Changes in soluble carbohydrates during storage of Caesalpinia echinata LAM. (Brazilwood) seeds, an endangered leguminous tree from the Brazilian Atlantic Forest

Abstract

Caesalpinia echinata seeds stored in laboratory environmental conditions lose their viability in one month whilst under low temperatures germination is maintained for 18 months of storage. These seeds are tolerant to desiccation, keeping their viability up to 0.08 gH 2 O.gDW -1 . Since soluble carbohydrates are believed to be involved with desiccation tolerance and seed storability, the aim of this work is to analyze the content and composition of soluble carbohydrates in C. echinata seeds during storage in paper bags (PB) and glass flasks (GF) at laboratory room (RT) and cool (CT) temperatures. In freshly harvested seeds, total soluble carbohydrates comprised approximately 10% of the dry weight, decreasing to ca. 8% over 18 months of storage at RT. In seeds stored at CT, sugars varied differently decreasing initially and being restored at the end of the analysis period. The main neutral sugars in seeds from all treatments were sucrose, fructose and glucose. Raffinose and stachyose were present as traces. Free myo-inositol and other cyclitols were also detected. The main tendency observed was the variation in levels of both glucose and fructose in relation to sucrose, the highest levels of monosaccharides which were found in seeds stored at CT. The values of glucose and fructose were practically constant in seeds stored in paper bags for 18 months at CT, decreasing consistently in the other treatments, mainly at RT. Sucrose contents remained relatively stable. Changes in soluble sugars during storage suggest that the loss of germinability of seeds of C. echinata could be associated with low levels of glucose and fructose in relation to sucrose.Keywords: seed longevity, desiccation tolerance, pernambuco, soluble sugars, cyclitols. RESUMO Modificações nos carboidratos solúveis durante o armazenamento de sementes de Caesalpinia echinata LAM. (pau-brasil), uma leguminosa arbórea da Mata Atlântica em risco de extinçãoSementes de Caesalpinia echinata (pau-brasil) perdem a viabilidade em um mês quando armazenadas no ambiente de laboratório, enquanto a capacidade germinativa é mantida quando armazenadas sob temperturas baixas. O presente trabalho teve como objetivos analisar o conteúdo e a composição dos carboidratos de sementes de C. echinata armazenadas em câmara fria (CT) e em temperatura ambiente do laboratório (RT), em duas embalagens distintas (permeável e impermeável), visando a avaliar o envolvimento desses compostos com a capacidade germinativa das sementes. Os resultados mostraram que os carboidratos solúveis são constituídos principalmente de sacarose, glicose, frutose, myo-inositol e traços de rafinose e estaquiose, totalizando cerca de 10% da massa seca das sementes. As variações nos carboidratos solúveis foram semelhantes nos dois tipos de embalagem, mas diferentes quanto à temperatura de armazenamento. Em CT, as proporções dos monossacarídeos encontradas nas sementes recém-colhidas foram mantidas por cerca de 18 meses de armazenamento, coincidindo com alta porcentagem de germinação (80%). Nas arma...

Variations in sugars and cyclitols during development and maturation of seeds of brazilwood (Caesalpinia echinata Lam., Leguminosae)

“…However, these sugars were practically absent in mature whole seeds of C. echinata, accumulating 10-15% of their dry mass as soluble carbohydrates. Analysis of sugars during storage under different temperature conditions showed low levels of glucose and fructose in relation to sucrose in seeds of C. echinata that had lost germinability (Garcia et al, 2006),…”

“…The HPAEC/PAD system used consisted of a 4 x 250 mm CarboPac PA-1 column, eluted by a linear gradient of 25 mol m -3 to 500 mol m -3 sodium acetate in 150 mol m -3 sodium hydroxide at a flow rate of 1 mL min -1 as established by Garcia et al (2006). Sugars were identified by co-chromatography with authentic standards purchased from Sigma/Aldrich Co. (USA).…”

“…Mature seeds of C. echinata contain 30-40% starch and 10-15% of soluble carbohydrates, predominantly sucrose and trace amounts of raffinose and stachyose (Garcia et al, 2006). These seeds are tolerant to desiccation, keeping their viability up to 0.08 g H 2 O g -1 MS after drying at 40-50ºC (Barbedo et al, 2002).…”

“…When stored at low temperatures (7 ± 1ºC), however, germination is maintained during 18 months of storage (Barbedo et al, 2002). Changes in soluble sugars during storage suggested that the loss of germinability of C. echinata seeds could be associated with low levels of glucose and fructose in relation to sucrose (Garcia et al, 2006). Among other cell compounds, soluble carbohydrates are involved in desiccation tolerance during seed development and maturation (Obendorf, 1997;Hoekstra et al, 2001).…”

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

“…Initially, the lifespan of those seeds was considered short, tolerating no more than three months in natural storage ( Barbedo et al 2002). Later, important advances were obtained with the application of suitable techniques, such as the harvest at the physiological maturity point (Borges et al 2005), the control of drying (MartiniNeto & Barbedo 2015) and the storage, including the freezing (Hellmann et al 2006), fungus control (Lisbôa- Padulla et al 2009, Padulla et al 2010 and monitoring the chemical composition changes (Garcia et al 2006, Borges et al 2006, Hellmann et al 2008, Mello et al 2011, extending storage for up to five years (Mello et al 2013). However, this storage period is not enough to allow its inclusion in germplasm banks.…”