Proc. Indian Acad. Sci. ( Sci.), Vol. 92, Number 6, December 1983. pp. 451-459. 9Printed in .

Further contribution to anatomy of maritime strand of India

T ANANDA RAO, T R B NAIDU and G C DAS* Botany Department, Bangalore University,Bangalore 560 056, India *Botanical Surveyof India, Howrah 711 103, India

MS received 8 July 1982; revised 13 August 1983.

Abstract. Anatomyof vegetativeparts and its ecologicalsignificance in 10 taxa of Indian maritime strand floral namelyAllmania nodiflora, Canavalia maritima, Euphorbia atoto, Halopyrum mucronatum, Indigofera uniflora, Messerchimidia argentea, plumi- erii, Scaevola taccada, Sesarnum prostratum and are described.

Keywords. Maritimestrand plants; ecologicalanatomy.

1. Introductlon

In continuation of our previous study (Rao and Das 1971) anatomy of 10 more representative taxa of Indian maritime strand flora is described. The ecological significance of the anatomic features is discussed.

2. Observatlon

2.1 Allmania nodiflora R. Br. (Amaranthaceae) Erect annual herb with long tap root. The species exhibits phenotypic plasticity especially in the leal shape which ranges from linear, spathulate, oblong to obovate. Leal colour varies from green to scarlet red. With decreasing salinity this species attains bushy habit bearing broad green leaves. It has been recorded from the sandy beaches of Orissa, Andhra Pradesh, Tamil Nadu and Kerala (Rao 1971). It grows with sedges and grasses along the beaches and in inland areas.

2.la Root: Cylindrical xylem endarch phloem in continuous ring, pith absenc Vascular bundles in concentric rings. Cortex parenchymatous. Exodermis multiseriate, periderm in discrete rings. 2.1b Stem: Cylindrical with knobed outline in transection, knobs collenchy- matous. Epidermis uniseriate, intercepted by a few depressed stomata and outer wall cutinized. Cortex: differentiated into inner and outer regions; inner cortex, 2 or 3 layered, cells parcnchymatous, elongate. Outer cortex 2 or 3 layered, cells parenchymatous, polygonal, thin-walled. Pith large, cells in the centre large, hexagonal, intercepted by a few internal bundles along the periphery. Vascular bundles in 2-5 concentric rings (anomalous growth).

451 452 T Ananda Rao, T R B Naidu and G C Das

Figures 1-2. TS of leaves (x125) 1. Allmania nodiflora. 2. Canavalia maritime.

2.1c Leaf (figure 1): Dorsiventral. Epidermallayer, uniseriate, cellsalongthe margin large, 3-1ayered. Hairs simple, bicellular. Palisade 2-1ayered along the margin. Spongy parenchyma q polygonal.

2.2 Canavalia marŸ {Aubl.) Thou. (Fabaceae) Biennial tropical strand plant, widespread along the beaches of Kerala, Tamil Nadu and Orissa on the outer limits of land vegetation, and in association with Ipomoea pea-caprae (Rao 1971). Its adaptive features are the bushy and trailing Anatomy of lndian maritime strand flora 453

habit, thick coriaceous xeromorphic teaves, attractive pink flowers, and com- pressed elliptic brown to dark mostly buoyant seeds. 2.2a Stem: Subcylindrical. Outer cortex, 6 or 7 layered, intercepted by a few tanniniferous cells; in'ner cortical cells parenchymatous. Pith small, compact, thin walled, parenchymatous. Vascular tissue in a ring, alternate with wedge-shaped phloem. 2.2b Lea[ (figure 2): Dorsiventral. Adaxial epidermis uniseriate, cells large, thick-walled, prominently cuticularized. Abaxial epidermis uniseriate. Palisade multi-layered, compact butintercepted by big cavities. Spongy parenchyma 4 to 7- layered. 2.3 Euphorbia atoto Forst. (Euphorbiaceae) Dwarf shrub with long root system. It shows fidelity to upper beaches frequently mixed up with the other common strar~d pioneers, and is widely distributed in , Malayan archipelago, China, Australia, Sri Lanka and West Coast of India especially along the shores of Kerala and Karnataka. 2.3a Stem: Cylindrical. Cortex: multi-layered, parenchymatous, intercepted by laticifers rich in starch grains; cork formation common. Secondary xylem present, phloem in ring, Pith, parenchymatous, but intercepted by laticifers.

2.3b Leal (figure 3): Dorsiventral; adaxial epidermis, uniseriate, hyposto- matous. Palisade 1-1ayered, compact; spongy cells 2-3 layered, compact but intercepted by vascular bundles sheathed by chlorophyllous cells which sometimes contain starch grains. Water storage tissue 3 to 4 layered of varied length, compact but intercepted by laticifers. Abaxial epidermis uniseriate, slightly cutinized. Stomata rare. 2.4 Halopyrum mucronatum Stapf. (Poaceae) Tallstout grass often found in clumps along the back shores of Cape Comorin and Krusadi in Tamil Nadu, the West Coast and the Saurashtra coast as far as Dwarka shore (Rao 1971). It forms an excellent ground cover, and thus protects the sand from wind erosion.

2.4a Root: Subcylindrical. Xylem polyarch, ground tissue sclerosed. Endo- dermis surrounded by a few layers of inner sclerenchymatous ring. Cortical cells polygonal, lacunar. Epiblema biseriate. Hairs many, long, unicellular~ 2.4b Stern: Cylindrical with irregular outline. Epidermis uniseriate. Vascular bundles in four series, nearly uniform, collateral, closed, encircled by smaU, colourless, thick walled cells. Vascular bundles of the outermost series embedded in a parenchymatous and sclerenchymatous ring. Bundtes of other series scattered in ground tissue. Ground tissue of large, thin-walled cells and small with triangular intercelluiar spaces. 454 T Ananda Rao, T R B Naidu and G C Das

2.4c Leal (figure 4): Curved or semi-lunar in TS. Vascular bundles of two sizes, small vascular bundles alternating with large ones. Adaxial epidermis uniseriate, outer cell waU covered with thick cuticle; subepidermal sclerenchyma present; vascular bundles collateral surrounded by a uniseriate parenchymatous sheath abutting the sclerenchyma on abaxial side, sheath surrounded by 2 or 3 layered chlorophyllous tissue. Abaxial epidermal cells not uniform, some develop macrohairs of varied shape; subepidermal sclerenchyma present. Bigger bundles constitute typical I-girders.

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Figures 3-5. TS of leaves q• 3. Euphorbia atoto 4. Halopyrum mucronatum 5, Indigofera uniflora. Anatomy of Indian maritime strand flora 455

2.5 Indigofera uniflora Buch-Hamo fFabaceae) Perennial, slender, prostrate, branched herb bearing minute red flowers and occurs along with back-shores of Karnataka and extends up to Kerala (Rao 1971). 2.5a Root: Cylindrical, exodermŸ 3 to 5 layered, cork present. Cortex large, multi-layered with scattered sclerotic patches. Secondary xylem well developed, tyloses present, phloem in a ring. 2.5b Stem: Cylindrical, epidermis uniseriate. Hypodermis 2 of 3 layered, sclerenchymatous. Pith cells polygonal, thick-walled, parenchymatous; vascular tissue in a ring, secondary growth present; phloem in a ring with sclerenchyma. 2.5c Leal (figure 5): IsobilateraL V-shaped in TS. Adaxial epidermis uni- seriate, hypostomatous. Outer wall thick-undulating, palisade on the adaxial surface 2 or 3 layered, cells slightly longer than those on abaxial surface; a few cells tanniniferous, palisade on abaxial surface, less chlorophyllous, cells towards abaxial surfaee more tanninŸ Secretory idioblasts present below and along margin. Abaxial epidermis uniseriate, hairs unicellular.

2.6 Messerchimidia argentea (L.f.) Johnst. (Boraginaceae) Erect shrub or tree found along the coral sand habitat. Its oceurrence along the main Indian coast is limited to southern Krusadi (Rao 1971). It is very well represented in Laccadeve and Maldeve Islands. Fully grown trees display many branches bearing thick fulvous-sericeous leaves.

2.6a Stem: Quadrangular, outer surface rough. Periderm conspicuous. Cor- tex" large, collenchymatous, polygonal, less lacunar, ducts present. Pith oblite- rated. Vascular bundles in a ring, collateral, secondary xylem conspicuous. 2.6b Leal (figure 6): Isobilateral. Epidermal layers uniseriate, cells uneven in size and shape, hairy. Hairs heteroblastic, unieellular, straight or slightly curved. Palisade 2-1ayered beneath adaxial and abaxial epidermal layers, interrupted at intervals by 5 to 10 layers of water storage cells. Spongy cells absento 2.7 Scaevola plumierii (1..) Vahl. ()

Compact glabrous shrub about 1.5 m tall found along the backshore strand. Its adaptive features ate stout decumbent branches and thick xeromorphic leaves. The species oeeurs along the sandy shore in Shingle , Tutieorin and Karnataka near Surathkal (Rao 1971). 2.7a Root: Cylindrical. Xylem pentarch. 2.7b Stem: Subcylindrical. Periderm: lenticulate. Cortex: Multi-layered, cells polygonal, thin-walled, parenchymatous. Pith large, cells hexagonal, compact, thin-walled, parenchymatous, xylem continuous in a ring along with active cambium; phloem wedge shaped. 456 T Ananda Rao, T R B Naidu and G C Das

V.: i

W 7

Figures 6,7. TS of leaves (• 6. Messerchimidia argentea. 7. Scaevola plu- mierff.

2.7c Leal (figure 7): Isobilateral. Adaxial epidermis uniseriate, hypostoma- tous, outer wall thickly cuticularized. Abaxial epidermis, uniseriate, outer wall, thick, cuticularised. Palisade parenchyma 2-1ayered; ¡ tissue centrally placed.

2.8 Scaevola taccada (Gaertn.) Roxb. (Goodeniaceae) Large bushy shrub growing along back-shore strand and widely spread all along the west coast up to Bombay shore. Its occurrence along the east coast has, however been observed so lar at Rambille in Andhra Pradesh. Its adaptive features are bushy habit, profusely decumbent branches and thick xeromorphic leaves. Anatomy of [ndian maritime strand flora 457

2.8a Root: Cortex: extensive exodermis 2 or 3 tayered; cells compact; Xytem present. 2.8b Stem: Cylindrical. Epidermis uniseriate, cells uniform. Outer and inner cortical cells.parenchymatous, lacunar. Xylem endarch, vascular bundles col- lateral, pith. cells large polygonal and thick-walled.

2.8c Leaf (figure 8): Adaxial epidermis biseriate; cells in upper layer larger than those in the lower, cutinized, Abaxial epidermis uniseriate, hypostomatous. Palisade 2-1ayered. Spongy cells 6 to 7-layered, intercepted by vascular bundles. 2.9 Sesamum prostratum Retz. (Pedaliaceae) Perennial prostrate herb with sprawling branches arising from a thick tap roo occurs along the back-shore strand of Adyar near Madras and on the Red Hills of Chingalpet. Undisturbed, this becomes gregarious and is often found associated with Mollugo nudicaulis, Trachya muricata and Perotis indica. Its large purple flowers amidst densely white tomentose leaves are attractive, and ir forros a good cover under sandy situations. 2.9a Stem: Quadrangular to .cylindrical. Periderm present. Epidermis uni- seriate, slightly wavy, sparsely hairy. Cortex: 7 to 8-1ayered cell~, parenchymatous, polygonal; pith parenchymatous; vascular tissue with secondary growth.

2.9b Lea)" (figure 9): Dorsiventral, hairy, hairs of 2 types, simple hairs, long, uniseriate with wide lumina, some with 2 celled base, abundant on both surfaces; mucilage hairs, simple, stalked, head 2-3 cetled, sparse on adaxial epidermis. Adaxial epidermis uniseriate, cells thin-walled. Palisade single-layered. Spongy parenchyma 3-1ayered, outermost layer of vertical cells abutting abaxial epidermis.

2.10 Thespesia populnea (L.) Sol. ex Correa (Malvaceae) Large evergreen tree bearing attractive yellow flowers, frequent along the drier re~ions of the tidal forests or a common component of beach forests. It attains a good size under strand conditions and is regarded as a prized tree under coasta• conditions beeause it resists salt spray and wind action. 2.10a Stem: Cylindrical. Cortex: wide, cells elongated or oval, parenchy- matous, interspersed by a few tanniniferous idioblasts; mucilaginous canals pro- minent; subepidermal layer suberized, densely charged with starch grains; cork periderm 8 to 10 layered. Pith absent, secondary growth prominent, xylem forms a continuous ring; phloem in triangular strand, with its vertex outwardly directed, interspersed by tanniniferous r 2.10b Lea)" (figure 10): Adaxial epidermis uniseriate, compact; scales peltate an d depressed. Palisade 2-1ayered interrupted by chlorophy•t [ree ceUs abutting vascular bundles. "Spongy 2 or 3-1ayered cells, less chlorophyllous, polygonal or irregular. 458 T Ananda Rao, T R B Naidu and G C Das

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9

10

Figm'esS-10. TSofleaves(• 8. S. taccada. 9. Sesamumprostratum. |0. Thes. pesia populnea.

:3. Conclusions

This study on 10 taxa showing complete fidelity to the strand/dune areas of the India¡ coasts sho~s that there is diversity in their anatomy. Some aspects of their ecological and functional anatomy are discussed. Anatomy of lndian maritime strand flora 459

Notwithstanding that these taxa are not related to each other they show remarkable similarity in their anatomy. Three main functions can be distinguished from their anatomical features.

(i) Protection against excessive transpiration: Ii is shown by presence of bark, cutinised epidermis, sclerosed exodermis, sunken stomata, multi-ceUular out- growths, multiple-layers of palisade and peltate scales. (ii) Protection against drought: Anatomic features favouring this function portrayed by the investigated species are long uni- or bi-cellular root hairs, sclerosed root cortex anda wide root stele; wide cortex in stem comprising mucilage canals, tanniniferous idioblasts; phloem embedded in patches of sclerenchyma, and leaf possessing hyaline cells around photosynthetic patches; water storage cells and hyaline cells around vascular bundles extending up to both epidermal layers.

(iii) Protection against other stresses: Anatomic attributes salutary to this functio.~ and possessed by the strand species are scterosed cortex, sclerenchy- matous ring interior to endodermis, in both root and stem, multiple composite girders in stem, sclerotic patches around phloem in stem, sclerenchymatous caps around vascular bundles, sclerosed epidermis layers and tannin idioblasts in leal. It must be emphasized that the strategy of protection against transpiration, drought and other stresses is assumed on a priori basis, and no evidence has been presented that the ob~erved structural features are vital for the species to survive. Experimental research in this regard should be greatly rewarding.

Acknowledgements

TAR acknowtedges the UGr for financiat hetp and thanks Prof. D A Govindappa for faeilities.

References Rao T A 1971 Distributional resume of the maritime strand flora of India, Bull. Bot.'Surv. India 13 192-203 Rao T A and G C Das 197 1A contribution to the Ecological Anatomyof maritimestrand plants in India, Bull. Bot. Surv.-lndia 13 319-327