A torch in the rain forest: thermogenesis of the Titan arum (Amorphophallus titanum)

An outstanding flagship species in the plant kingdom is the Titan arum ( Amorphophallus titanum ), which produces a fountain-like bloom up to 3 m high. The unique appearance of three simultaneous inflorescences in May 2006 was a chance to analyse the flowering behaviour and thermogenesis of this giant. For the first time, the heating of the central column (spadix) could be documented using a high-performance thermographic camera. Time series analyses of the infrared image sequences revealed that the 3-m high spadix surface heats up in pulses emanating from the base of the inflorescence. The surface temperature reaches over 36 °C, compared to the ambient temperature of 27 °C. Waves of the carrion-like odour are synchronised with these heat pulses. The combination of heat pulses, the fountain-like shape plus the enormous size lead to a unique type of 'convection flower'. On the basis of our observations, we assume that Amorphophallus titanum is able to overcome thermodynamic decoupling by a self-produced convective process.     

Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA

Familial, subfamilial, and tribal monophyly and relationships of aroids and duckweeds were assessed by parsimony and Bayesian phylogenetic analyses of five regions of coding (rbcL, matK) and noncoding plastid DNA (partial trnK intron, trnL intron, trnL-trnF spacer) for exemplars of nearly all aroid and duckweed genera. Our analyses confirm the position of Lemna and its allies (formerly Lemnaceae) within Araceae as the well-supported sister group of all aroids except Gymnostachydoideae and Orontioideae. The last two subfamilies form the sister clade of the rest of the family. Monophyly of subfamilies Orontioideae, Pothoideae, Monsteroideae, and Lasioideae is supported, but Aroideae are paraphyletic if Calla is maintained in its own subfamily (Calloideae). Our results suggest expansion of the recently proposed subfamily Zamioculcadoideae (Zamioculcas, Gonatopus) to include Stylochaeton and identify problems in the current delimitation of tribes Anadendreae, Heteropsideae, and Monstereae (Monsteroideae), Caladieae/Zomicarpeae, and Colocasieae (Aroideae). Canalization of traits of the spathe and spadix considered typical of Araceae evolved after the split of Gymnostachydoideae, Orontioideae, and Lemnoideae. An association with aquatic habitats is a plesiomorphic attribute in Araceae, occurring in the helophytic Orontioideae and free-floating Lemnoideae, but evolving independently in various derived aroid lineages including free-floating Pistia (Aroideae).     

Respiration of thermogenic inflorescences of Philodendron melinonii: natural pattern and responses to experimental temperatures

The patterns of temperature and respiratory changes in the protogynousinflorescences of Philodendron melinonii (Araceae) were studiedin the field in French Guiana. These are the first respiratorymeasurements from a member of the large subgenus Philodendron,a group previously thought to lack thermoregulatory inflorescences,in contrast to thermoregulatory Philodendron species of thesubgenus Meconostigma. Heating by the male and sterile maleflorets was strong on the first evening of anthesis when beetlesare attracted and the female florets are receptive. Heat productionof the inflorescence peaked at 0.9 W and spadix temperaturereached 39.5 °C, a level somewhat independent of ambienttemperature. Thermogenesis continued throughout the night andthe next day, but at a lower level, and floral temperaturesfell. On the second evening, when pollen was shed, there wasa small elevation in respiration and spadix temperature. Responsesof cut spadix sections to experimental step changes in ambienttemperature resulted in a prompt response in floral temperatureand respiration rate in the direction of the change and thena much slower regulatory adjustment in the opposite direction.These responses are consistent with an immediate van 't Hoffeffect, followed by up- or down-regulation of thermogenesis.However, the responses required several hours. It is concludedthat the male floret tissues possess the same thermoregulatorymechanism of more precise thermoregulatory species, but a combinationof small spadix size (that favours heat loss), moderate thermogeniccapacity (that limits heating rate), and slow reaction time(that causes long lags between temperature change and the regulatoryresponse) result in poor thermoregulatory performance duringthe second day. Key words: Arum lily, heat production, inflorescence, Philodendron, protogynous, regulation, respiration, thermogenesis, van 't Hoff effect Received 29 December 2007; Revised 23 January 2008 Accepted 24 January 2008     

Ubiquitous expression of a gene encoding for uncoupling protein isolated from the thermogenic inflorescence of the dead horse arum Helicodiceros muscivorus

Uncoupling proteins (UCPs) are a family of mitochondrial inner membrane proteins that have been implicated in heat production in mammalian cells. The inflorescences of several members of the arum lily family (Araceae) have also been shown to produce heat during flowering, but the involvement of UCP-mediated heat production in plants is not known. In this work a gene has been isolated termed HmUCPa that encodes for a putative uncoupling protein from Helicodiceros muscivorus, a highly thermogenic arum lily. RT-PCR analysis revealed that the expression of HmUCPa was ubiquitously found, both in thermogenic male florets and appendix, and the non-thermogenic female florets, spathe and club-shaped organs of the spadix. These results suggest that HmUCPa is not primarily involved in organ-specific heat production in H. muscivorus.     

Building simulation model of infant-incubator system with decoupling predictive controller

This paper introduces theoretical modelling working on the thermal behavior of the premature infant. This study aims at developing a model useful for the prediction and design of the appropriate controller in objective to reduce evaporative heat loss. A calculation code has been developed to simulate the thermal response of a premature baby to climatic solicitation inside the incubator system. The model allows us to take into consideration radiative, conductive, convective, and evaporative heat transfers inside the incubator system. The air temperature and the humidity rate, which play a salient part in the convective and evaporative exchanges, are calculated by a coupled transfer function. At present, the environmental conditions (temperature and humidity) inside incubator are controlled with a classical Proportional Integral Differential (PID). In this work, we proposed a decoupling Generalized Predictive Controller (DGPC) based on the model described below to achieve an optimal thermal conditions (36.5–37.5) for immature newborn infants (birthweight <1000 grams). Real and simulations results prove the feasibility and effectiveness of the proposed model and controller.     

THE EVOLUTION OF POLLINATOR–PLANT INTERACTION TYPES IN THE ARACEAE

Most plant–pollinator interactions are mutualistic, involving rewards provided by flowers or inflorescences to pollinators. Antagonistic plant–pollinator interactions, in which flowers offer no rewards, are rare and concentrated in a few families including Araceae. In the latter, they involve trapping of pollinators, which are released loaded with pollen but unrewarded. To understand the evolution of such systems, we compiled data on the pollinators and types of interactions, and coded 21 characters, including interaction type, pollinator order, and 19 floral traits. A phylogenetic framework comes from a matrix of plastid and new nuclear DNA sequences for 135 species from 119 genera (5342 nucleotides). The ancestral pollination interaction in Araceae was reconstructed as probably rewarding albeit with low confidence because information is available for only 56 of the 120–130 genera. Bayesian stochastic trait mapping showed that spadix zonation, presence of an appendix, and flower sexuality were correlated with pollination interaction type. In the Araceae, having unisexual flowers appears to have provided the morphological precondition for the evolution of traps. Compared with the frequency of shifts between deceptive and rewarding pollination systems in orchids, our results indicate less lability in the Araceae, probably because of morphologically and sexually more specialized inflorescences.     

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, ??, ??–??.     

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.     

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.     

Convective and radiative heat transfer coefficients for individual human body segments

 Human thermal physiological and comfort models will soon be able to simulate both transient and spatial inhomogeneities in the thermal environment. With this increasing detail comes the need for anatomically specific convective and radiative heat transfer coefficients for the human body. The present study used an articulated thermal manikin with 16 body segments (head, chest, back, upper arms, forearms, hands, pelvis, upper legs, lower legs, feet) to generate radiative heat transfer coefficients as well as natural- and forced-mode convective coefficients. The tests were conducted across a range of wind speeds from still air to 5.0 m/s, representing atmospheric conditions typical of both indoors and outdoors. Both standing and seated postures were investigated, as were eight different wind azimuth angles. The radiative heat transfer coefficient measured for the whole-body was 4.5 W/m² per K for both the seated and standing cases, closely matching the generally accepted whole-body value of 4.7 W/m² per K. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.4 and 3.3 W/m² per K when standing and seated respectively. In the forced convective regime, heat transfer coefficients were higher for hands, feet and peripheral limbs compared to the central torso region. Wind direction had little effect on convective heat transfers from individual body segments. A general-purpose forced convection equation suitable for application to both seated and standing postures indoors was h _c=10.3v ^0.6 for the whole-body. Similar equations were generated for individual body segments in both seated and standing postures. Received: 21 May 1996/Accepted: 27 November 1996     

Mechanism of heat transfer in different regions of human body

The processes of heat transfer in a human body were studied with the use of a mathematical model. It has been shown that only conductive or only convective heat transfer may occur in different body areas. The rate of blood-mediated heat transfer in the presence of blood circulation is many times higher than heat transfer due to temperature gradient; therefore, the convective process prevails over the conductive process. The body core contains a variety of blood vessels, and the bulk of blood concentrates there in the norm. Hence, heat transfer in it is mainly convective. In surface tissues, where the rate of blood circulation is lower and the vasculature has certain specific features, heat transfer is mainly conductive. Hence, the core and surface tissues are absolutely different body zones in terms of heat transfer.     

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     

Modelling of pyrolysis of large wood particles

A fully transient mathematical model has been developed to describe the pyrolysis of large biomass particles. The kinetic model consists of both primary and secondary reactions. The heat transfer model includes conductive and internal convection within the particle and convective and radiative heat transfer between the external surface and the bulk. An implicit Finite Volume Method (FVM) with Tridiagonal Matrix Algorithm (TDMA) is employed to solve the energy conservation equation. Experimental investigations are carried out for wood fines and large wood cylinder and sphere in an electrically heated furnace under inert atmosphere. The model predictions for temperature and mass loss histories are in excellent agreement with experimental results. The effect of internal convection and particle shrinkage on pyrolysis behaviour is investigated and found to be significant. Finally, simulation studies are carried out to analyze the effect of bulk temperature and particle size on total pyrolysis time and the final yield of char.     

Pollination mutualism between a new species of the genus Colocasiomyia de Meijere (Diptera: Drosophilidae) and Steudnera colocasiifolia (Araceae) in Yunnan, China

A new species of the genus Colocasiomyia de Meijere (Diptera: Drosophilidae) was discovered from inflorescences of Steudnera colocasiifolia K. Koch (Araceae) in Yunnan, China. The new species is described as Colocasiomyia steudnerae Takenaka and Toda, sp. nov., and we investigated the reproductive ecology of both the fly and the plant species. This fly species reproduces in the inflorescences/infructescences of the plant, and depends almost throughout its entire life cycle on the host plant. The fly species is the most abundant flower visitor for S. colocasiifolia and behaves intimately with the flowering events, suggesting that it is the unique and most efficient pollinator for the host plant. Bagging (insect‐exclusion) treatment of inflorescences resulted in no fruits. These findings strongly suggest that intimate pollination mutualism has evolved between the fly and the host plant, as are known in other Colocasiomyia flies and Araceae plants. One notable feature of this system is that the new species almost monopolizes the host‐plant inflorescence as a visitor, without any cohabiting Colocasiomyia species. In comparison to other cases where two Colocasiomyia species share the same inflorescence and infructescence of Araceae host plants for reproduction by separating their breeding niches microallopatrically between the staminate (upper male‐flower) and the pistillate (lower female‐flower) regions on the spadix, C. steudnerae exhibits a mixture of stamenicolous and pistillicolous breeding habits.     

Thermoregulation during flight: body temperature and sensible heat transfer in free-ranging Brazilian free-tailed bats (Tadarida brasiliensis)

Bat wings are important for thermoregulation, but their role in heat balance during flight is largely unknown. More than 80% of the energy consumed during flight generates heat as a by-product, and thus it is expected that bat wings should dissipate large amounts of heat to prevent hyperthermia. We measured rectal (T(r)) and surface (T(s)) temperatures of Brazilian free-tailed bats (Tadarida brasiliensis) as they emerged from and returned to their daytime roosts and calculated sensible heat transfer for different body regions (head, body, wings, and tail membrane). Bats' T(r) decreased from 36.8°C during emergence flights to 34.4°C during returns, and T(s) scaled positively with ambient temperature (T(a)). Total radiative heat loss from bats was significantly greater for a radiative sink to the night sky than for a sink with temperature equal to T(a). We found that free-ranging Brazilian free-tailed bats, on average, do not dissipate heat from their wings by convection but instead dissipate radiative heat (L) to the cloudless night sky during flight ([Formula: see text] W). However, within the range of T(a) measured in this study, T. brasiliensis experienced net heat loss between evening emergence and return flights. Regional hypothermia reduces heat loss from wings that are exposed to potentially high convective fluxes. Additional research is needed to establish the role of wings in evaporative cooling during flight in bats.     

Temperature-triggered periodical thermogenic oscillations in skunk cabbage (Symplocarpus foetidus)

The natural occurrence of temperature-triggered and light-independent thermogenic oscillation in the spadix of skunk cabbage, Symplocarpus foetidus, was discovered. The identified thermogenic oscillator had an accurate periodical cycle (ca. 60 min per cycle) that apparently responded to an increase or decrease in the spadix temperature with a threshold of less than 0.9 degrees C. Neither a constant ambient air temperature nor transient changes in the ambient air temperature within 10 min (19 degrees C --> 15 degrees C --> 19 degrees C) induced the temperature oscillation in the spadix. Moreover, the periodical cycles were independent of the weight of the spadix (2.5-9.2 g) and the amplitudes of the temperature oscillations were correlated with the magnitude of the changes in the spadix temperatures. These results imply that periodical temperature oscillations in the spadix of S. foetidus possess a quantitative regulatory process that involves a temperature sensation and subsequent heat production. Based on these results, we propose a time-dependent thermogenic oscillatory model that acts as a precise thermal regulator under dynamic environmental temperature changes.     

Reasons and consequences of the lack of a sporopollenin ektexine in Aroideae (Araceae)

The ultrastructure of pollen walls in Araceae is characterized by the absence of a stable sporopollenin outer exine layer in subfamily Aroideae, and by the presence of several distinctive pollen characters typical for the other aroid subfamilies. This article discusses if and to which extent such distinctive pollen characters are mirrored in various classifications of Araceae, basing either on morphological or on molecular data. Accordingly, the pollen characters perfectly reflect the actual subfamily classification, and also recent arrangements of clades in trees basing on molecular data. The actual subfamilies appear no longer eurypalynous, but now strictly stenopalynous. Aside from the (settled) classification problem the fundamental question is addressed why do Aroideae lack an elaborated sporopollenin ektexine. Possible pollination biology benefits, deriving from an absence of an elaborated sporopollenin ektexine in Aroideae, are presented and discussed. Compared with all other subfamilies the most advanced and by far largest subfamily Aroideae has lost several crucial characters and simultaneously acquired corresponding opposed characters, amongst others a non-sporopollenin exine layer and an unusual thick and spongy endexine. Taken together, losses and acquisitions are interpreted as a major paradigm shift in Araceae evolution, which took place according to the fossil record probably in the Paleogene.     

Temperature regulation in adult quail (Colinus virginianus) during acute thermal stress

1. Evaporative heat loss, O2 consumption, CO2 production, and internal body temperature were measured in unanesthetized, unrestrained bobwhite (Colinus virginianus) at specific ambient temperatures (Ta). 2. No significant change in body temperature occurred at any Ta tested, but metabolic heat production (H) increased from 42.17 W/m2 at Ta 35 degrees C to 102.89 W/m2 at Ta 10 degrees C. 3. Evaporative heat loss (E) increased approximately two-fold from Ta 10-35 degrees C, with E/H increasing exponentially over the same temperature range. 4. No significant change in thermal insulation occurred from Ta 10-30 degrees C. 5. Combined convective and radiative heat transfer for the bobwhite was 2.96 W/m2 X C from Ta 10-35 degrees C.     

Switching off the heater: influence of ambient temperature on thermoregulation by eastern skunk cabbage Symplocarpus foetidus

The protogynous inflorescences of eastern skunk cabbage, Symplocarpus foetidus, are thermogenic and regulate spadix temperature (Ts) well above ambient temperature (Ta). Continuous records of oxygen consumption, carbon dioxide production, and temperatures of plants were made at a field site in Canada. At Ta between 3-24C, Ts ranged between 16-26C, and the warmest inflorescences were those in the receptive female or early pollen-bearing stages. Respiratory rates of the 2-g spadices increased with declining Ta, and reached a maximum of 0.54 mol O2s^-1 (0.73 ml min^-1), equivalent to 0.26 W of heat production. At Ta below 3°C, several inflorescences failed to maintain high Ts and abruptly switched Ts to near freezing. Some froze when Ta dropped to about -10°C. Those that did not freeze could quickly switch to the warm state if Ta rose above about 3°C. Switching was related to the balance between heat production and heat loss that tended to produce stable equilibria at either high or low Ts. Switching between warm and cool states resulted in a bimodal distribution of Ts in the field. A respiratory quotient of 1.0 showed that carbohydrate was the substrate for thermogenesis, and bomb calorimetry of florets confirmed that energy was imported from the root. Only 11 invertebrates, including only one flying insect, were found in 195 inflorescences, suggesting that heat production and temperature regulation are not closely associated with cross-pollination.     

Pattern of respiration by intact inflorescences of the thermogenic arum lily Philodendron selloum

Inflorescences of the neotropical arum lily, Philodendron selloum, are strongly thermogenic for 2 d during anthesis. Continuous measurements of spadix temperature (Ts) and rate of oxygen consumption (VO2) were made outdoors in whole inflorescences attached to the plants. Some inflorescences were exposed to uncontrolled ambient temperature (Ta) while others were enclosed in clear water-jackets that produced nearly constant ambient conditions. A repeatable, diphasic pattern of heat production appeared, most clearly in water-jacketed inflorescences, and it comprised a short peak phase at sunset followed by a plateau phase that lasted until the following sunset. Regulation of Ta occurred in both phases, but at different levels. Peak phase Ta was regulated in the region of 38-42C, but plateau phase Ta was usually in the range of 25-36C. Both VO2 and total heat produced throughout anthesis increased at lower Ta. The data imply that the short peak phase is related to the enhancement of odour production that attracts a single species of large scarabaeid beetle in its native Brazil, and regulation of maximum Ta may prevent overheating. Thermoregulation in the long plateau phase produces equable temperatures inside the inflorescence that may facilitate the resident beetles' activities as a direct energetic reward.