time, which may cause the respiratory damage and tissue injury lowering the
viability, vigor, and physiological quality of seeds [105, 106 ]. The conflict in
literature about advocating the usage of slow drying [107] or fast drying [95, 108]
methods may arise due to using coffee seeds with different quality, ecology, variety,
or genotypes, etc., in different studies as it is also documented that different species
of Coffea have different level of tolerance to withstand desiccation process. The till
known sequence of level of tolerance to desiccation is in the order of Coffea
racemosa > C. canephora > C. arabica > C. liberica [109]. So we may assume
that desiccation sensitive species may not possess the full range of desiccation
tolerance mechanism by lacking sugar accumulation and glass formation upon
drying and storing which suggested that desiccation tolerance mechanism may not
involve in the water removal in coffee seeds as it occurred in desiccation tolerant
seeds [106]. Therefore, the coffee seeds may not tolerate the desiccation up to
<10–11% as reported by various drying and storage studies [110]. Even at intermediate moisture contents (<20%), water supply is restricted to major metabolism
process, but still at the 11%, the loosing of viability is a sign of occurring the
metabolic process. The literature does not have reasonable reason of this except
the after ripening processes which are considered responsible for the “switching on”
the certain genes during drying and storage of seeds [111]. The other reason for the
desiccation tolerance is the induction of heat tolerant proteins, which are more
significant in shade dried seeds and their abundance may be correspondence to the
level of desiccation tolerance [112]. Santos and coworkers [103] studied some of the
enzymes (i.e., esterases, catalases, peroxidases, β- mannanase, isocitrate lyse
dehydrins, γ -aminobutyric acid GABA) of these “after ripening processes.”
Where the higher amount of these enzymes have been found in slow drying and
high moisture content seeds. The transcriptomics study revealed the accumulation of
catalases and peroxidases for germination and cope with the changing physiological
conditions [112]. But the transcripts of these enzymes have not been seen beyond the
low moisture level (12%), moisture level which may be to lessen the use of ending
metabolic energy [113]. The activity of deterioration indexing enzyme “esterases”
found in dried seeds before and after the storage. The activity of peroxidase enzyme
found more in quick dried seeds, whereas no activity of superoxide dismutase was
found in fresh and nondried seeds [112]. Isocitrate lyse and GABA plus dehydrins
are symbolic enzymes indicating germination and water stress, respectively. The
level of isocitrate lyse found to be higher at high moisture (>40%), whereas
expression of GABA and dehydrins were high at onset of water stress (30%
moisture) [114]. The desiccation causes the water and oxidative stress which create
the reactive oxygen species (ROS, e.g., hydrogen peroxide) which lead to overexpression of catalases to balance the oxidative stress. However, the level of
expression of Catalase and peroxidase is in complex configuration in endosperm
and embryo, which may be due to maintaining the specific level of ROS [103, 112].
The other reason might be the expression of gene is controlled at various levels from
DNA to phenotype and it is very hard to separately extract the RNA from endosperm
and embryo for calculating the expression. A through separation of endosperm and
embryo is also inevitable to study whether the stress-induced metabolic reactions
27 “Coffee Bean-Related” Agroecological Factors Affecting the Coffee
661
viability, vigor, and physiological quality of seeds [105, 106 ]. The conflict in
literature about advocating the usage of slow drying [107] or fast drying [95, 108]
methods may arise due to using coffee seeds with different quality, ecology, variety,
or genotypes, etc., in different studies as it is also documented that different species
of Coffea have different level of tolerance to withstand desiccation process. The till
known sequence of level of tolerance to desiccation is in the order of Coffea
racemosa > C. canephora > C. arabica > C. liberica [109]. So we may assume
that desiccation sensitive species may not possess the full range of desiccation
tolerance mechanism by lacking sugar accumulation and glass formation upon
drying and storing which suggested that desiccation tolerance mechanism may not
involve in the water removal in coffee seeds as it occurred in desiccation tolerant
seeds [106]. Therefore, the coffee seeds may not tolerate the desiccation up to
<10–11% as reported by various drying and storage studies [110]. Even at intermediate moisture contents (<20%), water supply is restricted to major metabolism
process, but still at the 11%, the loosing of viability is a sign of occurring the
metabolic process. The literature does not have reasonable reason of this except
the after ripening processes which are considered responsible for the “switching on”
the certain genes during drying and storage of seeds [111]. The other reason for the
desiccation tolerance is the induction of heat tolerant proteins, which are more
significant in shade dried seeds and their abundance may be correspondence to the
level of desiccation tolerance [112]. Santos and coworkers [103] studied some of the
enzymes (i.e., esterases, catalases, peroxidases, β- mannanase, isocitrate lyse
dehydrins, γ -aminobutyric acid GABA) of these “after ripening processes.”
Where the higher amount of these enzymes have been found in slow drying and
high moisture content seeds. The transcriptomics study revealed the accumulation of
catalases and peroxidases for germination and cope with the changing physiological
conditions [112]. But the transcripts of these enzymes have not been seen beyond the
low moisture level (12%), moisture level which may be to lessen the use of ending
metabolic energy [113]. The activity of deterioration indexing enzyme “esterases”
found in dried seeds before and after the storage. The activity of peroxidase enzyme
found more in quick dried seeds, whereas no activity of superoxide dismutase was
found in fresh and nondried seeds [112]. Isocitrate lyse and GABA plus dehydrins
are symbolic enzymes indicating germination and water stress, respectively. The
level of isocitrate lyse found to be higher at high moisture (>40%), whereas
expression of GABA and dehydrins were high at onset of water stress (30%
moisture) [114]. The desiccation causes the water and oxidative stress which create
the reactive oxygen species (ROS, e.g., hydrogen peroxide) which lead to overexpression of catalases to balance the oxidative stress. However, the level of
expression of Catalase and peroxidase is in complex configuration in endosperm
and embryo, which may be due to maintaining the specific level of ROS [103, 112].
The other reason might be the expression of gene is controlled at various levels from
DNA to phenotype and it is very hard to separately extract the RNA from endosperm
and embryo for calculating the expression. A through separation of endosperm and
embryo is also inevitable to study whether the stress-induced metabolic reactions
27 “Coffee Bean-Related” Agroecological Factors Affecting the Coffee
661