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191.
ent-kaurenoic acid (KA) isolated from Viguiera robusta was tested for activity on vascular smooth muscle contactility. Cumulative concentration-response curves were obtained for a stepwise increase (10(-10)-10(-05) mol/l) in the concentration of phenylephrine (Phe), a selective alpha(1)-adrenergic agonist. The effects in the presence of KA (0.2, 2.0 and 20.0 microg/ml), and 90 min after the removal of KA from the medium bath were compared to controls. At 20.0 microg/ml, KA inhibited the in vitro contractility of rat carotid artery elicited by Phe, but had no effect at lower concentrations (0.2 and 2.0 microg/ml). The effect elicited by KA was reversible after 90 minutes. 相似文献
192.
三倍体毛白杨的木材构造与材性的研究 总被引:4,自引:0,他引:4
对三倍体毛白杨的木材构造特征、纤维形态、基本密度进行了观察记载和测定,发现其生长轮宽度达2.5~3.0cm,纤维平均长度大于同年轮的其它杨木,基本密度小于毛白杨成熟材,木纤维的含量较高,同时纤维的壁腔比较小,所以三倍体毛白杨是一种较好的造纸和纤维工业原料。 相似文献
193.
In vitro shoot development was slower for apical shoot explants of young oak (Quercus robur L.) seedlings growing on Woody Plant Medium containing activated charcoal than for nodal shoot explants. The rate of in vitro shoot development was slowest in explants taken from seedlings that were undergoing rapid shoot elongation and most rapid in explants taken from seedlings that had stopped elongating and had fully expanded leaves. Maximum rooting was achieved on half-strength Woody Plant Medium containing activated charcoal. Rooting ability was not influenced by explant source. 相似文献
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197.
The forest group is a new policy instrument in Flanders (northern Belgium) to realise multifunctional forest management. This
group was introduced in 1995 and organises the various kinds of forest owners, private as well as public, on a local basis
(mean working area 751 km2), with voluntary participation (as in all forest owner organisations). This study evaluates forest groups in Flanders through
an analysis of their relevance, effectiveness, utility and implementation. The targets of forest groups are relevant to the
evolving needs and priorities at the local, regional, national and international level. The effectiveness analysis reveals
that most indicators — including the quantity of timber harvest, the number of members, the forest area with an accepted management
plan, the area under management and the area with small-scale ecological measures — have been improving between 1995 and 2004.
The utility analysis emphasises that the owners are motivated because the forest group provides information and increases
knowledge, includes the owner into a collective management plan, offers a platform for sharing management experiences and
acts as a union force against the government. However, the forest group is not the solution to introduce multifunctional forest
management by all forest owners. The implementation analysis identifies a number of impeding factors, including the imbalance
between rights and duties, inconsistencies between various policy aims, and failure of forest groups to act as a common forum
for all stakeholders in their working area. 相似文献
198.
The effects of simulated acid mist treatment on net photosynthesis were determined on Eucalyptus globulus trees. Net assimilation decreased for all the three levels but after 3—4 days recovered only in the pH 3.5 one. Acidity effects are discussed in terms of morphological change to the leaves and as alteration of stomatal and mesophyll resistances. 1 Research work supported by C.N.R., Italy. Special grant I.P.R.A. sub-project 1. paper N. 2014 相似文献
199.
The T'OLCHE' is a protected forest belt about 10–20 m wide that runs through the Mayan landscape on the limits of the maize fields of the farmers. This study explores its traditional use and management and traces how it has changed in the last 30 years in the study village in Yucatán, Mexico. A major change is in its extent; little remains of the 10–20% of the area it occupied in the past. Two of the causes of this are identified as being a credit programme of the local bank and 1973 state legislation concerning cattle. The causes and consequences of this decline are discussed in relation with other farmer-perceived changes in overall landuse, including a fall in maize yields. The ecological roles of the T'OLCHE' are examined. It is argued that the T'OLCHE' plays an essential role in the regeneration of the fallow vegetation and in the maintenance of biological diversity. The case of the T'OLCHE' suggests the need for a diversified and politicized look on Common Property Resource Management. 相似文献
200.
Jan Čermák Jan Gašpárek Francesca De Lorenzi Hamlyn G. Jones 《Annals of Forest Science》2007,64(5):491-501
The objectives of this paper were (1) to provide general biometry data for an 80-year-old olive (Olea europea L., cv. Coratina) grove in Andria, southern Italy, and (2) to compare different methods for estimating leaf area distributions. Stand biometry was represented by a stocking density of 132 trees ha?1, mean spacing of 8.7 m and mean social area (proportional to spacing and tree size) of about 76 m2 per tree. Trunk total circumference averaged 110 cm and after subtraction of missing or dead parts of stems averaged 81 cm, projected area of crowns averaged 17.7 m2 and the mean tree height was 4.9 m. Leaf distribution was evaluated using calibrated ground-based side photographs through image analysis and through using a simple canopy-layer model (considering hollow volume within tree crowns) and double-Gaussian curves. The mean leaf size was about 5 cm2 (distributed in a log-normal manner over the range of 2 to 12 cm2). Considering whole tree crowns, the mean leaf density was about 2.6 m2m?3; the maximum leaf area occurred in canopy layers between 1.5 to 3 m, tailing with a steeper slope to the crown base and a less steep slope to the tree-top. The foliated volume of olive crowns (mean 33.2 m3) contained on average 145 thousand leaves of the total area of 72.6 m2. The corresponding leaf area index on the stand level (LAI grove = 0.96), was rather low due to low stocking density. However when taking into account only the projected crown areas (and avoiding free space between trees), the mean LAI reached about 3.5 (range from 1–7). The radial pattern of leaf distribution derived from image analysis indicated peak LAI rad values at a distance from the stem of about 60 to 70% of crown radius in trees of different size. The applicability of different approaches to the estimation of the necessary allometric parameters is discussed. 相似文献