dark green in maturity (see Fig. 1c). Spores can be green
(known as chlorophyllous spores; see Fig. 1d-left) or from
diverse colors ranging from pale yellow to brown (known as
non-chlorophyllous spores; see Fig. 1d-right). It is useful to
know the color of a ripe spore for the family being studied as
chlorophyllous spores are very short-lived and need to be
processed quickly (within 1–2 weeks from harvest).
5. Chlorophyllous spores, such as those from the genera Equisetum sp., present very short life spans. Some species can deteriorate very fast during drying, and viability can be lost in a few
days. During the first day of drying, most spores will be released
from the fronds or strobili if they are dried at low RHs (e.g.,
<40% RH). Drying the fronds or strobili for 2 or 3 days may
release more spores, but those already released will start to age.
Drying the fronds or strobili for more than 2 or 3 days may
affect severely the spore viability and will not increase largely
the number of spores harvested.
6. Check if the controller of the hood is not too high to avoid
spores being absorbed by the flow of the hood.
7. Brushing the fern frond to obtain more spores should be
avoided as it can add contaminants and excess debris to the
collection.
8. If necessary, tap the paper to aid the spores to fall to the bottom
of the packet; this is easier than brushing or using fingers.
9. It is important to check that the collection received contains
dehisced spores. Dehisced spores can be seen in the packet as a
dust (see Fig. 1e). Check that the dust are spores by looking
under the microscope. If the collector harvested old fronds
with empty sporangia (see Fig. 1c-right), spores may not be
present or may be deteriorated. Storing empty/dehisced sporangia may preserve a few spores attached to them but of
unknown age and quality and with high risk of crosscontamination from other species.
10. There is a “critical moisture” content for seed, fern spore, and
pollen storage below which desiccation stress is imposed to
these desiccation tolerant tissues. This “critical moisture”
increases as temperature decreases [30, 39]. When spores and
pollen are dried at very low RHs (e.g., 10–15%) and room
temperatures (e.g., 15–25
C), the moisture content reached
may be lower than the critical moisture content needed for
adequate storage at sub-zero temperatures (e.g., such as those
reached in LN: 180–196
C). Drying at room temperatures
(e.g., 15–25
C) and slightly higher RH (e.g., 30–40%) will
generate an adequate moisture content to avoid that desiccation stress is not imposed when both temperature and moisture
contents are reduced to extreme levels [39].
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Anna Nebot et al.
(known as chlorophyllous spores; see Fig. 1d-left) or from
diverse colors ranging from pale yellow to brown (known as
non-chlorophyllous spores; see Fig. 1d-right). It is useful to
know the color of a ripe spore for the family being studied as
chlorophyllous spores are very short-lived and need to be
processed quickly (within 1–2 weeks from harvest).
5. Chlorophyllous spores, such as those from the genera Equisetum sp., present very short life spans. Some species can deteriorate very fast during drying, and viability can be lost in a few
days. During the first day of drying, most spores will be released
from the fronds or strobili if they are dried at low RHs (e.g.,
<40% RH). Drying the fronds or strobili for 2 or 3 days may
release more spores, but those already released will start to age.
Drying the fronds or strobili for more than 2 or 3 days may
affect severely the spore viability and will not increase largely
the number of spores harvested.
6. Check if the controller of the hood is not too high to avoid
spores being absorbed by the flow of the hood.
7. Brushing the fern frond to obtain more spores should be
avoided as it can add contaminants and excess debris to the
collection.
8. If necessary, tap the paper to aid the spores to fall to the bottom
of the packet; this is easier than brushing or using fingers.
9. It is important to check that the collection received contains
dehisced spores. Dehisced spores can be seen in the packet as a
dust (see Fig. 1e). Check that the dust are spores by looking
under the microscope. If the collector harvested old fronds
with empty sporangia (see Fig. 1c-right), spores may not be
present or may be deteriorated. Storing empty/dehisced sporangia may preserve a few spores attached to them but of
unknown age and quality and with high risk of crosscontamination from other species.
10. There is a “critical moisture” content for seed, fern spore, and
pollen storage below which desiccation stress is imposed to
these desiccation tolerant tissues. This “critical moisture”
increases as temperature decreases [30, 39]. When spores and
pollen are dried at very low RHs (e.g., 10–15%) and room
temperatures (e.g., 15–25
C), the moisture content reached
may be lower than the critical moisture content needed for
adequate storage at sub-zero temperatures (e.g., such as those
reached in LN: 180–196
C). Drying at room temperatures
(e.g., 15–25
C) and slightly higher RH (e.g., 30–40%) will
generate an adequate moisture content to avoid that desiccation stress is not imposed when both temperature and moisture
contents are reduced to extreme levels [39].
632
Anna Nebot et al.