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1.
The stability of twining vines under gravitational loads suggests an important role for friction. The coefficient of friction, μ, between vine stems and wood is high, often five times greater than between leather and wood, as determined by slip tests on an inclined plane. Stem trichomes function like ratchets to facilitate climbing upward (or to facilitate slipping if the stem is inverted). A mathematical model predicts large masses (kg) must be applied to the base of a twining vine to cause slipping. Vines slip as predicted when μ is low and arc length on the pole is short, and they break before slipping when μ is large or arc length is long. In contrast, twining vines are unstable in compression, collapsing when small masses (<10 g) are hung from the top of the vine. However, if the loads are applied below the uppermost gyre, the stabilizing tensional effect dominates. Therefore, in nature vines twining on a cylindrical support are stable under gravitational loads, unless these loads occur near the apex. A corollary is that a short apical coil can hold up large masses of maturing shoot.  相似文献   

2.
Virtually all plant parts rotate slightly about a central axis, a movement called circumnutation, but vines show exaggerated circumnutation. This study contrasts circumnutation in two congeneric twining vines, specifically focusing on differences in erect and prostrate shoots, and examines the impact of circumnutation on exploitation of available climbing supports and exploration for more distant ones. Elongating shoots of Lonicera japonica and L. sempervirens growing in a common garden were classed as (1) erect but not climbing, (2) climbing on a trellis, or (3) prostrate, and their circumnutation quantified by tracking the compass direction of shoot tips. To quantify the impact of different circumnutation behaviors, the climbing success of erect shoots and the maximum dispersion and rooting success of prostrate shoots were measured. Erect shoots of both species circumnutated at similar rates (averaging 31°/h), and did not differ in their success rate of exploiting trellises (averaging 76.8%). Prostrate shoots differed, with those produced by L. japonica having reduced circumnutation. In contrast, prostrate shoots of L. sempervirens continued to circumnutate as much as erect shoots. The specialized circumnutation behavior of the prostrate shoots of L. japonica results in increased rooting success and maximum dispersion compared to the unspecialized shoots of L. sempervirens.  相似文献   

3.
Scher JL  Holbrook NM  Silk WK 《Planta》2001,213(2):192-198
Using the TWIFOR, an electronic device for continuous, in vivo measurement of the forces exerted by twining vines, we examined the forces generated by vines growing on cylindrical poles of slender (6.35 mm) and thicker (19.05 mm) diameter. In stems of Ipomoea purpurea (L.) Roth. magnitudes of twining force (axial tensions) were, on average, less at a particular time and location on the more slender poles; while twining loads (normal force per unit length of vine) were much greater on the slender poles because of the greater curvature of the vines. Thus, the geometry of the helix formed by the vine on the pole affects the ability of the vine to maintain a frictional interaction with its support. In addition, the plant-to-plant variation in twining force was twice as great on the thicker support poles. Metaxylem and fibers developed closer to the plant apex in vines on the slender poles. On the thicker poles, a significant fraction of the maximum twining force developed during the establishment of the first gyre, before fibers were lignified, indicating that primary growth can be sufficient to establish high twining forces. On the slender poles, however, twining force increased with developmental stage until the gyre was at least 1.5 m from the apex. Thus, twining force can increase after cessation of primary growth. No simple relationship was found between the site of fiber differentiation and twining force.  相似文献   

4.
湖南德夯风景区藤本植物多样性研究   总被引:2,自引:1,他引:1  
对德夯风景区藤本植物进行了调查,结果表明:本区有藤本植物249种(含变种),隶属于49科110属.科属的区系性质均以热带为主,分别占54.17%、60.91%.生活型以木质藤本为主,占68.67%.攀援类型分为4大类、9小类,其中缠绕类最多,占38.96%,卷曲类占27.31%,搭靠类占20.07%,吸固类最少,仅占13.66%.藤本植物按资源类型可分为药用植物、观赏植物、纤维植物、芳香植物、食用植物及其他,药用植物居多,而最具潜力的是观赏类植物.  相似文献   

5.
Differential herbivory and/or differential plant resistance or tolerance in sun and shade environments may influence plant distribution along the light gradient. Embothrium coccineum is one of the few light-demanding tree species in the temperate rainforest of southern South America, and seedlings are frequently attacked by insects and snails. Herbivory may contribute to the exclusion of E. coccineum from the shade if 1) herbivory pressure is greater in the shade, which in turn can result from shade plants being less resistant or from habitat preferences of herbivores, and/or 2) consequences of damage are more detrimental in the shade, i.e., shade plants are less tolerant. We tested this in a field study with naturally established seedlings in treefall gaps (sun) and forest understory (shade) in a temperate rainforest of southern Chile. Seedlings growing in the sun sustained nearly 40% more herbivore damage and displayed half of the specific leaf area than those growing in the shade. A palatability test showed that a generalist snail consumed ten times more leaf area when fed on shade leaves compared to sun leaves, i.e., plant resistance was greater in sun-grown seedlings. Herbivore abundance (total biomass) was two-fold greater in treefall gaps compared to the forest understory. Undamaged seedlings survived better and showed a slightly higher growth rate in the sun. Whereas simulated herbivory in the shade decreased seedling survival and growth by 34% and 19%, respectively, damaged and undamaged seedlings showed similar survival and growth in the sun. Leaf tissue lost to herbivores in the shade appears to be too expensive to replace under the limiting light conditions of forest understory. Following evaluations of herbivore abundance and plant resistance and tolerance in contrasting light environments, we have shown how herbivory on a light-demanding tree species may contribute to its exclusion from shade sites. Thus, in the shaded forest understory, where the seedlings of some tree species are close to their physiological tolerance limit, herbivory could play an important role in plant establishment.  相似文献   

6.
Although the coiling of tendrils and the twining of vines has been investigated since Darwin's time, a full understanding of the mechanism(s) of this coiling and twining ability has not yet been obtained. In a previous study (Planta 225: 485-498), gelatinous (G) fibers in tendrils of redvine occurred concomitantly with the ability to coil, strongly indicating their role in the coiling process. In this study, tendrils and twining vines of a number of species were examined using microscopic and immunocytochemical techniques to determine if a similar presence and distribution of these fibers exists in other plant species. Tendrils that coiled in many different directions had a cylinder of cortical G fibers, similar to redvine. However, tendrils that coiled only in a single direction had gelatinous fibers only along the inner surface of the coil. In tendrils with adhesive tips, the gelatinous fibers occurred in the central/core region of the tendril. Coiling occurred later in development in these tendrils, after the adhesive pad had attached. In twining stems, G fibers were not observed during the rapid circumnutation stage, but were found at later stages when the vine's position was fixed, generally one or two nodes below the node still circumnutating. The number and extent of fiber development correlated roughly with the amount of torsion required for the vine to ascend a support. In contrast, species that use adventitious roots for climbing or were trailing/scrambling-type vines did not have G fibers. These data strongly support the concept that coiling and twining in vines is caused by the presence of G fibers.  相似文献   

7.
Eugene W. Schupp 《Oecologia》1986,70(3):379-385
Summary In this 15 month investigation I experimentally demonstrated that sapling Cecropia aff. obtusifolia in lowland western Ecuador grow more vigorously when occupied by the ant Azteca constructor than when the ants have been removed. Thus the interaction is directly beneficial to Cecropia juveniles. The difference in growth is associated with differences in herbivory and vine cover. Removal of ants significantly increases nocturnal Coleoptera herbivory on unoccupied plants. In contrast to the influence on beetle numbers, Azteca are ineffective against Homoptera and cecidomyiid gall flies. Although ant-occupied saplings had less chewing herbivore damage throughout the study, the ants were more effective protectors in the dry season than in the rainy season, when herbivore pressure increased. In addition to reducing herbivory, Azteca efficiently remove vines from occupied saplings.  相似文献   

8.
Numerous hypotheses suggest that natural enemies can influence the dynamics of biological invasions. Here, we use a group of 12 related native, invasive, and naturalized vines to test the relative importance of resistance and tolerance to herbivory in promoting biological invasions. In a field experiment in Long Island, New York, we excluded mammal and insect herbivores and examined plant growth and foliar damage over two growing seasons. This novel approach allowed us to compare the relative damage from mammal and insect herbivores and whether damage rates were related to invasion. In a greenhouse experiment, we simulated herbivory through clipping and measured growth response. After two seasons of excluding herbivores, there was no difference in relative growth rates among invasive, naturalized, and native woody vines, and all vines were susceptible to damage from mammal and insect herbivores. Thus, differential attack by herbivores and plant resistance to herbivory did not explain invasion success of these species. In the field, where damage rates were high, none of the vines were able to fully compensate for damage from mammals. However, in the greenhouse, we found that invasive vines were more tolerant of simulated herbivory than native and naturalized relatives. Our results indicate that invasive vines are not escaping herbivory in the novel range, rather they are persisting despite high rates of herbivore damage in the field. While most studies of invasive plants and natural enemies have focused on resistance, this work suggests that tolerance may also play a large role in facilitating invasions.  相似文献   

9.
Photosynthesis in a deciduous forest understory was studied for three exotic vine species (Pueraria lobata, Lonicera japonica, and Hedem helix) and five common native species (Rhus radicans, Clematis virginiana, Smilax rotundifolia, Vitis vulpina, and Parthenocissus quinquefolid) possessing a variety of climbing mechanisms. The adventitious-root climbers (H. helix and R. radicans) had the lowest maximum photosynthetic rates of all species (5.5 and 6.4 μmol m–2 s–1, respectively). The twining vine P. lobata was the most poorly adapted to the understory with a high light-compensation point (43 μmol m–2 s–1), low photosynthesis under low light (0.5 μmol m2 s–1 at 50 μmol m–2 s–1), and the highest light requirement for obtaining 90% of maximum photosynthesis (860 μmol m–2 s–1). Lonicera japonica, another twining vine, was better-adapted to low light conditions, but vines with tendril climbing mechanics were physiologically the best adapted to low light. The adhesive-tendril climber P. quinquefolia was the most highly adapted to shade, with a low light compensation point (20 μmol m–2 s–1), a high photosynthetic rate under low light (3.5 μmol m–2 s–1), and a low light saturation point (160 μmol m–2 s–1). Results suggest that physiological adaptability of vines to low-light environments may be related to climbing mechanics.  相似文献   

10.
Biomass allocation to roots, rhizomes, runners and climbing stems (i.e. twining axis and attached leaves) was studied inCalystegia sepium L., a clonal vine. In an experiment which took 2 months, nutrient availability (low and high) and intraspecific competition (none, shoot root and both shoot and root) were manipulated. Under low nutrients the highest biomass of climbing stems was found in plants with shoot competition; the lowest was found in plants with both shoot and root competition. Total biomass under high nutrients was also greatest in plants with shoot competition. Thus, plants benefited from climbing up a shared stake rather than separate stakes. Larger plants allocated a higher proportion of biomass to runners in the nutrient-poor environment than in the nutrient-rich environment. This behaviour may increase the chance of finding nutrient-rich patches in the neighbourhood of the mother plant in a heterogeneous environment.  相似文献   

11.
The effect of waterlogging the vines of two yam varieties for 24, 48 and 72 hours at two stages of growth, with or without fertiliser application, was studied in the field. Waterlogging caused a progressive degeneration of the leaf starting with the development of fresh lesions on the lower leaf surface, through necrotic spots or portions, to complete leaf necrosis. The degree of leaf damage was greater with Um 680 (Dioscorea alata) than with Obiaoturugo (D. rotundata). Waterlogging also caused the breakdown of the apical buds of the vines. The degree of damage increased with the duration of waterlogging. Younger plants suffered more damage than older plants, and plants treated with fertiliser suffered more than plants without fertiliser. Waterlogging ultimately hastened the final senescence of the yam vine. Waterlogging vines for 24 h had no effect on tuber yield, while waterlogging for 48 and 72 h reduced tuber yield by 32.4% and 43.2% respectively (P< 0.01). Waterlogging vines at the early growth stage produced 47.6% (P <0.01) less yield than waterlogging at a later stage. It is suggested that short-term or long-term waterlogging of the yam vine, or parts thereof, is the main cause of reduced leaf area and low yield in unstaked compared with staked yarn crops. Waterlogging may also be a predisposing factor to disease infection of yam vines by soil-borne micro-organisms.  相似文献   

12.
Summary Xylem (wood) tissue in plants functions both for mechanical support and water transport. Since vines are mechanical parasites, they allocate less biomass for xylem tissue than do free-standing trees or shrubs. With-in the genus Bauhinia, stems of vine species were found to have not only less xylem per distal leaf area, but also less phloem and cortical tissue when compared to tree and shrub species. The phloem and cortical reductions are interpreted as an indirect effect of the developmental/geometric constraints imposed by the evolution of a reduced mechanical system. Apparently vines overcame these constraints with the evolution of wider vessels and wider sieve tubes and with many types of variant (anomalous) secondary growth. The long and wide vessels of vines, which compensate hydraulically for the reduced xylem areas, may help limit the distribution of vine species in nature.  相似文献   

13.
Barber NA  Marquis RJ 《Oecologia》2011,166(2):401-409
Theory predicts that variation in plant traits will modify both the direct interactions between plants and herbivores and the indirect impacts of predators of those herbivores. Light has strong effects on leaf quality, so the impacts of herbivores and predators may differ between plants grown in sun and shade. However, past experiments have often been unable to separate the effects of light environment on plant traits and herbivory from direct effects on herbivores and predators. We first manipulated light availability in an open habitat using a shade cloth pre-treatment to produce oak saplings with different leaf qualities. Leaves on plants exposed to high light were thicker and tougher and had lower nitrogen and water contents, and higher carbon and phenolic contents than leaves on plants under a shade cloth. Then, in the main experiment, we moved all plants to a common shade environment where bird predators were excluded in a factorial design. We measured insect herbivore abundance and leaf damage. Herbivores were significantly more abundant and caused greater leaf damage on sun trees, although these leaf characteristics are usually associated with low-quality food. Bird exclusion did not change herbivore abundance but did increase leaf damage. Contrary to our predictions, the effects of birds did not differ between trees grown in sun and shade conditions. Thus, differences in effects of predators on herbivores and plants between light habitats, when observed, might be due to variation in predator abundance and not bottom-up effects of host plant quality.  相似文献   

14.
The climbing habit has evolved independently in many plant taxa, offering vines the ability to compete with non-climbing vegetation for resources such as light, nutrients, and water. This review examines the structural and functional characteristics that allow climbing plants to (1) achieve widespread dispersal, (2) transport large amounts of water throughout vessels, (3) maintain high photosynthesis levels through a large leaf area to biomass ratio, (4) achieve rapid vertical and horizontal expansion by fast growth rates and various climbing mechanisms and (5) survive and recover from disturbances. Due to the competitive effects of vines on trees, management of vine growth is used to preserve tropical timber plantations, combat invasive weeds, and promote rainforest recovery. In order to sustainably manage the vines into the future, it is necessary to understand the mechanisms by which they can alter tropical forest succession and the impacts of various management techniques.  相似文献   

15.
Krupnick  Gary A.  Weis  Arthur E. 《Plant Ecology》1998,134(2):151-162
Flower-feeding insects may influence the reproductive behavior of their host plant. In plants with labile sex expression, the ratio of maternal to paternal investment may change in response to damage, an effect that goes beyond the direct reduction of plant gametes. We examined the effects of floral herbivory by the beetle Meligethes rufimanus (Nitidulidae) on the ratio of hermaphroditic flowers to male flowers in an andromonoecious shrub, Isomeris arborea (Capparaceae) in southern California. Plants exposed to herbivory had a greater rate of flower bud abortion than those protected from herbivory. Exposed plants produced a greater proportion of hermaphroditic flowers to male flowers, although damaged inflorescences still produced fewer fruit. An additional manipulative experiment showed that the removal of pistils on inflorescences led to an increase in the proportion of hermaphroditic flowers. This suggests that the presence of fruit may lead to pistil suppression in developing flowers. Adaptive responses to herbivory which favor andromonoecy thus include the continued production of hermaphroditic flowers when floral damage is high (and hence low fruit set), and a switch to male flower production when floral damage is low (and fruit production increases). The consequences of an altered six ratio induced by insect herbivores may lead to indirect effects on both the male and female reproductive success of this plant.  相似文献   

16.
Plant populations often exist in spatially heterogeneous environments with varying light levels, which can affect plant growth directly through resource availability or indirectly by altering behavior or success of herbivores. The plant vigor hypothesis predicts that herbivores are more likely to attack vigorously growing plants than those that are suppressed, for example in more shaded conditions. Plant tolerance of herbivory can also vary under contrasting resource availability. Observations suggest that damage by Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae), introduced into the United States in 2004 as a biological control agent for mile-a-minute weed (Persicaria perfoliata [L.] H. Gross), is greater in the sun than in shade. We compared weevil densities and plant growth in paired plots in full sun or under shade cloth; a second experiment included insecticide-treated plots in sun and shade, to assess the ability of the plant to compensate for herbivore damage. Greater density of weevils and more node damage (indicating internal larval feeding) were found on P. perfoliata plants growing in sun than on those in shade. Nodes were 14% thicker in the sun, which may have provided better larval habitat. Biomass produced by plants without weevils in the sun was about twice that produced in any other treatment. Herbivory had a greater effect on plant growth in the high-light environment than in the shade, apparently because of movement into the sun and increased feeding there by the monophagous herbivore, R. latipes. Results support the plant vigor hypothesis and suggest that high weevil densities in the sunny habitats favored by P. perfoliata can suppress plant growth, negating the resource advantage to plants growing in the sun.  相似文献   

17.
Abstract. The CAM vine Hoya australis and three C3 vines, Smilax australis, Ipomoea pes-caprae and Kennedta rubicunda, were studied at a site on the coast of northeastern New South Wales, Australia. The level of CAM activity (nocturnal acid accumulation) was comparable in H. australis growing in full sunlight and in deep shade. Acclimation to shade by H. australis was indicated by thinner leaves, increased chlorophyll content, decreased chlorophyll a/b ratios, lower dark respiration rates, and lower light compensation points. When growing in full sunlight H. australis exhibited reductions in photochemical efficiency, as indicated by reduced quantum yields and Fv/Fm fluorescence from PS II as well as low rates of photosynthesis at high light. Sun leaves of H. australis experienced a massive quenching of fluorescence from PS II during normal exposure to midday irradiance which was rapidly reversible under low irradiance conditions in the late afternoon. This quenching indicated a reduction in photochemical efficiency, part of which could be accounted for by an increase in non-radiative energy dissipation, while part of it was due to one or more processes not yet identified. Changes in PS II fluorescence from shade H. australis exposed to full sunlight suggest a decrease in the rate constant for photochemistry indicative of damage to the reaction centre, as well as an increase in non-radiative energy dissipation. The C3 vine S. australis was also shade tolerant, but exhibited little evidence of photoinhibition when growing in full sunlight. Ipomoea pescaprae and K. rubicunda, both of which were apparently shade intolerant (being found only in full sunlight), possessed high quantum yields and much higher photosynthetic capacities than either H. australis or S. australis. From this study, and several others, it appears that plants possessing CAM experience photoinhibition to a greater degree than do C3 species in full sunlight under natural conditions, which is probably exacerbated by some degree of CAM-idling.  相似文献   

18.
Summary The effect of full sunlight, 60%, or 90% attenuated light on photosynthetic rate, growth, leaf morphology, dry weight allocation patterns, phenology, and tolerance to clipping was examined in the glasshouse for steppe populations of the introduced grass, Bromus tectorum. The net photosynthetic response to light for plants grown in shade was comparable to responses for plants grown in full sunlight. Plants grown in full sunlight produced more biomass, tillers and leaves, and allocated a larger proportion of their total production to roots than plants grown in shade. The accumulation of root and shoot biomass over the first two months of seedling growth was primarily responsible for the larger size at harvest of plants grown in full sunlight. Plants grown under 60% and 90% shade flowered an average of 2 and 6 weeks later, respectively, than plants grown in full sunlight. Regrowth after clipping was greater for plants grown in full sunlight compared to those grown in shade. Even a one-time clipping delayed flowering and seed maturation; the older the individual when leaf area was removed, the greater the delay in its phenology. Repeated removal of leaf area was more frequently fatal for plants in shade than in full sunlight. For plants originally grown in full sunlight, regrowth in the dark was greater than for shaded plants and was more closely correlated to non-flowering tiller number than to plant size. This correlation suggests that etiolated regrowth is more likely regulated by the number of functional meristems than by differences in the size of carbohydrate pools. Thus, shading reduces the rate of growth, number of tillers, and ability to replace leaf area lost to herbivory for B. tectorum. These responses, in turn, intensify the effect of competition and defoliation for this grass in forests. B. tectorum is largely restricted to forest gaps at least in part because of its inability to acclimate photosynthetically, the influence of shade on resource allocation, and the role of herbivory in exacerbating these effects.  相似文献   

19.
Question: In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location: Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40°39′S, 72°09′W; 350 m a.s.l.) and Pastahue (42°22′S, 73°49′W; 285 m a.s.l.). Methods: We sampled vines in 60 25‐m2 plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree ≥1.50‐m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results: Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion: We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor.  相似文献   

20.
In hardwood subtropical forests of southern Florida, nonnative vines have been hypothesized to be detrimental, as many species form dense “vine blankets” that shroud the forest. To investigate the effects of nonnative vines in post‐hurricane regeneration, we set up four large (two pairs of 30 X 60 m) study areas in each of three study sites. One of each pair was unmanaged and the other was managed by removal of nonnative plants, predominantly vines. Within these areas, we sampled vegetation in 5 X 5 m plots for stems 2 cm DBH (diameter at breast height) or greater and in 2 X 0.5 m plots for stems of all sizes. For five years, at annual censuses, we tagged and measured stems of vines, trees, shrubs and herbs in these plots. For each 5 X 5 m plot, we estimated percent coverage by individual vine species, using native and nonnative vines as classes. We investigated the hypotheses that: (1) plot coverage, occurrence and recruitment of nonnative vines were greater than that of native vines in unmanaged plots; (2) the management program was effective at reducing cover by nonnative vines; and (3) reduction of cover by nonnative vines improved recruitment of seedlings and saplings of native trees, shrubs, and herbs. In unmanaged plots, nonnative vines recruited more seedlings and had a significantly higher plot‐cover index, but not a higher frequency of occurrence. Management significantly reduced cover by nonnative vines and had a significant overall positive effect on recruitment of seedlings and saplings of native trees, shrubs and herbs. Management also affected the seedling community (which included vines, trees, shrubs, and herbs) in some unanticipated ways, favoring early successional species for a longer period of time. The vine species with the greatest potential to “strangle” gaps were those that rapidly formed dense cover, had shade tolerant seedling recruitment, and were animal‐dispersed. This suite of traits was more common in the nonnative vines than in the native vines. Our results suggest that some vines may alter the spatiotemporal pattern of recruitment sites in a forest ecosystem following a natural disturbance by creating many very shady spots very quickly.  相似文献   

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