Early harvest increases post-harvest physiological quality of Araucaria angustifolia (Araucariaceae) seeds

Abstract

Araucaria angustifolia is a native conifer from Brazil and an endangered species. Its seeds have a short period of viability, and this factor contributes to its vulnerability. This study aimed to evaluate physiological quality during the development and post-storage period of A. angustifolia seeds. Cones A. angustifolia were collected in the Curitibanos – Santa Catarina - Brazil in March, April, May, June, July and classified in cotyledonary, I, II, III and IV development stage according to the month of collection. Thereafter, seeds were stored in a refrigerator for 60 and 120 days and submitted to germination test in a germination chamber (25°C – photoperiod 12 h), moisture content (105 °C by 24 hours), tetrazolium test (0.1% by 1 hour) and vigor tests: electric conductivity (75 mL distilled water at 25 °C) and germination speed index, shoot, root length. During seed development, the moisture content decreased from the cotyledonary stage (66.54%) to stage IV (47.44%), and an increase in viability and vigor at the last stage, was observed. During the storage, the moisture content at the cotyledonary and I stage was stable. On the other hand, at stages II and III, stored seeds showed decrease after 120 days.  Physiological quality at the cotyledonary stage increased germination to 86% and 93% after 60 and 120 days of storage, respectively. Unlike the stages II and III, that showed a decrease in seeds viability and vigor after storage. Electrical conductivity was higher for fresh seeds at the cotyledonary stage than for those stored for 60 days and 120 days. However, at other stages, released leachates content, after 120 days of storage, was higher with the advance of collection period. Germination speed index, shoot and root lengths showed seeds at cotyledonary and I stage had the highest values after storage period, unlike at stages II and III, where short root and shoot lengths were observed during storage. Thus, the maintenance of seed moisture content during storage was variable and dependent on the period of collection. Furthermore, the behavior of the physiological quality was different at the early and later stages. An early collection favored seeds physiological quality, and may be a strategy to increase the conservation of A. angustifolia seeds.