Pteridophyte spores viability

Abstract

Spore viability is defined as the time that spores retain their capacity to germinate. It is a factor of primary importance in the establishment of fern species and populations in a new habitat after spore dispersal. Viability is typically maintained for a long period in pteridophytes, but there are great variations in both interspecific and intraspecific levels. Factors affecting viability are either intrinsic, such as genotype, age and dormancy, or extrinsic, such as the conditions of physical environment or presence of competitors. One of the main features that affect fern spores viability is the presence of chlorophyll in the cell. Green spores have chloroplasts and their germination ability does not persist long after harvest, showing a viability that is in the range of few weeks. Most pteridophytes have non-chlorophyllous spores whose viability is much higher, of about 3 years on average. For a long time, fern spores viability has been measured by means of germination percentage. This is a very simple method but requires a certain time to ensure that all or most viable spores germinate. Ultimately, some other detection techniques have been proposed, based on the capacity of living cells to enzymatically react with some chemicals giving colour or fluorescence. These methods allow estimating viability in a shorter time. Since spore viability is important for ex-situ conservation purposes, a relatively high amount of studies concerning germination and loss of viability of spores have been carried out in the last 2 decades. Several methods have been assayed to preserve spores of a number of species. Viability of most pteridophyte spores was believed to be retained when stored in dry and cold conditions. However, several exceptions have been found. Also of interest is the cryopreservation technique, very useful when dealing with economical interesting plants, as an important component in plant biotechnology programmes.