The Roots of Carnivorous Plants

Carnivorous plants may benefit from animal-derived nutrients to supplement minerals from the soil. Therefore, the role and importance of their roots is a matter of debate. Aquatic carnivorous species lack roots completely, and many hygrophytic and epiphytic carnivorous species only have a weakly devel-oped root system. In xerophytes, however, large, extended and/or deep-reaching roots and sub-soil shoots develop. Roots develop also in carnivorous plants in other habitats that are hostile, due to flood-ing, salinity or heavy metal occurance. Information about the structure and functioning of roots of car- nivorous plants is limited, but this knowledge is essential for a sound understanding of the plants’ physiology and ecology. Here we compile and summarise available information on: (1) The morphology of the roots. (2) The root functions that are taken over by stems and leaves in species without roots or with poorly developed root systems; anchoring and storage occur by specialized chlorophyll-less stems; water and nutrients are taken up by the trap leaves. (3) The contribution of the roots to the nutrient supply of the plants; this varies considerably amongst the few investigated species. We compare nutrient uptake by the roots with the acquisition of nutri-ents via the traps. (4) The ability of the roots of some carnivorous species to tolerate stressful conditions in their habitats; e.g., lack of oxygen, saline conditions, heavy metals in the soil, heat during bushfires, drought, and flooding     

野生经济植物与水土保持

目前我国人均占有的水、土资源少的情况下,既加强水土保持,恢复原有的生态系统,又为山区经济发展创造条件,以达到人与自然的和谐发展的工作中,野生经济植物资源的合理利用有着特别重要的作用。第一,许多好的经济植物是当地的乡土植物,适应当地的气候、土壤条件,稍加人工抚育即可成活、生长和取得较好的效益。第二,实行谁种植、谁管理、谁受益的制度,管理的投入可以从收入中提取,以减少国家对水土流失治理的投入。第三,发展优良的经济植物,也给全社会增加吃、穿、用的各种物质资源,有些可以出口创汇,增加国家财富积累。发展山区野生经济植物,对治理水土流失和增加农民收入都有重要的现实意义。     

Radiocarbon dating of peat macrofossils in the Cairngorm Mountains,Scotland

Summary

Radiocarbon dates for tree stumps at another three sites in the Cairngorm Mountains are presented. These are considered along with a previous set (Pears, 1969) and the evidence they provide for determining altitudinal limits of forest growth in the Flandrian Period is discussed. They support earlier tentative conclusions that the topographical factor and local site hydrology are the key factors in interpreting the macrofossil pattern.     

Risk Assessment and Invasion Characteristics of Alien Plants in and Around the Agro-Pastoral Ecotone of Northern China

Two risk assessment protocols were adopted to assess the risks posed by alien plants that naturalized or non-naturalized in the agro-pastoral ecotone of northern China (AGENC). In this study the Risk Assessment for Central Europe method revealed that more than two-thirds of the 19 naturalized and four-fifths of the 17 non-naturalized alien plants presented high or moderate risk, and all 36 alien plants were considered to be rejected for their potential agricultural and environmental risks under the Australian Weed Risk Assessment system. On the characteristics of plant invasions, more attention should be given to disturbed habitats rather than these relative natural or closed ecosystems, and also be prudent and careful of the alien plants that are introduced as useful plants from North or South America and unintentional introduction from Europe. Moreover, annuals needed special attention: three-quarters of the alien plants were annual species, only a few were biennial (8.3%), perennial (11.1%), liana and tree plants (2.8%). Plant invasions are not extremely serious in the AGENC, but there are several alien plants that have naturalized and spread themselves in the region. However, attention should be given in the future to predicting and preventing plant invasions in this fragile region.     

The impact of different soil moisture and soil compaction on the growth of triticale root system

Effects of different soil moisture (soil drought and waterlogging) and soil compaction (1.33 and 1.50 g·cm⁻³) on the growth and morphological traits of the root system were studied in four breeding forms and seven cultivars of triticale. Morphological changes, including the restriction of root extension, expansion and proliferation of laterals roots, occur in plants grown in different soil moisture and in compact soil. The investigations comprised quantitative and qualitative analyses of a developed plant root system through determining the number, length and dry matter of the particular components of the root system. Obtained results have demonstrated a relatively broad variation in the habit of the triticale root system. Plants grown under compact soil and low or high soil water content showed a smaller number and less dry matter of lateral branching than plants grown in control conditions. The harmful effects of compact soil and drought conditions on the growth of roots was greater when compared with that of plants exposed to waterlogging. The observed effects of all treatments were more distinct in a drought sensitive strains. The drought resistant forms were a more characterize with extensive rooting and by smaller alterations in the root morphology under the stress conditions compared with drought sensitive one. Results confirm that the breeding forms (CHD-12 and CHD-173) of a high drought susceptibility was found to be also more sensitive to periodical soil water excess. A more efficient water use and a lower shoot to root (S/R) ratio were found to be major reasons for a higher stress resistance of the breeding forms (CHD-220 and CHD-247). The reasons for a different response of the examined breeding forms and cultivars to the conditions of drought or waterlogging may be a more economical water balance and more favourable relations between the shoot and root dimensions in the drought resistant forms and cultivars. The results suggest that the morphological traits of the triticale root system may be used in practice as direct or indirect selection criteria in maize breeding.     

UV-B Radiation Mediated Alterations in the Nitrate Assimilation Pathway of Crop Plants 1. Kinetic Characteristics of Nitrate Reductase

The kinetics and other characteristics of nitrate reductase (NR, EC 1.6.6.1) in cowpea [Vigna unguiculata (L.) Walp.] seedlings irradiated with biologically effective UV-B radiation (280-320 nm, 3.2 W m^-2 s^-1) were recorded. The in vivo and in vitro NR activities were inhibited by 34 and 41 % under UV-B treatment, respectively. Both V_max and K_m for the substrate were enhanced by UV-B radiation. The K_m for nitrate increased from 1.2 to 1.7 mM after the UV-B irradiation. The change in K_m for NADH was from 0.12 to 0.17 mM. The increases in K_m indicate that UV-B radiation seriously changes the topology of NR, particularly with respect to the nitrate and NADH binding sites. The rate of NR turnover indicates the extent of damage inflicted by UV-B radiation on the nitrate metabolism. The half-life (t_1/2) of NR was reduced from 7 to 4 h in the UV-B treated seedlings. UV-B also inhibited the kinetics of nitrate uptake by plants: its K_m increased from 0.08 to 0.12 mM. This revised version was published online in June 2006 with corrections to the Cover Date.     

Modification of soil aggregation by watering regime and roots growing through beds of large aggregates

The influence of root growth and soil watering regime on aggregation was studied under controlled conditions. The study examined the influence of pea (Pisum sativum cv Greenfeast), ryegrass (Lolium rigidum cv Wimmera) and wheat (Triticum aestivum cv Kite) roots on changes in aggregation and on the properties of the aggregates. The soil was a non swelling red-brown earth which was either kept wet or was allowed to wet and dry during the experiment. Root growth increased the percentage of small sized aggregates (<18 mm diameter), organic carbon, tensile strength and stability of aggregates in comparison with a non planted soil. Changes in aggregate size distribution and properties of the aggregates were related to root length density of the species and also to the soil watering regime. Root length density was in the order ryegrass>pea>wheat. Wetting and drying of soil increased the strength and stability of aggregates. Incubating aggregates allowed some roots to decompose but did not increase the strength or stability of aggregates compared with unincubated soil. The results of this experiment are of practical significance in soil structural management, and in studies of soil aggregation dynamics. It may be possible to use plant roots to alter the size and properties of aggregates.     

The Invasion Ecology of Japanese Barberry (Berberis thunbergii) in the New England Landscape

Japanese barberry (Berberis thunbergii) has been characterized as one of the most widely known and planted exotic shrubs in the United States. It was first introduced to the US in the late 1800s. By 1920 the planting of Japanese barberry was encouraged as an ornamental shrub replacing the common barberry (Berberis vulgaris). Japanese barberry began spreading from cultivation in suburban and selected rural retreats by the 1920s, and had dispersed rapidly throughout the northeast by the 1960s. By the 1970s it was recognized as a problematic invasive in the northeast. It is readily dispersed primarily by birds. Fruit production varies with light level, but even under very low light levels (4% full sun) some seeds are produced. Fruits are dispersed in late fall through late winter. Seed dispersal curves are highly leptokurtic; most seedling are found under or adjacent to adults, but a small number may be found tens of meters from the nearest adult. Japanese barberry thrives under a broad range of light and soil moisture conditions. Significant variation in stem growth can be explained as a function of light level. Even at less than 1% full sun, some positive stem growth can occur. Survival is quite high at intermediate to high light levels, and only under the lowest light levels (<1% full sun) does survival drop significantly. Biomass of Japanese barberry in field plots can be largely explained as a function of light availability and soil moisture. The biomass of co-occurring species is suppressed by Japanese barberry, and recovery is slow in the first year following Japanese barberry removal except under high light levels. Glyphosate (Roundup) applied in early spring at first leaf out, when little else is in leaf, provides an effective means of eradicating Japanese barberry populations.