Natural cold acclimatisation and de-acclimatisation of Magnolia wufengensis in response to alternative methods of application of abscisic acid

Abstract

SUMMARYTo improve our understanding of the role of exogenous abscisic acid (ABA) during natural cold acclimatisation and de-acclimatisation to cold stress in the rare species, Magnolia wufengensis, physiological and biochemical changes in field-grown M. wufengensis seedlings subjected to a single foliar (T1) or root (T2) application of ABA were compared. During cold acclimatisation, treatments T1 and T2 accelerated the increase in freezing tolerance in shoots and the level of bud dormancy, but T2 was 40.0% and 17.5% more effective than T1 for these two parameters, respectively. During de-acclimatisation, the decline in freezing tolerance in shoots and levels of bud dormancy were not greatly influenced under T1, but were slowed by 12.5% and 15.2%, respectively, under T2. Bud-burst in Spring was delayed by 13.78 d under T2, and the rates of bud survival increased by 18.9% and 31.8% under T1 and T2, respectively. Cold-hardiness was associated with changes in water, proline, total soluble protein, total soluble sugar, glucose, and fructose concentrations. We conclude that foliar or root application of ABA advanced the process of cold acclimatisation in M. wufengensis, that root treatment was relatively more effective, and that root application played a role in inhibiting de-acclimatisation. We suggest that a single root application of ABA would be a superior method to improve winter-hardiness in M. wufengensis grown in northern China.