temperatures. The model predicted the rates of net CO2 assimilation and transpiration of S. aemula reasonably well. Without additional calibration, the model was capable of predicting the temperature dependence of net CO2 assimilation and transpiration rates. Applying the model to predict the effects of supplemental lighting and CO2 enrichment on canopy photosynthesis and transpiration rates, we show that this model could be a useful tool for examining environmental control options for S. aemula production in the greenhouse. 相似文献
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M. Carof S. De Tourdonnet Y. Coquet V. Hallaire & J. Roger-Estrade 《Soil Use and Management》2007,23(3):230-237
We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no‐till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's‐foot‐trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (?0.6, ?0.2 and ?0.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0–10 cm layer and in the 10–20 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0–10 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous‐root type) and the leguminous ones (tap‐root type). However, we recorded larger functional pores and more tubules in the no‐till treatments with a cover crop, compared with the no‐till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time. 相似文献
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【目的】通过揭示不同土壤含水量对蔬菜产量及蔬菜地土壤水分渗漏量的影响,为蔬菜生产中合理灌溉提供指导。【方法】通过3年田间试验,利用TDR连续监测土壤含水量,运用田间定位通量法计算土体水分渗漏量,分析不同水分处理下蔬菜产量和土体水分渗漏量之间的差异。【结果】传统水分处理下蔬菜地水分累积渗漏量为982mm,其中蔬菜生长期内累积渗漏量为748mm,占蔬菜生长期内供水量的36%;优化水分处理和充分水分处理下蔬菜地水分累积渗漏量230mm和468mm,其中蔬菜生长期内水分累积渗漏量分别144mm和293mm,占各处理下供水量的9%和17%。除2002年优化和充分水分处理下花椰菜产量高于传统水分处理下花椰菜产量并达到显著水平外,其余年份蔬菜产量并无显著差异。【结论】保持土壤含水量在蔬菜生长有效土壤含水量50%~80%的优化水分处理在蔬菜生产中有很大的推广价值。 相似文献
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常德市经济林树种约50多种,总面积25万多ha,本文讨论了常德市经济林生产现状;同时,采用不等维信息模型对油茶、油桐、乌柏3种木本油料进行了灰色预测. 相似文献
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Integrated pest management in field vegetable crops in northern Europe — with focus on two key pests
Improvements in (1) insecticide application, (2) supervised control, and (3) pest forecasting systems have each helped to reduce considerably the amounts of insecticides required to control fly, caterpillar and aphid infestations in vegetable crops in northern Europe. By growing plants that are partially resistant to certain major pests, it is now possible to apply even less insecticide than the dose recommended for the crop. In crops where only small amounts of insecticides are applied, natural predators should prevent large increases in pest insect populations and natural parasitoids should reduce the numbers of pest insects entering subsequent generations. The possible impact of introducing transgenic plants and the use of physical (crop covers), cultural (crop rotation, undersowing) and microbial (e.g. fungi, bacteria and nematodes) methods of control are also discussed. The withdrawal of certain insecticides, as a result of environmental and commercial pressures, means that some crops may soon be without appropriate insecticides for controlling one or more of the major pest species. Whether such systems will be sustainable, remains to be seen. 相似文献