LEAF GROWTH AND PHENOLOGY OF THE DIMORPHIC HERBACEOUS LAYER FERN DANAEA WENDLANDII (MARATTIACEAE) IN A COSTA RICAN RAIN FOREST

Leaf growth and spore release in Danaea wendlandii were monitored under temperate greenhouse conditions and in a rain forest at the La Selva Biological Station in Costa Rica. Sterile leaf (trophophyll) growth occurs in four phases, and fertile leaf (sporophyll) growth occurs in five phases. Trophophylls show an initial rapid increase in length for a 4-week period, attain full maturity at 8 weeks, and remain on the plant for about 3 years. There appears to be a seasonal pattern of trophophyll growth, with crozier emergence rates in May and June three times higher than the mean annual rate. Sporophyll growth shows a double sigmoid pattern. For about 3 weeks after crozier emergence, there is a rapid increase in length. This phase is followed by a 10-week period with no appreciable change in length. Rapid elongation over a 2-week period precedes spore release; this is followed within 2 weeks by disappearance of the sporophyll. Sporophylls in the rain forest are subject to 14% mortality prior to maturation, with most mortality occurring in later stages of growth. A projected phenology based on the sporophyll growth curve shows peaks in spore release late in the wet season with a concomitant peak in sporophyll emergence early in the wet season during the 15-month period from June 1986 through September 1987.