Catálogo de publicaciones - libros

Melatonin (-acetyl-5-methoxytryptamine)(MEL), a well-known animal hormone synthetised by the pineal gland, was originally identified in 1958. In vertebrates it plays a key role in various physiological processes, including circadian rhythmicity, sleep and seasonal photoperiod regulation. Since 1995, MEL has been detected in the roots, leaves, fruits and seeds of a considerable variety of plant species. Studies in plants have mainly focused on the quantification of MEL levels in different plant organs and species.

Relative to the current knowledge about ethylene, much less is known on the interaction between this hormone and auxins during fruit growth and ripening in some species as for example kiwifruit (). The 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA), a synthetic auxin, is able to increase fruit size in peach affecting some fruit quality traits (Augustí , 1999).

Jasmonates (JA) are cyclopentanonic compounds synthesized from linolenic acid. Allene oxide synthase (AOS) is the first specific enzyme and the major control point of their biosynthetic pathway. JA are involved in plant responses to stress and in several developmental processes, including fruit development and ripening (Franceschetti et al., 2004, Redman et al., 2001 and Westernack and House, 2002). Exogenously applied at the end of S3 stage on ‘Stark Red Gold’ nectarines ( L. Batsch), 100 ppm of methyl jasmonate (MJ) and 50 ppm of the synthetic analogous -propyl dihydrojasmonate (PDJ) dramatically inhibited ethylene production at harvest and slowed down fruit softening (Torrigiani et al., 2004) (Table 1).

Leaf emergence is ethylene dependent (Smalle and Van Der Straeten, 1997). The mutant was isolated based on a delay of leaf emergence (Van Der Straeten 1999). was shown to encode a pentatricopeptide repeat (PPR) protein.

Ethylene (ET) is a signal molecule involved in the regulation of gene expression during adaptation to abiotic stresses. The relationship between ET and ABA production in vegetative tissues under abiotic stresses appears mostly controversial. In order to ascertain the interplay between ET and ABA in young plants (5 leaf stage), grown hydroponically in control (3 mS cm−1) and salt stress (10 mS cm−1) conditions, ET emission, ABA content and dry weight (DW) of roots, basal and apical leaves were measured in five different tomato genotypes: cv Edkawi (EDK), salt tolerant; cv Gimar (GIM), relatively salt sensitive and its near isogenic line for the nor gene (NOR) defective in ET synthesis; the ABA mutants sitiens (SIT) and notabilis (NOT), both with different ABA biosynthetic capacity (8% vs 47%).

Apical hook establishment and maintenance is an important developmental process driven by multiple hormonal cross talk. The importance of ethylene and asymmetric auxin-distribution, the requirement of gibberellins and the role of brassinosteroids have been demonstrated previously (Bleecker 1988; Lehman 1996; Chory 1991; Achard 2003; Vriezen 2004). In the light, a similar complexity of hormonal regulation has been revealed wherein all aforementioned hormones can stimulate hypocotyl elongation.

To enable discovery of factors controlling specific developmental processes, screens on developmental stages other than etiolated seedlings are needed. Smalle . (1997) showed that leaf emergence was enhanced by the ethylene precursor ACC. This was exploited as an assay for mutants in ethylene response.

It has been well established that plants are able to fine tune phytohormone responses by control of synthesis and/or perception. Ethylene biosynthesis has been widely studied in a number of species but none more than Arabidopsis and tomato. Tomato provides a unique system to study ethylene biosynthesis because of the large, climacteric-associated increase in production at the onset of ripening.

It is generally accepted that ethylene is a potent hormone involved in regulation of many events in plant growth and development (Abeles, 1973). Ethylene is produced and released from fungi and bacteria as well as from higher plants.

In flowering plants, double fertilization involves a complex series of interactions between essentially three plants – male gametophyte, female gametophyte, and sporophyte – culminating in the fusion of sexual cells and nuclei and the formation of an embryo and endosperm. The progamic phase of fertilization that consists in delivery of sperms to ovule and includes a cascade of events triggering pollen germination on the surface of stigma and growth of pollen tubes within tissues of the style and ovary plays a crucial role.