A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN HORTICULTURE MAY 1996

ENDOSPERM CULTURE OF COCONUT
Lazarus Agus Sukamto

Polyploid heterosis has occurred in apples, pears, citrus and grapes and results in greater vigor, larger fruit size and generally greater yield (Sanford, 1983). In Petunia axillaris triploids were more vigorous and had bigger flowers than the diploid or tetraploid plants (Gupta, 1982). Populus tremuloides triploids were superior for wood production compared to diploid counterparts (Johri et al., 1980).

Producing triploid plants by crossing method is cumbersome since it takes a long time for economical purpose; an alternative is to regenerate plants from endosperm explants in vitro (Sita, 1987).

Endosperm is triploid in over 81% of flowering plants. It is the result of fusion of two polar nuclei of female gametophyte and one of male gametes (Johri et al., 1980). Therefore, it differs genotypically from the embryo in gene-dosage (Kovoor, 1981). Endosperm is a fairly homogeneous mass of parenchymatous cells and lacks vascular elements (Johri and Bhojwani, 1977; Johri et al., 1980). However, cells can vary in size and ploidy (Abraham and Mathew, 1963).

The function of endosperm is to nurture the embryo during its heterotrophic phase of growth and to provide combustible sources of energy during seed germination (Johri and Bhojwani, 1977; Raghavan, 1986). Endosperm may be consumed entirely by the embryo so that mature seed is called nonendospermous. If it persists in mature seed as a massive tissue, it can store reserve food materials in the form of starch, fat or protein and is called endospermous (Johri and Bhojwani, 1977; Johri et al., 1980; Bhojwani, 1984) .

Endosperm of angiosperms can grow and differentiate into organs (Nag and Johri, 1971; Bhojwani and Razdan, 1983). Triploids from culture may be superior to those from crossing tetraploid and diploid plants, due to the genetically 'unreduced' nature of the 2n polar fusion nucleus in the central cell of the megagametophyte (Knight and Alston, 1969).

Endosperm culture produced shoots or plantlets in Ricinus communis, Exocarpus cupressiformis, Actinidia chinensis, Codiaeum variegatum, Jatropha panduraefolia, Putranjiva roxburghii, Oryza sativa, Dendrophthoe falcata, Scurrula pulverulenta, Taxillus vestitus, Prunus persica, Pyrus malus, Juglans regia, Citrus grandis, C. sinensis and Santalum album (Rangaswamy and Rao, 1963; Satsangi and Ram, 1965; Johri and Bhojwani, 1977; Bhojwani, 1984; Tulecke et al., 1988; Chen et ale 1990). Thus it may be possible to regenerate coconut plants from cultured endosperm.