The possible rôle of xanthoxin in plant growth and development

1978 ◽  
Vol 284 (1002) ◽  
pp. 499-507 ◽  
Keyword(s):  
Abscisic Acid ◽  
Hormonal Regulation ◽  
Growth And Development ◽  
Higher Plants ◽  
The Other ◽  
Regulatory Function ◽  
Root Tip ◽  
Root Tips ◽  
Root Primordia ◽  
Lateral Root Primordia

In higher plants, abscisic acid and xanthoxin are two potent growth regulators. Although similar properties in both substances have been demonstrated in several biological tests including biochemical interconversion of the substances, evidence is available that in the plant as a whole, xanthoxin has regulatory functions other than those of abscisic acid. Several environmental factors, such as water supply, photoperiod and low temperature, which affect growth and development also greatly change the level of abscisic acid in the plant; however, only small variations in the xanthoxin level have been observed in response to changes in the environmental conditions. On the other hand, a strong enhancement of the xanthoxin level can be induced when dark-grown seedlings are briefly illuminated; this treatment, however, has no influence on the abscisic acid level. This observation supports the hypothesis that light-induced inhibition of growth may be mediated by an increased formation of the growth inhibitor xanthoxin. Light-induced enhancement of the xanthoxin level may also contribute to the phototropic bending in dictyledonous seedlings. Evidence has been obtained from experiments in this laboratory that xanthoxin may be involved in the regulation of root branching. Decapitation of root tips causes a significant increase in the number of lateral root primordia. Chromatographic studies reveal the presence of two substances in the root, which, in a specific bioassay, are active inhibitors of the development of root primordia. The activity of these root inhibitors in the basal part decreases when the root tip is removed. They are probably produced in the root tip and are transported to the base. One of these inhibitors has been identified as xanthoxin, the other is cytokinin. The hormonal regulation of abscission is another process where xanthoxin may have a regulatory function. Senescent, abscinding petioles contain a factor called ‘senescence factor’ which promotes the abscission of leaves. In an attempt to identify its chemical nature, it was found that at least three different abscission accelerating substances, including xanthoxin, participate in the composition of the senescence factor.

scholarly journals A Screen for Genes That Function in Abscisic Acid Signaling in Arabidopsis thaliana

Genetics ◽  
2002 ◽  
Vol 161 (3) ◽  
pp. 1247-1255 ◽  
Author(s):  
Eiji Nambara ◽  
Masaharu Suzuki ◽  
Suzanne Abrams ◽  
Donald R McCarty ◽  
Yuji Kamiya ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Growth And Development ◽  
Plant Hormone ◽  
The Other ◽  
Aba Signaling ◽  
Wild Type ◽  
Plant Growth And Development ◽  
Diverse Range ◽  
Abscisic Acid Signaling ◽  
Aba Insensitive

Abstract The plant hormone abscisic acid (ABA) controls many aspects of plant growth and development under a diverse range of environmental conditions. To identify genes functioning in ABA signaling, we have carried out a screen for mutants that takes advantage of the ability of wild-type Arabidopsis seeds to respond to (−)-(R)-ABA, an enantiomer of the natural (+)-(S)-ABA. The premise of the screen was to identify mutations that preferentially alter their germination response in the presence of one stereoisomer vs. the other. Twenty-six mutants were identified and genetic analysis on 23 lines defines two new loci, designated CHOTTO1 and CHOTTO2, and a collection of new mutant alleles of the ABA-insensitive genes, ABI3, ABI4, and ABI5. The abi5 alleles are less sensitive to (+)-ABA than to (−)-ABA. In contrast, the abi3 alleles exhibit a variety of differences in response to the ABA isomers. Genetic and molecular analysis of these alleles suggests that the ABI3 transcription factor may perceive multiple ABA signals.

scholarly journals The evolution of abscisic acid (ABA) and ABA function in lower plants, fungi and lichen

2010 ◽  
Vol 37 (9) ◽  
pp. 806 ◽  
Author(s):  
Wolfram Hartung
Keyword(s):  
Abscisic Acid ◽  
External Medium ◽  
Higher Plants ◽  
Regulatory Function ◽  
Physiological Concentration ◽  
Mycorrhizal Associations ◽  
Terrestrial Habitats ◽  
High Concentrations ◽  
Cyanobacteria And Algae ◽  
Almost All

Abscisic acid (ABA) – the universal stress hormone of cormophytes – was detected in very low concentrations in almost all organisms tested from a range of cyanobacteria, algae, bryophytes, fungi and lichens and higher plants (Fig. 1). There are a few reports only on stress-induced ABA biosynthesis in cyanobacteria and algae. This extra ABA is released to the external medium. Application of external ABA has been shown to produce weak and contradicting effects on development and metabolism of algae. In most studies, extremely high concentrations of external ABA have been applied, those being far beyond any physiological concentration range. It is, therefore, extremely difficult to discuss those data satisfactorily. When organisms start to colonise terrestrial habitats (e.g. aquatic liverworts, mosses), endogenous ABA is increased even under mild drought stress, then desiccation protecting mechanisms are stimulated and the formation of terrestrial organs is induced. The same can be observed in water ferns (Marsilea) and in a range of heterophyllous angiosperms. Sporophytes of hornwort and mosses that bear true stomata, have particularly high ABA levels and their stomata respond to ABA as is the case in cormophytes, although a significant regulatory function of these stomata does not exist. Fungi produce large amounts of ABA that are released into the external medium and do not seem to have a function for the fungus. Fungal ABA, however, may be significant in associations of fungi with cyanophytes and algae (lichens), in mycorrhizal associations and in the rhizosphere of higher plants.

Tetrahydrofolate biosynthesis and distribution in higher plants

2005 ◽  
Vol 33 (4) ◽  
pp. 758-762 ◽  
Author(s):  
T. Sahr ◽  
S. Ravanel ◽  
F. Rébeillé
Keyword(s):  
Carbon Metabolism ◽  
Growth And Development ◽  
De Novo ◽  
Higher Plants ◽  
The Other ◽  
Transfer Reactions ◽  
Intracellular Traffic ◽  
Vitamin B9 ◽  
Carbon Transfer ◽  
One Carbon Metabolism

One-carbon transfer reactions are mediated by H4F (tetrahydrofolate), a soluble coenzyme (vitamin B9) that is synthesized de novo by plants and microorganisms, and absorbed from the diet by animals. H4F synthesis in plants is quartered between the plastids, the cytosol and the mitochondria, a spatial distribution that is not observed in the other organisms and that suggests a complex intracellular traffic. Also, the activity of H4F synthesis fluctuates during plant growth, depending on the tissue and the developmental stage of the seedling, thus illustrating the flexibility of one-carbon metabolism in these organisms. This paper will focus on our recent knowledge about H4F synthesis in the plant cell and will briefly describe the activity of the pathway during the growth and development of the seedling.

Uptake and Release of Abscisic Acid by Runner Bean Root Tip Segments

1983 ◽  
Vol 38 (9-10) ◽  
pp. 719-723 ◽  
Author(s):  
Wolfram Hartung ◽  
Barbara Dierich
Keyword(s):  
Abscisic Acid ◽  
Uptake Rate ◽  
Root Tip ◽  
Root Tips ◽  
Root Cells ◽  
Ph Gradients ◽  
External Ph ◽  
Uptake And Release ◽  
Stimulation Of ◽  
Undissociated Molecule

Uptake of abscisic acid by 5 mm long decapped root tips is a linear function of the external ABA concentration in the range of 2.9 × 10-8m to 10-4м and decreases dramatically with in­creasing pH. At pH 8.0 uptake rate is extremely low, even at high ABA concentrations. This indicated that nearly all of the ABA is taken up as the undissociated molecule ABAH. Uptake of ABA is influenced by agents modifying the pH gradients between the medium and the tissue such as salts of weak acids incubated at low external pH (inhibition of uptake and stimulation of ABA release by abolishing the pH gradients), protonophores such as CCCP (inhibition of uptake) and fusicoccin (stimulation of uptake by increasing the pH between medium and cytoplasm). It is concluded that ABA distributes between the compartments of the root cells according to the pH gradients with the undissociated molecule as the only penetrating species. Uptake and release occur without participation of a saturable component by diffusion. In contrast IAA permeates the plasmalemma as both IAAH and IAA-.

scholarly journals Overexpression of the manganese/cadmium transporter OsNRAMP5 reduces cadmium accumulation in rice grain

2020 ◽  
Vol 71 (18) ◽  
pp. 5705-5715 ◽  
Author(s):  
Jia-Dong Chang ◽  
Sheng Huang ◽  
Noriyuki Konishi ◽  
Peng Wang ◽  
Jie Chen ◽  
...  
Keyword(s):  
Lateral Root ◽  
Ion Homeostasis ◽  
Toxic Metal ◽  
Rice Grain ◽  
Wild Type ◽  
Root Tips ◽  
Root Primordia ◽  
Lateral Root Primordia ◽  
Cd Accumulation ◽  
Cd Translocation

Abstract Rice is a major dietary source of the toxic metal cadmium (Cd), and reducing its accumulation in the grain is therefore important for food safety. We selected two cultivars with contrasting Cd accumulation and generated transgenic lines overexpressing OsNRAMP5, which encodes a major influx transporter for manganese (Mn) and Cd. We used two different promoters to control the expression, namely OsActin1 and maize Ubiquitin. Overexpression of OsNRAMP5 increased Cd and Mn uptake into the roots, but markedly decreased Cd accumulation in the shoots, whilst having a relatively small effect on Mn accumulation in the shoots. The overexpressed OsNRAMP5 protein was localized to the plasma membrane of all cell types in the root tips and lateral root primordia without polarity. Synchrotron X-ray fluorescence mapping showed that the overexpression lines accumulated more Cd in the root tips and lateral root primordia compared with the wild-type. When grown in three Cd-contaminated paddy soils, overexpression of OsNRAMP5 decreased concentration of Cd in the grain by 49–94% compared with the wild type. OsNRAMP5-overexpression plants had decreased Cd translocation from roots to shoots as a result of disruption of its radial transport into the stele for xylem loading, demonstrating the effect of transporter localization and polarity on ion homeostasis.

scholarly journals Cytokinin-Controlled Gradient Distribution of Auxin in Arabidopsis Root Tip

2021 ◽  
Vol 22 (8) ◽  
pp. 3874
Author(s):  
Lei Wu ◽  
Jun-Li Wang ◽  
Xiao-Feng Li ◽  
Guang-Qin Guo
Keyword(s):  
Growth And Development ◽  
Molecular Mechanisms ◽  
Plant Root ◽  
Primary Root ◽  
Root Tip ◽  
Root Tips ◽  
Arabidopsis Root ◽  
Gradient Distribution ◽  
Shed Light ◽  
Auxin Gradient

The plant root is a dynamic system, which is able to respond promptly to external environmental stimuli by constantly adjusting its growth and development. A key component regulating this growth and development is the finely tuned cross-talk between the auxin and cytokinin phytohormones. The gradient distribution of auxin is not only important for the growth and development of roots, but also for root growth in various response. Recent studies have shed light on the molecular mechanisms of cytokinin-mediated regulation of local auxin biosynthesis/metabolism and redistribution in establishing active auxin gradients, resulting in cell division and differentiation in primary root tips. In this review, we focus our attention on the molecular mechanisms underlying the cytokinin-controlled auxin gradient in root tips.

Localization of Adenosine Triphosphatase Activity in the Phleom of Nicotiana Tabacum

1972 ◽  
Vol 30 ◽  
pp. 230-231
Author(s):  
James Cronshaw ◽  
Jamison E. Gilder
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Adenosine Triphosphatase ◽  
Higher Plants ◽  
High Surface ◽  
Root Tip ◽  
Animal Cells ◽  
Physiological Processes ◽  
Tip Cells ◽  
Atpase Localization

Adenosine triphosphatase (ATPase) activity has been shown to be associated with numerous physiological processes in both plants and animal cells. Biochemical studies have shown that in higher plants ATPase activity is high in cell wall preparations and is associated with the plasma membrane, nuclei, mitochondria, chloroplasts and lysosomes. However, there have been only a few ATPase localization studies of higher plants at the electron microscope level. Poux (1967) demonstrated ATPase activity associated with most cellular organelles in the protoderm cells of Cucumis roots. Hall (1971) has demonstrated ATPase activity in root tip cells of Zea mays. There was high surface activity largely associated with the plasma membrane and plasmodesmata. ATPase activity was also demonstrated in mitochondria, dictyosomes, endoplasmic reticulum and plastids.

Emotions Under the Skin

2015 ◽  
Vol 29 (4) ◽  
pp. 161-170 ◽  
Author(s):  
Catarina Silva ◽  
Ana Cláudia Ferreira ◽  
Isabel Soares ◽  
Francisco Esteves
Keyword(s):  
Attachment Style ◽  
Attachment Styles ◽  
The Other ◽  
Regulatory Function ◽  
Physiological Reactivity ◽  
Emotional Stimuli ◽  
Skin Conductance Responses ◽  
Lower Accuracy ◽  
Emotional Pictures ◽  
Valence And Arousal

Abstract. The present study examined physiological reactivity to emotional stimuli as a function of attachment style. Skin conductance responses (SCRs) and heart rate (HR) changes were simultaneously recorded while participants engaged in a visual attentional task. The task included positive, neutral, and negative emotional pictures, and required the identification of a target (neutral picture rotated 90° to the left or right), among a stream of pictures in which an emotional distracter (positive or negative) was presented. Participants additionally rated each of the emotional distracters for valence and arousal. Behavioral results on the attentional task showed that positive pictures facilitated overall target detection for all participants, compared to negative and neutral pictures, and that anxiously attached participants had significantly lower accuracy scores, relative to the other groups. Affective ratings indicated that positive pictures were rated as being more pleasant than negative ones, although no differences were found in HR changes to picture valence. In contrast, negative pictures were evaluated as being highly arousing. Consistent with this, negative pictures elicited larger SCRs in both insecure anxious and avoidant groups, especially for the anxious while the secure group showed SCRs unaffected by stimuli’s arousal. Present results show that individuals with different attachment styles reveal distinct patterns of attentional bias, appraisal, and physiological reactivity toward emotionally arousing stimuli. These findings further highlight the regulatory function of the attachment system.

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