Structural requirements for the perception of ambient temperature signals in homeothermic heat production of skunk cabbage (Symlocarpus foetidus)

The spadix of skunk cabbage, Symplocarpus foetidus, is capable of maintaining an internal temperature of around 20 degrees C even when the ambient temperature drops to around 0 degrees C. To determine the crucial structure that is required for detection of ambient temperature signals, detailed measurements of the temperatures of the spadix were made under field conditions. The spadix temperature was well regulated even when the spathe or the leaf of the plant was removed. Furthermore, maintenance of the temperature of the central stalk at either 10 or 20 degrees C had no effect on the thermoregulation when the ambient temperature increased from 10 to 25 degrees C or decreased from 20 to 8 degrees C. Therefore, it seemed that the heat production in the spadix required neither the spathe, the leaf, nor the central stalk for perception of the external temperature signals. Finally, analysis of sugar composition in xylem exudates showed that the concentrations of sucrose, glucose, and fructose, all of which are potential energy sources of thermogenesis, did not change significantly at different ambient temperatures. It is concluded that the spadix is a unique organ in which the perception of ambient temperature signals and heat production occurs in S. foetidus.     

Respiration,temperature regulation and energetics of thermogenic inflorescences of the dragon lily Dracunculus vulgaris (Araceae)

Dracunculus vulgaris is a protogynous arum lily with thermogenic inflorescences consisting of male and female florets on a spadix within a floral chamber. Above the chamber, an odour-producing appendix and a carrion-coloured spathe attract flying insects. The inflorescence shows a triphasic warming pattern. The floral chamber warms weakly on the first night as the spathe opens. Then the appendix produces a large amount of heat and a powerful scent during the first day. As the appendix cools on the second night, scent production ceases and the floral chamber rewarms. Warming ceases when the pollen is shed on the second day. The heating pattern is associated with attraction of pollinating insects by the appendix on the first day, entrapment in the warm chamber at night and release after pollen shedding. The temperature in the floral chamber is regulated at around 18 °C during the second night. The oxygen consumption rate of the florets is inversely related to the ambient temperature as in other thermoregulatory flowers. Conversely, the oxygen consumption rate of the appendix is directly related to the ambient temperature, indicating that it does not thermoregulate. Thus, temperature regulation is not associated with scent production, but with some activity inside the floral chamber.     

THE MOTION OF WINDBORNE POLLEN GRAINS AROUND CONIFER OVULATE CONES: IMPLICATIONS ON WIND POLLINATION

Comparisons are presented between the three-dimensional airflow patterns created around and by a scale model of a conifer ovulate cone and the trajectories of windborne pollen grains around Picea, Larix, and Pinus ovulate cones. Three general components of the airflow pattern around an ovulate cone model are 1) doldrum-like eddies, rotating over the adaxial surfaces of cone scales and directed toward attached ovules, 2) airflow spiralling around the cone axis along cone scale orthostichies and parastichies, and 3) a complex pattern of vortices (“umbilicus”) directed toward the leeward surface of the ovulate cone. The observed trajectories of pollen grains around cones of Picea, Larix, and Pinus conform to two of these three airflow components: 1) pollen grains are seen to roll along cone scales toward the distal scale margin and to become reentrained in airflow directed backward toward attached ovules, and 2) pollen grains passing around the cone are deflected into the “umbilicus” airflow pattern, where they either settle on or impact with cone scales (approach trajectories), or where they approach the leeward cone surface but are deflected away by airflow passing under the cone (Z-shaped trajectories). Vectoral analyses of pollen grain motion reveal a complex pattern of trajectories influenced by boundary layer conditions defined by ovulate cone geometry and ambient airflow speed. Wind tunnel studies of ovulate cones subtended by leaves and stem indicate that leaves circumscribing the cone act as a snowfence, deflecting windborne pollen toward the cone. Vectoral analyses of airflow patterns and pollen grain trajectories close to ovulate cones indicate that wind pollination in conifers is a non-stochastic aerodynamic process influenced by cone-leaf morphology and the behavior of pollen grains as windborne particles.     

Studying Lords and Ladies,Arum maculatum (L.)

Historical uses of Arum maculatum (L.) are summarized. Field and laboratory investigations show plants with purple and pale spadices are equally attractive to flies of the genus Psychoda; and these are attracted to the scent in the absence of visual stimuli. Over 75% of the flies which enter spikes escape. Temperature changes during spadix maturation, and spathe uncurling in the presence of flower tissue, indol-3-yl acetic acid, and gibberellic acid are investigated in the laboratory. Dilute solutions of both phytohormones cause significant spathe uncurling. Further investigations, suitable for project work in schools and colleges, are suggested.     

Arisaema lushuiense sp. nov. (Araceae) from Gaoligong Mountains in Yunnan,China

Arisaema lushuiense G. W. Hu & H. Li, a new species of Araceae from Gaoligong Mountains in northwestern Yunnan, China, is described and illustrated. It is similar and closely related to A. auriculatum Buchet, but differs by its basically green spathe with semi‐rotund to broadly ovate, 6–8 mm long auricles; the appendix of the spadix is 3.5–5.0 cm long and the apex of the appendix depressed with faint longitudinal ridges and grooves, slightly curved forward, with purplish black color, and exserted 1.0–1.5 cm from the spathe throat.     

Amorphophallus titanum Becc.: a Historical Review and Some Recent Observations

Amorphophallus titanum Becc., discovered in 1878 by OdoardoBeccari in Sumatra has flowered only a few times in botanicalgardens. Its corms may weigh as much as 50 kg, have a diameterof 50–55 cm, a circumference of nearly 2 m and be 40cmhigh. The inflorescences, which produce a fetid smell, may last3–4 days and can reach a height of 2 m. The spadix isyellow-red in colour and the spathe greenish purple. Amorphophallus titanum, Araceae, inflorescence, spadix, spathe, corm, pistillate flowers, staminate flowers     

Adaptations for insect‐trapping in brood‐site pollinated Colocasia (Araceae)

The Araceae include both taxa with rewarding and deceptive trap pollination systems. Here we report on a genus in which rewarding and imprisonment of the pollinators co‐occur. We studied the pollination of four species of Colocasia in Southwest China and investigated the morpho‐anatomical adaptations of the spathe related to the attraction and capture of pollinators. All four species were pollinated by drosophilid flies of the genus Colocasiomyia. The flies are temporally arrested within the inflorescence and departure is only possible after pollen release. Trapping of the flies is accomplished by the closure of the spathe during anthesis. Moreover, in two species the spathe is covered with papillate epidermal cells known to form slippery surfaces in deceptive traps of Araceae. However, in Colocasia the papillae proved not slippery for the flies. The morpho‐anatomical properties of the spathe epidermis indicate that it is an elaborate osmophore and serves for the emission of odours only. Despite its similarity to deceptive traps of other aroids, Colocasia and Colocasiomyia have a close symbiotic relationship, as the attracted flies use the inflorescence as a site for mating and breeding. The trap mechanism has presumably evolved independently in Colocasia and is supposed to facilitate more efficient pollen export.     

Flowering and Pollination of Philodendron melinonii (Araceae) in French Guiana

Abstract: The pollination ecology of Philodendron melinonii was studied at two locations in French Guiana. Inflorescences of P. melinonii were regularly visited by Cyclocephala colasi, a scarab beetle also found in inflorescences of P. solimoesense in the same area. The flowering cycle lasted two days and the inflorescence exhibited features typical for beetle pollination (e.g., floral chamber, food rewards, flower heating). The flowering process is well synchronized with the night activity of Cyclocephala visitors. The spadix temperature was measured during the entire flowering cycle in the field in French Guiana and in greenhouse conditions at the Montreal Botanical Garden. Both measurements gave a similar temperature pattern with a two hour delay at the Botanical Garden. The spadix warmed up twice during the flowering period and its temperature was not significantly different from that of ambient air between the two peaks. These two temperature peaks are also well synchronized with the arrival and departure of the beetles on two consecutive nights.     

Pollen movement in a natural population of Arisaema serratum (Araceae), a plant with a pitfall-trap flower pollination system

Arisaema serratum possesses a pitfall-trap flower pollination system. However, little is known about the efficiency and pattern of pollen movement in A. serratum. Thus, the aims of this study are to (1) determine the paternal parents of the seeds and (2) elucidate pollen movement in a natural population. Paternity analysis using microsatellite markers was performed. Seeds were collected from a natural population of A. serratum in 2001 at Horigane, Japan. Small midges became trapped in female spathe tubes during the flowering period. We found that (1) seeds in a fruit were fertilized by multiple sires; (2) seeds sired by a paternal parent were either clumped, exclusively, or randomly distributed on the spadix, depending on the parent; (3) to a great extent, a few males contributed as sires; (4) distance from a female was not a factor in the inequality of reproductive success among males; (5) male reproductive success was not correlated with its size. We conclude that pollen carryover and the trap-flower pollination system are likely to result in multiple paternity and inequality in male success.     

THE AERODYNAMICS OF POLLEN CAPTURE IN TWO SYMPATRIC EPHEDRA SPECIES

Wind-tunnel analyses of the behavior of airborne pollen around ovules of two Ephedra species (E. trifurca and E. nevadensis) indicate that at certain airflow speeds (0.5 m/sec and 1.0 m/sec) each species is capable of biasing pollination in favor of conspecific pollen. A computer procedure was designed to evaluate the physical basis for this aerodynamic discrimination. This procedure indicates that differences in size and density confer significantly different inertial properties to the two pollen species. Operating within the specific aerodynamic environments generated around ovules from each species, these differences are sufficient to account for the biases observed in the probability of pollination. Within natural populations, there exists significant variation in pollen size (and possibly in density). Accordingly, it is possible that, under certain ambient wind conditions, ovules from each species can select subsets of the entire airborne population of Ephedra pollen.     

What is critical for plant thermogenesis? Differences in mitochondrial activity and protein expression between thermogenic and non-thermogenic skunk cabbages

Thermogenesis during the blooming of inflorescence is found in several but not all aroids. To understand what is critical for thermogenesis, we investigated the difference between thermogenic and non-thermogenic skunk cabbages (Symplocarpus renifolius and Lysichiton camtschatcensis), which are closely related in morphology and phylogeny. Critical parameters of mitochondrial biogenesis, including density, respiratory activity, and protein expression were compared between these two species. Mitochondrial density, respiratory activity, and the amount of alternative oxidase (AOX) in L. camtschatcensis spadix mitochondria were lower than in S. renifolius spadix mitochondria, while the level of uncoupling protein (UCP) was higher. AOX and UCP mRNAs in L. camtschatcensis were constitutively expressed in various tissues, such as the spadix, the spathe, the stalk, and the leaves. cDNA encoding two putative thermogenic proteins, AOX and UCP were isolated from L. camtschatcensis, and their primary structure was analyzed by multiple alignment and phylogenetic tree reconstruction. AOX and UCP protein of two the skunk cabbage species are closely related in structure, compared with other isoforms in thermogenic plants. Our results suggest that mitochondrial density, respiratory activity, and protein expression, rather than the primary structure of AOX or UCP proteins, may play critical roles in thermogenesis in plants.     

BEETLE POLLINATION OF DIEFFENBACHIA LONGISPATHA (ARACEAE)

Dieffenbachia is an monoecious understory herb of tropical rain forests that exhibits a complex and specialized relationship with its beetle pollinators. The erect protogynous inflorescence has the spadix divided, with the female flowers in the basal half and male flowers in the upper half. Dieffenbachia longispatha Engler & Krause is pollinated by scarab beetles in the genera Cyclocephala and Erioscelis. The enveloping spathe of the inflorescence opens in the evening, but no flowers are sexually functional until the stigmas become receptive about 24 hr later. Beetles fly to the inflorescence in darkness, suggesting that floral odors play a role as an attractant. Beetles remain in the inflorescence for 24 hr, eating protein-rich staminodia that surround the stigmas. On the evening of the third day the anthers dehisce and beetles become covered with pollen as they crawl up the spadix in the process of leaving. Beetles fly an average of 80 m between inflorescences, usually to the nearest female inflorescence, although distances of 400–1,000 m have been observed. Minimal estimate of genetic neighborhood sizes are large for D. longispatha (750 to 8,900 plants) and neighborhood areas encompass 41,000 to 67,000 m². Experiments demonstrate that the species is self-compatible and that fruit production is pollinator limited.     

AERODYNAMICS OF WIND POLLINATION IN SIMMONDSIA CHINENSIS (LINK) SCHNEIDER

Wind tunnel analyses of Simmondsia chinensis (Link) Schneider or “jojoba” were conducted to quantify the behavior of airborne pollen grains around individual branches and leaves and near individual carpellate flowers. Field data (wind velocity) were used to ensure a correspondence between wind tunnel and natural conditions. Based upon the visualization of individual pollen grain trajectories, it is concluded that pollen deposition on stigmatic surfaces is influenced by large-scale aerodynamic patterns, generated by foliage leaves, and small-scale airflow patterns, formed around and by floral parts and stigmas. Leaves are seen to deflect airborne pollen grains into trajectories that can intersect ambient airflow at 90° angles, showering decumbent carpellate flowers with pollen. Similarly, flowers can deflect pollen upward and downwind, toward other flowers. The extent of floral bract and sepal recurvature is shown to influence the extent of pollen deposition by determining the characteristic airflow pattern around stigmas. Available evidence concerning the relatively recent evolutionary transition to anemophily in Simmondsia is interpreted within the context of morphological adaptations and exaptations favoring wind pollination.     

Pothos crassipedunculatus,a new species ofPothos sect.Allopothos (Araceae) from India

Pothos crassipedunculatus Sivadasan & Mohanan (Araceae), a new species closely related to the SW. Indian endemic and little known speciesP. thomsonianus Schott is described. It is characterized by the the non-ligulate, shortly vaginate petiole, thickly peduncled inflorescence, broadly ovate spathe and a sessile spadix. It is included in ser.Brevivaginati Engler of sect.Allopothos Schott.     

Integrated small RNA profiling and degradome analysis of Anthurium andraeanum cultivars with different-colored spathes

MicroRNAs (miRNAs) are known to play vital roles in coloration of leaves, flowers, and fruits in plants. However, their functions in spathe coloration are poorly known. Anthurium andraeanum is a popular ornamental plant with various spathe colors. In this study, small RNA and degradome libraries from three A. andraeanum cultivars with different-colored spathes were constructed and sequenced. Illumina sequencing resulted in 94 conserved miRNAs, and 34 novel miRNAs in total were then identified based on precursor sequences and hairpin structures. Differential expression analysis showed that 52, 51, and 49 miRNAs were differentially expressed in comparisons of orange- versus white-colored spathe, purple- versus white-colored spathe, and purple- versus orange-colored spathe, respectively. The expression patterns of miRNAs and their corresponding targets involved in spathe coloration were further analyzed, and displayed that miR156b and miR529 were highly abundant in the spathes with higher anthocyanin content. These two miRNAs co-targeted a gene encoding SPL17, which may function as a negative regulator in anthocyanin accumulation. In addition, miR408 was also abundantly expressed in purple- and orange-colored spathes, and its typical targets were also identified. This comprehensive integrated analysis provides insight into the miRNA-mediated genetic regulation in spathe coloration of A. andraeanum.

     

AIRFLOW PATTERNS AROUND SOME EARLY SEED PLANT OVULES AND CUPULES: IMPLICATIONS CONCERNING EFFICIENCY IN WIND POLLINATION

Aerodynamic analyses showing characteristic airflow patterns and the potential for wind-mediated pollination are presented for models of Paleozoic (Carboniferous) ovules and ovulate cupules (i.e., Genomosperma kidstoni, G. latens, Salpingostoma dasu, Physostoma elegans, Eurystoma angulare, and Stamnostoma huttonense). Lobes on ovules and cupules are shown to produce localized regions of turbulent flow with a concomitant reduction in airflow velocity. Data based upon models that mimic the characteristics of windborne pollen (= pseudopollen) show that these regions of turbulent flow correspond to those in which suspended pseudopollen impact with ovule and/or cupule surfaces. These data have bearing on a sequence of ovule morphologies purported to show the evolution of the integument by the progressive reduction in length of “preintegumentary” lobes and their acropetal fusion. As the preintegumentary lobes of the models studied consolidate around the megasporangium, regions of turbulent flow and high pseudopollen impact become localized around the pollen chamber or salpinx. The general morphologic trend envisioned for the evolution of the ovule is seen to be associated with an aerodynamic streamlining and an increased potential for wind-mediated pollination. Data for hair-bearing ovules and for ovulate cupules are discussed within the context of possible selective pressures favouring streamlining.     

Horizontal orientation of zygomorphic flowers: significance for rain protection and pollen transfer

• Floral traits are recognized to have evolved under selection for abiotic and biotic factors. Complex zygomorphic flowers usually face horizontally. It has been proved that a horizontal orientation facilitates pollinator recognition and pollination efficiency, but its significance in adaptation to abiotic factors remains unknown.
• The floral orientation of Abelia × grandiflora naturally varies around horizontal (with an angle of ?30 to +33° between the floral main axis and the horizontal). We examined whether three different floral orientations affected flower thermal conditions, response to rain and pollination.
• Results showed that floral orientation had no effect on diurnal variations in flower temperature. The anthers of all three flower orientations were wetted by rainfall, but the inclined upward‐facing flowers contained significantly more rainwater. The horizontal flowers received significantly higher visitation by hawkmoths and had a higher stigmatic pollen load. In contrast, the upward flower orientation reduced pollination precision, while downward‐facing flowers had decreased pollinator attraction.
• This study indicates that horizontal flowers may have evolved as a trade‐off between rain protection and pollination. Zygomorphic flowers that deviate from a horizontal orientation may have lower fitness because of flower flooding by rainwater and decreased pollen transfer.

     

The cowl does not make the monk: scarab beetle pollination of the Neotropical aroid Taccarum ulei (Araceae: Spathicarpeae)

Taccarum ulei (Araceae, Spathicarpeae) is a seasonal geophytic aroid, native to north‐eastern Brazil, that flowers during two months of the rainy season. Patterns of floral thermogenesis, pollination biology, and floral traits associated with pollination syndromes were studied and compared with those of other Araceae. Two species of cyclocephaline scarabs (Scarabaeidae, Cyclocephalini) were recognized as effective pollinators: Cyclocephala celata and Cyclocephala cearae. Larvae of an unidentified species of fruit fly (Melanoloma spp., Richardiidae, Diptera) were also frequently observed in inflorescences at various maturation stages, feeding on the connectives of male florets and fruits, and thus lowering the reproductive success of individual plants. Beetles were attracted by odoriferous inflorescences in the early evening of the first day of anthesis, during the female phase. The emission of attractive volatiles was coupled with intense thermogenic activity in the entire spadix, unlike other aroids in which only certain zones of the spadix heat up. Pollen release, which marks the beginning of the male phase on the subsequent evening, was not related to floral thermogenesis. Comparative multivariate analysis of the floral traits of T. ulei points to a beetle‐pollinated aroid, although some of the observed traits of the species are not common to other taxa sharing this pollination strategy. Such incongruence might be explained by the evolutionary history of the tribe Spathicarpeae and potential pollinator shifts. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.