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Studii şi Cercetări Martie 2010 Biologie 18 13-17 Universitatea”Vasile Alecsandri” din Bacău ANATOMICAL ASPECTS OF THE ORNAMENTAL PLANT SPATHIPHYLLUM WALLISII REGEL Rodica Bercu, Marius Făgăraş Key words: anatomy, adventitious root, leaf, flower penduncle, spathe, Spathiphyllum wallissi INTRODUCTION MATERIAL AND METHODS Spathiphyllum is a genus of about 40 Spathiphyllum wallisii plants were species of flowering plants belonging to the collected form S.C. IRIS INTERNATIONAL Araceae family. S.R.L. greebhouse. Small pieces of the The genus species are native to tropical adventitious root, leaf, the flower peduncle and regions of the Americas and southeastern Asia spathe were fixed in FAA (formalin:glaciar acetic (Bogner & Nicolson, 1991; Bunting, 1960). acid:alcohol 5:5:90). Certain species of Spathiphyllum are commonly Cross sections of the vegetative organs known as peace lilies. Spathiphyllum wallisii were performed with a rotary microtome (Bercu Regel white sails, spathe flower or the moon & Jianu, 2003). The samples were stained with flower is a tropical herbaceous perrenial plant. alum-carmine and iodine green. Histological It was discovered in the late 19th century observations and micrographs were performed growing wild in central America (Everett, 1981; with a BIOROM-T bright field microscope, Croat, 1988). In our country the plant is equipped with a TOPICA-6001 A video camera. commonly known as being a very popular indoor house plant. RESULTS AND DISCUSSIONS It produces typical Aroid flowers, a densely crowded inflorescence called a spadix is Cross section of the advetitious root of subtended by one large bract called a spathe. Spathiphyllum wallisii exhibits small rizodermal The spadix is generally cream or ivory cells. Hairs are present. when young, and turns green with age; the spathe The cortex is well-developed and is generally white or white with green nerves differentiated into two zones. The outer cortex – distally from the margin, turning green with age. exodermis, present below the rhizodermis, is one- Leaves are basal, glossy and somewhat deeply layered with slightly suberized cell walls. The veined, ovate and acuminate. inner cortex of is a well-developed region of The petioles are long and the leaves arch loosely arranged parenchymatous cells enclosing gracefully (Mayo et al., 1997). The paper purpose large intercellular spaces. is to show the anatomy of the main decorative Characteristically, the primary endodermis organs, exhibiting some features of anatomical consists of slightly suberized cells possessing, at interest concerning this Aroids species. In the places, passing cells opposite xylem (Kroemer, literature, there are some studies concerning the 1903). morphology and anatomy of the leaf of this The vascular system is quite well species correlated with genetic purpose developed. The vascular bundles of both species (Vanstechelman et al., 2009) or with cytological are radial type in an alternative arrangement and value (Nicolson, 1960). such as other Araceae species Monstera deliciosa, Anatomical studies concerning the Spatyphyllum sp. (Bavaru & Bercu, 2002; vegetative organs of Spathiphyllum wallisii are Batanouny, 1992), numbering more than six (Fig. sporadic (Metcalfe et al., 1960), and those 1, A). concerning the flower peduncle and the modified leaf (spathe) almost lack. 13 The vascular elements consist of xylem The mesophyll is more or less and phloem. The metaxylem vessels are few (one homogenous, represented by a spongy tissue with for each bundle) and 2-3 protoxylem vessels, with large intercellular spaces. It is composed of large high lignified cell walls. The phloem consists of thin-walled cells with a number of chloroplasts mainly sieve cells and companion cells showing (Fig. 2). exarch condition. The central portion of the root Such as Batanouny (1992), Fahn (1990) is occupied by pith made up of compactly and Bercu (2009), caracteristically for Aroids arranged sclerenchymatous thick-walled cells species the both epidermis continuity is broken by (Fig. 1, B). the presence of stomata with large substomatal The cross section of the blade exhibits an cavities. It is to be remarked druses in some of the upper epidermis, a lower epidermis and the mesophyll cells. mesophyll. The one-layered upper and lower The lower epidermis forms a large epidermis are composed of large radially arranged prominence in the mid vein zone. The vascular cells, covered by a thick cuticle. system of the mid vein of Spathiphyllum wallisii is composed of numerous collateral bundles (Fig. 3 A). Fig. 1. Cross sections of the adventitious root. Portion with rhizodermis and cortex (A). X 320. The stele (x 220): (B). AS- air space, Ed- endodermis, Ex- exodermis, H- hair, Pc- pericycle, Ph- phloem, Pi- pith, X- xylem (orig.) Fig. 2. Portion of a cross sections of the blade (x 240): Cl- chloroplasts , Ct- cuticle, - druse, LE- lower epidermis, Ms- mesophyll, S- stoma, SC- substomatal cavity, UE- upper epidermis (orig.) 14 Fig. 3. Cross section of the mid vein. Portion with vascular bundles (A) (x 107). Portion with lower epidermis (B) (x 150): Co- collenchyma, LE- lower epidermis, Ms- mesophyll, UE- upper epidermis, VB- vascular bundle (orig.) Fig. 4. Portion of a cross sections of the petiole (x Fig. 5. Cross sections of the flower peduncle (x 240): 240): E- epidermis, H- hypodermis, Ph- phloem, PC- BT- basic tissue, PC- parenchymatous cortex, SPc- parenchyma cortex, SS- sclerenchymatous sheath, X- sclerenchymatous pericycle, VB- vascular xylem (orig.) bundle (orig.) Fig. 6. Cross section of Anthurium andreanum spathe (x 300): LE- lower epidermis, Ms- mesophyll, UE- upper epidermis, VB- vascular bundle (orig) 15 Xylem and phloem consists of vascular collateral bundles, aleatory embedded in the elements (2-3 meta- and protoxylem vessels and a ground tissue of the mid vein. Stomata are present reduced number of phloem vessels and phloem in both epidermises (upper and lower epidermis). parenchyma). Each vascular bundle is protected The petiole and flower peduncle cortex is by a sclerenchymatous sheath. differentiated into a collenchymatous region, with Collenchymatous cells are present in the chloroplasts, and the inner zone is abaxial zones of the mid vein (Fig. 3 B).The parenchymatous. The flower peduncle stele is circular undulate-shaped petiole, in transversal represented by a number of poor developed section, discloses that the regularly arranged vascular bundles, embedded in the ground tissue epidermal cells are covered by a thick cuticle. whereas those of the petiol are well developed. It The petiole cortex is differentiated into two is to be remarked the many-layered pericycle of zones. The external region (hypodermis) is the flower peduncle. slightly collenchymatous, possessing The mechanical tissue is poor-developed chloroplasts, followed by the inner zone in all Spathiphyllum wallisii studied organs. represented by 2-3 layers of parenchyma tissue. However, in the blade it is represented by some The Spathiphyllum wallisii petiole stele is collenchyma cells placed in the abaxial position represented by a number of poor developed of the mid vein whereeas in the petiole by a collateral vascular bundles embedded in the basic colenechymatous tissue. In the flower peduncle it tissue, with the typical caulinar arrangement of is represented by the many-layered the conductive tissues. Xylem and phloem are sclerenchymatious cells of the pericycle. represented by 2-3 xylem vessels, few xylem parenchyma cells and few phloem elements, ABSTRACT surrounded by a sclerenchyma sheath (Fig. 4). The flower peduncle in cross section The article comprises anatomical aspects discloses almost the same features such as the of the adventitious root, leaf, flower peduncle and petiole but it is to be remaeked that the petiole bract of one of the most beloved ornamental inner cortex zone represented by a 3-6 layers of houseplants in Romania Spathiphyllum wallissi parenchyma tissue. It is to be remarked the Regel. The plant organs disclose certain features presence of a sclerenchymatous many-layered of anatomical interest, in accordance with pericycle (Fig. 5). Araceae family nature. The petiole stele is represented by more or Each tissue has been described and less nine close collateral vascular bundles, discussed, illustrations included. The anatomical aleatory embedded in the basic tissue, with the features of the adventitious roots exhibit a typical caulinar arrangement of the conductive primary structure but some specific anatomical tissues. Each vascular bundle possesses 3 xylem aspects occur. The blade possesses a typical vessels and few phloem elements, unprotected by homogenous mesophyll. The vascular bundles of bundle sheaths. Characteristically some air spaces the mid vein are well developed with an aleatory are present (Fig. 5). arrangement of the vascular bundles. The petiole The Spathiphyllum wallisii transversal and flower peduncle stele is composed of section of the spathe (bract) reveals the usually numerous vascular bundles, embedded in the succession of a blade tissues. The upper and ground tissue. lower epidermis is one-layered with large Mechanical tissue is poor developed in epidermal cells, covered by a thin cuticle. almost all studied plant organs. In the literature, Between them, a homogenous mesophyll is studies concerning the vegetative organs anatomy present, consisting of parenchymatous cells of Spathiphyllum wallisii are sporadic and those (spongy tissue) and intercellular spaces. Few poor concerning the flower

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