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

Abstract

Variações nos açúcares e ciclitóis durante o desenvolvimento e maturação de sementes de pau-brasil (Caesalpinia echinata Lam., Leguminosae). Sementes de Caesalpinia echinata são tolerantes à dessecação, mantendo sua viabilidade com níveis de 0,08 g H 2 O g -1 MS. Quando armazenadas sob condições de laboratório perdem a viabilidade em um mês, enquanto sob baixas temperaturas a capacidade germinativa é mantida por dois anos. A concentração e a composição de açúcares solúveis, ciclitóis livres e ciclitóis galactosilados durante o desenvolvimento e a maturação dessas sementes foram analisadas no presente trabalho, com o propósito de compreender-se o envolvimento daqueles compostos na maturação e na qualidade da semente. Inflorescências foram marcadas na antese e posteriormente coletadas desde 32 até 59 d após antese (DAA) e após a deiscência. A maturidade fisiológica de sementes de C. echinata ocorreu entre 60-65 DAA, imediatamente antes da dispersão, quando as sementes apresentavam 0,43-0,67 g H 2 O g -1 MS. Carboidratos solúveis totais corresponderam a cerca de 10% da matéria seca das sementes. Análises por cromatografia gasosa e espectroscopia de massas permitiram quantificar 12 compostos presentes nos eixos e cotilédones durante o desenvolvimento das sementes. Estes incluem frutose, glicose, sacarose, rafinose, os ciclitóis mio-inositol, D-chiro-inositol, D-pinitol e os ciclitóis galactosilados, galacto-pinitol A, galacto-pinitol B e ciceritol. Sacarose foi detectada em grandes proporções durante todo o processo de desenvolvimento das sementes. Traços de rafinose foram detectados, principalmente em sementes imaturas. D-chiroinositol e mio-inositol foram encontrados em baixas quantidades e pinitol aumentou de forma contínua nos eixos e nos cotilédones. Seeds of Caesalpinia echinata are tolerant to desiccation, keeping their viability up to 0.08 g H 2 O g -1 DM. When stored under laboratory conditions they lose their viability within one month, while under low temperatures germination ability is maintained during two years of storage. Here, we report on the variations of soluble carbohydrates, cyclitols and cyclitol galactosides in seeds of C. echinata during development and maturation, aiming for a better understanding of the involvement of these compounds in the maturation process and seed quality. Individual flowers were tagged on the day of anthesis and pods were collected directly from the branches from 32 to 59 d after anthesis (DAA). Seeds were also collected after shedding. The physiological maturity of C. echinata seeds occurred 60-65 DAA, immediately before shedding, when seeds had 0.43-0.67 g H 2 O g -1 DM. Soluble carbohydrates made up about 10% of the seed dry mass. Gas chromatography and mass spectrometry allowed the identification and quantification of 12 soluble carbon compounds present in both the axis and cotyledons of developing C. echinata seeds. These included fructose, glucose, sucrose, raffinose, the cyclitols myo-inositol, D-chiro-inositol, D-pinitol, and the cyclitol galactosides, galacto-...

Do recalcitrant seeds really exist?

“…Some of these studies can also include water potential, respiration rate and chemical composition (Borges et al 2006, Ramya et al 2012, Mata et al 2013. Several works also include the fruit characteristics, mainly while establishing a visual diagnosis of the appropriate time to harvest or to identify the characteristics of the fruit that correspond to the best physiological quality of the seeds (Borges et al 2005, Matheus et al 2011.…”

“…Such accumulation could contribute to the fl exibility of cell membranes. Additionally, seeds of these species accumulated raffi nose family oligosaccharides (RFOs), such as raffi nose and stachyose (Mello et al 2010), or polyols, such as pinitol and ciceritol (Borges et al 2006), which could also contribute to glass state formation. Some studies suggest yet that the role of sucrose and RFOs as protective molecules do not depend only on their content, but rather depend on the sucrose/RFOs ratio (Steadman et al 1996, Vandecasteele et al 2011 and with sucrose/cyclitols ratio (Leduc et al 2012).…”

Variações dos carboidratos de reserva de sementes de Caesalpinia echinata (pau-brasil) armazenadas sob diferentes temperaturas

“…20%) e carboidratos não-estruturais (40%-50%). Dentre estes, a maior fração é composta pelo amido, enquanto que os carboidratos solúveis representam de 10% a 15% da matéria seca, sendo constituídos principalmente por sacarose, glucose e frutose e, em menores proporções, por ciclitóis e oligossacarídeos da série da rafinose (ROs), como rafinose e estaquiose (Borges et al 2006, Garcia et al 2006.…”

Germination, carbohydrate composition and vigor of cryopreserved Caesalpinia echinata seeds

“…Sucrose and raffinose oligosaccharide families have been associated with the membrane stability in the orthodox seeds that are resistant to desiccation (Nkang 2002). Furthermore, there are indications that, in addition to sucrose, glucose and fructose, the cyclitol carbohydrates are closely related to the protective mechanisms of the membranes and organic molecules in Brazilwood seeds (Borges et al 2006). In general, the loss of germination potential with the storage time is associated with the deterioration of soluble carbohydrates, particularly the raffinose family oligosaccharides accumulated during the seed maturation (Sharma et al 2007).…”

“…The main soluble carbohydrates in C. echinata seeds are sucrose, glucose, fructose, myo-inositol and traces of raffinose and stachyose, totaling about 10% of the dry weight of the seed (Garcia et al 2006;Hellmann et al 2008). Ciceritol, galactopinitol A, galacto-pinitol B and sucrose represent the largest reserves of soluble carbohydrates (Borges et al 2006). Hellmann et al (2008) found that starch was most abundant carbohydrate reserve, representing 30-40% of the seed dry weight, followed by the proteins (8-12%) and lipids (20%).…”