Coffee seeds (C. arabica) are no longer considered recalcitrant as they can
survive below the threshold level (0.20 g H 2 O/g dw) of recalcitrant seeds. Coffee
seeds are now believed to have storage behavior defined as intermediate [102]. The
minimum water content to which seeds of C. arabica, C. canephora, and C. liberica
can be dried without damage is about 0.09 g H 2 O.g-1 dw and 0.10–0.12 g H 2 O.g-1
dw, respectively [102]. The water content of seeds and ambient temperature are
interdependent and have been considered critical for the growth and survival of
seeds in soil [103]. The seed water content decreases with lowering the temperature
until chilling proving unfavorable for the viability of growing seeds. Generally, seed
moisture content followed by storage temperature was the most important factor that
influenced coffee seedling quality, whereas the fruit maturation stage least influenced
quality. Some cultivars of C. arabica were found to be still possessing high germination rate (>85%) while storing at 10–15
C when germination temperature range
found suitable for higher germination is 20–30
C [95, 102]. But Rosa and her
coworkers [95] found that maturation stage has significant effects over standard
germination rather than moisture content or physiological germination or their
interaction between these two factors.
Immediately after harvesting, seed maturation stage does not affect the germination rate of dry seeds with moisture contents (10–12%). But in longer seed storage
period, stage of harvesting found to be significantly affecting the physiological
aspects of seed quality. Physiological quality of dry seeds was also found to be
influenced more by storage temperature when dried up to 12% moisture contents.
Actually there is a triple interaction of factors (e.g., storage time, storage temperature, and stage of harvesting) which found to play a crucial role in determining the
quality of coffee seedlings. The premature harvested seeds with high moisture
contents have a higher emergence speed indices than the cherry stage harvested
stage with intermediate moisture (16–20%) contents that also produced poor quality
seedlings. The seeds of either harvesting stage with mediocre moisture contents also
have more impact on poor physiological quality and insignificantly affecting the
coffee seedling production. The quality of seeds found to be synonymous if they are
stored at 20
C provided that they must be stored with 12% or 47% moisture contents
irrespective of stage of harvesting. So the highest and lowest moisture contents
(12%, 47%) of harvested coffee seeds have higher physiological quality as compared
to the seeds with intermediate level of moisture [95]. The possible reason behind this
oxidative or respiratory damage and deterioration is seeds with poorly activated
injury repair mechanisms [109]. After the work on storage and drying by Rost et al.
[95], this topic was further explored by addition of using the drying methods (e.
g., slow and fast) [103] and somehow supports the results of Rosa and his team [95].
Physiological quality of seeds found to be compromised in both drying methods.
Good percentage of viability and vigor was observed in seeds with higher (40%) and
lower (12%) moisture dried by slow drying as compared to seeds with intermediate
moisture level dried by fast drying that also lost the vigor. The microscopic rupturing
of cell membranes may be the reason for this which is enormous at fast drying with
intermediate moisture [104]. The fast drying process should be avoided in this regard
as seeds may tend to have intermediate level of moisture content for longer period of
660
A. Hameed et al.
survive below the threshold level (0.20 g H 2 O/g dw) of recalcitrant seeds. Coffee
seeds are now believed to have storage behavior defined as intermediate [102]. The
minimum water content to which seeds of C. arabica, C. canephora, and C. liberica
can be dried without damage is about 0.09 g H 2 O.g-1 dw and 0.10–0.12 g H 2 O.g-1
dw, respectively [102]. The water content of seeds and ambient temperature are
interdependent and have been considered critical for the growth and survival of
seeds in soil [103]. The seed water content decreases with lowering the temperature
until chilling proving unfavorable for the viability of growing seeds. Generally, seed
moisture content followed by storage temperature was the most important factor that
influenced coffee seedling quality, whereas the fruit maturation stage least influenced
quality. Some cultivars of C. arabica were found to be still possessing high germination rate (>85%) while storing at 10–15
C when germination temperature range
found suitable for higher germination is 20–30
C [95, 102]. But Rosa and her
coworkers [95] found that maturation stage has significant effects over standard
germination rather than moisture content or physiological germination or their
interaction between these two factors.
Immediately after harvesting, seed maturation stage does not affect the germination rate of dry seeds with moisture contents (10–12%). But in longer seed storage
period, stage of harvesting found to be significantly affecting the physiological
aspects of seed quality. Physiological quality of dry seeds was also found to be
influenced more by storage temperature when dried up to 12% moisture contents.
Actually there is a triple interaction of factors (e.g., storage time, storage temperature, and stage of harvesting) which found to play a crucial role in determining the
quality of coffee seedlings. The premature harvested seeds with high moisture
contents have a higher emergence speed indices than the cherry stage harvested
stage with intermediate moisture (16–20%) contents that also produced poor quality
seedlings. The seeds of either harvesting stage with mediocre moisture contents also
have more impact on poor physiological quality and insignificantly affecting the
coffee seedling production. The quality of seeds found to be synonymous if they are
stored at 20
C provided that they must be stored with 12% or 47% moisture contents
irrespective of stage of harvesting. So the highest and lowest moisture contents
(12%, 47%) of harvested coffee seeds have higher physiological quality as compared
to the seeds with intermediate level of moisture [95]. The possible reason behind this
oxidative or respiratory damage and deterioration is seeds with poorly activated
injury repair mechanisms [109]. After the work on storage and drying by Rost et al.
[95], this topic was further explored by addition of using the drying methods (e.
g., slow and fast) [103] and somehow supports the results of Rosa and his team [95].
Physiological quality of seeds found to be compromised in both drying methods.
Good percentage of viability and vigor was observed in seeds with higher (40%) and
lower (12%) moisture dried by slow drying as compared to seeds with intermediate
moisture level dried by fast drying that also lost the vigor. The microscopic rupturing
of cell membranes may be the reason for this which is enormous at fast drying with
intermediate moisture [104]. The fast drying process should be avoided in this regard
as seeds may tend to have intermediate level of moisture content for longer period of
660
A. Hameed et al.