Musa gracilis is the only wild banana species in Johore, Malaysia. In Kelantan and Trengganu it grows together with M. acuminata Colla. M. gracilis and M. violascens Ridley (in section Callimusa) are compared. Both are endemic to Peninsular Malaysia but their geographic distribution does not overlap. The anatomy of the seed of M. gracilis is described and the function of the chalazal mass is discussed. Growth (increase in stem height and rate of leaf production), its ecology and conservation status are also mentione

Kiew, Ruth

Universiti Putra Malaysia Institutional Repository

f;~\. ~. MalaysianHeritage &: Scienti!ic Expedition: Endau-Rompin' ... T11f4J Malayan Nature Journal 198t4I: 239-248.87 264PEHERBITAN IIrQAWII-'£;AWAIUNIVERSITI PEftTANIAN MALAYSIANotes on the Natural History of the Johore Banana, Musa gracilisHolttumRUTH KIEWIAbstract: Musa gracilis is the only wild banana species in Johore, Malaysia. In Kelantanand Trengganu it grows together with M. acuminata Colla.M. gracilis and M. violascensRidley (in section Callimusa) are compared. Both are endemic to Peninsular Malaysiabut their geographic distribution does not overlap. The anatomy of the seed ofM. gracilisis described and the function of the chalaza! mass is discussed. Growth (increase in stemheight and rate of leaf production), its ecology and conservation status are alsomentioned.INTRODUCTIONSimmonds (1955) recognised onIy three wild species of banana in PeninsularMalaysia, namely Musa acuminata, M. gracilis and M. violascens. Musaacuminata (for which he recognised several forms) is the tallest (it maygrow up to 3 m or more) and its inflorescence is similar to that of thecultivated banana in being pendant and having brownish-red bracts. It ispollinated by bats, The other two species, M. gracilis and M. violascens,have erect inflorescences with polished bracts and the latter is pollinatedby birds (Holttum, 1969). These two species, which are included in SectionCallimusa, have similar barrel-shaped seeds (Fig. lA), as compared with thesubglobose , angular ones of M. acuminata, which belongs to Section Eumusa.Musa gracilis is the shortest banana in Peninsular Malaysia. Somestems produce an inflorescence on reaching about a metre tall, but morefrequently the stem is between 120-130 cm tall, although a few stemscan grow up to 194 cm_ It is distinguished from M. violascens by thecharacters shown in Table 1.There is some variation in the colour of the bract in M. gracilis. TheUlu Endau, Johore, population is uniform in all plants possessing almostcompletely white bracts (except for the green tip). However, populationsin Trengganu and elsewhere in Johore have pale rosy-purple or pale purplebracts.IDept. Biology, Universiti Pertanian Malaysia, 43400 Serdang, Selangor,Malaysia.239..Table 1. The morphology of Musa gracilis and M. violascens .. (diagnostic characters are in italics)Character Musa gracilis . M. uiolascensStem ht at flowering (cm) 145-180 98-194Stem diameter (cm) 20 6.5-15Type of clump dense well-spacedNo. leaves in crown 5-7 (7-) 10 (-15)Angle of young leaves arched, ± horizontal arched, ± horizontalLeaf shape broadly lanceolate narrowly lanceolateSize of largest leaf in crown (cm) 200 by 42 128-192 by 28-41Length petiole (cm) 88 53-64Leaf apex acute acuteLength of peduncle 7 30Total length of inflorescence (cm) 62 70No rows of flowers at node 2 (biseriate] 1 (uniseriate)Shape of male bud heart-shaped spindle-shaped (Fig. 2)No male flowers per bract 3+6 2Colour male flowers cream, orange towards tip grass-greenColour male bracts white flushed pinky- white or pale pinky-violet with green tip purple, with green tipShape of male bracts ovate lanceolateSize of male bracts (cm) 11 by 4 12-19 by 3-5Female bracts withering and persistent, deciduous(sometimes deciduous)No bananas per hand 4 + 4 or 5 2 or 3, rarely 4No fruits per infructescence 64-72 6-15Fruit shape squat, strongly angled elongateFruit size (cm) 6 by 3 14-15 by 3.5-4.5Fruit colour dark green almost white toglaucous green-Fruit stalk ± sessile 1-2cmApical aperture of seed wide wideANATOMY OF THE SEEDMusa gracilis belongs to the group of bananas (section Callimusa) withbarrel-shaped seeds. Its basic anatomy conforms to that described byMcGahan (1961) for M. balbisiana Colla, which belongs to the Eumusasection having subglobose, angular seeds. A salient difference in M. gracilisis the wide aperture of the apex and the thin-walled parenchymatous tissueimmediately inside, which on exposure to air dries rapidly to leave a hollowcavity which occupies about half the interior of the seed (Fig.1B). Thistissue is interpreted as part of the chalazal mass. In M. balbisiana theparenchymatous tissue of the chalazal mass forms a small central coresurrounded by cells packed with a red-brown substance. Compared with240M. balbisiana, the parenchymatous tissue in the seed of M. gracilis is greatlyenlarged.A longitudinal section of the fresh seed of M. gracilis (Fig. 1B) showsthat the chalazal mass comprises large, thin-walled parenchymatous cells(Fig. Ie) which contain tannin and occasionally raphids. Below this areabout 8 layers of thin-walled cells completely filled with a red-brownmaterial (Fig. ID). The testa divides the chalazal mass from the perisperm.The perisperm cells (Fig. IE) are congested with compound starch grainsand in some cells a solitary protein crystalloid. Embedded in the basalpart of the perisperm and surrounded by the micropylar collar (Fig. 1B, mc)is the embryo (e). Its haustorial cotyledon (hc) is embedded in the perisperm.The testa is extremely hard and is almost black when mature. It consistsof macrosclereids (Fig. 1F, ms) with conspicuously pitted, thick walls, whichare impregnated with a dark brown material. In places externally theepidermis persists, but mostly it has sloughed off. The outer 2 layers ofmacrosclereids are perpendicular to the longitudinal axis of the seed, whilethe inner 12-15 layers are parallel. Interior to these is a layer of multi-luminate sclereids (mls). McGahan (1961) considered these outer layers tobe derived from the outer integument and the ones interior to them to bederived from the inner integument. The inner layers (iw) comprise 2 layersof elongate thinner-walled sclereids with a thick cuticle (c) between themand the outer layers. The sclerotesta does not extend over the apical aperture,where the parenchymatous cells of the chalazal mass are covered by asingle layer of suberised cells.Histochemical tests (Table 2) confirm the anatomical findings thatthe perisperm contains starch and protein, while the parenchymatous tissueof the chalazal mass does not. The fact that the parenchymatous tissueturns brown on exposure to air also indicates that tannin is present in itscells.Table 2. Histochemical tests on seed contents of Musa gracilis. *(+ positive result; - negative result)Test Substance tested Perisperm Parenchymatoustissue ofchalazal massIodine and potassium iodineBiuretBenedictNinhydrinstarchproteinreducing sugarsamino acids+slightly +* carried out by Dr Z. C. Alang.941A a EIpcoFc rnls rnsowFigure 1. Anatomy of the seed of Musa gracilis. (A) exterior of seed showing the wideapical aperture, a. (B) L. S. seed, tw - thin-walled cells of chalazal mass; cm - cells ofchalazal mass with brown-red cell contents; p - perisperm; hc - haustorial cotyledon;e - embryo; mc - micropylar collar; iw - inner wall of testa; ow - outer wall; scale bar= 1mm. (C) thin-walled cells of chalazal mass; r- raphids; t - tannin; scale bar= 100 I'm.(D) cells of chalazal mass with brown-red cell contents. (E) & (Ei) cells of perisperm,pc - protein crystalloid, s - starch grain. (F) testa, c - cuticle, mls - multiluminatesclereids, ms - macrosclereids.These tests therefore confirm that the parenchymatous tissue of thechalazal mass does not have a storage function. The fact that it completelyshrivels on exposure to air (because it is exposed by the large aperture atthe apex) suggests that it largely consists of water. This is supported by thelarge weight loss (60 per cent) on drying (lOO seeds had a fresh weight of10.7 g and a dry weight of 4.6 g). McGahan (1961) found in M. balbisianathat the red-brown contents of cells at the base of the chalazal mass con-tained a gelatinous substance. This may function as a buffer by retainingwater after the parenchymatous tissue has shrivelled, so preventing theembryo from drying out. .There appears to be a relation between water loss from the paren-. chymatous tissue of the chalaza! mass and germination. When freshy242removed from the fruit, the parenchymatous tissue is turgid. At this time,the seed has the ability to germinate immediately. However, once thistissue has shrivelled, the seed becomes dormant.BIOLOGY OF MUSA GRACILISBananas exhibit several characters of weeds, such as rapid growth, a shortmaturation period and dispersal by seed. Rapid growth is illustrated bythe cultivated banana which produces a new leaf every 7-10 days, flowersafter producing between 35 and 50 leaves (at the age of 9 or more months)by which time it is between 2 and 9 m tall (Purseglove, 1972).Studies on young plants grown in pots show that the first two leaves ofM. gracilis consist of the leaf sheath only, thereafter leaves are producedwith a lamina of increasing size.Monitoring the growth of young plants of M. acuminata, M. gracilisand M. violascens showed that a new leaf was produced at between one tofour weekly intervals for all three species (Table 3). The number of leaves inthe crown remained more or less constant, the slower leaf production ofM. gracilis being offset by the longer life of individual leaves (12-18 weeks)compared with 6-12.weeks for M. acuminata and M. violascens (Table 3).Over a period, the slightly faster leaf production and longer internodes ofM. acuminata resulted in a taller plant (an increase in height of 28 cm in36 weeks). In contrast, M. gracilis, which has very short internodes andslightly slower leaf production, produced a shorter stem (22 cm) in thesame period.Table 3. Leaf production in young plants of three Malayan banana species.Musa gracilis M. uiolascens M. acuminataLeafing interval (weeks)Leaf longevity (weeks)Total no. leaves producedwithin 36 weeks(1.3-) 2.3 (-3.5)(12-) 14.5 (-18)17(1-) 2 (-3.5)(6-) 9 (-12)21(1-) 1.8 (-4)(6-) 9 (-12)26Monitoring the growth of plants of M. gracilis in the wild at mu Endauover a ten-week period showed that during that period the average increasein height for plants between 60 and 127 cm tall was 14 cm (range 6-30 cm)with three new leaves (range 2-6) being produced. The shortest plant toflower in this population was 120 cm tall suggesting that, at a rate of 1.4cm per week, 120 cm may be attained after 85 weeks. This is probably anunderestimate as growth (as measured by increase in stem height) is muchslower during the seedling phase.In potted plants, suckers were produced first in. M. gracilis (after 39243weeks) compared with M. oiolascens (after 51 weeks) and M. acuminata(not at all in 51 weeks). The suckers of M. gracilis have a rhizome whichdisplaces the sucker about 5 cm from the main stem resulting in an openclump system. The suckers of M. violascens grow much closer to the mainstem producing a dense clump of stems.The production of suckers increases the number of seeds producedper plant. An infructescence of M. gracilis produces between 6 and 12 fruitsand each fruit contains between 60 and 130 seeds, giving a potential seedcrop of between 360 and 1,560 seeds per stem. Since the interval between.germination and seed production is well over a year (estimated at least85 weeks), the production of suckers (after 36 weeks) shortens the intervalbetween inflorescence production, as well as enabling an individual plantto produce more seed.Figure 2. Male flower bud of Musa gracilis, the bract open and the flower exposed.244Pollinators were not observed at Ulu Endau but from the similarinflorescence structure to M. violascens and M. campestris Becc. (which inSarawak was observed being visited by birds), it is likely that M. gracilis isalso bird-pollinated. Several types of insects, such as flies and the butterfly,Ancistrodes nigrita, visit the male flowers to suck nectar from the base ofthe perianth. These are not pollinators as they do not collect pollen orcome into contact with the anthers;At Ulu Endau, the banana populations suffered heavily from periodicvisits by elephants, which uproot and eat the stems. The devastation isextensive, not only from the number of stems taken, but also from the effectof trampling. The populations recover by the growth of young suckers.ECOLOGYBananas are forest weeds which are intolerant of shading and root com-petition (Simmonds, 1962). Like other wild bananas, M. gracilis is a plantof forest fringes and its abundance has probably increased with the wide-spread logging of the forests in Johore and Trengganu. It is particularlycommon along the edge of old logging tracks. Of 15 herbarium collectionswhich describe its habitat, 13 were collected from secondary or disturbedhabitats. Its habitat in virgin forest is the banks of open streams.Compared with M. acuminata and M. violascens, M. gracilis appearsless tolerant of exposed windy locations. This may in part be due to the angleat which the leaf is held. The leaf of M. acuminata is held at 45° to thehorizontal and gUStSof wind cause the petiole and midrib to rotate in acircular manner (Fig. 3a). The leaf of M. gracilis is arched and the upperhalf is held almost horizontally. Wind movements cause a stress at point"s' (Fig. 3b), which result in the midrib breaking at this point.bFigure 3. Angle at which the young banana leaf is held, showing the direction of rotationof the lamina by wind. (a) Musa acuminata, (b) M. gracilis, s - stress point).245Banana seeds are some of the few tropical seeds that exhibit dormancy.They will germinate as soon as they are removed from the fruit, but oncecovered by soil, they become dormant and can retain their viability forseveral years (Simmonds, 1962). Once the soil is exposed, banana seedlingsquickly appear in great numbers. This is probably due to the heating of thesoil when exposed to full sunlight. Nik Muhamad & Kamaruzaman (1987)recorded an increase in maximum soil temperature from 23.5°C in virginforest to 28°C in logged-over forest. Germination studies carried out byChin (pers. comrn.) show that moist heat treatment (35-40oC for oneweek) effectively breaks dormancy in the seeds of M. acuminata, M. gracilisand M. violascens.GEOGRAPHIC DISTRIBUTIONMusa gracilis and M. violascens are endemic to Peninsular Malaysia. Incontrast, M. acuminata has a widespread distribution from India to Samoa.The distribution of M. gracilisdoes not apparently overlap withthat of M. violascens (Fig. 4). Onthe west coast M. gracilis has beencollected as far north as BatangMelaka, Malacca, and M. violascensas far south as Bk. Tampin, NegriSembilan. On the east coast M.gracilis has been collected through-out Trengganu and from Ulu Lebirin Kelantan. M. violascens has notbeen collected further east thanSg. Tahan, Pahang.In Peninsular Malaysia, Musaacuminata has been collected fromall states, exceptJohore (Simmonds,1955). In Trengganu and Kelantan,it grows together with M. gracilis.Musa gracilis is, therefore, the onlybanana in Johore.Information based on col-lections in herbaria is, however,only sketchy as there is a generalreluctance among botanists to col-lect such large and unwieldyplants. There is still much to belearned about the distribution ofM. gracilis and M. violascens and whether their distributions overlap.,., ,>-".", ''-), Il r'>«:,"'-' ,"\,' " :..1,: " ,. . \ ..... ' \.~"""'- -..-~ ~I ,~I ~ '..A .",:Figure 4. Distribution of Musa gracilis andM. violascens based onherbarium collections.(o M. gracilis collected between 1890 and1940; • M. gracilis collected after 1960;• M. violascens).246Compared with M. oiolascens, which is common from the lowlandsto hills at 1000-1500 m, M. gracilis is a lowland plant. It usually occursbelow 170 m, but on G. Panti, Johore, it has been collected at 333 m inkapur forest (Comer SFN 30056).There is no accepted local name for M. gracilis. Regional names includepisang kerteh, Kelantan; pisang onik and pisang wek, Trengganu (Simmonds,1955); and pisang sot, the Orang Hulu name at Kampung Peta, Sg. Endau,Johore.CONSERVATION STATUSMusa gracilis, in common with other banana species, is favoured by loggingwhich provides extensive habitats along abandoned logging trails. At one timeit was thought to be reduced to two small, separated populations (in LesongF. R., Pahang and Kemaman, Trengganu) and its conservation status wasconsidered as vulnerable (Ng, 1984). Many of the prewar collections fromJ chore (Fig. 4) are from areas that have since been clear-felled but it isstill likely to persist on the slopes of hills such as G. Panti. In Trengganuand Kelantan, on the other hand, it has probably increased in abundancesince extensive logging of the foothills has taken place. Recent collectionsshow it to be widespread in Trengganu (Sekayu F. R., Ulu Setui F. R, BatuBiwa and Merchang F.R.).In addition, it has been taken into cultivation. It has also respondedwell to cryogenic storage (Chin, pers. comm.). So at present its long-termconservation is not under threat.However, it deserves to be much more widely cultivated. Its dwarfstature, its elegant slender. rosy-purple inflorescences and its white fruitsmake it an attractive garden plant. Its horticultural potential has yet to berealised.ACKNOWLEDGEMENTSI should like to thank the Malayan Nature Society for providing transport to and facilitiesat the Base Camp of the Malaysian Heritage and Scientific Expedition: Endau-Rompin. Iam also grateful to Mr. S. Anthonysamy for help in the field, to Miss S. Madhavan for thepreparation of sections of the seed, to Dr. Z. A. Alang for carrying out the histochemicaltests, to Prof. Chin H. C. for seedlings ofM. acuminata and M. uiolascens and for sharingsome of his unpublished results with me, and to Mr. Heah H. H. and Dr. Kiew B. It fortaking field measurements.REFERENCESHolttum, R. E. 1969.Plant Life in Malaya. Longman Malaysia, Kuala Lumpur, Malaysia.McGahan, M.W. 1961. Studies on the seed of banana. 1. The anatomy of the seed andembryo of Mus a balbisiana. American Journal Botany 48: 230-238.Ng, F. S. P. 1984. Portraits of Threatened Plants. 6_Musa gracilis Holttum. MalayanNaturalist 38 (1): 9-10.247Nik Muhamad Majid & Kamaruzaman Jusoff. 1987. The impact of logging on soil tem-perature in a low elevation forestof Malaysia. Tropical Ecology 28: 35-44.Purseglove, J. W. 1972. Tropical Crops. Monocotyledons. Longman, London.Simmonds, N. W. 1955. Wild bananas in Malaya. Malayan Nature ]oumall0: 1-8.Simmonds, N. W. 1962. The Evolution of the Bananas. Longman, London.248

Notes on the natural history of the Johore banana Musa gracilis holttum

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Notes on the natural history of the Johore banana Musa gracilis holttum

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