Results
Isolation of ABA-insensitive
alfalfa seedlings
Exogenous 50μM ABA significantly inhibited alfalfa seed germination
(Figure 1A). Only about 5% of the seeds were germinated in the presence
of 50 μM ABA (S0-50) (Figure 1B). The seedlings obtained during
re-germination after washing to get rid of ABA were labeled as S0-0.
There were no significant differences were found, except that the S0-50
plants were slightly but not significantly higher than the S0-0 plants
when we compared their phenotypes after four-month growth in pot (Table
S1). The stomata of detached leaves from S0-0 and S0-50 were noticed to
close obviously after treatment with
25μM ABA or 15% PEG6000 (Figure
1C). However, the stomatal apertures of S0-50 were significantly smaller
than those of S0-0 after ABA or PEG treatment (Figure 1C, D). The
relative stomatal conductance of S0-50 was lower but there was no
significant difference with that of S0-0 in the presence of 25 μM ABA
for 40 min (Figure 1E), and was significantly lower than S0-0 after 15%
PEG6000 treatment (Figure 1F). Taken together, the alfalfa plants that
were insensitive to ABA-mediated seed germination inhibition were more
sensitive to ABA or PEG treatments in leave stomatal movement.