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.