MORPHOLOGICAL STUDIES IN I. Anatomy of the Node*

BY P. S. KAPOOR:[: (School of Morphology, Meerut College, Meerut) Received November 8, 1966 (Communicatedby Prof. V. Puri, I~.A.s¢.) ABSTRACT Nodal anatomy of sixteen species has been worked out. Of these, fifteen are three-traced trilacunar, the three traces uniting in the nodal cortex to form a single pctiolar strand of various types. In only one species the structure has been found to be one-traced unilacunar. These results are in disagreement with the earlier report of an exclusively unilacunar condition. The trilacunar node has been considered to be primitive and the unilacunar derived from it.

INTRODUCTION SAPOTACEAE with forty genera and six thousand species (Lawrence, 195I) is exclusively tropical and arborescent. It is known for a number of products it yields, chiefly timber, gutta-parcha, endosperm oil and edible berries and fleshy corolla tubes which give indigenous liquor if fermented. Laticiferous sacs and tannin-filled cells; simple coriaceous and alternate leaves; actino- morphic, hypogynous, hermaphrodite and tomentose flowers, either solitary or in clusters, characterise the family. Considerable number of papers have appeared on the classification of the family and the delimitation of its various genera and species (Baehni, 1938; Larn, 1939, etc.). Metcalfe and Chalk (1950) have exhaustively reviewed the work done on the woods of the family. No attempt, however, has so far been made towards a morphological study in this family. Only Saunders (1934) made a passing reference to the vasculature of the flower in certain species; and Sinnott (1914) published a table, depicting the anato- mical condition in the vegetative node of various families. The condition in Sapotaceae, has been shown in this table as exclusively unilacunar. The present work is a study of the node of sixteen species, only one of which is

* Research Contribution No. 81 School of Plant Morphology, Mccrut College, Meerut. ~' Head of the ~ot~y Department, Mah~ra,ni L~I Ktmwati College, Bah'ampur (Oonda). 153 154 P.S. KAI'OOR

unilacunar, while the remaining fifteen are trilacunar three-traced. These observations are much in contrast to the earlier report of an exclus vely unilacunar condition and therefore justify this communication.

MATERIAL AND METHODS Sixteen specics belonging to twelve genera (see Table 1) have been studied. The material was fixed and preserved in F.A.A., softened in 7% KOH, the duration of the treatment varying from a few days to a few months depending upon the hardness of the material. Dehydration and clearing was done in alcohol-xylol combinations. Serial microtome sections of 15-20 microns were obtained. Staining, whichwas done in crystal violet and erythrosin, was generally poor because of prolonged softening treatments.

TABLE I

Name Place- Collector

Payena lucida A. DC. .. Malaya Ch. Res. Officer, F.R.I.

Madhuca penangiana H.F. Lam. u, Madhuca indica J. F. G onel .. Balrampur Author " butyracea Roxb. .. .. Saharanpur Satyendra Kumar rostratum Burck .. Malaya Ch. Res. Officer, F.R.I. Palaquium maingayi King and Gamble .... Achras sapota Linn. .. .. Balrampur Author Pouteria malaccensis (C. B. Clarke) Baehni ...... Malaya Ch. Res. Officer, F.R.I. Planchonella dulcificum .... Ceylon Superintendent, B.G. Vincentella passargei (Engl.) Anbrev Sierra Leone T. S. Bakshi Argania spinosa .... Morocco J. Mathez Chrysophyllum cainito L. .. Lucknow Chandra Prabha Pachystela brevipes Engl. .. Sierra Leone T. S. Bakshi Mimusops elangi Linn ..... Balrampur Author Manilkara hexandra Roxb. .. Balrampur Author

Ch. Res. Officer--Chief Research Officer. F.R.l.--Forest Research Instilute, B.~,--Botlanic~al (3arden, Morpkological Studies in Sapotaeeae--I 155

OBSERVATIONS Leaves in all species, presently studied, are exstipulate except in the case of Madhuca indica and Bassia butyracea where caducous and free-lateral stipules are found. The structure in fifteen species is trilacunar and Payena lucida has beel~ described in detail as a representative of this type. The minor variations observed in certain other species (Pouteria malaccensis, Vincentella passargei, Madhuca indica and Ackras sapota) have also been recorded. The unilacunar one-traced type seen in Argania spinosa has been dealt with at the end. Payena lucida.--A cross-section of the sub-nodal region exhibits a single layered epidermis of closely placed cells with thick outer walls. This is followed by a multi-layered cortex. The vascular cylinder is complete and ectophloic, surrounded by 3-4 ceils thick sclerenchymatous pericycle. The cylinder is possessed with bulging areas on points on which the traces to the leaves have to depart. There are three such distant spots which serve to supply a leaf. The median is comparatively very large, almost double the size of the laterals and is distinguished much in advance of them. The cylinder later becomes much stretched out in its direction, while there is no such stretching in the region of the lateral bulgings. Three collateral traces for a leaf, the median arc-shaped, depart from the cylinder causing their own gaps in it (Fig. 1). The lateral traces rush towards the large median trace and join with it, at the margins, forming an ectophloic siphonic cylinder, which enters the base of the petiole (Figs. 2-3). The gaps caused by the lateral traces are immediately bridged but the margins of the broken cylinder, in its stretched region, meet slowly to form a horse-shoe-shaped projection, which, causing a gap again, separates from the cylinder, and constitutes the supply of the axillary buds (Fig. 3). The margins of this horse-shoe-shaped vascular strand meet and a complete cylinder is formed, which as a result of a progressively deepening constriction in its middle region is equally divided into two cylinders which supply two buds developed in the axil of the leaf. The gap in the cylinder of the axis caused after the departure of the vascular supply of the axillary bud is soon bridged and the cylinder again becomes complete (Figs. 4-5). In Pouteria malaccensis the margins of the arc-shaped traces expand and curve inwards to come very near to each other. The laterals merge with the median trace by filling up the gaps caused in it due to the separation of its marginal strips. The latter meet each other on the adaxial side and a three-lobed siphon is formed, which enters the base of the petiole (Figs. 6-8), 156 P.S. K^PooR The petiolar strand in Vincentella passargei also, is three-lobed, but incom- plete on the adaxial side (Figs. 14-16).

I

5 I.,., ,6 7

F~s. 1-13. Serial transections of nodal region showing divergence of vascular supply. Figs. I-5. Payena lucida one leaf and its axillary branches; Figs. 6-8. Pouteria malaccensis one leaf. Figs. 9-13. Bassia butyracea--one leaf and the stipules (St., stipular trace). In Bassia butyracea and Madhuca indica, the lateraT traces give out a short branch from each, for the stipules of their respective sides (Figs. 9-I I). The marl,ins of the median tra~e curve inwards and break to lie on the adaxial Morphological Studies in Sapotaceae--I 157 side. The gaps caused on the sides, due to this stripping, are filled by the incoming laterals. The vascular strand thus formed is C-shaped and enters the petiole (Figs. 11-13). In Achras sapota, however, there is an end-to-end joining of the laterals with the median trace and the fused petiolar strand is arc-shaped (Figs. 17-19). In Argania spinosa, as in other cases, the sub-nodal region has a complete ectophloic siphonostele. It becomes lobed as it prepares to send a leaf trace in the nodal region (Fig. 20). There is only one arc-shaped collateral trace which causes a gap in the cylinder and passes into the base of the petiole

'14 16

'~ taro i

t9

r ~ mrn

20 2!...... 2., 23 4

FIGS. 14-24. Serial transeetions of nodal region showing divergence of vascular supply. Figs. 14-16. Vincertella passargei-two leaves. Figs. 17-19. Aehras sapota--on¢ leaf. Figs. 20-24. Argania spinosa--one leaf and its axinary bud. 158 P.S. KAPOOR

(Fig. 21). The margins of the cylinder, bordering the gap, meet together and subsequently a horse-shoe-shaped trace is given off, whi:'h recreates a gap in the cylinder and supplies the axillary bud (Figs. 22-23). Above the nodal region the vascular region again becomes complete (Fig. 24).

DISCUSSION Of the sixteen sapotaceous species, studied here, fifteen have a three- traced trilacunar node, the median trace being more massive. The three traces always unite in the nodal cortex, to form a single petiolar strand which may be siphonie (Payena lucida, etc.), C-shaped (Bassia butyracea) or arc- shaped (Achras sapota). In Madhuca indica and Bassia butyracea, the lateral traces, before fusing with the median, send off a branch each to the stipules, which are small and caducous. In other species, the stipules as well as their vascular supply are wanting. In Argania spinosa, the node is unilacunar with a single large arc-shaped trace. The only work that the author has come across on the nodal anatomy of Sapotaceae is that of Sinnott (1914), who described the structure as ex- clusively unilacunar and one-traced. Since he did not name the genera and species, he studied, it is not possible to assess the value of his conclusions which are in gross disagreement with those of the present author. Sinnott (1914) recognised three principal types of nodal structure in the dicotyledons--the trilacunar with three traces, the unilacunar with one or three traces, the multilacunar with more than three traces, each causing a separate gap in the cylinder. The trilacunar condition, on account of its frequent occurrence, in the Ranales and Rosales, was considered the most primitive; and, the other conditions--the unilacunar and multilacunar, were believed to be derived from it. For over thirty years the validity of this view remained undisputed. But recently, a fourth type of node consisting of two discrete traces arising from a single gap has been claimed to be the primitive pattern (Marsden and Bailey, 1955; Canright, 1955, etc.). This by fusion is believed to have given rise to one-traced unilacunar condition and by subsequent incorporation of traces in independent gaps to tri- and multMacunar conditions. The type of node which Takhtajan (1964) considers primitive is trilacunar with four traces, two arising from the middle gap and one each from the lateral gaps. This gives rise to the three-traced trilacunar and two-traced unilacunar'types. The former leads to tile one-traced unilactmar and lnany- traced multi-lacunar conditions, and tile latter also to the one and to the three-traced unilacunar conditions. Morphological Studies in Sapotaceae--I 159 On the basis of the present study, it appears difficult to accept that the unilacunar node is primitive and that the trilacunar has been derived from it. There is also no valid ground available here to suggest that the median trace of the three-traced trilacunar node is a fusion product of two indepen- dent traces in the median gap. The main points that stand out prominently in this connection are: 1. The statistics collected by Sinnott and Bailey (1915) have shown that a tropical environment is as unsuited to the development of a trilacunar nodal condition as it is suited to that of a unilacunar one. Sapotaceae being strictly tropical, the chances of the occurrence of a triIacunar node as the original condition should be remote but those of its derivation from a unilacunar one should be remoter still. 2. The statistics of these workers have further shown that unilacunar and trilacunar conditions are usually respectively linked with penni- and palrni-nerved leaves. If the three traces have been derived from a single one, it should have been more natural for them to pass unfused through the petiole and give rise to palmate venation in the leaf. But instead, they fuse in the nodal cortex into a single petiolar strand which gives rise to pinnate venation in the leaf. 3. The above-mentioned behaviour of the three nodal traces can, on the other hand, lead one to think that the three-traced trilacunar condition can give rise to one traced unilacunar condition. This can be possible by a working back of the fusion process to the level of the origin of the three traces and the disappearance of the intervening strips. 4. In Achras, an arc-shaped petiolar strand is formed by the fusion of the three traces of the node. If this type of strand was required for the vascularization of the leaf, the evolution of trilacunar node from the uni- lacunar one was perhaps not necessary, for, as is illustrated by the nodal condition in Argania, such a petiolar supply can well be obtained from a one-traced unilacunar condition. The present author, therefore, is more inclined to agree with Sinnott (1914) in considering the trilacunar node as primitive and the unilacunar one as derived from it.

ACKNOWLEDGEMENTS The author is deeply indebted to Prof. V. Puri, o.se., F.A.SC., F.N.I., for his keen interest in the work and guidance, and to Dr. Y. S. Murty for numerous valuable suggestions and encouragement. He is also indebted to B3 160 P.S. KAPOOR Dr. V. Singh and Mr. C. M. Govil for help in several ways. Grateful thanks are due to the Chief Research Officer of the Forest Research Institute at Kepong (Malaya), the Superintendent of the Botanical Gardens at Paradeniya (Ceylon), Dr. T. S. Bakshi (Sierra Leone), Dr. J. Mathez (Morocco), Miss Chandra Prabha (Lucknow, India) and Mr. Satyendra Kumar (Saharanpur, India) for their generosity in sending the valuable material.

REFERENCES

Baehni, C. .. "Memoires sur les Sapotacees I. Systeme de dassitication," Candollea, 1938, 7, 394-508. Canright, J. E. .. "The comparative morphology and relationships of the Magnoliaceae. IV. Wood and nodal anatomy," Jour. Arnold Arb., 1955, 36, 119-40. Lam, H. J. .. "On the system of the Sapotaceae with some remarks on taxonomical methods," Rec. Tray. Bot. Need., 1939, 36, 509-25. Lawrence, G. H. M .... of Vascular , New York, 1951. Marsden, M. P. F. and Bailey, "'A fourth type of nodal anatomy in dicotyledons, illustrated LW. by Cletodendron trichotomum, Thunb," .Tour. Arnold Arb., 1955, 36, 1-51. Sinnott, E. W. ~. "Investigations on the phylogeny of the Angisperms. I. The anatomy of the node as an aid in the classification of Angio- sperms,'" Amer. Jour. Bot., 1914, 1, 303-22. and Bailey, I.W. .. "Investigations on the phylogeny of Angiosperms. V. Foliar evidence as to the ancestry and early climatic environment of the Angiosperms," Amer. Jour. Bot., 1915, 2, 1-22. Takhtajan, A. .. Evolution of Angisoperms, 1964, 1 (in Russian), Moscow.