L'amido E L'endosperma Delle Cariossidi Dure E Tenerizzate DiTriticum DurumDesf

Abstract

Abstract Starch and endosperm of vitreous and starchy (yellow-berries) kernels of Triticum durum Desf. — Starch and endosperm in kernels of T. durum Desf. have been examined in relation with the problem of the origin and nature of the vitreous or starchy texture which this tissue shows in the ripe fruits. This research has demonstrated that the starch of the vitreous differs from that of the starchy kernels in the shape, respectively irregular and regular; in the distribution of the frequencies y versus the length of the diameter x which is exponential and of the type log y = log a — x log b, in the vitreous kernels the value of log b is generally lower than in the starchy kernels; in the submicroscopical texture, because the irregular grains of the vitreous kernels do not show either birefringence or polarisation cross and are coloured with Congo red: starchy kernels behave quite differently. The starchy kernels are also more swollen and regular, their apparent specific weight and their nitrogen content being less than in the vitreous; the process of starchiness is always in close contact with fibro-vascular bundle of the row; in the starchy cells the cytoplasm shows some interruptions of continuity which leave partly uncovered the starch grains; the endosperm and the starch of the hard kernels wetted with water or placed in moist atmosphere become micro- and macroscopically similar to the starchy ones; in the starch the process of trasformation of the orderly into the amorphous texture is reversible, but for this to happen the only contact with water is insufficient; according to the treatments the vitreous kernels might show a decrease in their nitrogen content. Both starch types are connected with the presence orabsence of slightly bound water; the hypothesis which considers the nitrogen supply of the fruit as immediate cause of the endosperm texture is criticised and it is considered more plausible that such cause might be the different structure and texture of the cytoplasmatic gels during, in function of temperature and moisture.