In this work we have established the best protocol to investigate
seed germination by calorimetry which consists in the
insertion of the seed in 1% agar leaving only one of the seed
faces in contact with the air in the ampoule. Soybean seeds have
been used but the method applies to other seed types. This is a
very convenient protocol when the action of metabolic effectors
is to be studied. On the other hand, determination of imbibition
curves together with pH measurements gives a precise indication
of the time at which seeds are ready for root protrusion. A
plot of mh versus WC (Fig. 5B, curve b) shows three stages of
metabolism. Two of them coincide with those observed in the
KCNh versus WC plot (Fig. 5B, curve a) up to 74–80% WC
which in turn corresponds with 2.5–3 h of imbibition. Above
this value, mh increases linearly with WC until 121.7 ± 7.6%
(9 h) time at which soybean seeds of this cultivar are ready for
germination. Plots of this type might be of great utility to evaluate
seed permeability to water, a problem of great importance
faced by seed breeders.