title Flowering phenology and reproductive biology of Drosera anglica (Droseraceae)
abstract Prompted by the sparse knowledge of the reproductive biology of carnivorous plants, compared with studies of their trapping habits, we investigated the flowering phenology and pollination biology of Drosera anglica Huds. in two fens in mid-western Canada. Seed set and germination were used to compare the effectiveness of a series of pollination treatments, including single insect visits to virgin flowers. Flowers opened during mid-morning but closed by early afternoon, and exhibited pseudo-cleistogamic behaviour in cool, overcast weather. D. anglica was found to be self-compatible, and able to self-pollinate and self-fertilize. Geitonogamy was an uncommon mode of self-reproduction because plants typically possessed a lone inflorescence upon which a single, short-lived flower opened, a few days before the next bud reached anthesis. Insect visits to the fragrance-lacking, nectarless flowers, chiefly by flies (Diptera: Syrphidae), were infrequent (one visit per 1 h 40 min of observation), and the low frequency of seed set and low numbers of seeds per fruit in pollination treatments involving insects, suggest the species does not rely on insects to effect pollination. Self-pollination, with or without the aid of a vector (insects, wind) was as effective as natural pollination; ultimately, autogamy is chiefly responsible for natural seed set. Thus, the species exhibits characteristics of facultative autogamy.
source Gillian L. Murza and Arthur R. Davis. Botanical Journal of the Linnean Society, 2005, 147, 417–426.
摘要 與捕蟲習性的研究比較起來，食蟲植物在生殖生物學方面的貧乏知識激使我們研究兩個位在加拿大中西部的沼澤中，D. anglica Huds的植物開花物候學及生殖生物學。結實率和發芽率用來比較一系列授粉處理方法的有效性，這些授粉處理方法包含單一昆蟲對處女花的拜訪。這種毛氈苔的花朵在早上綻放而在中午過後凋謝，在天氣較冷時顯現出假性閉鎖授粉的特性，在陰天時則表現出自交親和性，並可自花授粉與自花授精。同株異花授粉則為自體繁殖中不常見的模式，這是因為這種植物典型來說只長出單獨一根花序，當一朵短命的花開之時，鄰近的花苞則是在幾天前開過。昆蟲之中會拜訪這種沒有花香和花蜜的花，主要是蠅類(雙翅目：食蚜蠅科)。來訪的次數並不頻繁(在觀測期間每一小時40分鐘一次)，所以結實率之中與一個果實內的種子，只有少數比例是因為昆蟲授粉所造成。這些現象指出這種毛氈苔並不是依賴昆蟲來有效地授粉。有或沒有助力(昆蟲、風)參與的自花授粉則與自然授粉一樣有效；最後，自花授粉是主要造成自然結實率的原因。因此這種毛氈苔具有自花授粉的特徵。
csyin
發表於： 2006/01/31 04:20pm
title Food or sex; pollinator–prey conflict in carnivorous plants
abstract Carnivorous plants potentially trap their own pollinators and it has been argued that considerable spatial separation of flowers and traps has evolved to protect pollinators. We investigated flower-trap separation of Drosera and Utricularia. Short Drosera had a greater element of floral–trap separation than tall Drosera. Such a relationship is unexpected for plants whose peduncles were evolved to protect their pollinators. Utricularia can not trap pollinators but this genus still produces exceptionally long peduncles. We propose that flower-trap separation evolved because carnivorous plants are often short and need to project their flowers well above ground level to make them more attractive to pollinators.
title Patterns of prey capture and prey availability among populations of the carnivorous plant Pinguicula moranensis (Lentibulariaceae) along an environmental gradient
abstract In this study we explored the effect of the physical environment and the availability of prey (biomass and taxonomic composition) on the patterns of prey capture and reproduction on five populations of Pinguicula moranensis (Lentibulariaceae) in areas ranging from pine–oak forests to desert scrublands. Environmental variation was summarized using principal factor analysis. Prey availability and prey capture increased toward the shadiest, most humid, and fertile population. The probability of reproduction and average bud production per population did not follow the same tendency because both fitness components peaked at the middle of the environmental gradient. These results suggest that the benefits derived from carnivory are maximized at sites fulfilling a trade-off between light, moisture, and prey availability. We also found that the taxonomic composition of both the available prey and that of the prey captured by plants varied among populations. The results also indicated that the prey captured by plants are not a random sample of prey available within populations. Overall, the results from this study revealed a marked amount of heterogeneity in the physical and biotic environment among the populations of P. moranensis, which has the potential to affect the outcome of the interaction between this carnivorous species and its prey.
source American Journal of Botany. 2003;90:1341-1348.
abstract 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 developed 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 flooding, salinity or heavy metal occurance. Information about the structure and functioning of roots of carnivorous 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 nutrients 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.
source Adlassnig, W., Peroutka, M., Lambers, H., and Lichtscheidl, I. K. Plant and Soil, 2005, 274: 127-140.
title Insect aquaplaning: Nepenthes pitcher plants capture prey with the peristome, a fully wettable water-lubricated anisotropic surface
abstract Pitcher plants of the genus Nepenthes have highly specialized leaves adapted to attract, capture, retain, and digest arthropod prey. Several mechanisms have been proposed for the capture of insects, ranging from slippery epicuticular wax crystals to downward-pointing lunate cells and alkaloid secretions that anesthetize insects. Here we report that perhaps the most important capture mechanism has thus far remained overlooked. It is based on special surface properties of the pitcher rim (peristome) and insect "aquaplaning." The peristome is characterized by a regular microstructure with radial ridges of smooth overlapping epidermal cells, which form a series of steps toward the pitcher inside. This surface is completely wettable by nectar secreted at the inner margin of the peristome and by rain water, so that homogenous liquid films cover the surface under humid weather conditions. Only when wet, the peristome surface is slippery for insects, so that most ant visitors become trapped. By measuring friction forces of weaver ants (Oecophylla smaragdina) on the peristome surface of Nepenthes bicalcarata, we demonstrate that the two factors preventing insect attachment to the peristome, i.e., water lubrication and anisotropic surface topography, are effective against different attachment structures of the insect tarsus. Peristome water films disrupt attachment only for the soft adhesive pads but not for the claws, whereas surface topography leads to anisotropic friction only for the claws but not for the adhesive pads. Experiments on Nepenthes alata show that the trapping mechanism of the peristome is also essential in Nepenthes species with waxy inner pitcher walls.
source Bohn HF, Federle W. Proc Natl Acad Sci U S A. 2004, 101: 14138-14143.
title Antimicrobial activity and chemical investigation of Brazilian Drosera.
abstract The antimicrobial activity of three different extracts (hexanic, ethyl acetate, methanol) obtained from Brazilian Drosera species (D. communis, D. montana var. montana, D. brevifolia, D. villosa var. graomogolensis, D. villosa var. villosa, Drosera sp. 1, and Drosera sp. 2 ) were tested against Staphylococcus aureus (ATCC 25923), Enterococcus faecium (ATCC23212), Pseudomonas aeruginosa (ATCC27853), Escherichia coli (ATCC11229), Salmonella choleraesuis (ATCC10708), Klebsiella pneumoniae (ATCC13883), and Candida albicans (a human isolate). Better antimicrobial activity was observed with D. communis and D. montana var. montana ethyl acetate extracts. Phytochemical analyses from D. communis, D. montana var. montana and D. brevifolia yielded 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin); long chain aliphatic hydrocarbons were isolated from D. communis and from D. villosa var. villosa, a mixture of long chain aliphatic alcohols and carboxylic acids, was isolated from D. communis and 3b-O-acetylaleuritolic acid from D. villosa var. villosa.
source Ferreira DT, Andrei CC, Saridakis HO, Faria Tde J, Vinhato E, Carvalho KE, Daniel JF, Machado SL, Saridakis DP, Braz-Filho R. Mem Inst Oswaldo Cruz. 2004, 99: 753-755.
