positive relationship between sucrose and shade was detected for Catuai cultivar
[45], and negative relationship was detected for Catimor cultivar [222]. So light
regime affects the sugar metabolism differently in different cultivars of coffee. The
cultivars possessing the introgressed genome from C. robusta via the Timor hybrid
showed the reduction in sucrose in shade environment as compared to cultivars
introgressed from C. arabica [222, 226, 227]. The high sucrose content in former
mentioned introgressed cultivars is due to enhanced sucrose synthase enzyme
activity in mature endosperm because of higher expression of its second gene
CaSUS2 under shade [226]. However, we cannot ignore the variation in response
of different cultivars towards different topographic and climatic conditions other
than shade [204]. The existing controversies in literature over the other important
compositional contents, i.e., fat, trigonelline, chlorogenic acid, etc., of coffee may
also be referred towards the same set of reasons as described above. Although,
regardless of cultivar type, light regime significantly affects the reducing sugars and
sucrose of green beans, total sugar contents of coffee beans remains unaltered [226].
The sugar or carbohydrate state varies with the development stage of coffee seeds
where high to low ratios of reducing sugars/sugars was detected from immature to
mature stages. The larger beans size of shade grown coffee is also credited to the
maintenance of high reducing sugar/sugar ratio in perisperm. The increased size in
perisperm and endosperm may be due to high cell divisions or increased cell size or
both of them and may need further histological studies to confirm this. Further,
besides studying the main compositional components, variations of other components, e.g., amino acids, polypeptides, tannins, phenolics, minerals, also needed to
get a comprehensive view. All beneficial effects of shade are also site-specific and
under influence of changing environmental gradient. From lower to mediocre
elevated areas, where the temperature is high, shade influences and improves both
the physical and sensorial quality of coffee, but at higher altitudes, only sensorial
quality is significantly under influence of shade and physical quality (i.e., bean size)
is enormously under the influence of temperature and altitude [18, 30, 31].
Bosselmann et al. [18] did not detect a significant difference of bean size between
shade- and sun-grown coffee beans at higher altitudes except an insignificant
tendency of shade towards a size increment. On the contrary, at high altitudes,
shade has a destructive relationship with body, fragrance, acidity, sweetness, and
preferences [18, 45], and sunlight regime improves the body, aroma, sweetness, and
other sensorial attributes of coffee [18, 30, 31]. The significant negative effect of
shade at higher altitude may be attributed towards lowering of temperature below the
lower side of threshold level of optimum temperature range (i.e., 18
C) [228, 229],
as temperature is already in optimum range at higher altitudes and sun regime tends
to produce superior quality coffee beans while shading at this elevation can lead to
drop in temperature [18]. Moreover, in addition to decreased temperatures, shade
also influences the number of beans in each plant. Floral initiation is light dependent
and fewer flowers are developed in shade, allowing more assimilates for each
individual bean in the plant [57]. Overall, the shade or agroforestry system is
basically chosen for the marginal coffee production areas to protect the coffee crop
from adverse climatic condition. The level of shading, in these areas, should neither
27 “Coffee Bean-Related” Agroecological Factors Affecting the Coffee
683
[45], and negative relationship was detected for Catimor cultivar [222]. So light
regime affects the sugar metabolism differently in different cultivars of coffee. The
cultivars possessing the introgressed genome from C. robusta via the Timor hybrid
showed the reduction in sucrose in shade environment as compared to cultivars
introgressed from C. arabica [222, 226, 227]. The high sucrose content in former
mentioned introgressed cultivars is due to enhanced sucrose synthase enzyme
activity in mature endosperm because of higher expression of its second gene
CaSUS2 under shade [226]. However, we cannot ignore the variation in response
of different cultivars towards different topographic and climatic conditions other
than shade [204]. The existing controversies in literature over the other important
compositional contents, i.e., fat, trigonelline, chlorogenic acid, etc., of coffee may
also be referred towards the same set of reasons as described above. Although,
regardless of cultivar type, light regime significantly affects the reducing sugars and
sucrose of green beans, total sugar contents of coffee beans remains unaltered [226].
The sugar or carbohydrate state varies with the development stage of coffee seeds
where high to low ratios of reducing sugars/sugars was detected from immature to
mature stages. The larger beans size of shade grown coffee is also credited to the
maintenance of high reducing sugar/sugar ratio in perisperm. The increased size in
perisperm and endosperm may be due to high cell divisions or increased cell size or
both of them and may need further histological studies to confirm this. Further,
besides studying the main compositional components, variations of other components, e.g., amino acids, polypeptides, tannins, phenolics, minerals, also needed to
get a comprehensive view. All beneficial effects of shade are also site-specific and
under influence of changing environmental gradient. From lower to mediocre
elevated areas, where the temperature is high, shade influences and improves both
the physical and sensorial quality of coffee, but at higher altitudes, only sensorial
quality is significantly under influence of shade and physical quality (i.e., bean size)
is enormously under the influence of temperature and altitude [18, 30, 31].
Bosselmann et al. [18] did not detect a significant difference of bean size between
shade- and sun-grown coffee beans at higher altitudes except an insignificant
tendency of shade towards a size increment. On the contrary, at high altitudes,
shade has a destructive relationship with body, fragrance, acidity, sweetness, and
preferences [18, 45], and sunlight regime improves the body, aroma, sweetness, and
other sensorial attributes of coffee [18, 30, 31]. The significant negative effect of
shade at higher altitude may be attributed towards lowering of temperature below the
lower side of threshold level of optimum temperature range (i.e., 18
C) [228, 229],
as temperature is already in optimum range at higher altitudes and sun regime tends
to produce superior quality coffee beans while shading at this elevation can lead to
drop in temperature [18]. Moreover, in addition to decreased temperatures, shade
also influences the number of beans in each plant. Floral initiation is light dependent
and fewer flowers are developed in shade, allowing more assimilates for each
individual bean in the plant [57]. Overall, the shade or agroforestry system is
basically chosen for the marginal coffee production areas to protect the coffee crop
from adverse climatic condition. The level of shading, in these areas, should neither
27 “Coffee Bean-Related” Agroecological Factors Affecting the Coffee
683