Studies on the Initiation of Sporangia in Ferns

Citation

Labouriau, Luiz Fernando Gouvêa (1958) Studies on the Initiation of Sporangia in Ferns. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3BNE-T071. https://resolver.caltech.edu/CaltechETD:etd-10082004-105932

Abstract

A survey of available data in the literature shows that initiation of sporangia in ferns is not strictly localized, but is possible in many areas of the fern organism, such as the gametophytes, the first leaves and several areas of the leaf of the adult plant, which do not have to be contiguous.

In the usual sites of initiation, sporangia show correlations with the leaf veins and they may be replaced by a variety of alternative differentiations, such as cell proliferations, vegetative buds and aposporous prothalli.

Initiation and differentiation of sporangia may be arrested in several stages, both in natural conditions and experimentally. Some of the experimental procedures that produce this effect use changes in environmental factors.

Experimental results recorded in the literature indicate a day-neutral behavior in several species and a qualitative short-day behavior in one species (Salvinia natans).

The results of experiments reported in this thesis show that Asplenium bulbiferum is a quantitative long-day plant with a critical night of 23 hours at 20°C. In this species adventitious buds are capable of producing sporangia on their leaves, while attached to the adult leaf, but this capacity is lost upon isolation of the buds.

In Osmunda claytoniana determination of the sporophylls was found to be caused by processes that are independent of those that determine the cataphylls and to be enhanced by long days and high temperatures.

Salvinia rotundifolia was found to behave as a short-day plant at temperatures above 20°C and as a long-day plant at 17°C. Initiation of sporangia in this species responds also to daily thermoperiodicity.

Regnellidium diphyllum was found to develop sporocarps as a response to seasonal and to daily thermoperiodicity. This response is quantitatively modified by photoperiodism.

These results are discussed in relation to the available data on the differentiation of vascular tissues, on heteroblastic leaf development, photoperiodism and thermoperiodicity.

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