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991.
992.
993.
H. W. Fassbender L. Alpízar J. Heuveldop H. Fölster G. Enríquez 《Agroforestry Systems》1988,6(1-3):49-62
Models for cycles for organic matter and nutrients element (N, P, K, Ca and Mg) are presented for the agroforestry systems
of cacao (Theobroma cacao) withCordia alliodora orErythrina poeppigiana in Turrialba, Costa Rica.
For the models, system reserves (soil, humus, vegetation divided into leaves, branches, stems, fine roots, fruits) and transference
between compartments (production and decomposition of litter residues) inputs (fertilizer, rainfall) and outputs (harvests)
of the system are considered.
The implications of the models are discussed in detail.
Aspects of net primary production in the systems studied are considered.
N fixation is calculated on the basis of balances. Analysis of soil water showed high variations that coincided with rainfall
patterns and pruning of theE. poeppigiana.
For part I see Vol. 4, No. 3, 1986 For part II see this issue
Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesellschaft für Technische Zusammenarbeit),
Turrialba, Costa Rica 相似文献
994.
Harold E. Burkhart Amy M. Brunner Brian J. Stanton Richard A. Shuren Ralph L. Amateis Jerre L. Creighton 《New Forests》2017,48(4):479-490
Poplar species grow well across the temperate zone, but hybrid varieties have not previously been evaluated for planting in the Virginia Piedmont region. The top 12 clones in height growth and rust resistance from a screening trial involving 98 hybrid poplar varieties of three taxa (Populus deltoides × P. maximowiczii, DxM; P. deltoides × P. nigra, DxN; P. deltoides × P. trichocarpa, DxT) were selected for planting in replicated yield trials at two locations in the Virginia Piedmont. Results through the first four growing seasons showed that the DxM taxon had the most rapid height development. It was, however, the taxon most affected by a late spring frost at the Appomattox-Buckingham State Forest site and by Septoria stem canker at the Reynolds Homestead site. Analysis of variance of clonal and location effects showed highly significant differences among replicates within location and among clones within taxon. Among seven clones within the DxM taxon, pairwise comparison tests of height growth identified two groups: a group of four better clones that were significantly different (p = 0.05) from a second group of three. These early results suggest that multi-selection criteria, including growth, disease and frost resistance, are important when developing hybrid poplar clones for planting in the Piedmont region. 相似文献
995.
Jari Celulose S. A. is a Brazilian-owned industrial enterprise located along the Jari River (the first major south-flowing
tributary of the Amazon). The company produces bleached kraft pulp for international and domestic sales. The raw material
of this pulp production comes from the 75,000 ha of intensively managed plantations of Pinus caribaea (Morelet) and Eucalyptus spp. harvested on 10- and 6-year rotations, respectively. All currently active Jari plantations were converted from primary
forest between 1968 and 1982. Silvicultural practices have been modified over successive rotations, including plantation species
changes, increased intensity of site preparation, fertilization, and chemical weed control. A review of data from the early
1970s to present indicates an increase in productivity over successive rotations and several plantation locations and soil
types. The reasons for this improvement are primarily related to the higher levels of silvicultural inputs and dramatic genetic
gains. The long-term sustainability of this productivity is discussed in terms of current and future inputs.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
996.
Singsaas EL Laporte MM Shi JZ Monson RK Bowling DR Johnson K Lerdau M Jasentuliytana A Sharkey TD 《Tree physiology》1999,19(14):917-924
Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated natural fluctuations in leaf temperature and effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the top of the canopy at Harvard Forest. Throughout the day, leaves often reached temperatures as much as 15 degrees C above air temperature. The highest temperatures were reached for only a few seconds at a time. We compared isoprene emission rates measured when leaf temperature was changed rapidly with those measured when temperature was changed slowly. In all cases, isoprene emission rate increased with increasing leaf temperature up to about 32 degrees C and then decreased with higher temperatures. The temperature at which isoprene emission rates began to decrease depended on how quickly measurements were made. Isoprene emission rates peaked at 32.5 degrees C when measured hourly, whereas rates peaked at 39 degrees C when measurements were made every four minutes. This behavior reflected the rapid increase in isoprene emission rate that occurred immediately after an increase in leaf temperature, and the subsequent decrease in isoprene emission rate when leaf temperature was held steady for longer than 20 minutes. We concluded that the observed temperature response of isoprene emission rate is a function of measurement protocol. Omitting this parameter from isoprene emission models will not affect simulated isoprene emission rates at mild temperatures, but can increase isoprene emission rates at high temperatures. 相似文献
997.
Crossability percentages of bread wheat landraces from Sichuan Province,China with rye 总被引:1,自引:0,他引:1
Summary The crossabilities of 177 landraces of wheat (Triticum aestivum L.) from Sichuan Basin and its adjacent mountain ranges with rye (Secale cereale L.) have been tested. 16 landraces possess a higher crossability than Chinese Spring, 34 landraces have a similar and 127 landraces have a lower crossability than Chinese Spring or are non-crossable with rye. Most landraces with high crossability occur in Qinling Mountain and Dabashan Mountain Ranges in north of Sichuan and the valleys of Minjiang River, Fujiang River and Jialinjiang River in Sichuan Basin. 相似文献
998.
Summary A spring wheat genotype which produces somatic embryos in vitro, after short and long-term culture, was tested for its ability to sexually transmit this embryogenic trait. Reciprocal crosses were performed between a embryogenic line and a nonembryogenic variety.Immature embryos were cultured on Murashige and Skoog medium plus 2 mg/l 2,4-dichlorophenoxyacetic acid, gelled with 5.5 g/l agarose. Somatic embryogenesis was not expressed in the F1's. In contrast, from several hundred immature embryos of the F2 generation of one cross, 10.7% and 1.6% expressed somatic embryogenesis in short and long-term cultures respectively. These percentages of embryogenic: non-embryogenic fits a model of a few complementary genes. The embryogenic capacity of the F2 genotypes depends on the presence of recessive alleles at these gene loci. The long-term wheat somatic embryogenesis capacity requires a more complex mechanism than the short-term one.Abbreviations CS
Chinese Spring
- Aq
Aquila
- E
Embryogenic
- NE
Nonembryogenic
- SC
Subculture 相似文献
999.
Previous studies have indicated a relationship between genome size and cold tolerance in plants. Many species adapted to growth in cool environments have large genome sizes. These studies are based on interspecific DNA content variation. In this study, the nuclear DNA content of eight maize populations was determined. These populations were obtained from the University of Nebraska and represent populations selected for cold tolerance and their respective unselected original populations. Intraspecific DNA content variation was observed between the selected and unselected populations. Upon assessing the data based solely on cold tolerance, no clear relationship between genome size and cold tolerance was apparent. When both freeze tolerance and cold tolerance were considered, populations which were cold tolerant and exhibited a certain degree of freeze tolerance were observed to have significantly larger genomes relative to the unselected populations. Thus, it appears that the relationship between intraspecific genome size variation and cold tolerance is similar to the relationship between interspecific genome size variation and growth at cooler temperatures in plants. 相似文献
1000.
Summary An investigation was made of factors affecting the frequency of development of fertilized ovules following wheat x Hordeum bulbosum hybridizations. Seed survival, a term used here to represent the relationship between seed set and fertilization, was shown to vary between the wheat genotypes tested, but was unrelated to the crossability genes present within the wheat genotype. A high seed survival was obtained in crosses involving the variety TH3929 and the single chromosome substitution line, Chinese Spring (Hope 5B). Chinese Spring showed a poor seed survival. Some influence of the H. bulbosum genotype on seed survival was detected. The two environmental factors studied, namely the post-pollination application of gibberellic acid and the ambient temperature, were both shown to affect seed survival. The application of gibberellic acid immediately after pollination or 1 and 2 days after pollination improved seed survival, although the extent of the response was dependent upon the number and timing of the application(s). A genotype-dependent response to the ambient temperature was observed, TH3929 showing a slight but insignificant reduction and Chinese Spring a significant improvement in seed survival with an increase in temperature from 20°C to 26°C. The physiological processes which may be influenced by GA and the ambient temperature and may thereby affect seed survival are discussed. 相似文献