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A S T U D Y O F B R A C H Y S C L E R E i D S i N T W O M E M B E R S O F CAPPARIDACEAE

BY MANJU SHARMA (MRS.)* (Botany Department, Lucknow University, Lucknow)

Received September 4, 1969

(Communicated by Professor L. Narayana Rao, F.a.m.)

ABSTRACT

A study of brachysclereids in two members of Capparidaceae namely Capparis and Crataeva reveals certain points of taxonomic interest. Three species of Capparis, i.e., C. grandis L.F., C. sepiaria L.F. and C. horrida, and one species of Crataeva, i.e., C. religiosa Forst. show some similarities as well as differences in the distribution, structure and ontogeny of sclereids. In Capparis, brachysclereids have a more regular pattern of distribution in the stem and leaves. In Crataeva they are absent in leaves. In Capparis brachysclereids are simple, with very closely lamellated secondary wall devoid of pit-canals. There are some disorganised contents in the lumen. They develop from parenchymatous cells having dense protoplasmic contents which are differentiated as sclereid initials. In Crataeva sclereid initials are large empty cells, produced generally after the activity of secondary cambium has begun. The sclereids are very thick-walled, with numerous pit-canals and no contents. The differences in the sdereid features are helpful in distinguishing these two genera.

INTRODUCTION AND TECHNIQUES

FOLIAR and cauline sclereids of three species of Capparis, i.e., C. grandis L. F., C. sepiaria L. F. and C. horrida, and cauline sclereids of Crataeva religiosa have been investigated in the present paper. The form and relation= ship with the other tissues like the veins and veinlets in two species of Cap- paris, i.e., C. moonff and C. orbiculata has already been described by Rao (1951) without mentioningthe stem sclereids. The chief importance of this type of study as already pointed in earlier angiosperm and conifer species (Rao and Malaviya, 1962, 1963, 1964, 1965, Rao and Sharma; 1967, 1968,

*The present address of the author is Dr. Mrs. Manju Sharma, B-11, Kailash Colony, New Delhi-48.

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Malaviya, 1962-1963) is the role of sclereids in systematic botany. A study of their form and distribution is helpful in distinguishing the primary and secondary woods of the members of the same family and also closely allied families.

The material of C. grandis was obtained from Pilani and the other species were locally available. They were all fixed in form. acetic alcohol. The usual techniques of Foster (1946, 1949) were used for maceration, clearing and staining.

Sclereids of the two genera are described separately for the convenience of illustrations.

DISTRIBUTION, STRUCTURE AND ONTOGENY OF SCLFREIDS IN Capparis SPECIES

The sclereids are however not found in young primary stems, or very young leaves. They make their appearance at a fairly late stage of the plant, when the secondary growth has taken place in the stems. In C. grandis the sclereids form a sort of ring all round the vascular cylinder. They are found just after the region of the secondary phloem, after the sclerenchymatous patches, and also in between the sclerenchyma in the intervenirg parenchymatous tissue. This ring of brachysclereids which is broken up at certain places, usually becomes continuous in very old stems (Figs. 1 and and 2). There are no sclereids in the pith regions, in fact, the pith is hollow in older stems.

In C. s~eplaria, tlie distribution of sclereids in the stem (Figs. 3 and 4) is similar to the first species but the pith is solid here, and a few thick- walled cells occur in the pith region.

In C. horrida the sclereids are not so abundant as in the other two species. They do not form a separate ring as in the other species outside the secondary vascular cylinder, but they occur in between the sclerenchymatous patches and are also found in the cortex just below the epidermis (Figs. 5 and 6).

The leaves do not have many sclereids. There are no sclereids at all in the petiole of C. grandis. Just one or two scattered sclereids occur in the midrib region directly below the epidermis (Fig. 7). Very few sclereids occur in the mesophyll tissue (Figs. 8 and 9). They do not bear any direct apparent relationship to the veins and veinlets. In C. sepiaria also there are no sclereids in the midrib region and few occur in the laminar portion

A Study of Brachysclereids in Two Members of Capparidaceae 49

occasionally near a veinlet at its end. But this is so rare that it will not bo proper to call them terminal selereids (Fig. 10).

In C. horrida in the midrib region just surrounding the vascular cylinder, there is a sclerenchymatous ring. This is broken up at certain places by parenchymatous tissue. In this tissue a few sclereids are found which make the whole ring continuous (Fig. 11). Just one or two may also be found in the lamina (Fig. 12).

The form of the sclereids is more or less constant in the three species. They are sometimes roughly rounded (Fig. 13), oval (Fig. 14), or slightly elongated (Figs. 15 and 16). The form suggests their being placed under the section brachysclereids or stone-cells of Tschirch (1889) and Foster (!949). These stone-cells sometimes have nuclei in their lumen (Fig. 12) even at maturity. The contents do not disappear all together in adult sclereid s, and the protoplast usually remains in a shrunken disorganised state, usuall Y near the secondary wall (Figs. 13-16). The secondary wall is very thick, lamellated and devoid of any pits or pit-canals.

The ontogenetic development of the sclereids in different organs is the same in all the three species studied in this paper. The sclereids are transformed parenchyma cells of either the stem cortex, or the mesopl-)ll cell of the leaf. The development involves chiefly an increase in size of the initial cell accompanied by " secondary sclerosis " (Foster, 1949) of these cells. The sclereid initials with dense, granular protoplasmic contents make their appearance amidst the cortical parenchyma cells, after the beginning of secondary activity (Fig. 17). A few initials are also seen in between the patches of sclerenchyma in the intervening parenchyma cells. In later stage, the contents more or less start accumulating in the centre and there is a slight increase in the size of the cell (Fig. 18). The protoplast starts the deposition of lignin (Figs. 19 and 20). Afterwards as the secondary wall is built up there is degeneration of the cell contents (Fig. 20). The wall increases in thickness (Figs. 21 and 22) as more lignin is deposited gradually. Very soon, a sort of ring of brachysclereids is formed just outside the sclerenchymatous patches (Figs. 21 and 22). In some cases the protoplast in a fully developed sclereid is seen as a disorganised mass (Figs. 21, 23 and 24). The ontogeny of the sclereids in C. grandis and C. horrida is just similar.

In C. horrida a few sclereids also develop in the cortex, formed after the secondary activity. The initial may also be one of the epidelmal cells (Fig. 25) with dense cell contents ~and a promir_ent nucleus. This is very

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F~Gs. 1-28


soon converted into a sclereid by the usual " sclerosis " (Foster, 1949) (Fig. 26). In C. horrida, however, the ontogeny differs slightly from the above pattern seen in the other two species. Here new sclereid initials are further produced in the cortex built up by the secondary vascular cambium. There are very few sclereids found, scattered in the mesophyll tissue. Their development does not differ at all from that of the stem. The initial with dense protoplasmic contents and no chloroplasts may be located i'n the spongy mesophyU region or sometimes near a vascular strand (Fig. 27) or it may be one of the cells of the palisade (Fig. 28). The initials may have oval or slightly angular outline in the spongy mesophyll. Sometimes there may be found a few partly lignified parench.yma cells in very old leaves. In these the wall is not very thick and no pits are seen. These are also sclereids, as they are developed from parenchyma cells, but their development is checked at certain stage, due to some unknown reasons, and so they do not reach maturity. These type of partially sclerised cells or incomplete sclereids were found in a few old leaves of C. horrida, in tke mesophyll region.

DISTRIBUTION, STRUCTURE AND ONTCGENY OF SCI_I~I~EIDS 1N Crataeva religiosa

Brachysclereids are absent in the leaves. In the stem they occur in the cortical region outside, the vascular cylinder generally in a diffuse manrer and also in between the cortical sclerenchymatous patches (Figs. 29-31) in groups of two to many. The number is very large in the nodal region of the stem from where the branches arise.

The sclereids may be rounded (Fig. 32), oval (Figs. 33 and 34) or even slightly angular (Fig. 38). According to the form they are placed under the section brachysclereids of Tschirch (1889). The lumen of the sclereid is generally empty at maturity. The secondary wall is very thick, closely lamellated, liguified and provided with numerous pit-canals (Figs. 34-38).

Sclereids generally do not develop till the initiation of the secondary activity. But in the future nodal regions of the primary stems, even before the secondary activity starts and the lateral branches arise, sclereid initials may be recognised. No sclereid initials are found in the primary stems in the internodal sections. The initials are not easily recognisable, unless one sees for the developmental stages. They are the parenchyrna cells produced by the activity of the secondary cambium (Fig. 39). They are generally bigger in size than the surrounding cells. These further increase in size before the beginning of sclerosis (Fig. 40). Figures 41 and 42 show

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33

p h " O ~ " " '

FIGS.. 29--46


groups of cells in the cortex undergoing sclerosis. Some sclereid initials first appear at particular places of the primary stem which later on become the nodal regions (Figs. 43 and 44).

The parenchymatous cells in between the sclerench~ma also are scle- rosed and converted into sclereids (Figs. 45 and 46). Sclereids first appear in the cortex and later on in between the sclerenchymatous patches (Fig. 46). The secondary wall gradually increases in thickness and pit-canals appear later on.

DISCUSSION

Observations on the sclereids of two members of Capparidaceae, i.e., Capparis and Crataeva, show that there are some differences in the sclereid distribution and form between these two taxa.

There is some difference in the sclereid features of the different species of Capparis, although the form and ontogeny of the sclereids is similar. In C. grandis and C. sepiaria, sclereids form a more or less continuous ring outside the secondary phloem in the stem, while in C. horrida sclereids are present in between the sclerenchyma patches. This difference, though minor, is helpful in distinguishing them. In the two species of Capparis described by Rao (1951) C. moonii and C. orbiculata sclereids are present in leaf and have direct relationship with the veins and veinlets. But in the species studied in this paper sclereids are very few in the leaves and there is no such relationship with the veins or veinlets.

In Crataeva religiosa the sclereid distribution is similar with C. horrida and it differs from C. grandis and C. sepiaria. The form of sclereid is also slightly different. The secondary wall is very thick, closely lamellated, and provided with numerous pit-canals in C. religiosa. In the different species of Capparis the lamellations are not visible so distinctly and there are no pit-canals. The lumen has some disorganised remains of the protoplast, sometimes along with a nucleus in the adult sclereids of Capparis. In Crataeva religiosa the sclereid lumen is empty at maturity. Sclereid initials also differ in the stems of the two species. In Capparis they generally have dense, granular protoplasmic contents, while in Crataeva they are large empty cells.

These above-mentioned differences are helpful in distinguishing the leaves and secondary woods of these two genera and hence are of some taxonomic significance.

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The sclereids which are produced in between the sclerenchymatous patches, help to complete the cylinder. This view was put-forth by Haber- landt (1914). Foster (1949) had given another example of development of these brachysclereids in those stems that develop a so-called "composite cylinder " of bast fibres and sclereids. The original cylinder is ruptured due to an increase in the diameter of the stem. The parenchyma cells intrude into these gaps, some of them undergo " secondary sclerosis" and the so formed brachysclereids repair the cylinder.

In C. religiosa there are no bast fibres, instead brachysclereids develop in between the sclerenchymatous elements to complete the mechanical tissue cylinder. As already stated brachysclereids develop in large numbers in future nodal regions. Hence giving additional mechanical strength to these organs, at the time of branching. Therefore it seems that sclereids have a mxny-fold function. For example, that of repairing the mechanical tissue cylinder, giving mechanical strength and rigidity and also they are of some taxonomic significance.

ACKNOWLEDGEMENT

I am extremely grateful to Prof. A. R. Rao for his kind and valuable guidance. I am also thankful to Prof. B. N. Mulay of Science College, Pilani, for the material of C. grandis. Many thanks are also due to the Council of Scientific and Industrial Research for financial help.

REFERENCES

I. Foster, A. S.

2.

Haberlandt, G.

4. Malaviya, M.

5.

6. Rao, A. R. and Malaviya, M.

7.

8. and Sharma, M.

. . "Comparative morphology of foliar sclereids in the genus Mouriria," Aubl. J. Arnold Arbor, 1946, 27. 253-71.

. . Practical Plant Anatomy, D. Van Nostrand Company, Inc., Princeton, New York, I949.

. . Physiological Plant Anatomy, Macmillan and Company, London, 1914.

. . " A study of sclereids in three species of Nymphaea,'" Prec. Ind. Acad. Sci., 1962, 56B, 232-36.

. . " A study of sclereids in Nymphoides cristatum (Roxb.) O. Kuntz.," Ibid., 1963, 57B, 223-29.

"The peculair sclereids of Cephalotaxus drupacea Sieb. et Zuc. C.," Ibid., 1964, 59 (4), 228-36.

. . "On lhe distribution, structure and ontogeny of scleroids in Taxus baccata Linn." Prec. nat. Inst. Sci. India, 1965, 31B (3-4), 114-22.

. . "On the nature of sclereids in Picea morinda Dietrich,'" Phyto., 1967, 16(4), 408-11.


9. Rao, A. R. and Sharma, M. "On the selereids of three species of Agathis," Proc. nat. Inst. Sci. India, 1968, 34(5), 244--53.

10. Rao, T . A . . . "Studies on foliar sclereids. A preliminary survey," J. Indian bot. Soc., 1951, 30, 28-39.

11. Tshirch, A. . . Angewandte Pflanzenanatom&, Wien und Leipzig, 1889.

EXPLANATION OF FIGURES

Fins. 1-28. Fig. 1. T.S. of stem of Capparis grandis showing distribution of sclereids diagrammatically, × 32. Fig. 2. Part of the transection of stem of C. grandis, × 100. Fig. 3. T.S. of stem of C. sepiaria, × 32. Fig. 4. Part of the transection of stem of C. sepiaria, × 100. Fig. 5. T.S. of stem of C. horrida, × 32. Fig. 6. A portion of 5, magnified, × 100. Fig. 7. T.S. through midrib in C. grandis showing a few sclereids, x 100. Fig. 8. T.S. of the leaf of C. grandis showing sclereids in the mesophyll region, × 100. Fig. 9. T.S. of the leaf of C. grandis showing sclereids in the mesophyll region. × 100. Fig. 10. T.S. of the leaf of C. sepiaria, X 100. Fig. 11. T.S. of the midrib of C. horrida showing sclereids in between the sclerenchymatous arc, x 100. Fig. 12. T.S. of the leaf of C. horrida showing laminar sclereids, × 100. Figs. 13-16. Various forms of sclereids, × 100. Figs. 17-28. Different stages in the ontogeny of sclereids, x 100.

(c, cortex; i, initial; m, mesophyll; n, nucleus; pl, palisade; scl, sdereid; sl, scieren- chyma; sph, secondary phloem; sw, secondary wall; sx, secondary xylem.)

Fl~s. 29-46. Fig. 29. T.S. of stem of Crataeva religiosa showing the distribution of sc/c- reids diagrammatically, × 7-2. Figs. 30-31. Small portions of the stem magnified to show the detailed structure, x 100. Figs. 32-38. Various forms of sclereids, x 512. Figs. 39-46. Diffe- rent stages in the development of sclereids, x 100.

(c, cortex; gt, ground tissue; i, initial ; l, lumen; p, pits; pc, pit-canal ; ph, phloem;pi, pith; pt, protoplast; scl, sclereid; sl, sclerenchyma; sph, secondary phloem; sw, secondary wall; sx, secondary xylem; x, xylem.)

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