Phenological and physiological studies during carob (Ceratonia siliqua L.) seed germination

Abstract

The best pre-sowing treatments for carob (Ceratonia siliqua L.) seeds germination were acid scarification or treatment with warm water (40°C) for 48 h. Different phenological phases were characterized essentially based on morphological events during carob germination. Changes in total protein, free animo acid content and ethylene production were also studied and used for physiological characterization of phenological events. The fresh and dry weight of seedlings showed a steady increase, after the emergence of the radicle. At this point ethylene production attained the highest level. Dry weight of seedlings and cotyledons increase was accompanied by a decrease of endosperm reserves until they reached a plateau by the eighth day. Both protein and amino acid content of cotyledons increased with germination up to 6 days and then decreased. That increase was related to the onset of germination and hook development. It remained almost unchanged on subsequent days but between the 12th and the 14h the protein and amino acid content of cotyledons slowly started to increase. Embryonic axis amino acid content followed the same pattern but protein content only showed small variations throughout the experimental period. The presence of cotyledons as a source of necessary products for the development of the embryonic axis is discussed.