While abscisic acid (ABA) exerts multiple effects on somatic embryogenesis, the most pronounced of these effects is the arrestment of torpedo-stage embryos, preventing them from developing into plantlets. In order to understand the mechanism of ABA inhibition of plantlet formation, we have isolated seven ABA-insensitive cell lines capable of developing into plantlets in the presence of ABA. The...

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare as a host, the flows, depositions, and metabolism of abscisic acid (ABA) within the host, within the parasite, and between host and parasite have been studied. When the plants were supplied with 5 mM NO(3)(-), there were weak or no effects of parasitism on ABA flows, biosynthesis, and ABA degradation in barley. However...

When intact plants of Xanthium strumarium L. were water stressed, the youngest leaves accumulated the highest levels of abscisic acid (ABA). On the other hand, when leaves of different ages were detached and then stressed, the capacity to produce ABA was highest in the mature leaves. Radioactive ABA was transported from mature leaves to the shoot tips and young leaves, as well as to the roots, ...

Suboptimal N nutrition increased the water potential for stomatal closure in water stressed cotton (Gossypium hirsutum L.) leaves. This increased sensitivity to water stress had two components, increased accumulation of abscisic acid (ABA) and increased apparent stomatal sensitivity to ABA. Low N increased the threshold water potentials for stomatal closure and ABA accumulation by about 4 bars ...

We examined whether the reduced mycorrhization of abscisic acid (ABA)-deficient tomato mutants correlates with their incapacity in ABA biosynthesis and whether this effect is dependent on ethylene production. The mycorrhization of notabilis and sitiens mutants, which have different ABA deficiencies and an excess of ethylene production, was analyzed. Comparative analysis of the ABA-deficient tom...

A noninvasive, cell-autonomous reporter system was developed to monitor the generation and distribution of physiologically active pools of abscisic acid (ABA). ABA response (abi1-1) and biosynthesis (aba2-1) mutants of Arabidopsis (Arabidopsis thaliana) were used to validate the system in the presence and absence of water stress. In the absence of water stress, low levels of ABA-dependent repor...

Isoprenylated proteins bear an isoprenylcysteine methyl ester at the C terminus. Although isoprenylated proteins have been implicated in meristem development and negative regulation of abscisic acid (ABA) signaling, the functional role of the terminal methyl group has not been described. Here, we show that transgenic Arabidopsis thaliana plants overproducing isoprenylcysteine methyltransferase ...

During drought, the plant hormone abscisic acid (ABA) triggers stomatal closure, thus reducing water loss. Using infrared thermography, we isolated two allelic Arabidopsis mutants (ost1-1 and ost1-2) impaired in the ability to limit their transpiration upon drought. These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal ope...

Abscisic acid (ABA) is a major phytohormone that mediates the adaptation of plants to environmental stresses such as drought and regulates developmental signals such as seed maturation. Studies on ABA signaling have progressed rapidly since the recent discovery of PYR/PYL receptor proteins as soluble ABA receptors. In plant cells, the receptor receives ABA to inhibit the phosphatase activity of...

Abscisic acid (ABA) induces stomatal closure and inhibits light-induced stomatal opening. The mechanisms in these two processes are not necessarily the same. It has been postulated that the ABA receptors involved in opening inhibition are different from those involved in closure induction. Here, we provide evidence that four recently identified ABA receptors (PYRABACTIN RESISTANCE1 [PYR1], PYRA...