COMPARATIVE ANATOMICAL STUDIES OF SOME POACEAE AND CYPERACEAE

COMPARATIVE ANATOMICAL STUDIES OF SOME POACEAE AND CYPERACEAE

Abstract: Morphological and anatomical comparison was made between selected grass belonging to the family of Poaceae (Acroceras amplectens Stapf and Andropogon ascinnodis C.B.CL) and the family of Cyperaceae (Scleria naumanniana Boeck and Fuirena umbellate Rottb) species. The fresh leaves of both grass and sedge were collected around the University of Port Harcourt Choba and its surrounding environment. The specimens were identified at the Herbarium of the Department of Plant Science and Biotechnology University of Port Harcourt. Further laboratory investigation like anatomy, morphology and epidermal studies were executed at the UPH Department of plant science and biotechnology majors’ laboratory. Results obtained showed that the epidermal studies generated more characters for comparison and were able to show differences between the Poaceae and Cyperaceae species. The results of the stem anatomy of the studied species of Cyperaceae and Poaceae showed little variations like; presence of Anomalous cambial ring around the vascular cylinder of Poaceae which was absent in the Cyperaceae as well as the Stem epidermal circumference which was angular with protuberance in both Cyperaceae species studied but round in the Poaceae species studied. The morphological characters generated showed little variation among studied species. Evidence from the micromorphological characters provided better data to make a comparison between the studied species from the two families.

CHAPTER ONE

INTRODUCTION/ LITERATURE REVIEW

INTRODUCTION (BACKGROUND INFORMATION)

The major subject of discussion among Plant taxonomist and systematists over the years has been plant classification and comparative study (Abdulrahaman et al., 2011).  As new evidence arises plants are classified and re-classified and this is going to be a continuous exercise over some years to come. Abdulrahaman and Oladele, (2010) reported that most plants are classified based on their flowers and fruits which are external morphological structures. These structures are seasonal in production and hence are not always available in Plants. Other means of identification need to be developed due to these reasons so that plant could be easily identified at any period of the year. Others methods include the use of molecular, cytological, and anatomical studies especially that of the leaves since it occurs at every season of the year mostly among the evergreen plants (Abdulrahaman and Oladele, (2010).

Plant morphology or phytomorphology is the study of the physical form and external structure of plants.This is usually considered distinct from plant anatomy (Raven et al., 2005), which is the study of the internal structure of plants, especially at the microscopic level (Evert and Esau, 2006). Plant morphology is useful in the visual identification of plants. A plant scientist makes comparisons between structures in many different plants of the same or different species. Making such comparisons between similar structures in different plants tackles the question of why the structures are similar. It is quite likely that similar underlying causes of genetics, physiology, or response to the environment have led to this similarity in appearance (Vergara-Silva, 2003).    Morphological characters of plants can be compared, measured, counted and described to assess the differences or similarities in plant taxa and use these characters for plant identification, classification and descriptions. When characters are used in descriptions or for identification they are called diagnostic or key characters which can be either qualitative or quantitative (Rutishauser and Isler, 2001).

The morphological study focuses on characters that are features of external appearance. They currently provide the major characters used for hypothesizing Phylogenetic relationships. These external features have been used for a longer time than other lines of evidence like anatomical since the beginning of plant systematics. The characters get from this line of evidence are easily observed and found practical use in keys and description (Akobundu and Agyakwa, 1987; Uka et al., 2014; Awomukwu et al., 2015). These characters include the external features of the plant parts used, including the details of their shape, color, and size. Most Plants are classified based on external morphological structures such as fruits and flowers although these structures are not always available on plants because they are seasonal (Uka et al., 2014; Awomukwu et al., 2015).

Morphological features can be used in identification and delimitation of taxa and genera into tribes and subfamilies generally (Shabnum et al., 2011). The leaf epidermal characters have proved to be very important in providing information on taxonomic importance (Ogie-Odia et al., 2010). Leaf epidermal characters have significance in grass systematics and characterization of broad groups, particularly subfamilies and tribes (Brown, 1958). Epidermal characters are very useful for the differentiation of the different taxa at a higher level (Tateoka et al., 1959). Leaf epidermal characters such as the arrangement of long and short cells, distribution and morphology of the macro hairs, micro hairs, prickles, silica bodies, and stomata are important taxonomically (Holm 1896; Metcalfe, 1960).  In the past anatomical studies incorporation with morphological and palynological studies for the resolution of taxonomic problems of monocots has been used (Shabnum et al., 2011).

Plant anatomy or phytotomy is the general term for the study of the internal structure of plants (Hagemann, 1992). Plant anatomy is now frequently investigated at the cellular level, and often involves the sectioning of tissues and microscopy (Evert and Esau, 2006). As a taxonomical or systematic line of evidence, the anatomical studies are used in combination with other lines of evidence to arrive at a good taxonomic condition (Stace, 1980; Awomukwu et al., 2015). Anatomical studies have been used successfully to clarify the taxonomic status and help in the identification of different species (Gilani et al., 2002). Apart from special references to the taxonomic position of the taxa, the anatomical studies can also be utilized in knowing the origin, distribution and the extent of cultivation and cultivars within species of plants (Lawson, 1967; Onwueme, 1978; Awomukwu et al., 2015).

Aim and Objectives

The aim of this research is to provide comprehensive morphological and anatomical taxonomic characters to make a comparison between selected grass (Andropogon ascinnodis and Acroceras amplectens) and sedge species (Fuirena umbellate and Scleria naumanniana)

These are the objectives of this study;

To provide morphological characters that will help in identification

To provide taxonomical data stem anatomy that will also help to distinguish between selected species.

To provide micro-morphological data from the leaves that will also help to distinguish between selected species.

Significance of the study

This study will help to see if taxonomical characters generated from anatomy and morphological systematics alone will be able to help in making a good comparison between the grass family (Poaceae) and the sedge family (Cyperaceae). And by extension help to clarify the relationship between the two closely related monocots families.

 The Cyperaceae family

The Cyperaceae is a cosmopolitan family of monocotyledonous plants with about 5 000 species, of which 1500 are C4 plants (Bruhl and Wilson, 2007).  The historically important paper-making plant papyrus (Cyperus papyrus) is well known from legend and for its use in horticulture, and a few sedges are economically significant, such as the pernicious agricultural weed Cyperus rotundus (nutgrass), and the commercial Chinese Water-chestnuts (Eleocharis dulcis). Ecologically, the Cyperaceae are very important, particularly in wet habitats at almost all latitudes. They include Carex, which with about 2 000 species (Reznicek, 1990) is one of the largest genera of flowering plants. Interest in Cyperaceae is engendered across biological disciplines by the occurrence of both C3 and C4 photosynthetic pathways in the family. The family is widely acknowledged as posing difficulties for taxonomists, as indicated by Metcalfe (1971): ‘The main difficulty about the classification of the Cyperaceae when the subject is approached solely along traditional lines is that the flowers are very small, the exact morphology of their parts is often obscure, and the morphology of the inflorescences is difficult to interpret.’ (Bruhl, 1995).

The anatomical structures related to C4 photosynthesis were initially described by Haberlandt (1882, 1914), who gave the term ‘Kranz anatomy’ to the concentric rings of chlorenchyma cells around the bundle sheaths in Cyperaceae and Poaceae species. The term ‘Kranz anatomy’ or ‘Kranz structure’ was later expanded to include the entire scope of anatomical features of C4 plants (Johnson and Brown 1973; Brown 1975), such as the presence of primary carbon-assimilation tissue (PCA) (mesophyll cells) and of photosynthetic carbon-reduction tissue (PCR) (bundle sheath with chloroplasts) (Dengler et al. 1985; Nelson and Dengler 1992). The Kranz species of Cyperaceae display the following four anatomical subtypes: chlorocyperoid, eleocharoid, fimbristyloid and rhynchosporoid. They are structurally distinguished by the number of bundle sheaths, whether these sheaths are continuous or not and the location of the chloroplasts (Carolin et al., 1977).

The Poaceae family

Poaceae or Gramineae is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses, commonly referred to collectively as grass. There are about 12,000 grass species in about 771 genera that are classified into 12 subfamilies (Soreng et al., 2015).  Poaceae are the fifth-largest plant family, following the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae (Piperno and Hans-Dieter, 2005). Poaceae includes the cereal grasses, bamboos and the grasses of natural grassland and cultivated lawns and pasture. The Poaceae are the most important source of the world’s dietary energy supply. They provide, through direct human consumption, just over one-half (51%) of all dietary energy; rice provides 20%, wheat supplies 20%, maize (corn) 5.5%, and others grains 6% (Christenhusz and Byng, 2016).

The grass family is one of the most widely distributed and abundant groups of plants on Earth. Grasses are found on every continent including Antarctica with the presence of Antarctic hair grass on the Antarctic Peninsula (Paul and Julie, 2003). Their economic importance stems from several areas, including food production, industry, and lawns. They have been grown as food for domesticated animals for up to 6,000 years and the grains of grasses such as wheat, rice, maize (corn) and barley have been the most important human food crops. Grasses are also used in the manufacture of thatch, paper, fuel, clothing, insulation, timber for fencing, furniture, scaffolding and construction materials, floor matting, sports turf and baskets (Christenhusz and Byng, 2016).