Osmopriming has a positive effect on the enhancement of seeds
germination and seedlings growth, especially under stress
conditions. This study investigated the effects of osmopriming
with polyethylene glycol on alfalfa (
Medicago sativa
L.)
seeds germination and seedlings antioxidant responses under
drought stress. Seeds of five Moroccan alfalfa populations
and an American Moapa variety were used to investigate
the effect of osmopriming on seeds germination, seedlings
growth, activities of antioxidant enzymes and membrane
stability under two water deficit levels (-0.45 and -0.75 MPa).
Seeds were primed with polyethylene glycol (PEG
6000) (-0.6
MPa) for 24 h at 25 °C. The results showed that treated seeds
presented higher germination rate and growth of 8 d-old
seedlings than untreated ones. Particularly, osmoprimed seeds
of ‘Adis-Tata’ (Ad) and ‘Riche’ (Rc) populations presented
the highest final germination percentages of 90.8% and 64%,
respectively, and seedlings shoot and root lengths under both
levels of water deficit. The priming treatment enhanced the
activity of peroxidase (PO) and catalase (CAT) and reduced the
malonyldialdehyde (MDA) content and the electrolyte leakage
under water deficit. Generally, the success of germination
was positively correlated to PO and CAT activities and the
degree of membrane stability in drought tolerant populations.
However, the positive effect of the osmopriming technique
on alfalfa drought tolerance remains limited in some tested
populations, and severe water stress could inhibit germination
and cause damages of alfalfa seedlings.
