Temperature Relationships of Flowers

IS RAFFLESIA А ПIERМOGENIC FLOWER? BACKGROUND The aim of this study was to compare the temperature relationships of flowers that grow in the understorey of the rain forest with flowers that grow in sites exposed to high solar radiation such as Ьeaches and disturbed areas. In the understorey of the rain forest, the environmental conditions are fairly constant, with low wind velocity, small variation in the air temperature from day to night, high relative humidity, low light intensity, and low net incoming radiation. In а recent study (Patino & Grace in preparation ) it was found that Rhizanthes lowi (Rafflesiaceae) а flower that grows in the understorey of the rain forest in Brunei, is а thermogenic shows flower signs that of thermoregulation (Figure 1). Thermogenic Figure 1. Rhizanthes lowi (Rafjlesiaceae), а parasiticc plant on the roots of Tetrastigma sp. flowers are usually entomophilous i.e. flowers whose pollen is conveyed from the anther to the stigma Ьу the agency of insects. The thermogenesis in flowers has Ьееn related to the emission of volatile compounds that anract insect pollinators. In cold environments. the thermogenesis in flowers seems to result in а direct reward to the pollinators Rajfiesia sps. and Rhizanthes sps. are entomophily flowers. Their pollination depends on the anraction of carrion flies. These flowers have Ьееп characterized for the production of а strong odour which attract carrion flies as their natural pollinators. The thermogenesis in Rhizanthes sps. flowers seems to be directly associated with the pollination process. The flower mimics a wound on the skin of a hairy mammal, a perfect place to deposit the eggs and find food (Banziger 1996). Thermogenesis may help to release the volatile compounds that produce the attractant smell. To date, the nature and chemical composition of the smell has not been investigated in these species. As the genus Rafflesia and Rhizanthes belong to the same family (Rafflesiaceae) and are both parasitic on the roots of Tetrastigma sps. vines, do not have stems, leaves, or any photosynthetic organ, and are sympatric species in the South East Asia rain forest we wanted to investigate if Rafflesia flowers are thermogenic as Rhizanthes flowers are. On the other hand, flowers that grow exposed to high solar radiation may have mechanisms to prevent overheating and present different strategies to attract their pollinators. To test this hypothesis, flowers from the Con volvulaceae chosen - (Ipomoea family were pes-caprae, Merremia borneensis and Ipomoea aquatica) These particular species were chosen because they were Figure 2. Jpomoeapes-caprae growing in Berakas beach, Brunei. some of the most predominant species in Brunei. These species are both entomophilous and have very bright and conspicuous flowers. L pes-caprue generally grows on beaches and sandy areas (Figure 2). M. borneensis is a good climber and grows in disturbed areas, along many roads in the countryside and on trees at the edge of the forest (Figure 3). L aquatica grows in swamps, dikes and flooded areas which are exposed to high solar radiation (Figure 4). Figure 3. Figure 4. Alerremia Ijorneensis growing at the edge of the forest in Brunei. Jpoinoea aqua/lea growing in a swamp in Brunei, This 9-month expedition to Borneo was a very rich experience in terms of my research work and my own personal experience. I travelled several times from Brunei to Sarawak and Sabah (Figure 5) and I was able to interact with the local people and get a glimpse of the culture. I learned enough of the language (Malay) to be able to communicate with the local people in Brunei and Malaysia. I also learned a little of the Iban dialect and gained much more my from walks with the park staff in the forest looking for Rafflesia buds and flowers and the social events at the long house in Batan Dun (Temburong, Brunei). Overall, it a was a very successful trip I studied 5 flowers of Rafflesia tuan-mudue in natural conditions and was able to find many sites on different beaches and disturbed areas in Brunei and Sarawak to perform my experiments and measurements on Jpomoea pes-caprae and Merretnia borneensis. During my first trip to Taman Negara Gunung Gading, Lundu, Sarawak from the 11th to the 31st of July 1998 I studied one male flower in bloom and three semimature buds of Rafflesia tuan-rnudae. I carried out experiments on the temperature of the flower and simultaneously collected the volatile compounds from the headspace of the flower (a more detailed account of the experiments and measurements is presented in Appendix I). In my second trip to Gunung Gading from the 18th September to the 13th October, I studied three female flowers. In November, I travelled to Kinabalu National Park to meet Dr. Jamili Nais, who studies Rafflesia sps. in Sabah. On this trip we could not find any Rafflesia in bloom. On my third trip to Gunung Gading from the 13th to 17th January 1999 1 studied one male flower. During this trip the Borneo Post, a Newspaper from Sarawak (a copy of the article is presented in the Appendix II), interviewed me. MAP I MAJOR GEOGRAPHICAL FEATURES OF BORNEO rrz. FigureS Map of Boineo Details Brunei (upright) and Kuching, Sarawak (left down). RESULTS The results presented in this report are only a superficial illustration of my research, as analysis is still underway. Rafflesia tuan rnudae 1- The temperature of different parts of the flower were usually higher than the temperature of the air, predominantly during afternoon hours. Figure 6a shows a typical diel course of temperature for one of the flowers in July 1998. There was 6 B 10 2 4 6 lB 20 22 24 2 4 6 Figure 6. Ajr --Bud surface 26 £ Wipadous 25 — Inside disk Ipiside prae,sI :4 2-4 4 2-0 1-6 a Diel part ems of excess temperature for different parts of the flower (b). The horizontal line indicates the time of the head space extraction. 21 & B Diel temperature course for R. Wan mudae on the 24th of July 1998 (a). bait - (-2 eSS 01 I 04 0-0 424 6 B 30 2 14 6 IS 22 22 34 2 Wipaduas I pistde alisL ps2idn pruessu 4 1 ianaIth’ — Held ce not a significant difference between the temperature of external and internal parts (Figure 6a). The maximum excess temperature (the difference of temperature between the air and any part of the flower) was 2.8°C for the window (Figure 6b, 6c). There seems to be a difference in the excess temperature pattern for internal and external parts since the pattern of the external parts are more related with the net radiation. The temperature of internal parts seems to be more independent of the net radiation. 2- From the R. Wan mudae headspace there have been five volatile compounds identify so far; Dimethyl disulfide, 1 ,2-diethylbenzene, 1 ,3-diethylbenzene, 1,4diethylbenzene, 2-ethyl-1-hexanol. Further analysis of the samples is necessary to complete the identification and classification of the volatiles that compound the odour. Figure 6 shows the periods of head space collection. Figure 8. Flowers of Merremia borneensis showing similar orientation and inclination angles. Exposed Flowers 1- Flowers show solar tracking (Figure 8). Measurements of orientation and inclination of I. pes-caprae and M. borneensis during different time of the year December 1997 and 1998 S August 1998 E N N w Figure 9. Polar plot of the orientation and inclination angles oflpomoeapes-caprae. At the end of the year (Winter in the northern hemisphere) the flowers seems to face south (left plot). In August (Summer in the Northern hemisphere the flowers seem to face towards north (right show that flowers change position depending on the seasonal solar position, (Figure 9). 2- Petals play the role of umbrellas to shade the gynoecium during morning hours. 3- After petal collapse, the sepals become the organ controlling the temperature of the gynoecium. CONCLUSIONS It is still early to give conclusions of my results since I do not have all the data analysis ready. I could comment about some points of my overall research. The temperature of some parts of R. tuan-mudae flowers i.e. column, disk, window, were always higher than the air temperature. That could indicate some degree of thermogenesis. During my trip to Sabah in search of Rafflesia, I learned from Dr. Jamili Nais that the population had dramatically diminisheed during the last year. Most of the buds died and there were not many blooms presumably because of El Niflo drought in 1997. This was the case in Brunei for Rhizanthes lowi. There were non flowers in bloom during the whole of 1998 and all the buds died, the survival of Rhizanthes lowi in Brunei is in doubt. There is not much known about the biology of these species and if El Nifto was the real cause of the diminishing population. I hope this research will give some insight into the eco-physiology. I hope to be able to publish the work about these two species and encourage the conservation and protection of the habitat. Appendix I METHODS. Rafflesia flowers The internal and surface temperature was continuously monitored in different parts of the flowers: centre of the disk (Ta), disk (Td), process (Tp), petal surface (T5), diaphragm surface (Tds) air inside diaphragm (Tha), anther (male) (Tat), stigma (female) (T), and bud surface (Tbs). Microclimate variables (Air temperature, (Ta), relative humidity (RH), wind velocity, net radiation, R0, photosynthetically active radiation (PAR) were measured near the flowers. All the measurements were carry out for several days starting on the day of blooming until the flower decayed (5 to 7 days). On the same flowers the head space technique was used to extract the volatile Figure 9. Exuaction of the volatiles emitted by Raffiesia man mudae using the head space method. compounds emitted by the flowers during the blooming period (Figure 9). The headspace was sampled for periods of three hours during the day and for 10-12 hrs during the night every two nights. The samples were analyzed on a Hewlett Packard (HP) 5890 gas chromatograph (CG-MS). Exposed flowers. Flowers of Merremia borneensis were studied in natural conditions in an open sandy area located at the University of Rrunei Darussalam campus. Flowers of Ipomoea pes-caprae were studied on four different beaches in Brunei and Sarawak. Temperature and microclimate. Several aspects of microclimate affecting flower temperature were studied for I. pes-caprae in August and September 1998 and M. borneensis during January 1999. Temperature of the gynoecium, corolla, and sepals were recorded on four flowers simultaneously. In two of the flowers, the sepals and the corolla were covered with silicone grease to prevent evaporation, whilst the other two were controls. After the corolla folded naturally between 12:00 and 13:00, it was excised and the thermocouples were re-located on the surface of the sepals. The microclimate variables, air temperature, relative humidity, wind velocity, net radiation, PAR, were measured in the same way as dçscribed above for Rafflesia tuan inudae. Inclination and orientation of the flowers were recorded for each experiment. Additional measurements were performed for flowers growing in different locations different times of year in Brunei and Sarawak. Sequences of flower photographs were taking to determine the floral area that is presented for interception of solar radiation