MORPHOLOGICAL STUDIES IN SAPOTACEAE I. Anatomy of the Node* BY P. S. KAPOOR:[: (School of Plant 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 "Bassia butyracea Roxb. .. .. Saharanpur Satyendra Kumar Palaquium 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.