Proc. Indian Acad_ Sci. ( Sci.), Vol. 99, No. 1, February 1989, pp. 15-20. Printed in .

Structure and deveiopment of fruit wal| ornamentations in daemia (Forsk.) Chiov (Asclepiadaceae)

P M KURIACHEN and YASH DAVE Department of Biosciences, Sardar Patel University, Vallabh Vidyanagar 388 120, India MS received 20 May 1988; revised 3 January 1989 Abstract. The follicle of Per9ularia daemia (Forsk.) Chiov is ornamented with large number of branched and unbranched soft spines. The spine initiate before anthesis. It develops from the epidermal and subepidermal (ground tissue) layers of the ovary wall. A mature spine consists of an epidermis enclosing parenchymatous ground tissue with vascular strands and Iaticifers. Two types of trichomes, uniseriate multicellular and multiseriate multicellular, are present on the spine and fruit surface. The cuticle on the fruit surface is thick with a waxy coating. Stomata present on the fruit surface are slightly raised. Keywords. Per9ulariadaemia; taticifer; spine; stomata; trichome.

1. lntroduction

The use of scanning electron microscope for the surface study of plant organs especially that of fruits and seeds ate emphasized by va¡ authors (Heywood 1968; Heywood and Dakshini 1971; Lane 1985; Otowokudujo 1985; Menon and Dave 1988). Studies that used the scanning etectron micrograph (SEM) are mostly of epidermal features (Barthtott 1981) and by this the proper identification and differentiation of any a trivial character can be done for the use in systematics or any other descriptions as exploited by Heywood (1968), Cole and Bhenke (1975), Wujek and Menapace (1986) and Bragg and MacMillan (1986). The outgrowths on the fruit surface of various taxa are interpreted variously as emergences, trichomes, glands, prickles, spines etc. by different authors at different times. For the description of such spiny structures in single fruit itself different confusing terms seem to be used in literature. Morphologically the outgrowths on the follicle of Per9ularia daemia (Forsk.) Chiov are also described variously in the description of fruits as long soft spines (Hooker 1885), echinate with soft spines (Kirtikar and Basu 1933; Cooke 1958; Santapau and Irani 1960), and softly echinate (Shah 1978; Matthew 1983). Lawrence (1951) defined the term echinate as with stout bluntish prickles and spine as a strong and sharp pointed woody body mostly arising from the wood of stems. Thus it appears very ambiguous to confirm the same structure as spine or p¡ (echinate) without any detailed histological investigations. Dave et al (1980) and Rao et al (1985) emphasized that such interpretations on the same structure ate due to the lack of morphohistogenic studies and can be rectified only by morphohistogenetical observations. In the present paper surface ornamentations of P. daemia follicle are observed under SEM and their ontogeny and structure are studied with light microscope.

2. Materials and methods

Flowers and fruits of P. daemia at their sequential developmental stages were 15 16 P M Kuriachen and Yash Dave collected and fixed in FAA. The fixed materials were dehydrated, embedded and microtomed as per the usual methods of Johansen (1940). Safranin and fast green were used for staining. Photomicrographs were taken using Carl-Zeiss photomicro- scope-1. For SEM studies fresh materials were mounted on specimen stubs using 'Fevicot' adhesive. The mounted materials were coated with a thin conducting film of gold-paltadium and observed with Cambridge Stereoscan $4-10 microscope at ~ Ahmedabad.

3. Results

The fruit of P. daemia is a pair of follicles ornamented with large number of branched and unbranched spines (figures 1-3). The mature fruit is covered by a thick wax coated cuticle (figure 4). The waxy coating on the fruit surface makes it powdery white in appearance. Stomata present on the mature fruit walt are slightly raised over the surface, but due to the development of thick cuticle with the powdery (waxy) coating they appear to be in surface level (figure 4). In the ovary stage when there is no thick cuticle the stomata appear highly raised above the surface (figure 5). Large number of trichomes develop on the epidermis of the spine and fruit (figures 6-8). The trichomes are of two types, uniseriate and multiseriate. The uniseriate trichome is 2-3 celled (figure 7). The multicellular multiseriate trichome is formed of a central column of cells surrounded by 3 or 4 vertical rows of cells (figure 8). It always terminates in a single cell, which is the continuation of the central row of cellr. This terminal cell has a broad base and narrow blunt end (figures 8, 9). The spines start their development at the ovary stage. In the ovary wall 2-4 epidermal and the underlying hypodermal (subepidermal) cetls become slightly protruded over the surface (figure I0). These cells are denser with prominent central nuclei. Later these protruded cells and the underlying ground cells divide several times and forma mound (figure 11). The epidermal initials divide only anticlinally, but the hypodermal and underlying layers divide both anticlinally and periclinally. The cells of the mound after fertilization of the ovary divide and elongate rapidly and the spines increase in size (figures 12, 13). The branching of the spine can be observed in the early stages of its development (figure 13). The epidermal spine initials develop into the spine epidermis by anticlinal divisions and celI elongation. The inner cells of the spine ate derived from the ground tissue layers by anticlinal and periclinal divisions. In the course of spine development the branches of the fruit vasculature enter into the spine (figure 14). Laticifers are atso seen in the spine. A mature spine measure 4-7 mm in length and 0-5-1 mm in thickness. The spines at the basal and terminal parts of the fruits are smaller than those in the middle region. The mature spine consists of an epidermis enclosing parenchymatous ground tissue with vascular strands and laticifers (figures 14, t5). The epidermal cells ate elongated paralM to the long axis of the spine covered by cuticle. Both the uniseriate and multise¡ trichomes are present on the spine (see figure 6). The trichomes are more on the spine than in the fruit surface. The central cells of the spine are polygonal to rounded in shape and the vascular strand passes through the centre of the ground tissue (figures 14, 15). The non-articulated laticifers ate found close to the vascular strands (figure 15). These spiny outgrowths never fall off from the fruit, even after the drying of the fruit watl tissues. Fruit wall ornamentations in P. daemia 17

Figures 1--6. 1. Morphology of follicle ~x0-9). 2. Transection of folIicle, see the branched spines at arrows and unbranched at arrowhead ~ • 31. 3. SEM of a developing fruit surface { x 43). 4. SEM of a mature fruit surface ( < 720). 5. SEM of the ovary wall ( x 660). 6. SEM of a spine s,urface ( • 56). (h, Hair: mh, multiseriate hair: s, spine; st. stomata: uh, uniseriate hair). 18 P M Kuriachen and Yash Dave

ioe i~ ~~~

..m~~ 84Ir-.

~ ~~i ~ ~

Figures 7-15. Fruit wall ornamentations in P. daemia 19

4. Discussion

The surface ornamentation of the fruit of P. daemia is well understood with the use of scanning electron microscope. The waxy coating of the cuticle forman additional protective layer of the fruit. The raised stomata on the ovary wall appear surface borne on the pericarp due to the development of a thick Cuticle, Trichomes developed on the fruit and spine surfaces. The spiny outgrowth in P. daemia is found developing from the cells of epidermal and hypodermal layers of the ovary wall. The epidermal layer develops into the spine epidermis and hypodermal cells contribute for the development of ground or inner cells. On the basis of ontogenic and structural studies it is worth to recheck the terms used for the outgrowths of P. daemia follicle. The terms soft spines, echinate and softly echinate are used so lar for describing the fruit of Pergularia (Hooker 1885; Kirtikar and Basu 1933; Cooke 1958; Santapau and Irani 1960; Shah 1978; Matthew 1983). According to Lawrence (1951) echinate means 'a stout bluntish prickle' and Jackson (1927) defined prickle as 'an outgrowth of the rind or bark ~. But in P. daemia this outgrowth develops from epidermal as well as hypodermal layers and is having well differentiated vascular supply coming from the mesocarp. This structure thus seems more analogous to the spines of Ricinus and Datura described by Sharma (1964) and Dave et al (1980) respectively than the soft spines of Momordica dioica (Thanki 1978). In Momordica the spines ate devoid of vascular supply and is described as superficial outgrowths of the fruit skin. In P. daemia the spine is found to be a well organized structure, having all the tissue components present in the fruit wall. The spine vasculature which is the continuation of the pericarpic vasculature firmly holds these tender structures in the mature as well as dehisced and dry fruits. Laticifers seen in the spine are similar to that found in the fruit. Trichomes are also present on the spine as on the fruit surface. Thus, the spiny outgrowth seems to be the continuation of the pericarpic tissue, but it keeps its integrity by the independent development from the epidermal and hypodermal spine meristem. According to Sharma (1964) 'a spine is a sharp pointed woody or hardened body provided with a distinct vascular supply, it may be a branch, a petiole, a stipule or other part of a plant body'. But in P. daemia the only difference is that this spiny outgrowth is softer than that of Ricinus and Datura. Hence the term 'soft spine' seems to be adequate for this fruit projection.

Figures 7-15. 7. Uniseriate hair ( x 457). 8. Multiseriate hair, see the terminal pointed cell with broad base and narrow tip (• 9. SEM of the terminal portion of multiseriate hair ( x 430). 10-13. Developing stages of spine. 10. A portion of ovary wall in transection, see the protruded spine meristem at arrow ( • 330). 11. A portion of young pericarp in transection, see the spine mound at arrow (x 320). 12. Enlarging spine mound (• 290). 13, Elongating spine, see the branching at arrow (x 90). 140 Longi- section of mature spine ( • 40). 15. Basal part of a mature spine in longisection ( x 120). (ep, Epicarp; gt, ground tissue; la, hair; I, laticifer; m, mesocarp; me, mesoderm (ground tissue); mvs, mesocarpic vascular strand; oe, outer epidermis; s, spine; vb, vascular bundle; vs. vascular strand). 20 P M Kuriachen and Yash Dave

Acknowledgements

We are thankful to the University Grants Commission, New Delhi for financial assistance and Mr P J Bose (ATIRA) for taking scanning electron micrographs.

ReŸ

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