GREEN SEED COAT COLOUR RETENTION IN LENTIL - University ...

temperatures. The more enzyme activity measured in the canola seed the less
chlorophyll remained in the seed at harvest maturity (Tsang et al., 2003). Johnson-
Flanagan et al. (1994) reported that the enzymes peroxidase and chlorophyllase
break down the chlorophyll in canola seeds. Both lead to chlorophyll degradation
and reflect different wavelengths of light causing a different colour being detected.
Another important type of chlorophyll loss occurs from photo bleaching.
Environmental factors like frost can inhibit the ability of the plant to degrade
chlorophyll. This most likely occurs as the cold temperature prevents the enzymes
from degrading chlorophyll during rapid seed desiccation. Several days after a frost
event the chlorophyllase and peroxidase activity may return to pre-frost levels as
long as the frost was not lethal to the plant. Johnson-Flanagan et al. (1994) also
report that the use of humidification on the seed, below the level required for
germination, will increase the activity of chlorophyllase and peroxidase after a non
lethal frost. In the field, moist weather could possibly increase enzyme activity and
further reduce the amount of chlorophyll in the seed. If canola seed is harvested at
too high a moisture content before the seed was fully ripened, the chlorophyll
content in the cotyledon would be difficult to reduce by environmental means. The
frequency of green cotyledons is usually reduced in the field by natural air drying
after swathing. If canola seed is dried artificially in commercial grain dryers the
chlorophyll would not be reduced even though the moisture content is reduced to a
level that is conducive to long term storage (Cenkowski et al., 1989a). In lentil this
would translate into beginning harvest prior to optimum moisture content for
storage, which could produce a more desirable sample.
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