Proc. Indian Acad. Sci. (Plant Sci.), Vol, 94, No. 1, March 1985, pp. 51-57. Printed in India.

Seedcoat micromorphology of Caryophyllales: Observations on some Molluginaceae

V V SIVARAJAN and M C GOPINATHAN* Department of Botany, University of Calicut, Calicut 673 635, India Department of Botany, University of Delhi, Delhi 110007, India MS received 16 September 1982; revised 8 December 1984 Abstrar The seeds of Caryophyllalesate suitable materials for mieromorphologicalstudies and might possiblyyield valuabletaxonomic information.This paper deals with SEMstudies on the seedcoat patterns of nine species of Molluginaceae. The findings support the generic delimitations and ate highly usr in infrageneric classification, as well. Keywords. Caryophyllales;Molluginaceae; seedcoat; micromorphology;systematic position; areolate4 tuberculate.

1. Introduction

The circumscription of the order Caryophyllales (Centrospermae) has been a highly debated issue in the recent past. Mabry et al (1963) and his school emphasised pigment dichotomy in the group (Caryophyllaceae and Molluginaceae having anthocyanins and atl other families with betalains) and the need for segregating them into two different orders. On the other hand Behnke (I 976, 1981) and Behnke et al (1983) postulated that ir is a homogeneous group with a common ancestry and were a|so supported by Nowicke and Skavarla (1977) and Mabry (1976, 1977). The nature ofsieve-tube plastid elements has been largely relied upon by Dahlgren (1980), Takhtajan (1980) and Cronquist (1981) in redefining the order Caryophyllales. Seedcoat micromorphology has provided useful information on the systematic position and interrelationships of various taxa (Brisson and Peterson 1976, 1977). Caryophyllales in general, have minute seeds with highly varied types of seed coat patterns suitable for ultrastructural studies. Despite this, little attention has been paid to this but for the work of Thieret (1966)and Wofford (1981). The results of the present investigations on some members of Molluginaceae have been encouraging and the authors propose to extend the work to other members of the group as well.

2. Materials and methods

Nine species belonging to four genera were selected for the studies. Mature seed samples selected from the herbarium specimens were coated with 100 A of silver and were observed and photographed ($4-10 Cambridge Stereoscan). The taxa selected and the details of the voucher specimens are given below: 51 P S 9 52 V V Sivarajan and M C Gopinathan

Locality deposited Taxa Coll. no. in

Corbichonia decurabens Chandrabose (Forsk.) Exell 51399 Tamilnadu M. Gisekia pharnaceoides L. VVS 1300 Kerala CALI Gtinus totoides L. Surendran 8691 Kerala c~.u G. oppositifolius (L.) DC. VVS 88 Kerala cAI_I Mollugo penraphylla L VVS 428 Kerala CALI M. stricta L. VVS 358 Kerala CAL/ M. d~sticha Ser. VVS 887 Kerala CXLI M. nudicaulis Lamk. VVS 1273 Kerala CALI M. cerriana (L.) Ser. VVS 891 Kerala CALI

3. Observatioas and discussion

In general, the seeds of the taxa examined are minute, pale brown to brownish black and reniform or konch-shaped. Observations using SZM revealed very distinctive seedcoat patterns almost corresponding to the existing generic delimitations within the family. Thus, the genus Glinus had tuberculate/verrucate seeds, Mollu#o areolate/reticulate ones, Gisekia punctate and Corbichonia r ones. In all sarnptes examined~ the seeds hada waxy coating on their surface. The generic status of Gtinus L. has been a matter of discussion, until recently. It is closely similar to Mollugo L in its macromorphotogical characters and several authors treated them as congeneric (Bentham and Hooker 1867; Clarke 1879) even after Fenzl (1836) demons•rated ah essential difference in their seed structure--the seeds of the former having an unequal pair of appendages called podosperms at the hilum while they ate absent in the seeds of Mollugo. Contemporary taxonomic opinion is in favour of keeping them as two distinct genera and finds support from the seedcoat pattern studies, as well. The two lndian species of the genus studied differ among thernselves in the seedcoat micromorphology. In Glinus oppositifolius they are tuberculate with cylindric, pillar-like tubercles in concentric circles around the hilum, the larger ones near the margins and the smaller ones towards the hilum. The waxy coating is more conspicuous in the inter-tubercular areas than on the tubercles themselves (figures 1-2). The seeds of G. lotoides though very similar under light microscope, appear quite distinct under SEM. They are verrucate with the ellipsoid verrucae transversely o¡ to the long axis of the seeds. They are concentrically arranged around the hilum and are increasingly smaller towards it (figures 3--4). This difference in the seedcoat patterns may be of decisive importance in the circumscription and delimitation of species because overlapping variations in the macromorphological characters and inter- mediates have already been reported in this species pair (Backer 1951). Of the four species of the genus Moltugo studied, M. cerviana and M. nudicaufis are very distinct and isolated in their general morphology and in their seedcoat patterns. M. cerviana has planoconvex, obconic seeds with prominentty reticulate seedcoat. Meshes of the reticulum are square or polygonal with mostly oblique walls. Along the margins the meshes are deeper. The entire seed surface is studded with minute gran nular excrescences (figures 9-10). In M. nudicaulis the seed surface is ctosely packed with uniformly distributcd, pebble-like, lyrate and chipped areoles. Those along the Seedcoat morphology of Caryophyllales 53

Figures 1--6. 1 and 2. Glinus oppositiJbli~s (1 • 120. 2 x 1200). 3 aud 4. Glinu~" lotoMes (3 • 120, 4 • 360). $ and 6. Mollu#o pentaphylta (5 • 60, 6 • 6(~~.

P-S-/o 54 V V Sivarajan and M C Gopinathan

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,,... #-;-?+,) 9 +, :.~.Ÿ 9)+ - . +" ~ : +:,'kiS:,'+~" , ,,44 .::9 ::- '+:

Figures 7-10. 7andS+M. nudicaulis(7x]20+$• M. cerviana(9x240, I0 ~ 600).

margins are ellipsoid and are not chipped. The lyrations on the surface of the areoles is apparently due to differential deposition of the waxy material (figures 7-8). M. pentaphylla has been undcrstood asa highly variable species until recently and included in it two different e[ements described under two binomials by Linnaeus. Of them, M. pentaphy/la (sensu stricto) is characterised by obovate-obtuse leaves and lax panicles and M. stricta by lanceolate, acute leaves with compact panicles. Observations on the seedcoat patterns havc corroborated the Linnaean concept of these species. M. pentaphylla has areolate seeds wi'h polygonal areoles and the entire seedsurface is covered with a microreticulum formed apparently by the decidt:ous waxy coating (figures 5-6). On the contrary, those of M. stricta are tuberculate with no such finer ornamentations as seen in the former (figures i4-16). Consequently, Sivarajan and Usha (1983) have resurrected M. 5tricta asa distinct species. M. stricta and M. disticha are closcly rclated species and are generatly distinguished Seedcoat morphology of Caryophyllales 55

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91.--. -.~ .:~. ~ ,'k'll ~~.,~;~/;'

Figures t1--.16. 11-13. M. dAsticha (11 x 95, 12 x 90, 13 x 600). 14-16. M. stricta (14 • 60, 15 :~ 2'40. 1£ • 600) 56 V V Sivarajan and M C Gopinathan by their inflorescence and seed characters, the former having corymbosely branched panicles and unmargined seeds and the lauer racemoselv branched inflorescence and strongly margined seeds, although Clarke {1879) has reported overlapping variations in the nature of the infloresc•nce. However, the seeds are quite distinctive. Unlike the tubercled seeds of M. srricta, those of M. disticha ate areolate and ate strongly margined with prominem ridges and groovcs atong the margins (figures 11-13). The systematic position of the genus Gisekia L. h.as been a matter of discussion and controversy and has been placed under different families by different authors. Ir is closely similar to Molluginaceae on the one hand but is unnatural here because ofits l- ovuled, apocarpous pistil and betalain pigments. These characters relate ir better with Phytolaccaceae and so, Takhtajan (1980) has transferred this gcnus to the latter family. Present studies have revealed that the single species of this genus in India---G. pharnaceoides--has a punctate seedcoat (figures 17-18) and in this respect too, it has no close relative in Molluginaceae.

~~'.-, .-'~~:-r'-",, ,...Z ~, ~
91~'~ r~;r~~ 9"W"~':,tk'l

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Figures 17-20. 17 and 18. Gisek~a pharnaceoides (17 x 80, 18 >(520). 19 and 20, Corbichonia decumbens (,19 • 56, 20 • 220). Seedcoat morphology of Caryophyllales 57

Corbichonia decumbens, earlicr described under the genus Glinus, is unique in having petalloid staminodes (Clarke 1879) often confused with petals (Wight and Arnott 1834). Quite unlike those of Glinus, the seeds of this taxon do not have the hilar appendages and have a very different seedcoat pattern. They are prominently costate with deep intervening grooves. The costae are concentrically arranged and are narrowed from base upwards to a sharp serrate crest. They also have closely placed, regularly arranged, transverse ridges, continuous between successive crests (figures 19-20).

AcknowledgemenCs

The authors are thankful to Mr S M Lal, Textile Technology Division, 11T, Delhi for the electron micrographs.

References

Backcr 1951 Moltu9inaceae: in Flora Malesiana (ed.) C G G J van Steenis (Djakarta: Noordhof0 4 267-275 Behnke H D 1976 U ltrastructure of sievc-element plastids in Caryophyllales (Centrospermae). Evidencc for the delimitation and classifir of the Order; Plant Syst. Evol. 126 31-54 Behnke H D 1981 Sieve--elemcnt characters; Nord. J. Bot. l 381-400 Behnke H D, Liliana Pop and Sivarajan V V 1983 Sieve-element plastids of Caryophyllales: Additional investigations with speoal rcference to the Caryophyllaceae and Molluginaceae; Plant Syst. Evol. 142 109-115 Bentham G and Hooker J D 1867 Ficoideac: in Genera Plantarum (London: Reevc & Co.) 1 851-859 Brisson J D and Peterson R L 1976 A critical review of the use of SEM in the study of seedcoat; lllinois Inst. Tech. Res. lnst. SEM/1976/11 477-495 Brisson J D and Peterson R L 1977 The SEMand x-ray microanalysis in the study of seeds. A bibliography covering the period of 1967-1976. lUinois lnst. Tech. Res. Inst. SEM/1977/II 697-712 Clarke C B 1879 Ficoideae: in Flora of British India (ed.) J D Hooker (Kent: Reeve & Co.) II 658-664 Cronquist A 1981 Ah integrated sysfem of classification offlowerin O plants [New York: Academic Press) Dahlgren R M T 1980 A revised systcm of ciassification of Angiosperms; Bot..1. Linn. Soc. 80 9I--124 Fenzl E 1836 Monographie dcr Moltogineen und Steudelieen; Ann. Wiener Mus. Naturgesch. 1 337-384 Mabry T J 1976 Pigment dichotomy and Dr~A-RNAhybridisation data for Centrospermous families; Plant Syst. Evol. 126 79-94 Mabry T J 1977 The order Centrospermae; ,4nn. Miss. Bot. Gard. 64 210--220 Mabry T J, Taylor A and Turner B L 1963 The betacyanins and their distribut]on: Phytochemistry 2 61--64 Nowicke J W and Skavarla J J 1977 Pollcn morphology and the relationship of the Plumbaginaceae, Polygonaceae and Primulaceae to the order Centrospermae; Smiths. Contrib. Bot. 37 I ---64 Sivarajan V V and Usha T 1983 On re-instating the Linnaean species Mollutto stricta (Molluginaceae}; Taxon 32 123-126 Takhtajan A 1980 Outline of the c 'l•ssification of flowering plants (Magnoliophyta); Bot. Re~'. 46 225--359 Thicrct J W 1966 Seeds of some United States Phytolaccaceae and Aizoaceae: Sida 2 352-360 Wight R and Arnott G A 1834 Prodromusflorae peninsulae lndiae Orientali~ (London: Taylor and Francis) Wofford B E 1981 External seed morphology of A rneria Southeastern Unitcd States: Syst. Bot. 6 126-135

PS II