Pregermination treatments of Taxus globosa seeds: Growth and in vitro embryo culture

Abstract

The Mexican yew (Taxus globosa) is important for the production of taxol, which is used to treat several types of cancer and its seeds undergo a latent period. The objectives of this research were to study the causes of seed dormancy in this species, the types of dormancy mechanisms it undergoes and how to break such dormancy. Seeds from two regions of Mexico (northern and central region) were evaluated using 12 pre-germination treatments. The treatments consisted of warm and cold stratification, applying 500 ppm of gibberellic acid (GA4/7) at different intervals, or using alternative seed scarification methods. In addition, embryo growth was studied and a protocol for in vitro embryo culture was also tested. Seeds from the central region did not germinate, probably because of inbreeding depression in seeds that came from small fragmented populations. In contrast, seeds from the northern region of Mexico subjected to warm plus cold stratification, warm plus cold stratification plus GA4/7 application, and warm stratification plus stratification with N2 plus GA4/7 application exhibited the highest germination rates (12–14 %). In vitro embryo culture indicated that only 30% of the embryos germinated. Thus, dormancy in the Mexican Yew seems to be caused by several factors, including both morphological and physiological factors.