Proo. Indian Aoad. Sci., Vol. 88 B, Part II, Number 5, September 1979, pp. 347-357, 9 printed in .

Taxonomic value of trichomes in Schreb. (Asteraeeae)

B M NARAYANA Department of Post Graduate Studies and Research in Botany, University of Mysore, Manasagangotri, Mysore 570 006

MS received 30 September 1978; revised 9 Juno 1979

Abstract. Trichomes of fifteen species of Vernonia occurring in South India have been studied to evaluate their interrelationships. Eighteentypes of trichomes have been described. Trichomecomplements of these taxa are variable in their structure and organographic distribution. On the basis of the latter, occurrence of biotypes in Vernonia albicans and varieties in Vernonia monosis and Vernonia peninsularis is visualised. Examinationof paired affinity indexes of the triehomecomplements of lower leaf surfaces indicates that V. albicans and V. cinerea; V. monosis wad V. shevaroyensis and V. indica and V. comorinensis are closely related.

Keywords. Vernonia; trichomes; .

1. Introduction The use of trichomes is well established in comparative systematic studies of several groups of angiosperms because of their variety, wide occurrence, ease of preparation for study and close relation of their variation patterns to the taxonomic system (Carlquist 1961). Solereder (1908) was, perhaps, the first person to reveal the systematic value of trichomes, although attempts were made earlier by De Bary (1884) and Goebel (1900). Later, Netolitzky (1932) reviewed the diffe- rent types of classifications of trichomes. Heintzelman and Howard (1948) used the characteristic forms of trichomes as criteria for distinguishing genera and species. Trichomes have been used as a reliable guide to understand the relationships and classification in Rhododendron species (Cowan 1950). In Nicotiana, Goodspeed (1954) found that the trichome complement is of phyletic significance because the types of trichomes point to species origins and their relationships. The hypo- thesis of Gleason (1923) forms a basis for comparative study of trichome patterns and schemes of phyletic groupings. Trichomes of Vernonia are very variable in their structure, development and organographic distribution. Solereder (1908) as well as Metcalfe and Chalk (1950) have mentioned the types of trichomes in Vernonia. Ramayya (1962 b, c) has described the structure, variation, development and distribution of trichomes in in general. A comparative study of trichomes in Vernonia by Hunter and Austin (1967) was fruitful in demonstrating the hybrid origin of a 347 348 B M Narayana species. After working on species of Vernonia, native to United States of America, King (1971), Urbatsch (1972) and Faust (1972) found trichomes to be of syste- matic value in the . Thirty species of Vernonia are reported from South India (Gamble 1956; Shetty and Vivekananthan 1970), but no biosystematic investi- gation has so far been undertaken to clarify the discrepancies in the classification of the genus. The present study on trichomes is an attempt to give a comparative account of the trichomes of leaves, stems and floral parts in the South Indian species of Vernonia for evaluating their interrelationships.

2. Materials and methods

Leaves, stems and floral parts of various species of Vernonia collected from diffe- rent parts of South India were fixed in 3 : 1 absolute alcohol and glacial acetic acid. Leaves were cleared in 1~ aqueous solution of sodium hydroxide at 60~ and transferred to 75~ lactic acid at 60~ until complete clearance took place. The epidermal layers were then separated, stained in safranin and mounted in glycerine jelly. A similar procedure was followed for peels of floral parts and stem to make semipermanent slides. In addition, cross-sections of leaves, stems and bracts were prepared by dehydrating in ethyl alcohol-butanol series. The trichome types were drawn using an Abbe camera lucida. Tables showing the types of trichome per species and the frequencies of leaf trichome per unit area were prepared. Paired affinity indexes were worked out for the trichome complements of the lower epidermis. Trichome types common to both species Paired affinity index = Total trichome types of both species :< 100. Terminology and nomenclature of trichomes is adopted partly after Ramayya (1962b) and some are newly introdttced which are, however, self-explanatory.

3. Observations 3.1. Types of trichomes 3. la. Biseriate vesicular glandular hair (figure 1). Foot : Simple or compound. Stalk : biseriate 2-to 8-celled in each row; cells broader than long; cells of two rows alternate or subopposite; contents translucent, outer walls thick, inner walls thin, cuticular vesicle enclosing 1-3 tiers. Terminal cell usually longer than other cells with dense contents (Ex. V. monosis Chalk). 3. lb. (figures 2 and 3). Foot : Simple or compound. Body : biseriate, 4 to 10 cells in each row, embedded in epidermal pit; cells of two rows subopposite and broader than long. Contents of terminal cell dense. Cuticular vesicle enclosing 1-4 terminal tiers (Ex. V. dalzelliana Drumm. and Hutch. and many other species of Vernonia).

3.2. Biseriate vesicular capitate glandular hair (figures 4 to 7)

Foot : simple or compound. Stalk : biseriate, 1- to 5-celled or more in each row, uniform in breadth or slightly tapering above; cells of two rows alternate, Taxonomic value of trichomes 349

varying in length; contents translucent. Head : biseriate, cells in 1 to 4 tiers, opposite to each other, with dense contents. Cuticular vesicle enclosing the head (Ex. V. gossypina Gamble, V. ramaswamii Hutch.).

3.3. Biseriate nonforked hair (figure 8)

Foot : biseriate. Body : biseriate, one- to many-tiered, cells of the two rows alternate or subopposite, not forked; apex nontapering, blunt (Ex. Vernonia monosis).

3.4. Biseriateforked hair (figures 9 to 11)

Foot 9biseriate. Body : biseriate, one to two or more tiered; forked into two equal or unequal portions, ends tapering, cells of the two rows alternate or subopposite, thick walled. (Ex. V. albicans DC. V. cinerea Less. V. conyzoi&S Wt). 3.5. One-armed hair (figures 12 to 15)

Foot 9simple or compound. Stalk : uniseriate 2- to 20-celled, usually tapering above, minutely constricted at cross walls, cells of various lengths, lateral walls thin or thick. Head : Unicellular, one armed, long, tapering, placed at an angle to stalk. Lateral walls thin or thick; other arm is much reduced. (V. bourneana W. W. Sin., V. conyzoides, V. divergens Edgew).

3.6. Two-armed hair (figures 16 and 17)

Foot : simple or compound. Stalk : uniseriate shorter than in T-shaped hair, I- to 4-celled, cylindrical, slightly constricted at cross walls; cells of varying lengths, cross walls thin, lateral walls thin or thick. Head : unicellular, two armed, arms equal or unequal cylindrical or flattened, walls thin or thick (Ex. V. elaeagnifolia DC., V. cinerea). 3.7. T-shaped hair (figures 18 and 19)

Foot : simple or compound. Stalk : longer than in two-armed hair; cells 5 to 25, lengths varying, cross walls thin, lateral walls thick or thin. Head : unicellular, two-armed, pointed at both ends, straight or bent, lateral walls thick or thin. Arms equal or unequal. (Ex. V. albicans, V. cinerea, V. conyzoides).

3.8. Swollen terminal celled hair (figures 20 to 23)

Foot 9simple or compound. Stalk : uniseriate one- to many-celled, cylindrical constricted at cross walls; cell lengths varying; lateral walls thick. Head : uni- cellular, swollen into different sizes and shapes. Lateral walls thin or thick. (Ex. II. travancorica Hook. f., V. monosis and V. ramaswamii).

3.9. Flagellate hair (figures 24 and 25)

Foot 9simple or compound. Stalk : uniseriate 1- to 4-celled, constricted at cross walls, lateral walls thin or thick. Head : uniseriate, long, tubular, thin wailed, easily collapsing. (Ex. V. gossypina, V. indica C. B. Clarke, V. comort nensis W.W. Sin.). 350 B M Narayana

9 I0

25 24 22 21 Figures 1-25. Trichomes in Vernonia. 1. V. monosis from ovary L.s. 2. V. dalzelliana suface view from a leaf. 3. V. shevaroyensis from leaf T.s. 4--7. V. dalzelliana, V. bourneana, V. ramaswamii, II. gossypina from corolla respectively ; note variation in capitate region. 8. V. monosis, from fruit wall. 9-11. V. elaeagui- folia, V.peninsularis, V. albicans from ovary L.s. respectively; note variation in length of forked arms. 12-15. V. conyzoides, V. bourneana, V. cinerea, from leaf veins. 16, 1~;-19. V. elaeagnifolia, V. conyzoides, V. albican~, from lower leaf epidermis respectively. 17. V. conyzoides from stem. 20. V. ramaswamii from midrib. 21 and 23. V. travancorica from stem. 22. V. dalzelliana from stem. 24-25. V. comorinensis and V. gossypina, from lower leaf epidermis respectively. Scale length equivalent to 85/~m for figures 1-3, 6-11, 17, 20-24; 135/~m for figures 4-5, 12, 14-15, 18-19; 300 t~m for figures 13, 16; 375 t~m for figure 25. Taxonomic value of trichomes 351 3.10. Whip-shaped septate hair (figure 26) Foot: simple or compound. Stalk: uniseriate 5- to 10-celled, cylindrical tapering, basal cells broader than the upper cells. Cells constricted at cross walls; lateral walls thin or thick. Head : uniseriate, very long, tubular, septate, whip like, thin walled, easily collapsing, septa found at a distance. This is the longest hair observed (Ex. 1I. gossypina). 3.11. Whip-shaped hair (figures 27 and 28) This is similar to the previous type except for the absence of septa in the head portion (Ex. 1I. indica, 1I. bourneana).

3.12. Cylindrical subulate hair (figures 29 to 31) Foot : simple or compound. Stalk : uniseriate short or long; constrictions found at cross walls; cross walls thin, lateral walls thin or thick. Head : uni- seriate, long-tubular, subulate, contents evanescent, lateral walls thick (Ex. II. monosis, 1I. shevaroyensis Gamble).

3.13. Filiform juvenile hair (figures 32 to 37) Foot : simple or compound. Stalk : uniseriate one- to many-celled; cells long or short, constricted at cross walls; lateral walls thick or thin. Head : one- to many-celled, cylindrical, tapering, cells long with intermittent short cells, thin- or thick-walled ; constricted at cross walls. The hairs fall off as the leaf develops. (Ex. 1I. monosis and 1I. shevaroyensis).

3.14. Filiform short terminal celled hair (figures 38 and ~9) Foot : simple or compound. Stalk : uniseriate short or long, two- to many- celled, tapering at apex ; cells of varying lengths, constricted at cross walls; lateral wails thick or thin. Head : unicellular, comparatively shorter, tapering at apex, thin walled (Ex. V. divergens, V.peninsularis C.B. Clarke, 1I. bourneana).

3.15. Filiform long terminal celled hair (figures 40 and 41) Foot: simple or compound. Stalk: uniseriate one-to many-celled, lateral walls thick or thin, cells long or short. Head : single celled, tapering at apex, thin or thick-walled. (Ex. corolla hairs and bract hairs in most species of Vernonia).

3.16. Simple filiform hair (figures 42 to 44) Foot : simple. Body : uniseriate, 5- to many-celled, filiform, often cylindrical or tapering above; constricted at cross walls; cell walls thin. (Ex. 1I. atbicans and V. peninsularis). 3.17. Unicellular cylindrical hair (figure 45)

Unicellular, cylindrical, stiff, blunt at apex, walls thin, contents translucent (Ex. Style hairs of 1I. bourneana, 1I. ramaswamii).

P.(B)--2 352 B M Narayana

3.18. Unicellular prickly hair (figures 46 and 47)

Uai~ellvlar, conical, stiff, tapering with acute apex; walls thick or slightly thin, caatents translucent (Ex. Style and bract hairs of V. peninsularis).

4. Discussion Of all the anatomical features, the trichomes are of particular taxonomical impor- tance. In Vernonia, as presently studied, they are very variable not only in struoture, but also in organographic distribution and frequency per unit area (table 1). Totally 18 types of trichomes have been distinguished. Some are restricted only to particular species. For example, T-shaped trichomes are very common to V. cinerea, V. albicans and V. conyzoides. Similarly cylindrical subulate hairs (figttre 30) are frequent in It. monosis, 1I. shevaroyensis and II. travancorica; flagellate and whip-shaped trichomes are restricted to tomentose forms such as V. indica, V. comorinensis and V. gossypina. Filiform short terminal-celled hair is represented in V. divergens and V. dalzelliana. Biseriate vesicular glandular hair (figures 2 and 3) is common in leaves of many species, but their frequency and organograpkic distribution show conspicuous variation (tables 1 and 2).

Table 1. Number of glandular and nonglandular hairs per unit area (1 sq. ram) in mid caulino lamina region. i Glandular Nonglandular S1. Species Place of collection No. Lower Upper Lower Upper surface surface surface surface 1. V. cinerea Mysore (M.G.M. campus) 2.6 Nil 24.5 3.1 2. V. albicans Hassan 63.9 5.2 66.0 46.8 3. ,, Kodaikanal 100.0 49.0 102.1 59.6 4. ,, Se,ngalthgri 46.8 32.0 32.0 32.0 5. tl. elaeagnifolia Dept. Garden 12- 3 Nil 868 Nil 6. V. dalzelliana Sakaleshpur 19.3 4.2 16.5 3.8 7. V. peninsularis Kodaikanal 35.3 Nil 4.9 1.2 8. ,, Kakaehi 51-0 14.9 4.5 1.2 9. V. monosis Madikori 85.1 33.7 46.8 14.4 10. ,, Bhagamandala 33.9 7- 3 24.7 12.9 11. ,, Devieolam 38.6 1.4 55.3 8.2 12. ,, Sakaleshpur 43.5 3.5 41.9 4.9 13. V. travancorica Kakachi 24.7 8.7 2- 8 1.4 14. V. conyzoides Kakaehi 33.2 8.2 20.7 8.7 15. V. bourneana Kodaikanal 57"4 17.9 44.7 7.5 16. V. ramaswamii Songaltheri 10.6 5.4 4.2 Nil (almost absent) 17. II. gossypina Songaltheri 34.0 29.2 53.2 4.7 18. V. divergens Pulneyhills 48.0 34.4 89.0 38.3 19. V. comorinensis Kakachi 159-6 42.6 285.7 10.6 20. V. shevaroyensis Yercaud 21.9 9.4 29.4 12.7 21. V. indica B.R. hills 14.1 Nil 233.1 2.1 Taxonomic value of trichomes 353

).

46 42 40 Figures 26-47. Trichomes in Vernonia. 26. V. gossypina from leaf vein. 27, 29-31. V. bourneana, V. shevaroyensis, V. monosis, V. dalzelliana from lowex leaf epidermis respectively. 28. V. indica from upper leaf epidermis. 32-37. V. monosis and V. shevaroyensis from epidermal peels of young leaves. 38-39. V. bourneana from stem and lower leaf epidermis respectively. 40 and 42. V. peninsularis from leaf midrib and corolla respectively. 41. V. divergens from bract margin. 43-44. It. albicans and V. peninsularis from bracts respectively. 45-46. V. bourneana and V. travavcorica from style regions respectively. 47. V.peninsularis from bract.

Scale length [equivalent to 375 t~m for figures 26--28, 32-38, 42-43; 300 izm for figures 28, 39; 135/Lm for figures 30-31; 85/tm for figures 40-41, 44-47. 354 B M Narayana

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;s [- 356 B M Narayana Although the climatic factors can bring about variation in the frequency distribution of stomata on leaf surface as reported by Salisbury (1928), the trichome types in species of Vernonia, can be regarded as a dependable character for identification. This conclusion can be drawn on the basis of the observations made in the present study with respect to V. albicans, where the collected from different ecological conditions and the plants raised in experimental garden of the department, exhibit similar frequency and types of glandular and non- glandular trichomes. Hence it can be regarded that the variaticn in density of trichomes is not always due to environment in all taxa; so long as they are genetical in origin, such plants can be suspected as biotypes. Ramayya (1969) has also expressed this view. In V. peninsularis, plants of Kodaikanal do not possess the simple filiform hair on corolla tube, but such a trichome is found on the corolla tube in plants of Kakachi. Similarly the tree form, V. monosis, collected from Devicolam and Bhagamandala region exhibit the biseriate vesicular glandular hair (figure 1) on the fruit wall. But the same species collected from Madikeri and Sakaleshpur do not have this trichome on the fruit wall. When we find that organ.graphic distri- bution of a hair is governed by genetical factors, the variants can be raised to the rank of a variety. Paired affinity indexes are a reliable guide to relationships (Cowan 1950). Table 3 indicates that V. cinerea and V. albicans ; V. monosis and V. shevaroyensis ; and V. comorinensis and V. indica have a paired affinity index of 100 to each other. The evidence from other morphological features examined by the author also suggests that these plants are closely related to one another.

Table 3. Paired affinity indexes of trichome complements of lower epidermis for 15 taxa of vernonia.

Sic No. Species -a b c d e f g h i j k 1 m n

1. b 25 2. c 20 75 3. d 25 100 75 4. e 25 20 17 20 5. f 25 20 17 20 50 6. g 25 20 40 20 50 50 7. h 33 25 20 25 25 25 25 8. i 25 20 17 20 20 50 20 25 9. J 25 20 17 20 20 50 20 25 100 10. k 33 25 20 25 25 67 25 33 67 67 11. 1 67 20 17 20 20 20 20 25 20 20 25 12. m 100 25 20 25 25 25 25 33 25 25 33 67 13. n 33 25 50 25 25 25 67 33 25 25 33 25 33 14. o 33 67 50 67 25 25 25 33 25 25 33 25 33 33

a ----- V. indica, b = V. cinerea, c = V. conyzoides, d = V. albicans, e = V. dalzelliana, f = V. peninsularis, g = V. divergens, h = V. ramaswamii, i = V. men,sis, j]= V. shevaroyensis, k = V. travancorica, l = V. gossypina, m = V. comorinensis, n = V. bourneana, o = V. elaeagnifolia. Taxonomic value of trichomes ]57

The present study suggests that trichomes can be a diagnostic character in Vernonia. However, their value as a taxonomic criterion will be greatly increased in combination with other lines of evidence. A study of trichomes in other species of Vernonia would also yield a comprehensive picture for a thorough classification of the genus.

Acknowledgements

The author is thankful to Dr D A Govindappa for his encouragement and necessary facilities. He is deeply indebted to Dr M A Rau, for his valuable sugges- tions during the course of this study.

References

Carlquist S 1961 Comparative anatomy (New York: Holt, Rinehart, and Winston) pp. 29-36 Cowan J M 1950 The Rhododoendron leaf; a study of epidermal appendages (London : Oliver and Boyd) Do Bary 1884 A comparative anatomy of the vegetative organs of the Phanerogams and ferns (Oxford : Clarendon Press) Faust W Z 1972 A biosystematic study of the interiores species group of Vernonia (Compositae) ; Brittonia 24 363-378 Gamble J S 1956 Flora of the Presidency of Madras Vet II Repr. ed. (Calcutta : Botanical Survey of India) Gleason H A 1923 Evolution and geographic distribution of the genus Vernonia in North America; Am. J. Bet. 10 187-202 Goebel H 1900 Organography of plants especially of the Archegoniatae and Spermatophyta, Part I (Oxford : Clarendon Press) Goodspeed T H 1954 The genus Nicotiana; (Waltham, Mass; Chronica Botanica) pp. 109-131 Heintzelman C E Jr. and Howard R A 1948 The comparative morphology of the Icacinaceae V. The pubescence and crystals; Am. J. Bet. 35 42-52 Hunter G E and Austin D F 1967 Evidence from trichome morphology of int~rspecific hybridi- sation in Vernonia (Compositae); Brittonia 19 38-41 King B L 1971 The systomatics of the Vernonia lindheimeri complex; M S Thesis Univ. Georgia (Athens) Motcalfr C R and Chalk L 1950 Anatomy of the dicotyledons Vol 2 (Oxford : Clarendon Press) Netolitzky F 1932 Die Pflanzcnhaarc Ilandbuch derpflanzenanatomie; K Linsbauor (cd) 4 1-253 (Berlin : Borntraeg~r) Ramayya N 1962b Studies on the trichomos of some Compositae I General structure; Bull. Bet. Surv. India 4 177-188 Ramayya N 1962e Studies on the trichomes of some Compositae II phylogeny and classification; Bull. Bet. Surv. India 4 189-192 Ramayya N 1969 The development of trichomes in the Compositae; Recent advances in the anatomy of tropical seed plants, K A Chowdhury (ed) (Delhi : Hindustan Publication Corporation) pp 85-113 Salisbury R C 1928 On the causes and ecological significance of stomatal frequency with special reference to the woodland flora; Philos. Trans. R. Soc. 13216 1-65 Shotty B V and Vivekananthan K 1970 (1972) New and little known taxa from Anaimudi and surrounding regions Devicolam Kerala IIl, A new species of Vernonia Schreb ; Bull. Bet. Surv. lnd/a 12 266-268 Solereder H 1908 Systematic anatomy of the dicotyledons (Oxford : Clarendon Press) Vol. 2 Urbatsch L E 1972 Systematic study of the Altissimae and Giganteao species groups of the genus Vernonia (Compositae); Brittonia 24 229-238