Agronomy and Horticulture Department
ASYMBIOTIC in vitro SEED GERMINATION, MICROPROPAGATION AND SCANNING ELECTRON MICROSCOPY OF SEVERAL TEMPERATE TERRESTRIAL ORCHIDS (ORCHIDACEAE)
Date of this Version
Twenty-five different orchid species were successfully asymbiotically germinated and raised on a modified FAST medium (Fast 1976; Szendrák and R Eszéki, 1993). The development of geminating protocorms and young plantlets were recorded and compared among species. Spontaneous vegetative proliferation was also observed. Natural dispersed daylight and prevailing day-length were more favorable than l6-hour cool white fluorescent light for plantlet development. After two to three years of culture, the young plants were suitable for transfer ex vitro.
The effects of organic compounds most commonly used for orchid micropropagation (peptone, coconut water, casein+lactalbumin and glucose) and medium consistencies were investigated for the development of temperate orchid protocorms from five species. Medium consistency had an important role in protocorm proliferation and development. In most cases, the liquid medium increased proliferation and the size of the protocorms. The media supplemented with the undefined organic compounds led to a greater proliferation rate and larger protocorms than the medium supplemented with glucose. In general, peptone and coconut water resulted in best development and proliferation of protocorms, but this varied with species.
Anatomical structures and developmental patterns of seventeen temperate orchid species were observed by scanning electron microscopy (SEM). New information was recorded about the early stages of seed germination and protocorm development, the structural details of roots with mycorrhiza, stored materials (calcium oxalate crystals and starch), leaf/stem stomatal structure and anatomical details of the generative organs and ovule/seed development.
Extensive SEM observations were also conducted on the seeds of more than 120 temperate orchid species. The length of the smallest seeds was ~200 mm (Spiranthes spp.) and the largest ones reached ~1700 mm (Cypripedium, Epipactis spp.) in length. Both quantitative and qualitative data were collected and detailed descriptions of the seeds of the different orchids were prepared. Several fascinating surface patterns and shapes were found, which were specific not only on the level of higher taxonomic units, but sometimes were distinctive even for the species or subspecies.
Advisor: Paul E. Read
A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska in Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy
Major: Interdepartmental Area of Horticulture and Forestry
Under the Supervision of Professor Paul E. Read
Lincoln, Nebraska; August, 1997 Copyright 1997 Erika Szendrák