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111.
112.
In a 14-week study, 1-year-old Aleppo pine seedlings were grownin two growth chambers. Seedlings were artificially hardenedby decreasing photoperiod and temperature. In each chamber halfof the seedlings were fertilized with nitrogen (8.4 mg seedling1).In order to determine the relative importance of the hardeningenvironment versus fertilization, each chamber was programmedto decrease night temperatures down to a low of 8 or 4°C.Chlorophyll fluorescence and frost hardiness was measured fivetimes during the experiment. A sample of seedlings from eachtreatment was exposed to an artificial frost at 5°Cand the freezing effects were assessed by measurements of chlorophyllfluorescence and visual evaluation of needle damage. Seedlingsincreased their frost hardiness during the experiment in allthe treatments but the ratio of variable to maximal chlorophyllfluorescence (Fv/Fm) measured before freezing did not vary duringthe experiment. This indicates that Aleppo pine maintains itsphotosynthetic ability during hardening in contrast to otherconiferous species from colder climates. The effect of nitrogenfertilization on frost hardiness was small in comparison withchamber effect. Nitrogen fertilization slightly delayed theacquisition of hardening in the coldest chamber. Seedlings inthe warmest chamber did not become fully resistant to 5°C,but in the coldest chamber, where night temperature reached4°C, all the seedlings were resistant to the frost. Severedamage caused by frost could be related to a rapid rise of minimalfluorescence (F0) but the best index of damage was the dropof Fv/Fm after freezing. 相似文献
113.
Harald Dinkelmeyer Johannes Lehmann Andreas Renck Lucerina Trujillo Jose Pereira da Silva Jr Gerhard Gebauer Klaus Kaiser 《Agroforestry Systems》2003,57(3):213-224
Mixed tree cropping systems have been proposed for sustainable nutrient management in the humid tropics. Yet, the nutrient interactions between intercropped trees have not been addressed sufficiently. In the present study we compare the temporal and spatial patterns of the uptake of applied 15N by four different tree crops in a mixed tree cropping system on a Xanthic Ferralsol in central Amazônia, Brazil, during one year. Most of the N uptake occurred during the first two weeks. Very little N was recovered by peach palm (Bactris gasipaes), more by cupuassu (Theobroma grandiflorum) and annatto (Bixa orellana) and most by Brazil nut (Bertholletia excelsa). Due to tree pruning the total accumulation of applied 15N in the above-ground biomass of annatto decreased throughout the year. It remained constant in cupuassu and peach palm and increased in Brazil nut. Brazil nut showed an extensive root activity and took up more fertilizer N applied to neighboring trees than from the one applied under its own canopy in contrast to the other three tree crops. Therefore, trees with wide-spread root systems may not need to receive N fertilizer directly but can take up N applied to other trees in the mixed cropping system. This means that such trees may effectively decrease N leaching when intercropped with trees that have dormant periods or places with low N uptake, but also exert considerable resource competition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
114.
A study was carried out in an alley cropping system in the Eastern Maize Belt of the United States with the objective of quantifying the competition for water between trees (black walnut (Juglans nigra L.) and red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial and temporal variation in soil moisture, tree and maize rooting patterns, tree and maize water uptake, and maize leaf area expansion were determined in three treatments; barrier (polyethylene root barriers separating maize and tree roots), trench (trenching without a polyethylene barrier), and no barrier (control). Significant temporal variation in soil moisture was observed in both black walnut and red oak alley cropping systems. The barrier and trench treatments resulted in higher soil moisture in the maize alley and lower soil moisture in the tree row than the no barrier treatment. Uptake of water by maize was higher in the barrier than the no barrier treatment. However, tree water uptake was higher in the no barrier treatment than in the barrier treatment because tree roots utilized water from the maize alley. Maize leaf area was negatively impacted by water stress in the no barrier treatment. Quantification of rooting patterns revealed that maize and tree roots were concentrated in the top 30 cm soil layer where water fluctuations were greatest. The barrier and trench treatments successfully eliminated the belowground root competition between trees and maize and resulted in greater leaf area and higher grain yields than the no barrier treatment. Thus, competition for water rather than competition for light seems to be critical in defining the productivity and sustainability of this alley cropping system.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
115.
Applications of growth retardants, daminozide and CCC (chlormequatchloride), were studied in order to determine their effects on morphology and post-planting growth of silver birch (Betula pendula Roth) container seedlings. Daminozide was sprayed once (on 28 June at concentrations of 1.0 – 6.0 g l–1) and CCC was sprayed twice (on 29 June and 27 July at concentrations of 0.5–3.0 gl–1). Height growth, morphology of seedlings at the end of the growing season, the shoot and root growth potential the following spring and field performance during the following seasons were measured. During the first summer in the nursery, both daminozide and CCC retarded height growth,but daminozide was more effective. The effects of compounds on stem diameter during the summer of application were small. Neither of the compounds affected the field performance of seedlings. The most suitable applications for retardation of height growth, without negative effects on other morphological variables, were 4 g l–1 (32 mg per seedling) for daminozide and 2 g l–1 (16 mg per seedling), sprayed in two applications, for CCC. 相似文献
116.
Field performance of silver-birch planting-stock grown at different spacing and in containers of different volume 总被引:1,自引:0,他引:1
Silver birch seedlings were grown in two types of trays differing incell volume. For each kind of tray, three different spacings were achieved bygrowing seedlings in all, half or one quarter of the cells. The planting-stockso produced was out-planted at two forest sites and growth followed for fiveyears. Container size had a large effect on seedling morphology and on fieldperformance. Density also had a large effect on seedling morphology, but littleinfluence on performance. The tightest relationship of field performance was tothe mean dry weight of the stems of the planting stock (R2 = 0.94).Mean height and sturdiness index, defined as diameter ÷height, were not correlated with performance. Of the non-destructivemeasurements, mean root-collar diameter was the most closely correlated withperformance. 相似文献
117.
118.
Felipe Nogueira Soares Maria Emilia Franco Oliveira Luciana Cristina Padilha-Nakaghi Luís Guilherme de Oliveira Marcus Antônio Rossi Feliciano Felipe Brener Bezerra de Oliveira Pedro Paulo Maia Teixeira Wilter Ricardo Russiano Vicente Cristian Faturi Luiz Fernando de Souza Rodrigues 《Tropical animal health and production》2015,47(8):1465-1471
119.
Marcelo Luiz Laia Acelino Couto Alfenas Sergio Hermnio Brommonschenkel Shinitiro Oda Eduardo Jose de Melo Inae Marie de Arau jo Silva Janana Fernandes Goncalves Ariadne Marques 《林业研究》2015,(3)
Disease-resistant genes play an important role in defending against a variety of pathogens and insect pests in plants. Most of the disease-resistant genes encode pro-teins with conserved leucine rich r... 相似文献
120.
Sanches Filho PJ Rios A Valcarcel M Melecchi MI Caramão EB 《Journal of agricultural and food chemistry》2007,55(3):603-607
In this paper, the use of supercritical fluid extraction (SFE) and micellar electrokinetic capillary chromatography (MEKC) is proposed for the complete analysis of volatile nitrosamines in sausages. The extraction fluid used was CO2 and variables such as density, temperature of thimbles, extraction time, modifier, fluid flow, and kind of traps were investigated. Several experiments were carried out to obtain the most favorable conditions for analysis of volatile nitrosamines in sausages. The recoveries ranged from 21 to 82% for the five nitrosamines studied. The optimal condition of extraction was 0.2 g of sample fortified with 10 mg/kg, using dynamic extraction during 20 min and with adsorbent Florisil in the trap. The solvent selected for the elution of the analytes was methanol. 相似文献