what i think, but just a thought, oh and a better one then stinky huh :wtf:

Boron-toxicity symptoms
Brownish leaf tips and dark brown elliptical spots on leaves.
B toxicity first appears as chlorosis of the tips and margins of older
leaves. Two to four weeks later, dark brown elliptical spots appear on
these discolored areas, which later turn brown and then dry up. Necrotic
spots are most prominent at panicle initiation. Some varieties exhibit
discoloration only at leaf tips and margins. Vegetative growth does not
decrease markedly.

Tobacco substitutes comprising an organic binder containing boric oxide or boron oxyacids and their ammonium, alkali metal and alkaline earth metal salts are disclosed. The disclosed tobacco substitute may comprise from about 2 to about 95% by weight boric oxide, boron oxyacid, or boron oxyacid salt and from about 5 to about 50% by weight, of the organic binder wherein during combustion the boron compound melts or fuses to form a stable ash. The tobacco substitute may also optionally include up to about 93% by weight of a filler such as CaCO3, MgCO3, charcoal, alumina or alumina trihydrate and up to about 15% by weight monoammonium or diammonium phosphate.