Pollination Procedure for Dieffenbachia
By R.J. Henny and Eleanor M. Rasmussen
Interest in breeding Dieffenbachia often leads to several questions concerning their unique floral structure and method of pollination. This paper is intended to serve as a guide for anyone planning to do breeding work with Dieffenbachia. In central Florida, green house-grown Dieffenbachia normally flower between April and July although some plants may be observed flowering at other times of the year. The Dieffenbachia inflorescence is made up of spadix and a spathe (Figure 1 A Q. The spadix consists of an upright central axis covered with several minute flowers without petals. Dieffenbachia have separate male (staminate) and female (pistillate) flowers clustered about the spadix. Female flowers consist of a stigma, style and ovary while the male flowers (anther and filament) produce the pollen (a dust-like substance) used to pollinate the stigmatic surface of female flowers. A pollination involves the transfer of pollen from a selected male flower to the stigma of the selected female flower. In Dieffenbachia male flowers are grouped on the upper half of the spadix and female flowers on the basal half (Figure 1C). The spathe covers the spadix until anthesis (the day of flower opening) when it unfurls and exposes the male portion of the spadix (Figure 113). Whenever possible the inflorescence should be pollinated the same day as the spathe unfurls. Usually the spathe unfurls in the evening or during the night so flowering plants need to be checked daily for newly opened inflorescences. For example, an inflorescence that opened during a Monday night should be pollinated Tuesday. The first step in pollinating Dieffenbachia is finding a source of pollen. The male flowers of Dieffenbachia do not produce pollen until 2-3 days after the spathe initially unfurled (Figure 1B). This means that it is necessary to collect pollen from a 2-3 day old inflorescence for use in pollinating a newly opened one. The female flowers are only receptive of pollen the same day the spathe unfurls and possibly the next. In nature this prevents self pollination, or inbreeding, and the mechanism is referred to as dichogamy.
Dieffenbachia pollen is easy to observe once it is produced (Figure 2). The portion of the inflorescence bearing pollen (male or staminate portion) can be cut off with a razor blade and placed in a dish or other container for easy access. A camel hair brush may be used to pick up the pollen and transfer it to the stigmatic surface of the female flowers (Figure 3). The brush will pick up pollen easier if it is first brushed lightly across the moist sticky surface of the stigma. The stigmatic surfaces of the female flowers may be identified by their golden yellow color and seeds dry out or they will lose viability rapidly. It is desirable to clean off the fleshy outer covering from the fruit before planting the seed to help prevent development of bacteria or fungi in the seed bed. Seeds may be planted on top of peat or spaghnurn moss and placed under intermittent mist or covered with 1/4" peat or spaghnum moss and hand watered often enough to prevent drying. Most Dieffenbachia seed will germinate in 1-3 weeks after planting. Seedlings do not show their adult variegation pattern until approximately 810 leaves have been produced.
Obtaining seed from Dieffenbachia not easy to accomplish and in many cases seed production may be poor. Research is currently in progress to study various methods of increasing seed production in Dieffenbachia.