Springcrest) during Development

Free abscisic acid (ABA) in integuments, nucellus, endosperm, and embryo was determined throughout seed development of peach (Prunus persica L. cv Springcrest). Quantification of ABA was performed using combined high performance liquid chromatography-radioimmunoassay based on a monoclonal antibody raised against free (S)-ABA. In the integuments and endosperm, ABA concentration remained constant during the first 100 days after anthesis and rose in the following days when fresh weight was rapidly decreasing. In the nucellus, the ABA concentration variation pattern paralleled that of tissue growth. ABA concentration in the embryo increased constantly with the growth of the tissues to reach a maximum at the last growth stage. The role of ABA in peach seeds is discussed in relation to the development of the different seed tissues. Growth of the peach fruit occurs in three stages, as shown by Connors (4): rapid growth (stage I), delayed growth (stage II), and second rapid growth (stage III). The growth of the nucellus and integuments during stage I is parallel to the rapid growth ofthe pericarp, while embryo development is arrested. At the beginning of stage II (delayed development of the pericarp), the nucellus and integuments enter a period of delayed development, and the endosperm begins a rapid enlargement. During stage III, the nucellus degenerates and the embryo begins its development; depending on the variety, it reaches maximum size during this period. The endogenous systems that regulate this growth pattern are not known, but several scientists have described a regulating role played by hormones. A high content of gibberellins has been observed during peach seed development (6, 17, 18). Ethylene production also occurs at relatively high rates and, at the same time, 1 -aminocyclopropane1 -carboxylic acid concentration peaks in the fruit (8, 10). Auxin level is also high during seed development, as shown by Miller et al. (1 1). Few data are available on ABA content in peach seeds (2) and particularly on ABA quantification in the various seed components during development. The availability of immunological methods for the quantification ofABA allows accurate analysis ofABA content over a great number of samples in much less time compared with the more traditional gas-chromatographic analysis. In fact, ABA content in the various tissues during seed development has been thoroughly measured in recent investigations carried out on Sechium edule (15) and Phaseolus coccineus (12). In this paper, we report on the quantitation of ABA in integuments, nucellus, endosperms, and embryos of Prunus persica cv Springcrest during seed development, with the aim of extending information on the hormonal relation between these seed components. MATERIALS AND METHODS