Environmental factors affecting spore germination and early life cycle stages of selected Platycerium desv. species

Abstract

Platycerium coronarium and P. superbum spores responded to 26(DEGREES)C on a thermogradient with greatest germination percentages. The same temperature was also optimum for gametophytic surface area increase and juvenile sporophyte growth. Spores of P. coronarium germinated optimally in the range of 18 - 100 (mu)Em('-2)sec('-1) while P. superbum spores germinated with greatest percentages at 18 - 25 (mu)Em('-2)sec('-1). Immature gametophytes of both species exhibited the greatest growth at irradiances of 18 - 25 (mu)Em('-2)sec('-1). The light compensation point for mature P. coronarium gametophytes was near 9 (mu)Em('-2)sec('-1) and photosynthesis saturated near 80 (mu)Em('-2)sec('-1). Juvenile P. coronarium fresh weight did not differ significantly when grown under a light gradient of 18 - 190 (mu)Em('-2)sec('-1) but chlorophyll a and b content decreased linearly as irradiance increased. Platycerium superbum gametophytes exhibited greatest surface area increase at pH 7 while P. coronarium gametophyte growth was not substrate pH sensitive. Amending a peat-vermiculite mix with 950 ppm hydrogel and 25 ppm vitamin B(,1) significantly increased P. Hilli 'Drummond' sporophyte production under diurnal temperature fluctuations.