Proc. Indian Acad. Sci. (Plant Sci.), Vol. 96, No. 4, October 1986, pp. 327-332. Printed in India.

Anatomical studies in the flower of some genera in the Geraniales

SHOBHANA RADHAKRISHNAN* and V D TILAK** Botany Department, The Institute of Scienr Bombay 400 032, India *Present address" 39/7, Air India Quarters, Kalina, Bombay 400 029, India **Fiar No. F-102, Bldg. No. 6, Neelumnagar, Mulund (Eas0, Bombay 400081, India MS received 3 January 1986; revised 11 August 1986 Abstraet. Observations on the vascular anatomy of the flower in Tristellateia australis A Rich and Stiomaphyllon ciliatum A Juss of the Malpigkiaceae and Sisyndite spartea E Mey and Guaicacum oJficinale Lina. of Zygophyllacatae ate presented. Thr studir record varied forces of cohesion and adhesion between vascular tra~es to different floral whorls. The sepals and petals ate unequal in size and a little oblique in some cases. Obdiplostemony is of less promJnence anda dise is absent. There is a weaker cohesion of carpels, cvidenced both; morphologicany as weU as anatomically. Placentation is axile. The vascular anatomical characters of the flower appear to be distinctive and exhibit a lower lr of specialization a.s compared to the other Geraniales, Keywords. Flower, anatomy; Geranialr

1. lntroduction

Anatomical studies in the flower of the Geraniales have br undertaken extensively, in the past. Such studies cover many families of the order including the families Malpighiaceae and Zygophyllaceae (Gosain 1955; Kashyap 1957; Nair1962, 1963; Nair and Sarma 1961; Narayana 1958a, b, 1959; Nene and Tilak 1977). In spite of this it was felt that there is some scopr to extend such studies ta some genera that need ah investigation. Results of such studies ate presented here.

2. Mate¡ and methods

The flowe¡ material of Tristellateia australis A Rich, Stigmaphyllon ciliatum A Juss and Guaiacum officinale Lin~ was coUected from the Jijamata Garden, Byculla, Bombay. That of Sisyndite spartea E Mey was, very graciously, made available by the Curator, Botanic Garden, Mª The material was fixed in FAA. The usual paratfin method was followed. Serial transections of the paraffin embedded material were cut at 12-15 ~tm and stained in crystal violet, using orange G/erythrosin as a counterstain.

3. Observations

3.1 T. australis

The median bundles of the sepals (MS) and the conjoint petal traces fusr with laterals traces of adjacent sepals (P-LS) em•rge from the vascular ring, simulta- 327 328 Shobhana Radhakrishnan and V D Tilak neously (figure l). The MS directly extend into the sepals. The conjoint P-LS traces quickly split into constituent petal traces (P) and lateral sepal traces (LS) with the former extending into the petals and latter into the sepalar margins (figures 1-3). The staminal bundles of both the staminal whorls emerge in quick succession (figure 3). The remaining vascular tŸ reorgartizes into 3 carpellary dorsals, the 6 anchorshaped septal bundles and 6 carpellary ventral bundles that are on septal radii (figures 4-5). The sepals have 5-7 bundles as these separate (figure 3). They have only 3 bundles at the top (figure 8). The petals are terete at the base and have a single petal bundle. The number of bundles towards the tip of petals increases to 8-10 (figures 7-9). The stamens are in a nng-and at the base, are laterally united (figure 5). Upwards, they ate obdiplostemonous. The antesepalous stamens are antheriferous first and are shorter (figure 9). The ovary is tricarpeUary and trilocular with 3 carpellary dorsals, 6 septal bundles and 6 carpellary ventrals (figure 5). The septal bundles, in their upward course shift close to and fuse with the carpellary dorsals (figures 6-8). The carpellary ventrais of the same carpels are free from each other at the base (figure 5). They fuse with each other but split again towards the top of the ovary as they give traces to the ovules (figures 6-7). In the style they ate seen on the sides of stylar canals (figure 8).

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Figura 1-19. Serial transverse sectioas of the flowers of T. australia (1-9) and S. ciliatum (10-19) at progressively highcr levels from the base to the tip of the flower. Anatomical studies in the flower of the Geraniales 329

3.2 S. ciliatum

The MS emerge first, quickly followed by the conjoint P-LS, i.e. petal bundles (P) fused with the lateral traces of the adjacent sepals (LS) (figure 10). The latter split into constituent P and LS traces immediately on emergente (figure 11). The median and the lateral sepat traces extend into the sepals, with the latter mostly in the glandular margin of sepals. The petal traces extend into the petals. The 10 staminal bundles emerge in quick succession. The remaining vascular tissue forros 3 carpellary dorsals, 6 septal bundles and 6 carpeUary ventrals on the septal radii (figures 12-13). The sepals have 3-5 bundles as these separate from each other (figure 14). The number does not increase upwards, in the sepals, At the tip the sepals have a single bundle (figure 18), The single bundle in the petal branches in its upward course to increase the number to 5--7 (figures 14-19). The petals are distinctly unequal in size and accordingly the number of bundles in it also varies (figures 18-19). The stamens are in a ring and laterally united (figure 14). Upwards, they separate from each other (figures 14-16). Four of the antepetalous stamens are larger than the remaining ones (figure 18). The fifth antepetalous stamen and the 6 antesepalous stamens differ in size and are smaller. The tricarpetlary ovary has incompletely fused margins at its inner surface (figure 14). It has 3 carpellary dorsals, 6 septal bundles and 6 ventrats (figure 13). The carpellary ventrals of the same carpel that are free from eaeh other at the base (figure 13) fuse with each other upwards (figure 14) and split up again as they gire vascular supply to the ovules (figure 15). These move away from each other as they extend into the short style and end therein (figures 16-17).

3.3 S. spartea

The median bundles of the sepals and the composite petal traces, lateral traces of the adjacent sepals and the antepetalous staminal bundles emerge together on the alternating radii (figure 20). From the latter the lateral traces of the sepals separate out first (figure 21), and the peral and antepetalous staminal bundles split out later (figures 22-23). The antesepalous staminal bundles emerge independently (figure 22). The remaining tissue forms a vascular ring that splits into 5 carpellary dorsals and 5 U-shaped arcs (figure 24). From the inner edges of these arcs is pinched off another vascular ring of the residual vascular tissue that extends for some length in the floral axis and 5 ventral bundles opposite the loculi can be observed (figures 25-26). The unequal sepals have about 10-15 bundles (figure 25). The number reduces towards the tip (figures 28-29). The petals are short. They are ver)' short and end with the single bundle (figure 23). The free stamens are in a ring (figures 24-27). They are antheriferous (figures 24-25) and end in quick succession (figure 29) with not much difference in their height. The ovary is pentacarpellary and as the loculi appear the placental bundles became distinct opposite the loculi (figure 27). These give traces to the ovules (figure 27). As the Ioculi close the ptacentat bundles split into two and they, alongwith the carpellary dorsals extend into the short base of the style for some length (figure 28).

3.4 G. officinale

The MS and the conjoint petal bundtes (P) fused with the laterals of adjacent sepals 330 Shobhana Radhakrishnan and V D Tilak

... : .... ~ ~~-"-~ 9 . .... - .,,~ : ~,~ ,~ ~~~~ : .. ;~ ~'a, .-,'--:~ : -g~2.~..'.""5 / ~c-'-"-:..>~2 G xL~.-'Z/~A!r ">' "%.. 9.N_ ,v..~>---- 25 .._-.. ~. ~------~ . .,,~,~ -- .. . ,~~~-/ ~

IF'tgir~ 20-39. Se¡ tranwr sections of the flower of S. spartea (20--29)and G. o~cinale (30-39) at progressively higher levels from the base to the tip of the flower. (MS, Median traces of the sepals; LS, lateral traces of the sepals; P, peral eords; ASS, antesepalous staminoI traces; APS, antepetalous staminot traces; APS, antepetalotm staminol traces; CD, carpellary dorsals; S, septal bundles; CV, carpdlary ventrals; RVT, residuory vascular tissue. For explanation sr text).

(LS) and antepetatous staminal bundles (APS) emerge in quick suecession (figure 30). The laterals of the adjacent sepals separate out almost immediately on emergence (figure 30) and extend into the margins of adjacent sepals. The petal bundles separate out from those of antepetalous stamens at a higher level (figure 31). The bundles of the antesepalous stamens emerge independently on the sepalar radii (figure 31). The ramaining vascular tissue splits out two arcs (figure 31) that later, forra the one carpellary dorsals and two, closely-placed carpeUary ventrals for eacb of the two carpets (figures 32-35). The unequal sepals have 6-12 bundles (figures 32-33), with the uumber reduced to 5 at the top of the sepals (figures 36-37). The petals are unequal in size and oblique in disposition (figures 36-37). They have 5-7 bundles at the base (figure 32). Upwards the number increases to about 10-12 (figure 35). The stamens are all in a ring, free and slighfly unequal in size (figure 34). They are antheriferous (figure 34) and end (figure 38) nearly at the same level. The bicarpellary ovary has two arcs of vascular tissue (figures 33-:34) that reorganizes into a carpetlary dorsal and two carpellary ventral bundtes for each of the two carpels, which are located opposite the loculi (figures Anatomical studies in the flower of the Geraniales 331

35-36). The carpellary ventral bundles are distinct from each other as they give traces to the ovules (figures 36-37). As the loculi close the ventrals more away from each other and fade out (figures 37-38). The dorsals disappear a little later (figure 39).

4. Discussion

In T. australis and S. citiatum the lateral bundles of the adjacent sepals ate, only weakly, fused with the petal bundles, as evidenced by their separation quickly on emergence. S. spartea and G. officinalis exhibit a step ahead in this direction, by the fusion of all the 3 bundles on the petalar radii viz. the laterals of the sepals, the petalar and the antepetalous staminal bundles. Again, in these two plants the conjoint bundles split into constituents, very near the base. The weaker magnitude of adhesion of these bundles reflects in the total absence of semiinferior or inferior condition of the ovary. In other Geraniales ijke the Meliaceae or Rhamnaceae the stronger forces of adhesion of bundles results in a semiinfe¡ of infe¡ ovary epigyny (Nair 1962; Nair and Sarma 1961). The stamens of the two whorls may be equal or unequat in size. Their vascular supply emerges from the axis in quick succession and independently of conjoint with other traces on the sarne radii. All the stamens are in a ring and laterally united at the base. They continue to be so in the upper part of the flower in S. spartea and G. officinarum. In the other two plants, upwards, the stamens are obdiplostemonous. Three explanations are generally given for the obdiplostemony of the stamens viz. the reduction, the intercalation and ontogenetic displacement theory (Eames 1961). Vestigial staminal strands of the suppressed, additional lost stamens of the outer whorl were not recorded in any of the plants. It does not, therefore, support the reduction theory. Further, although in S. spartea and G. officina!e the antepetalous staminal bundles emerge eonjoint with the sepal laterals and petalar bundles earlier than the independently emerging antesepalous staminal bundles, the stamens of both the whorls are in a fing. These observations do not support the obdiplostemony due to early emergence of antepetalous staminal bundles. Obdiplostemony is, therefore, due to ontogenetic displacement of stamens. A typieal vascularized or non-vascularized dise was not recorded in any of the plants studied. The ovary is 5 carpellary in S. spartea. Each carpel has a carpellary dorsal, single placental bundle that is formed by fusion of 2 carpellary ventral bundles. This plant exhibits the presence of residuary vascular tissue, a feature, generally considered to be a p¡ character. G. officinale has a biearpeUary ovary with a carpellary dorsal and 2 distinct ventral bundles for each of the two carpels. The remaining two plants have a tricarpellary ovary with a carpellary dorsal, two carpellary ventrals and two septal bundles in the ovary waU in the septal position for eaeh of the three earpels. Presence of free septal bundles is treated as indicating weaker forces of cohesion between the carpels. In addition, it may be noted that S. ciliatum has incompletely fused margins at the inner edges for some Iength in the flower. The placental situation in these plants shows a little variation. In S. spartea there is a single bundle formed by the fusion of carpellary ventrals of the same carpel, located opposite the loculi. The single bundle gives traces to the ovules. In G. officinale the earpellary ventrals of the same carpel are distinct from eaeh other. They ate elosely 332 Shobhana Radhakrishnan and V D Tilak placed and retain their indivŸ as they give traces to the ovules of the sarne carpel. In T. austratis and S. ciliatum the carpellary ventrals are in pairs opposite the septa at the base of the flower. Those of the same carpel shift closer to each other and merge for some length in the middle part of the ovary. Towards the top, they again split up, separate and more away from each other as they gire traces to the ovules. The placentation in all these plants is, therefore, morphologically as well as anatomically axile (Puri 1952). AII the same the moving away of the carpeilary ventrals of the same carpel away from each other may be taken as a initial and very incipient step in the direction of parietal placentation--a trend that is of frequent occurrence in the other taxa of Geraniales (Nair 1956, 1962, 1963; Narayana 1958a, b; 1959; Nene and Tilak 1977). A comparativety lesser adhesion of vascular bundles to different floral whorls reflected in the total absence of semi-inferior or inferior ovary, presence of residual receptacular vascular tissue, incipient obdiplostemony d'ue to ontogenetic displacement, total absence of disc, weaker forces of cohesion between carpels evidenced both, morphologically as well as anatomically, a distinct axile placentation ate all distinctive characters of the plants studied that stand away from and at a lower level of specialization as compared to other Geranialian taxa.

Acknowledgements

The authors are grateful to the Director, The Institute of Science for laboratory facilities, the Curator, Botanic Gardens Mª for providing the material of S. spartea, Prof. R M Pai, Marathwada University, Aurangabad, for helpful suggesUons, keen interest and encouragement.

References

Eames A J 1961 Morphology ofAnqtosperms (New York, Toranto, London: McGraw HiU Book Co. Inc.) Gosain K K 1955 Vascular anatomy of the flower of Hiptage ben#halensis (Lirm.) Kurz; A#ra Unir. J. Res. (Sci.) Pt 1, 602,-609 Kashyap G 1957 Studies in the family Vita~ae-IL Floral Anatomy of Vitis trffolia Linn., V. latifolia Roxb. and V. himalayana Brandis; J. lndian Bot. Sbc. 36 317-323 Nair N C 1956 Ptaeentation in Meli,~ azedarach Linn. (Azadirachta indica Juss.); Curr. Sci.2A 264-265 Na.ir N C 1962 Studies in the Meliaceae-V. Morphology and Anatomy of the flower of the t¡ Meliaceae, Trichilieae and Swietenieae; J. Indian Bot. Soc. 41 226-242 Nair N C 1963 Sludies in the Meliaceae-Vl. Morphologyand anatomy of the flower of the tribe Cedrelieae and di~-ussion on the floral anatomy of the family; J. lndian Bot. Soc. 42 177-189 Nair N C and Sarma V S t96t Organography and floral anatomy of some members of Rhamnaceae; J. Indian Bot. Soc. 40 47--55 Narayana L L t958a Floral anatomy and embryologyof Cipadersa baccifera Miq.; J. h~dian Bot. Soc. 37 147-t54 Narayana L L 1958b Floral anatomy of the Metiaceae; J. lndian Bot. Soc. 37 365-374 Narayana L L 1959 Floral anatomy of the Meliaceae-lI; J. Indian Bot. Soc. 38 288-295 Nene P M and Tilak V D 1977 Placentation in the Muliaceae; Proc. lndian Acad. Sci. (Plant Sci.) 85 378-383 Puri V 1952 Placentation in angiosperms; Bot. Reo. 18 60.~-651