If that is the question, the answer is that the top leaves (harvested at an appropriate stage of maturity) are hung in the shed. They color-cure to a very dark brown, and eventually dry (and die) at some point, in response to ambient conditions in the shed. Months later, on certain particularly thick top leaves, I observe that the underside of the fully color-cured (dead) leaf is a dull greenish brown. This sometimes clears with further hanging in the shed, but usually changes to brown after kilning. These leaves are intense, flavorful and excellent. My impression has been that harvesting these leaves even later than I usually harvest them has not made a difference in this color phenomenon.
The only way I can understand this sequence of events is to assume that the greenish coloration--only on the underside of the leaf lamina--is not chlorophyll, or it is a chlorophyll metabolite that has been chemically modified by the plant's intrinsic enzyme systems to a form that will easily break down, but that still reflects a green coloration. Another possibility is that the background carotinoid pigments, which provide the red and yellow colors to color-curing leaf (and autumn tree foliage), are at a substantially different concentration than in other leaf.
Persistent chlorophyll does not easily clear with kilning (though it may be bleached away with sun exposure), and always causes a noticeable taste in the smoked tobacco.
Bob
