POLLEN STUDIES ON HELICONIA

Abstract

Heliconia species are gaining in importance due to their desirable horticultural properties and postharvest characteristics. Much, though, remains to be known about this plant. Thus it has become doubly important to carry out investigations on its breeding behaviour and other factors affecting its fertility. This study was thus aimed at determining what these factors were and at optimizing these. Since germinability is very important in determining fertility, germination tests were carried out, investigating the effects of flower collection time, temperature conditions before and after harvest and medium components. It was found that all the above played very important roles, with temperature probably being the most important one. Harvesting of flowers very early in the day at low temperature conditions was found to enhance germinability. The components of the germination medium were also concluded to be important. Sucrose may have a role to play as an osmoticum and may also be involved in pollen metabolism. Boric acid may enhance pollen tube growth. Gibberellic acid and calcium enhance germination but not tube growth, with calcium being enhanced in its action by magnesium and potassium. Viability studies carried out gave consistent results for all tests except for the TTC test which gave no result for all taxa of Heliconia tested. This test was therefore concluded to be not reliable or valid for this genus. Stigma receptivity studies gave expected results for all taxa tested except for the hybrid cultivar 'Golden Torch' which had a receptive stigma despite no pollen production, and the cultivar 'Andromeda' which may possibly be exhibiting protogyny. In vivo germination and in vitro pollination studies gave no results, possibly because of the use of the wrong cuItivar. H. rostrata was found to behave in a similar fashion to H. psittacorum cultivars. This suggests that the similarity between members of this genus may be more than the degree of disparity. Future prospects for research include the use of Heliconia psittacorum cv. Black Cherry and cv. Susi as parents in hybridization, especially with 'Susi' as a pollen parent as it has such a good growth rate of the pollen tube, Also, the use of growth regulators to retard senescence and therefore promote germination and fruit set may have some potential.