Abscisic acid developing seeds

In the natural world, carotenoid oxidation products are important mediators presenting different properties. Volatile carotenoid-derived compounds such as noriso-prenoids are well known for their aroma properties. Examples include the cyclic norisoprenoid P-ionone and the non-cyclic pseudoionone or Neral. Carotenoid oxidation products are also important bioactive mediators for plant development, the best-known example being abscisic acid. Apo-carotenoids act as visual and volatile signals to attract pollination and seed dispersal agents in the same way as carotenoids do, but they are also plant defense factors and signaling molecules for the regulation of plant architecture. 

Harada, J.J., De-Lisle, A.J., Bakden, C.S. Crouch, M.L. (1989). Unusual sequence of an abscisic acid-inducible mRNA which accumulates late in Brassica napus seed development. Plant Molecular Biology 12, 395-401. 

There are two important classes of allelochemicals synthesized by oxidative cleavages of tetraterpene carotenoids. One is the plant hormone abscisic acid (ABA, 31) that plays important roles in growth and development of plants, especially in seed development and dormancy.17 Dry dormant seeds contain relatively large amounts of ABA, particularly in the seed coats. ABA and phenolic allelochemicals in the seed coats are easily released into the environment when the seeds are imbibed, resulting in inhibition of seed germination and seedling growth of plants in the vicinity. Both ABA and the phenolic compounds are rapidly broken down in the soil, and therefore the inhibition is short-lived. 

The phytohormone abscisic acid (ABA) plays an important role in many physiological processes in plants. This hormone is necessary for regulation of several events during late seed development [54,70]. Furthermore, ABA is crucial for the response to environmental stresses such as desiccation, salt and cold [10,39]. 

Induction of dormancy during seed development by endogenous Abscisic-Add -studies on Abscisic-Acid deficient genotypes of Arabidopsis thaliana (L.) Heynh. Pknta, Vol.157, No.2, pp. 158-165, ISSN 0032-0935... 

Regulation of gene expression program during Arabidopsis seed development roles of the AB13 locus and of endogenous abscisic acid. Plant Cell, Vol.6, No.ll, pp. 1567-1582, ISSN 1040-4651... 

Sondheimer E, Galson EC, Tinelli E, Walton DC (1974) The metabolism of hormones during seed germination and dormancy. IV. The metabolism of (S)-2- " C-abscisic acid in ash seed. Plant Physiol (Bethesda) 54 803-808 Steeves TA, Sussex IM (1972) Patterns in plant development. Prentice Hall, Englewood Cliffs... 

In in vitro cultured microspore-derived embryos a maximum in erucic acid content at about 15°C could not be observed. Levels of 22 1 never exceeded 30% average content was about 20% at the temperatures tested. Reston, that showed a clear increase of 22 1 at 15°C in plants, even showed an opposite tendency in vitro (fig 3). Obviously some factor is missing in this system which controls the erucic/oleic acids ratio in complete seeds. Abscisic acid (ABA), which is known to be important in seed development and does have a stimulating effect on the level of 22 1 [3], might be the missing factor. Application of ABA (0.5-50 liM) leads to a twofold... 

Since the pattern of hormone activity in the developing fruits of seeded and naturally parthenocarpic fruit is similar and only one phytohormone treatment is necessary in the chemically induced parthenocarpic fruits, it seems most probable some phytohormones act as inducing agents starting the filling of metabolic sinks , while others like abscisic and jasmonic acids stop protoplasmic growth (Dathe et al. 1981). Thus the role of plant hormones in fruit development remains obscure. 

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