J Econ. Taxon. Bot. Vol. 37 No. 2 (2013) ISSN: 2050-9768 EXOMORPHIC AND HISTOLOGICAL CHARACTERS OF FRUITS IN SOME TAXA OF THE TRIBE - LACTUCEAE (ASTERACEAE) BIDYUT KUMAR JANA & SOBHAN KR. MUKHERJEE Taxonomy and Biosystematics Laboratory, Department of Botany, University ofkalyani, Kalyani-741235, Nadia, West Bengal, India ABSTRACT Exomorphic and histological characters of fruits of 5 species (Urospermum dalechampii, Lactuca subumbellata, Cichorium intybus, Lapsana communis, Chondrilla juncea) of the tribe Lactuceae have been studied. Other than Cichorium intybus, remaining studied species have homomorphic fruits. In the fruits of Urospermum dalechampii, Chondrilla juncea, Lapsana communis pappus are absent. In the fruits of Urospermum dalechampii and Chondrilla juncea, beak - like structures are present. Anatomically, all the studied fruits are ellipsoidal in cross sectional configurations and pericarpic portion exhibits cellular differentiations. In the fruits of Chondrilla juncea, mesocarpic region is composed of heterogeneous tissues, whereas in the fruits of remaining studied species, mesocarpic region is constituted by more or less homogenously developed tissues. Based on the above mentioned exomorphic and histological characters, an artificial key has been constructed for proper identification of studied taxa at species level. INTRODUCTION Asteraceae are one of the largest and advanced family of dicotyledons, containing 43 tribes, 1600 genera and 23,000 species (Kadereit & Jeffrey, 2007). Among the 43 tribes of Asteraceae, Lactuceae consist of 12 subtribes and 86 genera (Kadereit & Jeffrey, 2007). This tribe is clearly recognizable from the other tribes of Asteraceae by the presence of milky latex and ligulate corolla. According to Mukheijee & Sarkar (1995), fruit features of Asteraceae play a prominent role for the separation of taxa. The available literatures 372 (Jana & Mukherjee, 2012; Dasgupta & Mukherjee, 2007 etc.), regarding the fruit features of the Lactuceae are very limited. To solve this problem, the present work has been undertaken. MATERIALS AND METHODS Dried, mature, identified, disease free fruits of five species of the tribe Lactuceae were collected from abroad herbaria of the world, which are given in the Table 1.
Table 1. Studied taxa and their sources. Name of taxa 1. Chondrilla juncea L. 2. Cichorium intybus L. 3. Lactuca pseudoumbrella D.Maity & Maiti 4. Lapsana communis L. 5. Urospermum dalechampii (L.) F.W.Schmidt Sources Humboldt- Universitat Zu Berlin. Institute fur Biologie spezielle Botanik u. Arbor-etum, Spathstra Be 80/81. 12437 Berlin, Germany. FLORA of AUSTRIA. Lower Austria, Thermenlinie, Wineyards east of the Heberlberg 2 km southwest of Gumpoldskirchen, 275 m s.m. 48 02'N, 16" 16' E, 23 September 2001, Along roadside From Sikhim Himalaya, supplied by the Authors of the Taxon Botanischer Garten der Universitat Zurich (Z). XXOZ 19964888 Botanischer Garten der Universitat Zurich (Z). XXOZ 19950008 Randomly selected dry fruits were immersed in 1-2% NaOH solution for 2-4 days to soften them. The softened fruits were stained in aqueous safranin solution (1%) to study the different morphological parts of fruits under dissecting microscope as well as compound research microscope. For anatomical study, free hand sections are taken from the middle part of fruits to observe the different internal structures under compound light microscope. OBSERVATIONS L Chondrilla juncea L. Morphology (Figs. 1 A-B ) Fruits homomorphic, 5 x 0.5 mm including beak, 4 x 0.5 mm excluding beak, pale yellow, oblanceolate, curved, upper part truncate whereas J. Econ. Taxon. Bot. Vol. 37 No. 2 (2013) lower part tapered. Ellipsoidal in cross sectional configuration. Surface pubescent, containing 20 ribs, alternating with furrows. Furrows wider than ribs. At the upper part of fruit, pappus absent. Beak like structure present at centre of the upper part. At the upper part of fruit, stylopodium present; unenlarge, partially immersed in the nectar. At the basal part of fruit, carpopodium present; narrow than the base, irregular ring like, symmetric. Carpopodial cells thick-walled, not pitted, arranged in 2-3 rows. Anatomy (Fig 2 A) Fruits elliptic in cross section. Ribs present, 20 in numbers, inconspicuous. Fruit wall 0.04 mm and 0.02 mm wide at ribs and furrow region respectively. Pericarp thick, differentiated into epicarp and mesocarp. Epicarp uniseriate, made up of thin-walled, rectangular- oval, compactly arranged, parenchyma cells, provided with cuticle. Internal to the epicarp, mesocarp present which is heterogenous, made up of thin-walled, compactly arranged, parenchyma cells and thick-walled, pentangular, compactly arranged, sclerenchyma cells containing vascular bundle. Testa attached with fruit wall, approximately 0.01 mm thick, parenchymatous, uniseriately arranged, containing vascular trace. Endosperm persists in mature fruit, uniseriate, parenchymatous. Mature embryo occupies a major part of the fruit; cotyledons 2 in number, arranged at right angle to the axis of fruit, containing 10 resin ducts (5 ducts in each cotyledon). 373 2. Cichorium intybus L. Morphology (Figs. 1 C-G ) Fruits heteromorphic. Ray fruit 2x1 mm, black, obovate, straight, upper part truncate whereas lower part slightly tapered. Disk fruit 2 x 0.5 mm, yellow brown, obovate, straight, upper part truncate, whereas lower part slightly tapered. Ellipsoidal in cross sectional configuration. Surface slightly pubescent. Surface hairs adpressed with the fruit wall. Surface cells are elongated. Surface containing 11-13 ribs, alternating with furrows. Furrows wider than ribs. Bristilate pappus present. At the upper portion of fruit, stylopodium present, enlarge, dome-shaped, fully immersed into the nectary. At the basal region of fruit, carpopodium
Java & Mukherjee present, same as the diameter of the base, pentangular, symmetric. Carpopodial cells thick - walled, cubical, uniseriately arranged. Anatomy (Fig 2 C) Fruits elliptic in cross section. Ribs present, 11-13 in number, inconspicuous. Fruit wall 0.07 mm and 0.03 mm wide at ribs and furrow region respectively. Pericarp thick, differentiated in to three zones- epicarp, mesocarp and endocarp. Epicarp uniseriate, made up of thick-walled, rectangular, compactly arranged, parenchyma cells, provided with cuticle. Internal to the epicarp, mesocarp present made up of thin-walled, pentahexagonal, compactly arranged, parenchyma cells containing vascular trace. Internal to the mesocarp, endocarp present made up of thin-walled, rectangular, compactly arranged, parenchyma cells, uniseriately arranged. Testa attached with fruit wall, approximately 0.01 mm thick, parenchymatous, uniseriately arranged. Endosperm persists in mature fruits, biseriate. Outer cells narrow barrel-shaped and inner cells wide barrel-shaped. Cells of both the layers thick-walled, parenchymatous, compactly arranged. Mature embryo occupies a major part of the fruit; cotyledons two in number, arranged at right angle to the axis of fruit, containing 8 resin ducts (4 ducts in each cotyledon). 3. Lactuca pseudoumbrella D. Maity & Maiti Morphology (Figs. 1 H-J) Fruits homomorphic, 12 x 1 mm including pappus, 6x1 mm excluding pappus, brown with yellow spot, linear, upper part truncate whereas lower part tapered. Ellipsoidal in cross sectional configuration. Surface pubescent, containing 11 ribs alternating with furrow. Furrows wider than ribs. Surface hair ascending in orientation with the surface, made up of body and basal cells. The tip portion of body cells arranged in different plains. At the upper portion of fruit, stylopodium present, unenlarge, trilobed, fully immersed in to the nectar. At the upper portion of fruit, pappus present, homomorphic, represented by 22 unequally arranged, barbellate types of pappus bristles, white, unequal. At the basal region of fruit, carpopodium present, narrow than the base, symmetric, ring like. Carpopodial cells thick-walled, arranged in 2 rows. Anatomy (Fig 2 B ) Fruits elliptic in cross section. Ribs 11 in number, inconspicuous. Fruit wall 0.06 mm and 0.02 mm wide at rib and furrow region respectively. Pericarp thick, differentiated into three zones - epicarp, mesocarp and endocarp. Epicarp uniseriate, made up of thin - walled, quadrangular, compactly arranged, tangentially placed, parenchyma cells, provided with cuticle. Internal to the epicarp, mesocarp present, homogenous, made up of thick-walled, pentangular, compactly arranged, sclerenchyma cells containing vascular trace. Internal to the mesocarpic region, endocarp present, thin-walled, parenchymatous, uniseriately arranged. Testa attached with fruit wall, approximately 0.01 mm thick, uniseriate, thickwalled, parenchymatous. Endosperm persists in mature fruit, uniseriate, thick-walled, parenchymatous. Mature embryo occupies a major part of fruit; cotyledons two in number, arranged at right angle to the axis of fruit, containing 6 resin ducts (3 ducts in each cotyledon). 374 4. Lapsana communis L. Morphology (Fig. 1 K- L) Fruits homomorphic, 3 x 0.5 mm, white brown, oblanceolate, slightly curved, upper part truncate whereas lower part tapered, ellipsoidal in cross sectional configuration. Surface rough and glabrous, containing 15-22 ribs, alternating with furrow. Furrows wider than the ribs. At the upper part of fruit, stylopodium present, inconspicuous, fully immersed in to the nectar. Pappus absent. At the basal region of fruit, carpopodium present, narrow than the base, irregular ring like. Carpopodial cells not clearly distinguish from the remaining part of fruit. Anatomy (Fig. 2 E) Fruits elliptic in cross section. Ribs present, 15-22 in number, conspicuous. Fruit wall 0.06 mm and 0.04 mm wide at rib and furrow region respectively. Pericarp thick, differentiated in to epicarp and mesocarp. Epicarp uniseriate, made up of thick-walled, elongated, large, tangentially orientated, parenchyma cells provided with cuticle. Internal to the epicarp, mesocarp present, homogenous, compactly arranged, sclerenchyma cells with sclerenchyma brace just below the ribs. Testa attached with fruit wall, approximately 0.01 mm
J. Econ. Taxon. Bot. Vol. 37 No. 2 (2013) thick, uniseriate, made up of, thick-walled, occupies a major part of fruit; cotyledons two in rectangular, parenchyma cells. Endosperm persists number, arranged at oblique to the axis of fruit, in mature fruit, biseriate, made up of thick-walled, containing 10 resin ducts (5 ducts in each barrel-shaped, parenchyma cells. Mature embryo cotyledon). 0.05 mm. E,I, J, 1 mm. A,B,C,D, F, G, H, K, L, M, N, O Figure 1. Exomorphic features of studied fruits - A-B. Chondrilla juncea: A. Fruit, B. Upper part of fruit showing stylopodium; C-G. Cichorium intybus: C. Ray fruit, D.Upper part, showing stylopodium, E. Carpopodial cells, F. Basal part of fruit showing carpopodium, G. Disk fruit; H-J. Lactuca pseudoumbrella : H. Fruit, I. Surface hairs, J. Middle part of pappus bristles; K-L. Lapsana communis: K Fruit, L. Upper part of Fruit, showing stylopodium; M-O. Urospermum dalechampii: M. Fruit, N. Basal part of Fruit, O. Upper part of fruit, showing stylopodium 375
Java & Mukherjee Figure 2. Cross sections of the studied fruits - A. Chondrilla juncea, B. Lactuca pseudoumbrella, C. Cichorium intybus, D. Urospermum dalechampii, E. Lapsana communis ABBRIVIATIONS: Ep- Epicarp, Me- Mesocarp, T-Testa, E-Endosperm, End-Endocarp, Pa- Parenchyma, Scl- Sclerenchyma, Scb- Sclerenchyma brace, V.T.- Vascular trace 5. Urospermum dalechampii (L.) F.W. Schmidt Morphology (Figs. 1 M-O) Fruit homomorphic, 15 x 1-2 mm including beak, 5 x 1-2 mm excluding beak, yellow brown, 376 obovate, slightly curved, upper part truncate whereas lower part tapered. Ellipsoidal in cross sectional configuration. Surface rough and glabrous, margin dentate, containing 10-13 ribs, alternating with furrow. Furrows wider than rib. Pappus
absent. Beak like structure present. Stylopodium not clearly visible. At the basal region of fruit, carpopodium present, quadrangular, symmetric. Carpopodial cells not clearly differentiated from the remaining part of fruit wall. Anatomy (Fig. 2 D) Fruits elliptic in cross sectional configuration. Ribs present, 10-13 in number, conspicuous. Fruit wall 0.05 mm and 0.02 mm wide at rib and furrow region respectively. Pericarp thick, differentiated in to two zones- epicarp and mesocarp. Epicarp uniseriate, made up of thin-walled, rectangular, compactly arranged, parenchyma cells. Internal to the epicarp, mesocarp present, homogenous, made up of compactly arranged, pentangular, sclerenchyma cells. Within the mesocarpic region, vascular trace present. Testa attached with fruit wall, approximately 0.008 mm thick, uniseriately arranged, parenchymatous. Endosperm persists in mature fruit, biseriate. Outer cells wide barrel-shaped and inner cells narrow barrel-shaped. Cells of both the layers thick-walled, parenchymatous, compactly arranged. Mature embryo occupies a major part of the fruit; cotyledons two in number, arranged at right angle to the axis of fruit, containing 14 resin ducts (7 ducts in each cotyledon). DISCUSSION Fruits of five species of the tribe Lactuceae were studied to observe the different exomorphic and histological characters. Except the fruit of Cichorium intybus, in the remaining studied species fruits are homomorphic. Shape, size, colour are of no significance for the separation of taxa. In the fruits of Urospermum dalechampii and Chondrilla juncea beak like structures are present at the upper part. In the remaining studied fruits, beaks like structures are absent. Beak like structure is also reported to be present in some other species (Hieracium racemosum, Taraxacum sp. etc) of this tribe (Dasgupta & Mukherjee, 2007). In the fruits of Lactuca psudoumbrella and Cichorium intybus, pappus are absent. In the remaining studied fruits, pappus is present. Mukherjee 377 J. Econ. Taxon. Bot. Vol. 37 No. 2 (2013) & Nordenstam (2008) have shown the identical type of pappus structure in some other tribes of the Asteraceae. In the studied fruits, pappus structure is prevalent and is always barbellate type. Plumose type of pappus bristles are absent in case of the studied fruits. Though, plumose type of pappus bristles are present in some other species (Leontodon autumnalis) of this tribe (Dasgupta & Mukherjee, 2007). Among the studied fruits, in case of Chondrilla juncea L., Cichorium intybus L. and Lactuca pseudoumbrella, carpopodia are symmetric, whereas in remaining 2 studied fruits, carpopodial cells are not clearly distinguishable from the remaining part of fruit wall, i.e. pseudocarpopodia. Carpopodial structures are very important for the separation of taxa. Mukherjee & Nordenstam (2004), have presented a comparative study of carpopodial structures of Asteraceae. Present study also indicates that cell layers of carpopodia have significant value for characterization of taxa. Carpopodium also helps in fruits detachment. Anatomically, all the studied fruits are elliptic in cross sectional configuration. In all the studied fruits, epicarp is uniseriate, parenchymatous. Among the studied fruits, mesocarpic regions are homogenous ( either parenchymatous or sclerenchymatous) in case of Lapsana communis, Cichorium intybus, and Urospermum dalechampii, whereas in case of fruits of Chondrilla juncea and Lactuca pseudoumbrella, mesocarpic regions is constituted by heterogeneous tissues ( both parenchyma and sclerenchyma cells). Within the mesocarpic region, pit formation is absent. Pit formation is present in another species (Crepis pulchra) of the tribe Lactuceae, according to Jana & Mukherjee (2012). In all the studied fruits, testal layers are parenchymatous and uniseriately arranged. Uniseriately arrangement of testal layers are also reported in some other species (Leontodon crispus, Hieracium racemosum
Java & Mukherjee etc.) of the tribe Lactuceae by Jana & Mukherjee (2012 a). Endosperm layer varies from 1-2 layers in case of all the studied fruits. Therefore, from the above discussion external and internal characters of fruits are stable and have some significant role for the separation of taxa along with other floral and vegetative characters. KEY TO THE STUDIED SPECIES la. Fruit heteromorphic; carpopodium pentangular; carpopodial cells uniseriately arranged; each cotyledon with 4 resin ducts Cichorium intybus lb. Fruit homomorphic; carpopodium not as above; carpopodial cells arranged in 2-3 layers; each cotyledon with 3, 5 or 7 resin ducts (2) 2a. Fruit with beak, about 15 mm long; each cotyledon with 7 resin ducts Urospermum dalechampii 2b. Fruit without beak, about 2-12 mm long; each cotyledon with 3 or 5 resin ducts (3) 3a. Fruit 5-12 mm long; Fruit surface pubescent; endosperm uniseriate; carpopodium definite and carpopodial cells clearly differentiated from epicarpic cells; each cotyledon with 3 or 5 resin ducts (4) 4a. Number of fruits ribs about 20, inconspicuous; pappus absent; carpopodial cells arranged in 2-3 rows; each cotyledon with 5 resin ducts Chondrilla juncea 4b. Number of fruits ribs about 11, conspicuous; barbellate pappus bristles present; carpopodial cells arranged in 2 rows; each cotyledon with 3 resin ducts Lactuca pseudoumbrella 3b. Fruit 3 mm long; Fruit surface glabrous; endosperm biseriate; carpopodium not definite and carpopodial cells not differentiated from epicarpic cells; each cotyledon with 5 resin ducts Lapsana communis ACKNOWLEDGEMENTS The authors are greatful and thankful to Dr. Peter Enz, Curator, Botanischer Garten der Universitat Zurich, Zurich, Switzerland; Dr. W. Till, Curator, Institut fur Pharmakognosie der Universitat Wein, Wein, Austria and Curator, Humboldt-Universitat zu Berlin, Institut fur Biologie, Berlin, Germany, for sending the mature, identified, disease free seeds for this study. REFERENCES DASGUPTA, A. & S.K. MUKHERJEE 2007. Cypselar morphology as a taxonomic marker in the study of some members of the tribe Lactuceae (Asteraceae). J. Econ. Taxon. Bot. 31 (3): 584-590. JANA, B.K. & S.K. MUKHERJEE 2012a. Diversity of cypselar features of seven species of the genus Crepis L. in Compositae. Indian Journal of Fundamental and Applied Life Sciences 2(1): 51-58. & 2012b. Carpological studies of some members of the tribe-lactuceae (Asteraceae). J. Interacad. 16(2): 188-195. KADEREIT, J.W. & C. JEFFREY (Eds). 2007. Flowering Plants: Eudicots-Asterales. In Kubitzki, K. (Ed). The Families and Genera of Vascular Plants, Vol. VIII. Springer, Berlin, Germany. MUKHERJEE, S.K & A.K SARKAR 1995. Micromorphological and anatomical structures of cypsela in some members of the tribe Lactuceae (Compositae). J. Natl. Bot. Soc. 49: 43-57. & B. NORDENSTAM 2004. Diversity of carpopodial structure in the Asteraceae and its taxonomic significance. Comp. Newsl. 41: 29-50. & 2008. Diversity of pappus structure in some tribes of the Asteraceae. Phytotaxonomy 8: 32-46. 378