104 AROIDEANA, Vol. 36 Recent Observations and Cultivation of Pseudohydrosme gabunensis Engl. (Araceae) Wilbert Hetterscheid Von Gimborn Arboretum Velperengh 13 3941 BZ Doorn, The Netherlands hetter@xs4all.nl (*31)318418187 Josef Bogner Botanischer Garten & Botanische Staatssammlung Menzinger Strasse 63 D-80638 München, Germany ABSTRACT Pseudohydrosme (Engler, 1892) counts as one of the most spectacular genera of aroids. After its discovery and description by Engler no new data or observations were reported until the second author gathered new observations on P. gabunensis based on his 1973 visit to Gabon (Bogner, 1981). For the first time the leaf and tuber were observed and described as well as details of spathe and spadix. When Engler described the new genus he recognized two species, P. gabunensis and P. buettneri Engl. To this very day, the second species has never been found again, although it was reported to grow in the same general area as the first species. Subsequent visits to Gabon by botanists from the Wageningen University (Netherlands) yielded only material of P. gabunensis. It is the opinion of the first author that the type specimen of P. buettneri might well have been an aberrant individual of P. gabunensis (or even a fully misinterpreted Anchomanes inflorescence). The only differences reported between P. gabunensis and P. buettneri are the existence of staminodes on the upper part of the spadix of P. buettneri whereas these are lacking in P. Gabunensis, and the male flowers of P. gabunensis to consist of 2–5 fully free stamens and those of P. buettneri purportedly of only 2 united stamens. Unfortunately the type specimen of P. buettneri has been lost from the Berlin herbarium. There is little doubt that Pseudohydrosme is a very close ally of Anchomanes Schott, differing only by having bi(–tri)-locular ovaries instead of unilocular in Anchomanes. This is the type of difference that is not quite a convincing argument on which to separate genera, as recent phylogenetic studies in several Araceae genera has proven. A molecular phylogenetic analysis of Anchomanes + Pseudohydrosme should easily indicate whether Pseudohydrosme is nested within Anchomanes and should then be named as such, or whether it is its sister genus, in which case the generic name could be maintained. Recent molecular studies of the Araceae family indicate Aroideana arod-36-00-09.3d 2/4/13 12:59:24 104 Fruiting behaviour and morphology of Pseudohydrosme Engl. are presented for the first time. Also a unique way of vegetative propagation, hitherto unknown in any member of the Araceae family, is presented. Cultivation requirements of P. gabunensis Engl. are given. Additional morphological data of the species are presented. KEY WORDS Pseudohydrosme, Anchomanes, cultivation, fruiting, Gabon, Araceae, pollination, propagation. INTRODUCTION W. HETTERSCHEID, J. BOGNER, 2013 at least a sistergroup relationship between Pseudohydrosme and Anchomanes but in all cases only one species of either genus was included in the analyses (Cusimano et al., 2011; Nauheimer et al., 2012). The outcome as sister genera therefore is a given when both genera are very closely related. NEW OBSERVATIONS ON P. GABUNENSIS Since 1990 several botanists of the Wageningen University regularly observed and collected P. gabunensis in Gabon. On instructions of the first author, several living collections were made and cultivated by him in the former botanic gardens of Wageningen University. Several attempts were made to effectively pollinate plants for fruit set. This succeeded only twice. In 1996 an attempt was made that yielded some 20 fruits. The attempt was hardly succesful as only a very small percentage of the ovaries grew into fruits. Unfortunately, unaware of the sensitivity to desiccation, the few fruits were kept too dry and only 2 seedlings could be raised in the end. One of these seedlings was crossed with another plant in 2007 and this time success was complete. The observations presented here are based on that event. POLLINATING PSEUDOHYDROSME Since Pseudohydrosme is outcrossing (several self-pollination attempts by the first author failed miserably), one needs two simultaneously flowering specimens (Fig. 1) or one must conserve pollen from an earlier flowering specimen and use it to pollinate a later flowering one. From Mr. Berthold Suchy (Germany) we understand that he succesfully kept fresh pollen in a dry tube at 218uC for about 10 months and then pollinated another flowering plant, which yielded a few viable seeds (success would probably have been greater had the pollen been applied at exactly the optimal time of female flowering). Since it is quite an achievement for a human being to imitate a flying insect and crawl into a fully flowering Pseudohy- Aroideana arod-36-00-09.3d 2/4/13 12:59:25 105 drosme inflorescence with pollen attached to him(–her)self, it is better to (partly) remove the spathe of the specimen to be pollinated (Figs. 2 and 3). The specimen must be in female flowering phase (Fig. 2), which is noticed by a faint yet clear lettucelike scent. This scent may already be noticed when the spathe is not yet fully opened! The stigmas in this stage will be quite wet from a very sticky fluid (Fig. 2). The fluid disappears after one or two days and then the stigmas turn darker brown very quickly and desiccate (Fig. 4). In this phase, no pollination attempt will be succesful anymore. Pollen must be rubbed on the stigmas with a little force to ‘‘make it stick’’. Many stigmas need to be treated in order to have maximum effect, since after all, there is always a percentage of pistils that will not be effectively fertilized. After administering the pollen on the stigmas, the spadix must be covered by a pot, with a hole in the top. It turned out from earlier attempts that the quick drying of the stigmas must be slowed down by keeping a humid atmosphere around them after pollination. This is what effectively also happens in the wild, when after pollination the narrow chamber around the stigmas is cut off from the outer world by the caving in of the huge hood of the spathe, closing the chamber and keeping moisture in it. How long the hood and spathe base stay on in the wild before rotting off is unknown. The hole in the top of the pot serves to keep a little airflow possible in order to avoid fungi from developing on the wet stigmas, which may happen very quickly. If so, try to remove it as best as possible (or spray some sulphur containing powder on the infected parts). Also keep the whole experiment in a humid atmosphere and at a temperature of at least 20uC during all day. After some 4– 5 days, take off the pot. FRUIT DEVELOPMENT The peduncle of the developing infructescence may elongate slowly a bit but never dramatically (Fig. 5). Maybe this is an artefact in cultivation because in most 105 106 Fig. 1. Fig. 2. Fig. 3. Fig. 4. stigmas AROIDEANA, Vol. 36 Pseudohydrosme gabunensis at full flowering. Spadix: pistillate zone (spathe removed) during female anthesis. Stigmas wet. Spadix exposed at onset of male flowering. Spadix at onset of male flowering: pollen strains emerging from male flowers, already drying. Aroideana arod-36-00-09.3d 2/4/13 12:59:25 106 W. HETTERSCHEID, J. BOGNER, 2013 Fig. Fig. Fig. Fig. 5. 6. 7. 8. 107 Infructescence 3 months after pollination. Infructescence 5 months after pollination. First maturing berries, 7.5 months after pollination. Upper half of berries mature, 8.5 months after pollination. Aroideana arod-36-00-09.3d 2/4/13 12:59:32 107 108 aroids with sessile inflorescences, the peduncle stretches quite strongly after effective pollination in order to expose the colourful berries to their dispersal agent (quite often birds). The maturing of the fruits takes a very long time and may last up to 10 months. During this time, the developing fruits are white at first (Figs. 5 and 6) and very late in the process turn pinkish (Fig. 7), then finally dark violet purple (Figs. 7–11), identical as in fruiting Anchomanes difformis (Bl.) Engl. At first maturation proceeds very slowly (Fig. 5) but after several months an increase in fruit size indicates that pollination has been succesful (Fig. 6). A most surprising fact is that the fruits develop a short stalk (Figs. 9 and 12), a feature not known from e.g. Anchomanes species. In fact we are unaware of any similar situation in any of the other aroid genera. At the time the fruit skin starts to wrinkle, take the seeds out of the fruits and sow immediately. Use a generalized potting mixture and keep it moist at all times, not wet, and create a drainage layer in the bottom of the pot. Cover the seeds with ca. 1 cm soil. After three weeks the first seedlings may appear (Fig. 15). The slower ones may take up to 10 months to germinate, so do not throw away nongerminated seeds too early but never keep them dry. As Pseudohydrosme seeds have no endosperm to protect the embryo (Fig. 14), they will desiccate quickly. Seeds that have been lying around long without germination may sometimes be triggered to do so by refreshing the potting soil. AROIDEANA, Vol. 36 ally larger than the previous. As of the second leaf the typical development of holes in the lamina may start (Fig. 17) and finally the laminas will have their typical umbrella shape with numerous leaflets. These resemble quite closely those of Anchomanes, including the development of two tips in many of the leaflets. Keep the plants always in moist soil (but never soaked) since the species orginates from wet shady forests. Add nutrients while watering regularly. After a while the plants will start a rhythm of developing only one leaf at the time, after the previous one has disappeared. A short ‘‘resting period’’ may start after the older leaf has died down. Refresh the potting soil every 1–2 years preferably after the old leaf has died down. When fully mature, an inflorescence may develop but never alongside a leaf. Otherwise the cultivation of P. gabunensis is not problematical and identical to cultivating Anchomanes difformis, also a species from similar wet forests (in cultivation often erroneously named A. giganteus, a species otherwise unknown in cultivation). In fact, both P. gabunensis and A. difformis are found to grow side-by-side in the forests near Libreville in Gabon. Also the rare Anchomanes nigritianus Rendle occurs in the general area. In the Munich Botanical Garden (Germany) first flowering was achieved only five years after sowing fresh seeds (April 2012). VEGETATIVE PROPAGATION After germination, a broadly arrowshaped first leaf will appear (identical to the situation in Anchomanes) (Figs. 15– 17). The young rhizome will develop quickly and the old seed remains attached to it for quite a while (Fig. 18). In a period of several months to 2 years, the seedlings will develop new leaves without a marked resting period, each consecutive leaf usu- The first author was surprised to find that in several occasions semi-mature and mature plants develop new plants quite distant from the main rhizome. Upon investigation it turned out that sometimes the large, fleshy, long-lived roots (Fig. 19) start to grow upwards in the soil and develop stem-like tissue from which a leaf emerges. Along the last few centimeters of the root, even thin cataphylls are developed (Fig. 21), proving that the root changes into a different organ before it develops a fully new rhizome at the tip. This then turns into a new plant which can Aroideana arod-36-00-09.3d 2/4/13 12:59:38 108 FURTHER CULTIVATION W. HETTERSCHEID, J. BOGNER, 2013 Fig. Fig. Fig. Fig. 109 9. Detail of maturing infructescence showing stipitate berries. 10. Fully matured infructescence, ca. 10 months after pollination. 11. Infructescence detail showing fully mature berries. 12. Mature stipitate, two-seeded berry. Aroideana arod-36-00-09.3d 2/4/13 12:59:38 109 110 Fig. 13. AROIDEANA, Vol. 36 Seed. Fig. 14. Seed cut in half, showing huge embryo without endosperm. be grown independently from the mother plant although the connecting root may last more than a year. This is vegetative propagation unknown to any aroid to our knowledge. It has also never been observed in the long cultivation history of Anchomanes species. Beside this extraordinary way, vegetative buds are also developed directly on the rhizome (Fig. 20), These usually do not develop into new plants unless they are artificially separated. This can be done when such buds are still present on the oldest part of the rhizome. On that part, they are usually large enough to be cut off. Seal the scar with a fungicide before potting. A new plant may develop from it but there is never a 100% chance. Aroideana arod-36-00-09.3d 2/4/13 12:59:46 110 W. HETTERSCHEID, J. BOGNER, 2013 Fig. 15. 111 Seedlings just after germination. EMENDED DESCRIPTION OF P. GABUNENSIS Because of the new observations presented above, the description of P. gabunensis, as presented by Bogner (1981), can now be expanded with the following observations: Rhizome elongate cylindrical (Fig. 19) or short, thick and tuber-like, with short broad internodes, sometimes growing nearly vertical in the soil, sometimes more obliquely, to ca. 15 cm long; lateral roots sometimes developing new plants at their tips Aroideana arod-36-00-09.3d 2/4/13 12:59:47 (Fig. 21). Seedling leaves broadly sagittate, ca. 5 cm long, ca. 3–4 cm in diam. (Figs. 15– 17). Fruiting peduncle slightly longer than during flowering, 6–7 cm long, 1–1.3 cm in diam. (Fig. 5); mature fruiting part (Figs. 8– 11) cylindric, 15–20 cm long, 4.5–5 cm in diam., fruits crowded, later slightly more distant; fruits somewhat succulent berries (Figs. 9, 11, 12), these stipitate (Figs. 9 and 12), stipe (2–)3–4 mm long, ca. 2 mm in diam.; berries broadly ovate (Figs. 11 and 12) or globose, laterally compressed when 2-seeded, ripening from white to violet to dark reddish purple (Figs. 6, 8, 10), 111 112 AROIDEANA, Vol. 36 Fig. 16. First leaf of seedling. Fig. 17. Second seedling leaf showing first fissures in lamina. Aroideana arod-36-00-09.3d 2/4/13 12:59:47 112 W. HETTERSCHEID, J. BOGNER, 2013 Fig. Fig. Fig. Fig. 18. 19. 20. 21. Seedling rhizome with berry still attached, 3 months after germination. Mature rhizome, showing long lasting, fleshy roots. Mature rhizome, detail of surface showing short, elongate offsets. Rhizomatous root, transforming into a new tuberous rhizome at the top (left). 0.8–1.2 cm long, 1.5 1.6 cm wide, style and stigma remaining, 1–2-seeded, pericarp thin and surface somewhat rugose. Seeds (Figs. 13 and 14) without endosperm, subglobose to broadly ovate, one side convex, the other slightly flattened, to 9 mm long and 7 mm in diam., testa (seed coat) very thin, whitish, smooth and papery, with the green embryo shining through, raphe distinct, hilum and micropyle with a light purplish tinge, plumule as a small knob visible also from outside of the seed (if the thin testa removed, it appears transparent); embryo with outer cell layers green (with chlorophyll) and inside white, plumule already with very small leaf primordia and light green. A new biogeographic record, is that P. gabunensis has now also been found in western Congo (teste photographs by R. Becker and a specimen deposited by him in WAG and identified by the first author). Aroideana arod-36-00-09.3d 2/4/13 12:59:48 View publication stats 113 LITERATURE CITED Bogner, J. 1981. Pseudohydrosme gabunensis Engl. Aroideana 4(1): 31–37. Cusimano, N., J. Bogner, S. J. Mayo, P. C. Boyce, S. Y. Wong, M. Hesse, W. L. A. Hetterscheid, R. C. Keating & J. C. French. 2011. Relationships within the Araceae: comparison of morphological patterns with molecular phylogenies. Am. J. Bot. 98(4): 1–15. Engler, A. 1892. Araceae Africanae I. Bot. Jahrb. 15: 447–466. Engler, A. 1911. Pseudohydrosme. In: A. Engler (ed.), Das Pflanzenreich, IV 23 C (Araceae-Lasioideae): 47–49. Leipzig. Nauheimer, L., D. Metzler & S. S. Renner. 2012. Global history of the ancient monocot family Araceae inferred with models accounting for past continental positions and previous ranges based on fossils. New Phytologist 195(4): 938–950. 113