Studies on the Trichomes of Some Oleaceae, Structure and Ontogeny

Home , Jasmineae, Nyctanthes, Oleaceae, Verbenaceae

STUDIES ON THE TRICHOMES OF SOME OLEACEAE, STRUCTURE AND ONTOGENY

B~ J. A. INAMDAR (Department of Botany, Sardar Patel Univeraity, Vallabh Vidyanagar, Gujarat) Received August 22, 1967 (Communicated by Prof. V. Puff, r.A.sc.)

ABSTRACT Some twelve types of tricho~aes are described for four species of Jasminum and Nyctanthes arbor-tristis L. They fall under two main categories, the eglandular and the glandular trichomes. The systematic position of Nyctanthes seems to be quite natural in the family Oleaceae.

INTRODUCTION The family Oleaceae has received considerable attention of the botanists particularly with reference to the systcmatic position of Nyctanthes and the monotypic genus Dimetra. Airy SEaw (1952) transferred these gcnera to the Verbenaceae on morphological grounds. Stant (1952) has supported Airy Shaw on anatomical grounds. Johnson (1957) in a review of the family Oleaceae opined that Nyctanthes should be excluded from Oleaceae based on the cytological findings of Taylor (1945). On the other hand the embryological data (Patel, 1963; Kapil, 1967) suggests that Nyctanthes should be retained in the Oleaceae. Several workers (De Bary, 1884; Cowan, 1950, Goodspeed, 1954; Carlquist, 1958, 1959a, 1959b, 1959c, 1961; Mathur, 1961 ; Ramayya, 1962 a, 1962b, 1963) have described the structure and development of trichomes and glands in several angisoperm families. The present investigation was carried out to find if the trichomes ~nd glands could be of any help in settling the doubtful systematic position of Oleaceous genera. The present paper deals with the study of eglandular and glandular (glands) trichomes on the vegetative organs of four species of Jasminum, viz., J. auriculatum L., J. flea'ile Vahl, J. officinale L., J. sambac Ait. and Nyctanthes arbm'-tristis L. The information on the trichomes of Oleaceae is still meagre as it is clear from Solereder's (1908, p. 521) account who described only three types 164 Trichomes of Some Oieaceae, Structure and Ontogeny 165 of trichomcs in Oleaceae. They are, peltate, unicellular and simple uniseriate trichomes. Metcalfe and Chalk (1950, p. 895) have followed Solereder.

MATERIALS AND MBTHODS The vegetative shoots were fixed in FAA and the customary methods of dehydration, infiltration and embedding were followed. Sections were cut at the thickness of 8 microns and stained with Regaud's haematoxylin and fast green. Temporary whole mounts cleared in warm 2.5 ,°l, NaOH and stained in aqueous safranine were also used.

OBSERVATIONS In the present investigation of 5 species of Oleaceae t2 types ofeglandular and glandular trichomes have been observed. They are: (i) Simple unicellular, (ii) Simple uniseriate filiform, (iii) Conical, (iv) Cylindrical, (v) Truncate, (vi) Fusiform eglandular, (vii) Cylindrical glandular, (viii) Pel. tate glandular, (ix) Capitate glandular, (x) Fusiform glandular, (xi) Clavate glandular, (xii) Capitate filiform glandular trichomes.

(i) Simple Unicellular Trichome~ (Fig. 1: 2, Fig. 4: 1-3, 5: 8) Simple unicellular trichome originates from a papillose protodermal cell which becomes delimited from the adjoining cells by its larger size, promi- nent nucleus and dense cytoplasm. This hair initial (Fig. 4: 1) gradually elongates and becomes vacuolated (Fig. 4: 2). This becomes more and more vacuolated as the hair undergoes elongation (Fig. 4: 3, Fig. 5: 8). Ulti- mately both the nucleus and the cytoplasm degenerate. The outer walls are either straight, somewhat convex or concave and cutinised. In Nyctanthes these trichomes are conical and are surrounded by eight epidermal cells at the base.

(ii) Simple Uniseriate Filiform Trichomes (Figs. 1: 1, Fig. 2: 1-5, Fig 3: 1--4, Fig. 4: 19, Fig. 5: 1) The simple uniseriate filiform trichome initiates from a papillate protodermal cell which becomes distinct from the adjoinitng cells by its larger size, promine:nt nucleus and dense stai~ni~g propertks (Fig. 2 : 1, Fig. 3 : 1). This hair initial becomes vacuolated and divides by a pericli~nal wall to form a basal cell (bc) and an outer cell (ac) (Fig. 2: 3, Fig. 3: 2). Successive pericli~aes in an outer cell result i,n an ul~iseriate 3-12-celled trichome (Fig. 1 : 1, Fig. 2: 4-5, Fig. 3: 4, Fig. 4: 19, Fig. 5: 1). Normally the basal cell relnains 166 J.A. INAMDAR undivided and forms a simple foot but sometimes as in J. flexile Vahl the basal cell divides anticlinally (Fig. 4), hence the foot becomes compound. The outer walls of the trichomes are cutinised. The trichomes are constricted at the cross walls. The cross walls are thin. The lateral walls are either straight, slightly convex or concave. The contents are translucent in some cases only.

FIo. 1. ,¢asminum attrieulatum L. (l-ll. >: 544) : I. Simplc uniseriate filiform tricholnc. 2. Simple unicellular trichome. 3. Clavate glandular trichome. 4. Clindricat glandular trichome. 5. Capitate glandular trichome. 6. T.S. through a head of captitate glandular trichome. 7. Fusiform glandular trichome. 8, Truncate trichome. 9. Conical trichome with wavy outline and simple foot. 10. Conical trichomc with compound foot. 11. Hooked cylindrical trichome. Trichome~ of Some 01eaceae, Structure and Ontogeny 167

(iii) Conical Trichomes (Fig. 1: 9-10, Fig. 4: 21-22) Their ontogeny is similar to that of simple uniseriate filiform trichomes. The body is unisetiate, entire, 2-many-celled, conical with an acute or obtuse apex. The foot is either simple or compound. The trichomes are constricted at the cross walls, often nodulose at the joints. The cross walls are thin or thick. The outer walls are either straight, slightly convex or concave and cutinised. In J. auriculatum L. sometimes the conical trichomes have wavy outer walls (Fig. 1 : 9). These are termed as wavy conical trichomes.

(iv) Cylindrical Trichomes (Fig. 1:11, Fig. 4: 20)

These trichomes have a simple foot and an uniscriate cylirdrical filiform 2-many-celled body with rounded apex. The trichomes constricted at the cross walls, rarely nodulose. The cross walls are thin or thick. The outer walls are mostly straight and cutinised. In J. auriculatum L. the cylindrical trichomes are sometimes hooked at the apex (Fig. 1: 1l).

(v) Truncate Trichomes (Fig. 1: 8) These trichomes are differentiated into a compound foot and an entire 2-celled body. They have a truncate rounded apex. They are constricted at the cross walls which are thin or thick. The outer walls are either straight, slightly convex or concave and cutinised.

(vi) Fusiform Eglandular Trichomes (Fig. 5: 7) These trichomes have been observed in Nyctanthes only. They are differentiated into a simple or compound foot, a unicellular stalk and a fusiform head. The nucleus and the cytoplasm both degenerate and the whole trichome becomes highly vacuolated. Their outer walls are straight, slightly convex or concave and cutinised. Their ontogeny is similar to that of fusiform glandular trichomes which is discussed later.

(vii) Cylindrical Glandular Trichomes (Fig. l: 4, Fig. 2: 14) In the present study they have been observed only inJ. auriculatum L. and J. flexile Vahl. They are not very common. They l~ave a simple foot and a uniseriatc cylindrical bedy. TEe distal cell is somctimes knobbed. The trichomes are cutinised at the outer walls ard constricted at the cross walls. The cross walls are t~in and the lateral walls are either straight, slightly convex or concave. The contents are glandular and translucent. 168 J, A. INAMDAIt

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Plo. 2. Jasminm flexlle Valfl. (I-20, x 544). i. Papillose protodermal cell-hair initial. 2. Hair intial showing periclinal division. 3. Formation of basal and an outer cell. 4. Simple uni~eriate trichome with compound foot. 5. Simple uniseriate trichome with simple foot. 6-9. Stages in the development of peltate glandular trichome. 10-11. Peltate glandular trichomes. 12. C,apitate ~andular tfichome. 13. C,apitate glandular trichome T.S. through the head. 14. Cylindrical glandular trichome. 15-17. Stages in the development of fusiform glandular trichome. 18-19. Fusiform glandular, trichomes. 20. Clavate glandular trichome. ((be, basal cell; a¢., outer fell; ~c, stalk cell and k¢, head cell.) Trichomes of Some Oleaceae, Structure and Ontogeny 169 (viii) Peltate Glandular Trichomes (Fig. 2: 6-11, Fig. 3: 5-10, Fig. 4: 4-11, Fig. 5: 13) The hair initial (Fig. 4: 4) divides perielinally into a basal cell (be) and an outer cell (ac) (Fig. 4: 5). The outer call divides again periclinally into a stalk cell (sc) and a head cell (bc) (Fig. 2: 6, Fig. 3: 5, Fig. 4: 6). The basal cell forms a simple foot and the stalk cell the unicellular stalk. Successive anticlines in the head c¢11 result in a peltate head or shkld (Fig. 2: 10-11, Fig. 3: 8-10, Fig. 4: 10, Fig. 5: 13). According to Solercdcr (1~cC8, p. 524) the shield consists of four calls only in J. ~2ffcinale L. and Nyctanthes arbor. tristis L. While in J. sarnbac Ait. and other specks of Jaemin~m the shkld consists of 16 cells. Dmirg the present study it has been invariably observed in J. a~cinale L. that the shkld consists of 4-8 cells rarely mole (Fig. 3 : 8-10). In Nyctanthes the shield consists of 4-8 cells. In J.flexile Vahl and J. sarabac Ait. the shield consists of 6-8 cells. The tficlzcmcs are situated in the shallow depressions of the epidermis: The outer walls are cutinised. The shield is densely cytoplasmic. The contents are granular ar, d translucent.

(ix) Capitate Glandular Trichomes (Fig. 1: 5-6, Fig. 2: 12-13, Fig. 3: 15-17, Fig. 4: 12-16, Fig. 5: 9-10) These trichomes follow the same course of development as the peltate trichomes but here the divisions in the head cell are not strictly anticli~:al. They may be anticlinal, periclinal, oblique or irregular. The trichcmes have a simple foot and an unicellular stalk wt, ich may be either short or long (Fig. 4: 12-15). The head is multiccllular censistirg of stvelal calls. There are several variants of these tricl-~cmes (see Figs.). Tl-.ey mainly vary in their shapes. The outer walls of the tricl:cmts are cutinis¢d. They are also situated in the shallow pits of the epidexmis. The contents are granular and translucent. In Nyctanthes rarely the basal cell undergoes anticlinal division, the stalk cell also divides anticlinally to form a biseriate stalk. The head consists of 4 cells only which lie parallel to each other (Fig. 5: 11-12). (x) Fusiform Glandular Trichomes (Fig. 1 : 7, Fig. 2: 15-19, Fig. 3: 11-12, Fig. 4: 17, Fig. 5: 14) The hair initial divides periclinally to give rise to a basal cell and an outer cell (Fig. 2: 15). The outer cell divides again pclielirally into a stalk cell and a head cell (Fig. 2: 16). The initial divisions in the head cell are periclinal (Fig. 2: 17). The divisions in the lower ceils are anticlhaal or 170 J.A. INAMDAR

Fl6. 3. Jasminum officinale L. (1-17, "< 544). t-3. Stages in the development of simple uniseriate filiform trichome. 4. Simple uniseriate filiform trichome with simple foot. 5-7. Stages in the development of peltate glandular trichome. 8-9. Peltate glandular trichomes. 10. T.S. through the head of a peltate glandular triehome. 11-12. Fusiform glandular trichomes. 13-14. Clavate glandular triehomes. 15-17. Capitate glandular triehomes. oblique. Ultimately a fusiform trichome is formed with a simple foot, unicellular stalk and a multicellular head. The outer walls of the trichomes are Trichomes. of Some Oleaceae, Structure and Ontogeny 171 cutinised. The head is densely cytoplasmic. The contents are granular and translucent.

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FrG. 4. Jasminum sambac Ait. (1-22, × 544). 1-3. Stages in the development of simple unicellular trichome. 4-9. Stages in the development ofpcltate glandular trichome. 10. Peltate glandular trichome. 11. T.S. through the head of a peltate glandular trichome. 12-15. Capitate glandulartrichomes. 16. T.S. through the head ofa capitate glandular mrichomeo 17. Fusifort glandular trichome. 18. Clavate glandular trichome. 19. Simple uniseriate filiform trichome. 20. Cylindrical trichome. 21. Conical trichome with compound foot and obtuse apex. 22. Conical trichome with simple foot and acute apex. (be, basal cell; ac., outer cell; sc, stalk cell and he, head ceil.) 172 J.A. INAMDAR

(TA) Clavate Glandular Trichomes (Fig. 1 : 3, Fig. 2: 20, Fig. 3: 13-14, Fig. 4: 18, 5: 15) The development of this trichcme is similar to that of fusifoim glazdul~r triehome but the plane of divisions in the head cell is not constant. It may be anticlinal, periclinal, oblique or irregular. Finally a club-sl:aptd trichcme is formed. It has a simple foot, unicellular stalk and a multicellular head.

FIe. 5. Nyctanthes arbor.tristis L. (1-15, ×544). 1. Simple unimiate filiform trichome. 2-5. Stages in the development of filiform capitate glandular trichome. 6. C.apitate filiform glandular trichoYne. 7. Fusiform egl~mdular trichome. 8. Simple unicellular conical trichome. 9. Capitate glandular trichome. 10. T.S. through the head of a capitate glandular trichome. 11. Biseriate capitate glandular tricbome. 12. T.S. through the head of a biseriate capitate glandular trichome. 13. Peltate glandular trichome. 14. Fusiform glandular trichome. 15. Ogvgte glandular trichome, Trichomes of Some Oleaceae, Structure ond Ontogeny 173

The outer walls of the trichome are cutinised. The head is densely cytoplasmic with granular and translucent contents. They are also slightly sunken in the pits of the epidermis.

(xi) Captiate Filiform Glandular Trichomes (Fig. 5: 2-6) The hair initial (Fig. 5: 2) divides periclinally to give rise to a basal cell and an outer cell (Fig. 5: 3) which divides again to give rise to a stalk cell and a head cell (Fig. 5: 4). The basal cell forms a simple foot, while the stalk cell undergoes one or two periclinal divisions (Fig. 5: 5) to form a stalk of 2--4 cells, the head cell remaining undivided. The trichomes are cutinised at the outer walls and constricted at their cross walls. The lateral walls are straight, slightly convex or concave. The head is unicellular, broader than the stalk swollen to an oblong-ovoid or ovate form (Fig. 5: 6). The contents in the head cell are dense, granular and translucent. These trichomes have been observed in Nyctanthes only.

DIscussioN

Solercder (1908) and Metcalfc and Chalk (1950) have described only three types of trichomcs, viz., unicellular, simple uniseriatc and peltatc trichomcs in the family Oleaceae. Further according to Solcreder in the family Oleaceae the pcltatc trichomcs l~ave a unicellular stalk and the shield is segmented by vertical wails only into variable number of cells showing different orientation. The present ontogrnetical stt:diesconfilm the observations of Solcrcdcr regarding the peltate trichomes, but there are several othcr glandular trichomcs in which thc shield or the head is not segmented solely by vertical walls but by anticlinal,pcriclinal, oblique or irregular walls, they have been termed as capitate, fusiform, clavate glandular trichcmes as the case may be. The twelve types of trichomcs observed during the present studies can be classilicd as follows: Trichomes of Jasminum (4 spp.) and Nyctanthes Eglandular Glandular

L Simple unicellular I. Cylindricalglandular -II. Simple uniscriateflliform -II. Pcltateglandular Ill. Conical Ill. Capitateglandular IV. Cylindrical IV. Fusiform glandular V. Truncate V. Clavateglandular VI. Fusiform eglandular VI. Captitate filiform glandular 174 J.A. INAblDAR

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Systematic position of Nyctanthes L. The genus Nyctanthes is placed in the family Oleaceae, Airy Shaw (1952) considered it to be a member of Verbenaceae and placed it in the new sub- family Nyctanthoideae of Verbenaceae. Stant (1952) and Johnson (1957) have supported Airy Shaw. It may be mentioned here that Hutchinson (1959) makes no refcrence to Nyctanthes either under the Verbenaceae or the Oleaceae.

From the available morphological data and the present studies the author believes that Nyctanthes stands nearer to Oleaceae rather than Verbe~aeeac on account of the following reasons: (i) Generally Nycmnthes shows presence of regular corolla and two stamens as in other Oleaceae. (it) Pleiomerism in the corolla and carpelloid stamens are fi'equent in Nyctanthes and Oleaceae. They are not reported in Verbenaceae. 0it) The contorted rotate corolla of Nyctanthes is not typically Verbenaceous. Airy Shaw (1952, p. 271) also expressed that the corolla of Nyetanthes is somewhat like that of a Jasminurn. (.iv) The ovary of Nyctanthes is bilocular with one ovule in each locule, a feature comparable with Jasminum of Oleaceae. The ovary of Verbenaceae is tetra-locular and possesses one ovule in each locule. (v) Foliar nectaries are absent in Nyctanthe6 and other Oleaceae while they are prcscnt in Verbenaeeae. (vi) Stomata are anomocytic in Nyctanthes and Oleaceae. In Verbenanceae the stomata are mostly diacytic.

Stant (1952) refers only two types of hairs in Nyclanthes, viz., unicellular trichomes and glandular hairs, but during the present studies some eight types of trichomes have been obserxed on the stem and leaf of Nyctanthe~ (see Table I). It seems Stant has failed to observe them. Out of these eight types observed in Nyctanthes, simple uniseriate filifoJm, capitatc glandular, fusifoJm glandular and clavate glandular trichomes are commola with all the four species of Jasminm while peltate glandular trichomes arc common with .L flexile Vahl, .L officinale L. and J. sambac Ait. The simple unicellular trichomes are common with J. auriculatzan L. al'~d J. scnTbac At1. All the six types are commc~n with J. sambac Ait. Moreover, lheir ontogtn:y is also similar. 176 J.A. INAMDAR

CONCLUSION

Thus from the morphological data and the present studies there is a strong evidence that Nyctanthes should be retained in the family Oleaceae and should not be transferred to the Verbenaceae. This view is substantiated by the embryological studies of Nyctanthes and other ~Oleaceae made by Patel (1963) wherein he has concIuded that the embryological features of Nyctanthes are similar to other Oleaceae rather than the Verbenaceac. Kapil (1967) while reviewing the literature on the embryology of the family Oleaceae has also remarked that 'Nyctanthes' has many features common with the Oleaceae and should not be included in Verbenaceae. From the present studies and the available literature it seems that the position of Nyctanthes is more natural in the tribe Jasmineae of Oleaceae.

ACKNOWLEDGEMENTS

The author is grateful of Prof. V. Purl for reviewing the paper. Thanks are due to Drs. J. J. Shah, G. L. Shah and R. J. Patel for help and encourage- ment. Special thanks are due to Dr. N. Ramayya af Osmania 'University for going through several of my diagrams and helping me in the interpreta- tions of the trichomes. Last but not the least thanks are due to my students Mr. K.V. Poulos and Mr. M. A. Francis for helping me in taking the photographs of my plates.

REFERENCES

I. Airy Shaw, H. K. .. "Note on the taxonomic position of Nyctanthes L. and Dimetra Kerr," Kew Bull., 1952, 271-72. 2. Carlquist, S. .. "Study and ontogeny of glandular trichomes of Madiinac (Compositae)," Amer. J. Bet., 1958, 54, 675-82. 3. .. "Studies on Madiinae: Anatomy, cytology and evolutionary relationships," Aliso, 1959a, 4, 171-236. 4. .. "The l~af of Calydenla and its glandular appendages," Ibid., 1959b, 46, 70-80. 5. .. "Glandular structures of Holoearpa and their ontogeny," Ibid., 1959c, 46, 300-08. 6. .. Comparative Plant Anatomy, Holt, Rin~hcrt and Winston, New York, 1961. 7. Cowan, J. M. _ The PJaxtodendron, Leaf; A Study of Epidermal Appendages, Oxford and Boyd, London, 1950. 8. De Bary, A. .. Comparative Anatomy of Vegetative Organs of Phanerogams and Ferns, Oxford, 1884. Trichome$ of Some Oleo~'eae, Structure and Ontogeny 177

9. Goo~hpeed, T. H. .. The Genus Nicotiana, Chronica Botanica, Waltham, Mass., 1954. 10. Hutchinson, J. .. Families of Flowering Plants, Vol. 2, Oxford, 1959. 11. Johnson, L. A. S. .. "A review of the family Oleaeeae," Contribution New S. Wales. Natl. Herb., 1957, 2, 395-418. 12. Kapil, R. N. .. "Seminar on Comparative Embryology of Angiosperms," Abstracts, 1967, p. 87. 13. Mathur, S. L. .. "'Structure and ontogeny of the epidermal appendages on floral organs of Oeimum basilicum L.," Curr. 5ct., 1961, 30, 471-73. 14. Metcalfe, C. R. and Anatomy of the Dicotyledons, Vol. 2, Clarendon Press, Oxford, Chalk, L. 1950. 15. Patel, N. K. .. "'A contribution to the morphological and embryological studies in Oleaeeae, Ph.D. Thesis, Gujarat University, Ahmedabad, 1963, Unpublished". 16. Ramayya, N. ... "'Studies on the trichomes of some Compositae. I. Genera] structure," Bull. bet. Surv. India, 1962a, 4(1-4), 177-88. 17. ... "'Studies on the trichomes of some Compositae. IL Phylogeny and classification," Ibid., 1962b, 4(1-4), 18992. 18. .. "'Modes of development in the trichomes of Compositae, '~ Curt. Sci., 1963, 32, 27-28. 19. Solereder, H. ... Systematic Anatomy of Dicotyledons, Vol. 2, Clarendon Prc~s, Oxford, 1908. 20. Stant, M. Y. .,. "Anatomical evidence for including Nyetanthes and Dimetra in the Verbcnaceae," Kew Bull., 1952, 273-76. 21. Taylor, H. .,. "Cyto.taxonomy and phylogeny of the Oleaceae," Britwnia, 1945, 5(4), 337-67.