| Abstract: | Cholinesterase activity and the endogenous titre of acetylcholinein cotyledons of germinating Phaseolus vulgaris change in approximatesynchrony as senescence of the tissue progresses. Total activityof the enzyme increases about 3-fold between the second andthird days of germination, and remains high until day 6 beforedropping coincident with the appearance of visible morphologicalsymptoms of senescence in the tissue (Lees and Thompson, 1975).The acetylcholine titre in the cotyledons is low initially,but rises to reach a peak by day 4. Thereafter it declines,reaching a low level again by day 6 and remaining essentiallyunchanged through day 10. Direct application of 10 mM acetylcholineto germinating seeds and growing seedlings has no effect ongrowth, but treatment over a 10 d period with 10 mM neostigminebromide, a potent inhibitor of cholinesterase, causes markedstunting of growth and raises the endogenous titre of acetylcholinein the cotyledons by about 10-fold relative to levels in cotyledonsof untreated plants. These observations suggest that acetylcholineplays some role in regulating the nutrient source-sink relationshipin germinating seedlings. |
