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61.
Effects of genotype, collection date, auxin treatment, crown position and artificial chilling on rooting and subsequent vegetative growth of Cupressus sempervirens L. softwood cuttings taken from 13-year-old plants were evaluated. Three different clones (318, 296 and 22) previously selected for resistance to cypress cortical cancer caused by Seiridium cardinale were used. In all these clones, both the IBA treated and the untreated cuttings showed seasonal periodicity of rooting. Untreated cuttings rooted best when collected in April (up to 49% for the best clone, i.e. 296) and rooted very poorly in July and October. Auxin treatments appeared unable to overcome this periodicity, as the cuttings taken in July and October did not respond to IBA stimulation. However, in January and April, IBA treatments enhanced adventitious root formation of poorly rooting clones (318 and 22), as well as of clone 296, which performed best (89%) when cuttings were treated in April with 1.5% IBA. Cuttings of each clone collected in the lower third of the crown of the donor trees showed a significantly higher rooting percentage, when compared with those from the upper third. A 4-week post-severance chilling treatment (4°C) significantly enhanced the rooting capacity of cuttings taken in January, while a longer chilling treatment (8 weeks) had a negative effect. The subsequent growth of the rooted cuttings was not affected by either the crown position of the severed cuttings, or the genotype. 相似文献
62.
Pasture or permanent crops after slash-and-burn cultivation? Land-use choice in three Amazon colonies 总被引:2,自引:1,他引:2
Land use was examined in three settlements – Pedro Peixoto in Acre and Theobroma in Rondonia, Brazil, and Pucallpa, in Peru.
Research aimed at characterizing the differences in land use after initial slash-and-burn, and presenting hypotheses to assess
the feasibility of improved land uses. Settlers in the Amazon practice slash-and-burn agriculture in forest lands to produce
annual crops. After cropping, lands are converted to pasture, or planted with perennial crops, or fallowed in anticipation
of future annual crop production. Land use after slash-and-burn cultivation in forest lands differed among the colonies examined.
Whereas colonists in Pedro Peixoto converted lands to pasture for cattle production, settlers in Theobroma adopted a strategy
encompassing both dual-purpose (milk and meat) cattle and perennial crop production. The more heterogeneous settlers in Pucallpa,
who included small-scale cattle ranchers and riverine and forest slash-and-burn farmers, gave more importance to perennial
crops. Hypotheses are suggested regarding the described land use differences, and implications for the adoption of agroforestry
are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
63.
Pampusch MS Kamanga-Sollo E Hathaway MR White ME Dayton WR 《Domestic animal endocrinology》2011,40(4):197-204
Insulin-like growth factor binding protein-3 (IGFBP-3) suppresses proliferation of numerous cell types, including myogenic cells, via both insulin-like growth factor (IGF)-dependent and IGF-independent mechanisms; however, the mechanism of IGF-independent suppression of proliferation is not clearly defined. In nonmuscle cells, binding of IGFBP-3 to the low-density lipoprotein receptor-related protein-1 (LRP-1)/activated α(2)M receptor is reportedly required for IGFBP-3 to inhibit proliferation. These findings suggest that binding to this receptor also may be required for IGFBP-3 to suppress proliferation of cultured myogenic cells. To investigate the role of the LRP-1 receptor in suppression of myogenic cell proliferation by IGFBP-3, we have examined the effect of receptor-associated protein, an LRP-1 receptor antagonist, on recombinant porcine (rp)IGFBP-3 inhibition of L6 myogenic cell proliferation. Treatment with receptor-associated protein results in a 37% decrease (P < 0.05) in the ability of rpIGFBP-3 to inhibit L6-cell proliferation. In L6 cells subjected to LRP-1 small interfering RNA treatment for 48 h (LRP-1 silenced), LRP-1 mRNA levels were reduced by greater than 80% compared with control cultures treated with nonsense small interfering RNA (mock silenced). In addition, the 85-kDa transmembrane subunit of LRP-1 was undetectable in Western immunoblots of total protein lysates from LRP-1-silenced cells. Even though LRP-1 mRNA and protein levels were dramatically reduced in LRP-1-silenced L6 cells compared with mock-silenced controls, rpIGFPB-3 suppressed proliferation rate to the same extent in both LRP-1-silenced and mock-silenced cultures. Our results strongly suggest that, in contrast to data obtained for nonmuscle cell lines, the LRP-1 receptor is not required for IGFBP-3 to suppress proliferation of L6 myogenic cells. 相似文献
64.
Managing productivity and drought risk in Eucalyptus globulus plantations in south-western Australia
Donald A. White D. Stuart Crombie Joe Kinal Michael Battaglia John F. McGrath Daniel S. Mendham Scott N. Walker 《Forest Ecology and Management》2009
More than 2.5 million ha of Eucalyptus globulus are now planted across the globe including approximately 500 000 ha in southern Australia. In this region average annual rainfall has declined since 1960 and this trend is predicted to continue in the coming decades. E. globulus is a premium species for paper manufacture and grows well under moderate seasonal water stress. The traits that underpin this rapid early growth also make the species vulnerable to prolonged water stress. We established nitrogen rate and nitrogen-by-stocking experiments in five 2-year-old E. globulus plantations along a climatic gradient in south-western Australia. We measured volume growth, predawn leaf water potential and leaf area index over 7 years or until the plantations were 9 years old. These data were used to explore the relationship between growth and water stress, to understand the mechanistic basis for the relationship and to identify best-bet management strategies for E. globulus plantations in southern Australia. 相似文献
65.
铺装是庭院里最实用的元素之一,若是能在铺装中注入设计元素,您的庭院将会别具一格。 相似文献
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In August 1990, a 2-ha plantation was established in an area where rainfall (about 515 mm year(-1)) was insufficient to meet evaporative demand. On nine occasions between September 1991 and April 1993, pressure-volume curves were constructed for irrigated and rainfed Eucalyptus globulus ssp. globulus Labill. and E. nitens (Deane and Maiden) Maiden trees. During the experiment, rainfed trees experienced six periods when predawn water potential was significantly lower than that of irrigated trees. In early spring of 1991 and 1992, osmotic potentials at full turgor and turgor loss point in the irrigated E. nitens were significantly lower than at other times of the year, probably because of winter hardening. Water stress reduced osmotic potential and increased bulk elastic modulus in E. nitens, whereas the reverse occurred in E. globulus. However, treatment differences with respect to changes in osmotic and elastic properties were commonly overshadowed by interspecific differences. These were most apparent at the end of the sixth period of water stress when osmotic potentials at full and zero turgor were significantly higher and bulk elastic modulus and relative water content at turgor loss point were significantly lower in E. globulus than in E. nitens. We conclude that the drought-tolerance responses of E. globulus make it a more suitable species than E. nitens for establishment on sites where moderate water stress is experienced. 相似文献
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By K. K. Newsham K. Oxborough R. White P. D. Greenslade A. R. McLeod 《Forest Pathology》2000,30(5):265-275
Quercus robur saplings were exposed at an outdoor facility in the UK to supplemental levels of UV‐B radiation (280–315 nm) under arrays of cellulose diacetate‐filtered fluorescent lamps which also produced UV‐A radiation (315–400 nm). Saplings were also exposed to supplemental UV‐A radiation under arrays of polyester‐filtered lamps and to ambient levels of solar radiation under arrays of unenergized lamps. The UV‐B treatment was modulated to maintain a 30% elevation above the ambient level of erythemally weighted UV‐B radiation. Naturally occurring infections by oak powdery mildew (Microsphaera alphitoides) were more abundant, and developed more rapidly, on lammas leaves of saplings which were exposed to treatment levels of UV‐B radiation than on leaves of saplings exposed to supplemental UV‐A or to ambient levels of solar radiation over 12 weeks in summer and autumn 1996. An analysis of leaf photosynthetic capacities revealed that M. alphitoides infection reduced the quantum efficiency of photosystem (PS) II by 14% at moderate irradiance. Although there was no direct effect of UV‐B radiation on PSII photochemistry, exposure of saplings to supplemental UV‐A radiation under polyester‐filtered lamps resulted in a 17.5% decrease in PSII quantum efficiency, compared with saplings exposed to ambient solar radiation. The results from our study suggest that photosynthesis of Q. robur may be constrained by exposure to UV‐B radiation in the natural environment through impacts on the abundance of M. alphitoides. 相似文献