Accrescimento del pericarpo,seme, endosperma ed embrione in prunus Amygdalus stokes

Abstract

GROWTH OF PERICARP, SEED, ENDOSPERM, AND EMBRYO IN PRUNUS AMYGDALUS STOKES. — The fruits of an almond-tree growing at Bari were collected weekly from February 22nd to July 11th and on August 16th 1960. The material was kept in fixative; the growth of the various organs was studied both from a morphological and a quantitative point of view. Special attention was given to growth of the endosperm, especially during the nuclear stage and at the beginning of cellularisation (Figg. 1-14), and to the developement of the embryo until it reaches the « heart-shaped » stage (Figg. 15–22). From a quantitative point of view, the volume and main diameters of pericarp and seed, and whenever possible endosperm and embryo, were measured for each fruit. Most of the data are given in Tables I to V and Figg. 23 and 24.

If reference is made to the 3 phases of fruit growth established for other species (notably peaches and cherries), the main conclusions are that:

1. phase I (growth of pericarp, testa and nucellus) is clearly recognisable; it ends after the micropylar portion of the endosperm has become cellular and the embryo heart shaped;

2. phase II is also present: during this phase most of the growth of endosperm and embryo takes place; while the seed has reached its definite size at the end of phase I, the pericarp undergoes a period of greatly reduced growth;

3. two weeks after the beginning of phase II the pericarp seems to resume growth just for a very short period, judging at least by the weekly values of the ratio pericarp volume to seed volume (see Fig. 23); this seems to indicate the existence of a new phase, that is phase III, which in fleshy fruits of the genus Prunus corresponds to a much longer and important process of pericarp growth than in the almond;

4. as in the peaches and cherries therefore a crisis in pericarp growth occurs during the period of maximum rate of growth of the cellular endosperm and embryo;

5. the sequence: cellularisation of the endosperm, growth of endosperm and embryo, ceasing of seed growth, and reduction in pericarp growth is very clear, particularly if we take into account growth in length rather than in volume; both morphological and quantitative data would indicate the importance of the endosperm not only for the beginning of embryo development, but also for the control of pericarp growth.