Shrubs

Ci-,H2,N04. Colourless prisms, m.p. 98°C. Obtained from coca, either by direct purification, or by acid hydrolysis of the mixed alkaloids to ecgonine, which is then methylated and benzoylated. Coca consists of the dried leaves of Eryihroxyluni coca and Erythroxylum iruxillense, shrubs growing in Bolivia and Peru. 

The natives of Pern were learning to ease their physical pains by chewing the leaves of coca shrub (E thro>ylon truxillence, which contain, among... 

In the United States and in Mexico there has been recent renewed interest in the guayule shrub as a source of natural rubbber. Whilst this shrub could provide an indigenous source of supply to these countries the rubber is more difficult to obtain. At present it is necessary to pull up the bush, macerate it, extract the rubber with solvent and then to preeipitate it from solvent. 

Bio-assay guided fractionation of the methanolic extract of the African climbing shrub Stephania dinklagei contains six bioactive alkaloids, among... 

Staude,/. shrub, bush perennial herb, stauen, stow dam up baffle choke con gest. — v.i. choke. 

Overhead transmission lines require that the area beneath them be cleared of trees or tall shrubs, which may result in erosion. When the transmission line right-of-way is not kept clear, the transmission line may come into contact with vegetation, causing a fault on the system and possibly starting a fire. Chemical contamination of soil may result from some types of transmission structures, such as treated wood. Burial of underground cables also can impact the environment due to erosion. 

As a general rule, young, immature plants should be chosen for any landscape-planting scheme on reclaimed, previously contaminated, land. This allows the plants to adapt gradually to such an environment. It is not normally appropriate to plant mature shrubs and trees to create an instant mature landscape in such an environment. 

Miscellaneous Identified Inhibitors. 3-Acetyl-6-methoxy-benzaldehyde is present in the leaves of the desert shrub Encelia farinosa. It is apparently leached from the leaves and washed into the soil by rain. Concentrations of approximately 0.5 mg. per gram of dried leaf material have been measured. In sand culture studies, growth of tomato seedlings was inhibited by 50 p.p.m. while 115 p.p.m. reduced growth by 50% (53). A concentration of 250 p.p.m. killed the test plants within one day. The structure was confirmed by synthesis, and the synthetic material was shown to be as active as the natural product (54). Derivatives were also prepared in which a cyano, nitro, or amino group was substituted for the aldehyde moiety. The amino derivative was reported to be the most highly toxic. 

Table I. Characteristics of soil and annual plant vegetation under shrub canopies and in intershrub spaces. Data from references 12, 27, 28, and 29.

There are no data on the flux rates of leaf volatiles into the atmosphere. In the L. tridentata shrublands of North America and in areas in Australia where unpalatable, woody shrubs have replaced grasses, the presence of volatile hydrocarbons in the air is detectable by the human nose. The distinct odors of these hydrocarbons is especially noticeable after a rain. It has been suggested that these compounds may undergo atmospheric reactions that produce ozone and other oxidizing substances (8). However, there are no data on these atmospheric reactions. 

A positive feedback between vegetation and atmospheric CO2 will occur if biomass declines. This will happen to the extent that climatic warming causes increased water stress, either through decreased precipitation or increased evap-otransporation, particularly on soils of low water-holding capacity. Decreases in soil nutrient availability, either directly caused by drought or indirectly caused by replacement with taxa with more recalcitrant litter, may further decrease the net release of carbon from the biosphere to the atmosphere. Positive feedback will also arise if the current standing biomass of trees is replaced by small trees, shrubs, and herbs that store less carbon. 

Terrestrial biomass is divided into a number of subreservoirs with different turnover times. Forests contain approximately 90% of all carbon in living matter on land but their NPP is only 60% of the total. About half of the primary production in forests yields twigs, leaves, shrubs, and herbs that only make up 10% of the biomass. Carbon in wood has a turnover time of the order of 50 years, whereas turnover times of carbon in leaves, flowers, fruits, and rootlets are less than a few years. When plant material becomes detached from the living, plant carbon is moved from the phytomass reservoir to litter. "Litter" can either refer to a layer of dead plant material on the soil or all plant materials not attached to a living plant. A litter layer can be a... 

Higher salt concentrations (enhanced water conductivity) from urban and industrial waste waters result in lower dilution. Salinity limits the distribution of sensitive plant and animal taxa, and triggers the abundance of others. The presence of the shrub Tamarix canariensis has increased in the saline soils of the low flow affected Tablas de Daimiel (Spain), while the once dominant RopM/Ms alba retreated. 

Plants take up inorganic nitrogen, either as atmospheric Nj, through symbiotic nitrogen fixation in legumes such as pulses, some shrubs and trees. 

Yoneyama, T., Murakami, T., Boonkerd, N., Wadisirisuk, P., Siripin, S. and Kouno, K. 1990 Natural N-abundance in shrub and tree legumes, Casuarina, and non- N2 -fixing plants in Thailand. Plant and Soil 128 287-292. 

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