Embryological studies in Coffea arabica L

Abstract

Studies on fruit development from flower bud formation and with special reference to bean development are presented in Coffea arabica cultivar 'Kents' and in the selections $228 3 5795 grown at the Central Coffee Research Institute, located in the southwestern coffee growing belt of India. The orientation and nature of the ovules in the pre-flowering period (megasporogenesis), which is initiated in response to 'flowering rains', have been found to be similar to previous reports of such occurrences in C. arabica. The way in which ovules develop into the characteristic size and shape of mature coffee beans has been followed in detail and the ovule as an enclosed whole within the stalk has been found to contribute to this.

The multilocular or multi-ovular condition (false polyembryony, polyspermy) is related to the formation of more than one locule and the initiation of more than one ovule respectively. However, the development of the ovule and endosperm remains the same as that of a normal ovule. The difference in size and shape obtained in these cases is related to the nature and number of ovules that reach maturity and the competition for space in the fruit. The result of the multilocular condition is triangular seeds, while the multiovular condition produces giant seeds or holes

In cases of true polyembryony, two separate or united endosperms in the same ovule have been reported. The various types of polyembryony observed are currently being considered, along with previous cases in C. arabica, and a reclassification has been suggested. The significance of the multiovular condition in C. arabica from the phylogenetic point of view in Rubiaceae and from the genetics and breeding of plants in experimental selections is also discussed.