Amylolytic activity in germinated Agrostemma githago L. seeds.
The perisperm of seeds of Agrostemma githago contains starch reserves which constitute 40% of the dry weight of the mature seed. These starch reserves were mostly broken down between 48 and 96 h after initiation of imbibition. (Germination occurred after 24 h.) The mode of starch degradation showed close parallels with the breakdown of the starchy endosperm in cereals. Thus, between 24 and 96 h the cotyledons secreted α-amylase (EC 3.2.1.1) whereas other degradative enzymes in the perisperm, β-amylase (EC 3.2.1.2) and maltase (EC 3.2.1.20), appeared to originate in the perisperm itself. Cotyledons secreted similar levels of α-amylase in the presence and absence of exogenous starch, indicating that secretion is an internal developmental event of the embryo. By isoelectric focussing the secreted α-amylase was separated into two isoenzymes. In the cotyledons, several other starch-degrading isoenzymes were present but were not secreted.
Botanisch Laboratorium, Universiteit Nijmegen, Toernooiveld, 6525 ED, Nijmegen, The Netherlands.
G J
GJ
de Klerk
P
P
Willekens
H
H
Kok
J V
JV
Jacobsen