Sub-zero temperature enables storage of seeds of Caesalpinia echinata Lam

Abstract

-Seeds of brazilwood usually have their germinability quickly reduced if stored under natural conditions. Low temperatures, mainly sub-zero, can extend this viability for at least two years. However, there is no information about the germination behavior of these seeds for longer periods, aiming at the germoplasm bank formation. The objective of this work was to evaluate the viability of brazilwood seeds during five-year storage period at 2, 8 and -18 °C. Before storage, seeds were subjected to artificial drying (50 °C) until the moisture content reached 10%. The germination and the normal seedling development of seeds maintained at low temperatures did not differ from other treatment during the first year of storage. However, after two years only seeds stored at -18 °C kept high germination percentage. Seeds stored for five years at -18 °C showed high values of germination and normal seedling development; however, after this period it was possible to identify some symptoms of seed deterioration. Storage at sub-zero temperatures is considered as an important initiative to maintain Caesalpinia echinata seed banks, contributing to the conservation of plant biodiversity.Index terms: brazilwood, conservation, freezing, Leguminosae. Temperatura sub-zero possibilita o armazenamento de sementes deCaesalpinia echinata Lam.RESUMO -Sementes de pau-brasil geralmente têm sua germinação rapidamente reduzida quando armazenadas em condições naturais. As temperaturas baixas, principalmente inferiores a 0 o C, podem estender essa viabilidade por até dois anos. No entanto, não há informações sobre a germinação de sementes dessa espécie, quando submetidas a períodos mais longos de armazenamento, visando à formação de banco de germoplasma. O objetivo deste trabalho foi avaliar a viabilidade de sementes de pau-brasil durante o armazenamento por cinco anos em câmaras com temperaturas de 2, 8 ou -18 °C. Antes do armazenamento, as sementes foram submetidas a secagem artificial (50 °C) até atingirem 10% de água. A germinação e o desenvolvimento de plântulas a partir de sementes mantidas em ambiente com temperaturas inferiores a 0 o C não foram diferentes dos demais tratamentos, durante o primeiro ano de armazenagem. No entanto, após dois anos, as armazenadas a -18 °C mantiveram porcentagem de germinação superior às conservadas nas demais temperaturas. Sementes armazenadas por cinco anos a -18 °C apresentaram valores elevados de germinação, com elevada porcentagem de desenvolvimento das plântulas, porém com indícios de início de deterioração. O armazenamento em temperaturas inferiores a 0 o C pode ser uma ferramenta importante para manutenção de bancos de sementes de Caesalpinia echinata, contribuindo para a conservação da biodiversidade vegetal.Termos para indexação: congelamento, conservação, Leguminosae, pau-brasil.

Deterioration rates of brazilwood seeds (Caesalpinia echinata Lam.) under high temperatures

“…These two conditions were chosen because they were close to the ones described in the literature for the species seed storage (Hellmann et al 2008, Mello et al 2013.…”

“…Seed deterioration -The seeds remained stored at -18 ºC (Mello et al 2013), in paper bags, during one year for the seeds collected in Paulínia, São Paulo and Mogi Guaçu in 2014, and during two years for the seeds collected also in Mogi Guaçu, in 2013. The seeds of each batch were divided into three sub-lots, in order to obtain treatments with three levels of seed water content (WC).…”

“…Nevertheless, environmental factors and storage conditions influence this longevity (Barbedo et al 2013). The suitable storage allows the conservation of genetic resources of the natural population through seeds.…”

“…The first studies with the storage of these seeds demonstrated that they deteriorate in less than three months when stored at temperatures close to that found in their habitat; however, they can remain viable for up to two or five years in, respectively, cooling (Barbedo et al 2002) and freezing (Mello et al 2013) temperatures.…”

“…We also evaluated the applicability and reliability of current simulation models of loss of viability under different storage conditions. For this, after obtaining the predictability equations, different storage conditions were used, comparing the simulated data with the real ones described in the literature for C. echinata seeds (Barbedo et al 2002, Mello et al 2013). …”