Proe. lndian Acad. Sci. ( Sci.), Vol. 93, No. 5, October 1984, pp. 567-570 Printed in India.

Development of the caryopsis in Chionachne koenigii Linn.

T V CH SATYAMURTY Department of Botany, Andhra University, Waltair 530 003, India Present address: Government Junior College, Erragondapalem 523 327, India MS received 13 February 1984; rcvised 2 July 1984

Abstract. The anther wall of C. koeni#ª showed the epidermis, endothecium, middle layer and tapetum. Cytokinesisin the pollcn mother cells was successive and isobilateral type of tetrads were formed. The mature ponen grains were three-celled. The development of the embryo sac conformedto the Polygonum type. The antipodal cells increased in number and persisted in the young fruit. Twin embryo sacs occurred in about 30 ~ of the ovules. Endosperm developmentwas nuclear.

Keywords. Chwnachnekoenigii; Maydeae; ; ; caryopsis development.

1. lntroduction

The sub-family Panicoideae of the Poaceae includes a number of important grasses which have both forage and food value. Investigations of Narayanaswami (1953; 1954; 1955a, b; 1956), Koul (1959), Chandra (1963) and Shanthamma (1979) have added to our knowledge of the embryology of this sub-farnily, while investigations of Brown and Emery (1958) have established the occurrence of apomictic phenomena in a number of species. Although appreciable embryological information is available in the tribe Maydeae of the Panicoideae (Koul 1959), Chionachne koenigii has not received the attention of embryologists. This paper deals with the more important details of various embryological aspects leading to the development of the caryopsis in C. koenigª

2. Material and methods

Spikelets at various stages of deveiopment were collected from the rice fields of Gudivada (Andhra Pradesh). Customary methods of fixation, dehydration, embed- ding and microtomy were followed. The mature ovaries were treated with 20 hydrofluoric acid for three days before dehydration. Sections were cut (8-12 #m thickness) and stained in Dela¡ haematoxylin.

3. Observations

3.1 Microsporangium, microsporogenesis and male gametophyte The development of the anther wall conformed to the monocotyledonous type (Davis 1966) and primary sporogenous cells underwent mitotic divisions in all planes resulting in a moderate mass of poUen mother cells (figure 1). Cytokinesis in the poUen mother cells was successive resulting in isobilateral type of tetrads (figure 2). The mature pollen grains were spherical and were shed at the three-celled stage (figure 3). 567 568 T V Ch Satyamurty

Figures 1-8. Developmentof the caryopsis in C. koenigii. 1. TS of an anther lobe showing microspore mother cells and wall layers. 2. Microspore tetrad. 3. Three-celled pollen grains. 4, 5. Linear tetrad and organised embryo sac. 6. Twin embryo sacs. 7. Nuclear endosperm. 8. LS of young caryopsis showing persistent antipodal cells. Abbreviations: ac, antipodal cells; hc, hypertrophied cells; nc, nucellar cap.

3.2 Nucellus, megasporogenesis and female gametophyte The nucellar epidermis at the apex of the ovule underwent one or more periclinal divisions resulting in a 5-10 cells thick nuceUar cap (figure 7). The nucellar tissue was 14 or 15 cells thick on the sides. It was wider at the base of the ovule when compared with the micropytar and middle regions. The micropyle was formed by the inner integument only. The nuceUar cells abutting the micropyle were hypertrophied (figure 7). These enlarged cells became noticeable by the time the four-nucleate embryo sac was formed and they disappeared along with the other nucellar ceUs in the caryopsis. The archesporium in the ovule consisted of 1-3 hypodermal cells. By the time the inner integument reached the apex of the nucellus, the megaspore mother cell enlarged and became deep-seated in the tissue formed by the periclinal divisions of the nucellar epidermis. A linear tetrad of megaspores was formed (figure 4) and the development of the embryo sac conformed to the Polygonum type. Caryopsis in C. koenigii 569

Initially there were three, prominent, uninucleate antipodal cells. The antipodal cells divided to form 4-8 cells in a mature embryo sac (figure 5). The nucleus of each of the antipodal cells divided without wall formation andas many as 10 nuclei could be counted in a cell. The antipodal cells persisted for a considerable time (figure 8). In about 50 ovules examined 30 ~ of the ovules showed twin embryo sacs (figure 6).

3.3 Post-fertilisation changes in the ovary and ovule The primary endosperm nucleus underwent rapid divisions and the nuclei formed were distributed in the pe¡ cytoplasm enclosing a central vacuole (figure 7). Cell wall forrnation in the endosperm began in the region around the proembryo and later extended towards the antipodal end. By the time embryonal organs were differentiated the peripheral layer of the endosperm formed the aleurone layer. The structure of the mature caryopsis wall w as similar to the one described for wheat (Esau 1974).

4. Discussion

Twin embryo sacs now observed in C. koenigii were reported earlier in dactyloides (Farquharson 1955) and Euchlaena mexicana (Koul 1959). Such embryo sacs may have developed from the functioning of two megaspore mother cells. The three antipodal ceUs divide and forma varying number ofcells. Such an increase in the number of antipodal cells were reported in grasses previously (Swamy 1944; Chikkannaih and Mahalingappa 1975; Muniyamma 1976). Khosla (1946) recorded the presence of 23 nuclei in the antipodal cells of Pennisetum typhoideum. The antipodal cells remain at the basal end of the mature embryo sac as in other members of the sub-family Panicoideae (Chandra 1963). Weatherwax (1926) and Randolph (1936) have observed the persistence of antipodal cells in the mature caryopsis of Zea mays. Narayanaswami (1955b) reported that in Echinochloa frumentacea the persistent antipodal cells might be involuted endosperm ceUs rather than real antipodal cells. The present study on C. koenigii reveals them to be undoubtedly antipodal cells.

Acknowledgements

Grateful acknowledgements are due to Dr V Seshavatharam for guidance; to Dr B S M Dutt for going through the manuscript and to the UGC for awarding a fellowship.

References

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