Differences In Abscisic Acid Concentration Research Articles

ABA flow modelling in Ricinus communis exposed to salt stress and variable nutrition.

In a series of experiments with Ricinus communis, abscisic acid (ABA) concentrations in tissues and transport saps, its de novo biosynthesis, long-distance transport, and metabolism (degradation) were affected by nutritional conditions, nitrogen (N) source, and nutrient limitation, or salt stress. In the present study these data were statistically re-evaluated, and new correlations presented that underpin the importance of this universal phytohormone. The biggest differences in ABA concentration were observed in xylem sap. N source had the strongest effect; however, nutrient limitation (particularly phosphorus limitation) and salt also had significant effects. ABA was found in greater concentration in phloem sap compared with xylem sap; however, the effect of treatment on ABA concentration in phloem was lower. In the leaves, ABA concentration was most variable compared with the other tissues. This variation was only affected by the N source. In roots, ABA was significantly decreased by nutrient limitation. Of the compartments in which ABA was quantified, xylem sap ABA concentration was most significantly correlated with leaf stomatal conductance and leaf growth. Additionally, ABA concentration in xylem was significantly correlated to that in phloem, indicating a 6-fold concentration increase from xylem to phloem. The ABA flow model showed that biosynthesis of ABA in roots affected the xylem flow of ABA. Moreover, ABA concentration in xylem affected the degradation of the phytohormone in shoots and also its export from shoots via phloem. The role of phloem transport is discussed since it stimulates ABA metabolism in roots.

Effects of stem girdling on cone yield and endogenous phytohormones and metabolites in developing long shoots of Douglas-fir (Pseudotsuga menziesii)

Stem-girdling treatments were applied in early spring to stimulate cone formation in two genotypes of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco). After girdling treatments, male cone yield increased significantly in the next growing season. The increase was 14-fold in genotype 9137. In genotype 9550, more than 8,700 male cones were induced from each tree whereas no male cones were found in controls. Female cone yield was zero in controls and low for girdled trees in both genotypes. Multiple phytohormone-related compounds, including gibberellins (GAs), cytokinins, indole-3-acetic acid (IAA), abscisic acid (ABA) and their selected metabolites, were analyzed in developing long shoots after girdling treatments by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC–ESI–MS/MS) in multiple reaction monitoring mode. Concentrations of GA4 were slightly higher at week 2 following girdling treatment, whereas at week 8 lower GA4 concentrations were found in girdled samples. Stem girdling did not affect concentrations of IAA and major cytokinins, such as zeatin riboside and isopentenyl adenosine. Concentrations of ABA differed two-fold between the genotypes. Although girdling treatment did not cause differences in ABA concentrations, it generally resulted in higher concentrations of ABA glucose ester. Concentration increase of 7′-hydroxy ABA by girdling was only found in genotype 9550 at week 8. Girdling caused little change in concentrations of phaseic acid in both genotypes.

Differences in abscisic acid concentration in roots and leaves of two young Olive (Olea europaea L.) cultivars in response to water deficit

Differences in abscisic acid (ABA) accumulation between two olive cultivars were studied by enzyme-linked immunosorbent assay in roots and leaves, leaf water potential (Ψl), stomatal conductance (g s) as well as photosynthetic rate (A) were also determined in well-watered (WW) and water-stressed (WS) plants of two olive cultivars ‘Chemlali’ and ‘Chetoui’. ‘Chemlali’ was able to maintain higher leaf CO2 assimilation rate and leaf stomatal conductance throughout the drought cycle when compared with ‘Chetoui’. Furthermore, leaf water potential of ‘Chemlali’ decreased in lower extent than in Chetoui in response to water deficit. Interestingly, significant differences in water-stress-induced ABA accumulation were observed between the two olive cultivars and reflect the degree of stress experienced. Chemlali, a drought tolerant cultivar, accumulated lower levels of ABA in their leaves to regulate stomatal control in response to water stress compared to the drought sensitive olive cultivar ‘Chetoui’ which accumulated ABA in large amount.

Characterization of maize lines differing in leaf abscisic acid content in the field. 1 abscisic acid physiology

The inbred maize lines Poljl7 and F-2 have previously been shown to differ by up to three-fold in leaf abscisic acid (ABA) concentration in the field. Lines from the cross Poljl7 × F-2 differing in leaf ABA concentrations, and the parents, were studied in the field to characterize the differences amongst the lines in ABA concentrations during the season, during the day and in different parts of the plants. The water status of the plants was measured and leaves were heat girdled to get information on possible causes for the genetic variation amongst the lines in ABA concentration. Leaf ABA concentrations of the high-AB A lines increased markedly and consistently from flowering time onwards, whereas leaf ABA concentrations of the low-ABA lines gradually fell after flowering. Leaf water potentials of high-ABA and low-ABA lines were similar during this time. Leaf ABA concentrations varied little during the day, and heat girdling caused a rise in ABA concentrations, which was similar in both high-ABA and low-ABA lines, only after girdling for at least 4 h. ABA concentrations were highest in the leaves and it was only in the leaves and developing kernels that substantial differences in ABA concentrations were found between the high-ABA and low-ABA classes. Although aerial brace roots also had high ABA concentrations, other roots and stem internodes had ABA concentrations which were consistently low and the same for both ABA classes. Differences between the ABA classes were unlikely to be due to differences in leaf water status or in ABA export from the leaves. Other possible explanations for the genotypic differences in leaf ABA concentrations are discussed.

Effects of soil freezing and drought stress on abscisic acid content of sugar maple sap and leaves.

In 1991 and 1992, mature maple trees (Acer saccharum Marsh.) were freeze-stressed or drought-stressed by preventing precipitation (snow or rain) from reaching the forest floor under selected trees. Lack of snow cover caused a decrease in soil temperature to well below 0 degrees C from December to April and a lowering of the soil water content to 10%. The abscisic acid (ABA) concentration in the spring sap of deep-soil frost-stressed trees was significantly higher than in control or drought-stressed trees. The increase in ABA concentration in the xylem sap in the spring of 1991 and 1992 preceded symptoms of canopy decline and a decrease in leaf area that were observed during the summers of 1991 and 1992. These results suggest a role for ABA in root-to-shoot communication in response to environmental stress. The largest differences in ABA concentration induced by the treatments was found in sap collected at the end of sap flow. The increase in ABA concentration in spring sap at the end of the sap flow could be used as an early indicator of stress suffered by trees during the winter. Not only did the increase in ABA concentration occur before any visible symptoms of tree decline appeared, but the trees that showed the most evident decline had the highest ABA concentrations in the spring sap. Leaf ABA concentration was not a good indicator of induced stress.

Genotypic variation in coleus in the ability to accumulate abscisic acid in response to water deficit

Terry, P. H., Krizek, D. T. and Mirecki, R. M. 1988. Genotypic variation in coleus in the ability to accumulate abscisic acid in response to water deficit. ‐ Physiol. Plant. 72: 441–449.Abscisic acid (ABA) concentration and plant and soil water potentials were determined in leaves of three cultivars of Coleus blumei Benth. cvs. Marty, Buckley Supreme and PI354190, chosen for their differences in sensitivity to drought, SO2 and/or chilling stress. Plants were subjected to ‘gradual’ soil moisture stress (SMS) for 0–6 days, during which time the soil dried out slowly and to more ‘rapid’ SMS for 0–9 days where the soil dried out at a faster rate. Plants were propagated from clonal stock in the greenhouse and transferred to the growth chamber, where they were maintained for 1 week prior to beginning water stress treatment. ABA concentration was determined as the methyl ester using a gas chromatography ‐ electron capture detector method. Samples for ABA determinations were taken from the third pair of leaves from the apex at the same time each day (1430 h). Measurements of stomatal conductance (C5) and leaf water potential (φl) were made on the fourth pair of leaves from the apex, using the same plants as those sampled for ABA. During the more rapid stress portion of the study soil matric potentials (φm) were monitored on a daily basis. Despite large cultivar differences in ABA concentration at 0–6 days, by 7–9 days these differences had largely disappeared. Except for drought‐insensitive cv. Marty, there was generally little correlation between ABA levels and measurements of plant and soil water status at 7–9 days.

Abscisic acid concentration in Douglas-fir needles in relation to lifting date, cold storage, and postplanting vigor of seedlings

Spring-lifted seedlings were grown in pots in the field and, after a natural fall photoperiod, exposed to three 25-day cold (+4 °C) storage treatments and two lifting times, mid-November and mid-January. The storage treatments were light storage in pots, dark storage in pots, and bareroot storage in polyethylene bags in the dark. In a second experiment, an extended fall photoperiod treatment was applied to seedlings that were then stored in pots and subjected to the same light and dark treatments above. In both experiments, needle samples were taken four times during and after the treatments for abscisic acid assay. Abscisic acid concentrations were determined using gas liquid chromatography after purification with high performance liquid chromatography. Lifting times and storage treatments did not result in statistically significant differences in abscisic acid concentrations. However, there were treatment differences in characteristics of postplanting performance. Mid-November lifting resulted in reduced survival and a greater number of days to bud flush compared with the mid-January lifting results. The extended fall photoperiod material produced similar results to the natural fall photoperiod material. The failure to detect a relationship between needle abscisic acid concentration and seedling vigor may have been due to a transitory role of abscisic acid in the storage conditions studied. The quantification method for abscisic acid is insensitive and laborious for practical seedling testing.