The Method of ABA Application Affects Salt Stress Responses in Resistant and Sensitive Potato Lines

Abstract

The phytohormone abscisic acid (ABA) has been proposed to act as a mediator in plant responses to a range of stresses, including salt stress. Most studies of ABA response apply ABA as a single dose. This may not resemble the prolonged increasing endogenous ABA levels that can occur in association with slowly increasing salinity stresses in nature or field situations. Salt stress response based on method of ABA application was examined in four potato genotypes of varying salt stress resistance: the sensitive ABA-deficient mutant and its normal sibling, a resistant genotype line 9506, and commercial cultivar 'Norland' of moderate resistance. ABA was applied by root drench at 0, 50, 75, or 100 lM concentrations through a single dose, or by slowly increasing multiple ABA doses in a sand-based growing system under greenhouse conditions. Salt tolerance was then evaluated after 2 weeks of exposure to 150-180 mM NaCl stress. The method of ABA application had a marked effect on the responses to salt stress. Plant responses to the method of ABA application were differentiated according to (1) growth rate, (2) root water content, and (3) apparent shoot growth response. Under a single dose, growth rate increased in all genotypes under salt stress, whereas slowly increasing multiple ABA applications generally maintained stable growth rates except in the ABA-deficient mutant where there was an upward growth trend. Percent root water content was elevated only under slowly increasing multiple ABA doses in two genotypes, whereas none of the single-dose treatments induced any change. The single ABA dose enhanced vertical growth, whereas the slowly increasing multiple ABA dose applications enhanced lateral shoot growth. Because exogenous application is still an artificial system, endogenous ABA was supplied through grafting of ABA-deficient mutant scions onto rootstocks with known elevated ABA levels. Multiple exogenous ABA applications as low as 50 lM elicited similar shoot water content responses as grafting treatments without ABA application in the mutant genotype but had no effect on the ABA normal sibling. Shoot dry weight was significantly increased through grafting over all exogenous ABA treatments. Our study further indicates that the method of ABA application regime in itself can alter plant responses under salt stress and that certain application regimes may reflect responses to elevated endogenous levels of ABA.

Changes induced by Cu2+ and Cr6+ metal stress in polyamines, auxins, abscisic acid titers and antioxidative enzymes activities of radish seedlings

“…ABA induced adaptation to salt stress in suspension cultures of tobacco (Nicotiana tabacum L. Cv. Wisconsin) has been also reported by Etehadnia et al (2008).…”

Hydrogen peroxide mediates abscisic acid‐induced HSP70 accumulation and heat tolerance in grafted cucumber plants

“…Grafting to either salt‐tolerant scions or rootstocks with inherently high ABA levels may positively modify the subsequent responses of plants under salt stress by increasing plant water contents and the accumulation of dry and fresh matter (Etehadnia et al . ). Here, we found that the low thermotolerance of Cs/Cs plants was associated with the lack of ABA biosynthesis in both roots and leaves when exposed to aerial heat stress (Fig.…”

“…For example, tetraploid Rangpur lime rootstock increases drought tolerance via the enhancement of constitutive root ABA production (Allario et al 2013). Grafting to either salt-tolerant scions or rootstocks with inherently high ABA levels may positively modify the subsequent responses of plants under salt stress by increasing plant water contents and the accumulation of dry and fresh matter (Etehadnia et al 2008).…”

Exogenous application of abscisic acid to root systems of grapevines with or without salinity influences water relations and ion allocation

“…Cram and Pitman () showed for maize and barley that the transport of K + and Cl − from the cut ends of roots could be inhibited when roots were placed in an ABA solution. The effect of ABA applied to roots on the response of potatoes to salt stress was dependent on the method of ABA application via a single dose or by slowly increasing multiple doses (Etehadnia et al ).…”

“…Little research has been undertaken on grapevines to investigate the role of exogenous ABA application on uptake of ions by roots, with the majority of reports dealing with the effect of foliar‐applied ABA on fruit ripening (Koyama et al , Gu et al , Balint and Reynolds ). Application of ABA to the roots in the present study was based on the general view from the literature that this would be more likely to impact on root‐to‐shoot ion transport (Etehadnia et al ). Also many soil stresses including salinity stimulate ABA synthesis in the roots of plants [reviewed in Davies et al ()], and ABA can be taken up readily from the soil solution (Hartung et al ).…”