MORPHOPHYSIOLOGICAL DORMANCY IN Taxus globosa SCHLTDL SEEDS

Abstract

Taxus globosa is a species that is restricted in the world and is included in category of special protection, its seeds germinate one or two years after being dispersed, so they are considered dormant. The objective of this research was to determine the morphological and physiological changes in T. globosa seeds exposed to different treatments to break dormancy. Seeds were subjected to three treatments: scarification with liquid N2 (Treatment 1); scarification, application of gibberellic acid (GA_4/7), cold stratification alternating with warm stratification, and cold stratification (Treatment 2), and double scarification with liquid N2, alternated with warm stratification and GA_4/7 (Treatment 3). No germinated seeds were observed in any of the tested treatments. In Treatment 1 there was embryo growth and 3.8 % of the seeds broke their coat at 90 days. After 120 days of applying the treatments, it was possible to detect trans-zeatin (0.008-0.009 μg mg^-1), cis-zeatin (0.029 μg mg^-1) and abscisic acid (ABA) (0.0002-0.0023 μg mg^-1) in the seed coat; kinetin (0.011 μg mg^-1), trans-zeatin (0.008-0.011 μg mg^-1) and indoleacetic acid (IAA) (0.009 μg mg^-1) were found in the megagametophyte. Hormones cytokinins (trans-zeatin, cis-zeatin, kinetin) and auxins (IAA) were at higher concentration in both the control and treated seeds. No gibberellins were detected in any of the treatments. Phloretin, p-hydroxybenzoic acid (HBA), catechin, naringenin and protocathaeuic acid were found in the coat of the treated seeds, while sinapinic acid, HBA, and catechin, which are considered as germination inhibitors, were present in the megagametophyte. Seeds of T. globosa show morphophysiological dormancy caused by immaturity of the embryo and the presence of germination inhibitors.