Dynamic changes in concentrations of auxin, cytokinin, ABA and selected metabolites in multiple genotypes of Douglas-fir (Pseudotsuga menziesii) during a growing season

Abstract

Changes in concentrations of several endogenous phytohormones and metabolites were analyzed in the long shoots of nine genotypes of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) at five developmental stages: (1) closed buds, (2) flushing buds, (3) rapidly elongating shoots, (4) growing shoots and (5) near full-length shoots during one growing season. When averaged across genotypes, indole-3-acetic acid (IAA) concentration was high at stages 1 and 3. The only pattern that correlated with cone productivity was the one that was unique to IAA, in which high concentrations at stages 3 and 4 were found in all genotypes with high female cone productivity. Concentrations of isopentenyl adenosine (iPA) decreased and zeatin riboside (ZR) concentrations increased as the buds initiated and differentiated; ZR was 30 and 28 ng g(-1) dry weight (DW) at stages 1 and 4, respectively, before increasing to 166 ng g(-1) DW at stage 5. Isopentenyl adenosine peaked at 92 ng g(-1) DW at stage 2 and declined to low concentrations at stages 4 and 5. Zeatin-O-glucoside was 30 ng g(-1) DW at stage 1, declined at stages 2 and 3 and increased at stages 4 and 5. High abscisic acid (ABA) concentrations were positively correlated with rapid shoot elongation (stages 1 and 2), but as growth slowed and terminated, ABA concentrations decreased. Abscisic acid was 7 microg g(-1) DW at stage 1, increased to 13 microg g(-1) DW at stage 2 and then declined. The glucosyl ester (GE) of ABA decreased rapidly in early summer, and increased inversely with an increase in ABA. Between stages 1 and 2, ABA-GE decreased from 10 to 0.2 microg g(-1) DW and then increased. Of the ABA catabolites studied, 7'-hydroxy-ABA was about 2 microg g(-1) DW at stage 1, declined at stages 2 and 3 and increased at stages 4 and 5; phaseic acid concentrations were low at all stages, whereas dihydrophaseic acid was detected only at stages 4 and 5.

Evolution of the Stomatal Regulation of Plant Water Content

“…The third requirement relates to the speed of ABA synthesis over a timeframe that matches apparent ABA-driven stomatal responses. In terms of changing soil water deficit (over days), this condition is met in all vascular land plants ( Kraus and Ziegler, 1993;Hoffman et al, 1999;Kong et al, 2009;McAdam and Brodribb, 2013), but only in angiosperm does ABA synthesis appear to occur over a timeframe that corresponds to the dynamics of stomatal response to VPD .…”

Comparison of endogenous cytokinins, ABA and metabolites during female cone bud differentiation in low and high cone-producing genotypes of lodgepole pine

“…In both angiosperms (Fiehn et al 2000) and gymnosperms (Kong et al 2009), different genotypes exhibit unique metabolic and hormone profiles. In Douglas-fir, correlations between female cone yields and endogenous phytohormone levels of shoot buds have been shown (Kong et al 2009). Studies of endogenous phytohormone levels during cone initiation can provide strategies to overcome cone yield limitations.…”

“…This is of interest in conifers, because exogenously applied GA has been proven to be an effective stimulant of cone formation (Ross 1983;Pharis and King 1985;Smith and Greenwood 1995;Kong et al 2008). The main ABA catabolic pathway in many higher plants is ABA oxidation with its end products of phaseic acid (PA) and dihydrophaseic acid (DPA) (Cutler and Krochko 1999), but in conifers such as Douglas-fir, the dominant product of ABA catabolism in long shoots is ABA glucose ester (ABA-GE) (Kong et al 2008(Kong et al , 2009.…”

Action of Natural Abscisic Acid Precursors and Catabolites on Abscisic Acid Receptor Complexes

“…Finally, 7#-OH ABA shows similar activity to ABA in inducing genes related to lipid and storage protein accumulation (Hill et al, 1995;Jadhav et al, 2008). In conifers, 7#-OH ABA is a significant ABA catabolite (Feurtado et al, 2007;Kong et al, 2009).…”