Date of this Version
Journal of Applied Horticulture, 13(2): 85-90, 2011.
Limited fresh water is a global problem that adversely affects crops, including young apple (Malus × domestica) trees. Innovative technologies will be needed to ensure tree survival and productivity. Recently, selected chemicals have been used to prepare plants for avoidance and recovery from water stress by a process termed priming. Two priming compounds, abscisic acid (ABA) and DL- β-aminobutyric acid (BABA) have been shown to confer plant protection against a range of biotic and abiotic stresses. Our objective was to determine the resistance to and recovery from dehydration of apple seedlings treated with s-ABA and BABA. Three greenhouse experiments were conducted in which combinations of s-ABA and BABA were applied as a root drench to one-year-old ‘Royal Gala’ apple trees and responses to dehydration were evaluated. Changes in leaf water potential (ψw), stomatal conductance (gs), transpiration (E), leaf ABA and growth were measured during dehydration and rehydration. In two experiments, pretreatment with BABA reduced early morning E but BABA was not as effective as s-ABA in delaying dehydration-induced wilt of shoot tips. In another experiment during the second week without water both BABA- and s-ABA-treated trees had 42 to 62% higher leaf ψw, respectively, and 45% lower leaf ABA than unwatered controls. Higher leaf ψw was not consistently associated with reduced gs and E suggesting that mechanisms other than increased stomatal resistance may provide drought resistance. Compared with control trees, there was nearly 80% more shoot growth following rewatering after dehydration in trees that were primed with BABA and s-ABA (1.0 mM each). Leaf senescence was more evident in s-ABA- than BABA-treated trees and, although growth resumed after dehydration, the amount of growth varied with concentration of the priming treatments. Both individual compounds provided dehydration protection to young apple trees but in combination they were not clearly superior to either compound alone.