The seed diversity of Carob (Ceratonia siliqua L.) and the relationship between seeds color and coat dormancy

The aim of the present study was to evaluate the morphological characteristics of seeds of nine populations of north-west Algerian Carob (Ceratonia siliqua L.) and to evaluate the relationship between seeds color and coat dormancy by studying the effect of soaking in pure sulfuric acid (chemical scarification) on seed germination, for several durations (Control, 1, 2, 4, 6, 8, 10, 14, 18, 24, 30 and 36 h). The results showed these seeds were very diverse morphologically. The mean seeds length (range between 0.826 ± 0.058 cm and 0.996 ± 0.055 cm), the mean seeds width (range between 0.656 ± 0.056 cm and 0.710 ± 0.048 cm) and the mean seeds weight (range between 0.143 ± 0.011 g and 0.186 ± 0.011 g) were studied. Four colors of the seed coats have been identified in this study: chocolate brown, clear brown, greenish brown and yellowish brown. The results have revealed that the seeds with clear color (yellowish brown) showed high coat dormancy, their maximum germination percentage were 2%. However, the seeds with a chocolate brown color, does not present dormancy, their maximum germination percentage was between 80 and 88 % without any pretreatment. Moreover, seeds of Ceratonia siliqua with yellowish brown color were more resistant to prolonged periods of soaking in pure sulfuric acid (18, 24 and 30 h), but the chocolate brown seeds are more fragile for prolonged soaking durations, they lose their viability beyond 10 h in acid. The histochemical features of the seed coats have indicated that there are not anatomic differences between the 4 seed colors of different cultivated and spontaneous populations.