Tolerance of Coffea arabica L. seeds to sub zero temperatures

Abstract

Preservation of the quality of coffee seeds is hindered by their intermediate behavior in storage. However, long-term storage at sub zero temperatures may be achieved by adjusting the water content of the seeds. The aim of this study was to evaluate the tolerance of coffee seeds to freezing, in relation to physiological and enzymatic modifications. Coffee seeds were dried in two manners, rapid and slow, to water contents of interest, 0.67, 0.43, 0.25, 0.18, 0.11, and 0.05 g H 2 O g -¹ dw (dry basis). After drying, the seeds were stored at a temperature of -20 ºC and of 86 ºC for 24 hours and for 12 months, and then compared to seeds in cold storage at 10 ºC. The seeds were evaluated through calculation of percentage of normal seedlings, percentage of seedlings with expanded cotyledonary leaves, dry matter of roots and of hypocotyls, and viability of embryos in the tetrazolium test. Expression of the enzymes superoxide dismutase, catalase, and peroxidase were evaluated by means of electrophoretic analysis. Only seeds dried more slowly to 0.18 g H 2 O g -1 dw present relative tolerance to storing at -20 °C for 12 months. Coffee seeds do not tolerate storage at a temperature of -86 ºC for 12 months. Water contents below 0.11g H 2 O g -¹ dw and above 0.43 g H 2 O g -¹ dw hurt the physiological quality of coffee seeds, regardless of the type of drying, temperature, and storage period. Coffee seed embryos are more tolerant to desiccation and to freezing compared to whole seeds, especially when the seeds are dried to 0.05 g H 2 O g -¹ dw. The catalase enzyme can be used as a biochemical marker to study tolerance to freezing in coffee seeds.Index terms: Drying; silica gel; saturated saline solutions; freezing; antioxidant enzymes. RESUMOA preservação da qualidade de sementes de café é dificultada pelo comportamento intermediário no armazenamento. Porém, a conservação a longo prazo em temperaturas subzero pode ser conseguido com o ajuste do teor de água das sementes. Objetivou-se neste trabalho avaliar a tolerância de sementes de café ao congelamento, com relação às modificações fisiológicas e enzimáticas. As sementes foram submetidas a dois tipos de secagem, rápida e lenta, até os teores de água de interesse, de 0,67, 0,43, 0,25, 0,18, 0,11, 0,05 g H 2 O g -¹ dw (base seca). Após secagem, as sementes foram armazenadas em temperatura de -20 e de -86 ºC, por 24 horas e por 12 meses, sendo comparadas às sementes armazenadas em câmara fria a 10 ºC. As sementes foram avaliadas pela porcentagem de plântulas normais, plântulas com folhas cotiledonares expandidas, matéria seca de raízes e de hipocótilos e viabilidade dos embriões no teste de tetrazólio. A expressão das enzimas superóxido dismutase, catalase e peroxidase foi avaliada por meio de análise eletroforética. Apenas as sementes secadas lentamente até 0,18 g H 2 O g -¹ dw apresentam relativa tolerância ao armazenamento a -20 °C por 12 meses. Sementes de café não toleram o armazenamento à temperatura de -86 ºC por 12 meses. Umidades abaixo de 0,11g H 2 O g -¹ dw ...

Antioxidant and antimicrobial activity of cathode and anode water in Coffea arabica L. seeds

“…After that, the seeds and papers were rolled and these rolls were kept in a seed germinator at a constant temperature of 30 °C under light for 30 days (Brasil, 2009). Along with evaluation of normal seedlings at 30 days in the germination test, the vigor of the seeds under the treatments was evaluated by means of root emergence (%) at 15 days, seedlings with expanded cotyledonary leaves (%), and seedling dry matter at 45 days after sowing, as well as strong normal seedlings (%) at 30 days, considering the seedlings with root-hypocotyl axis greater than or equal to 3 cm (Coelho et al, 2017).…”

“…For determination of dry matter of normal seedlings, the shoots were separated from the roots using a scalpel, and both parts were placed in paper bags and kept in an air-circulation laboratory oven at 60 °C until reaching constant weight, which occurred at five days, and the results were expressed in mg.seedling -1 (Coelho et al, 2017). These results were also used as an indication of coffee seed vigor.…”

“…Various studies have shown that seed deterioration is induced by the formation of free radicals, enzymatic degradation, inactivation or reduction in respiratory activity, and loss of cell membrane activity (Vidigal et al, 2009;Sharma et al, 2012;Marcos-Filho, 2015;Coelho et al, 2017;Abreu et al, 2018). Nevertheless, the negative effect of reactive oxygen species (ROSs) can be reduced by defense mechanisms.…”

Steps of cryopreservation of coffee seeds: physiological responses and antioxidant systems

“…The low longevity of coffee seeds is a limiting factor for long-term germplasm maintenance and endangers existing genetic variability. Because of their intermediate to recalcitrant behavior (ELLIS et al, 1990), seeds of the genus Coffea are not preserved in conventional seed banks at -18 °C to -20 °C due to their sensitivity to desiccation and cooling (PAMMENTER & BERJAK, 2014, COELHO et al, 2017b.…”

“…Coffee cryopreservation techniques have been studied to develop safe protocols for use in typical coffee seed/germplasm banks (DUSSERT et al 1998(DUSSERT et al , 2001(DUSSERT et al , 2003(DUSSERT et al , 2012DUSSERT & ENGELMANN, 2006;FIGUEIREDO et al, 2017;COELHO et al 2017aCOELHO et al , 2017bCOELHO et al and 2019. However, due to the wide variety of existing cultivars, in addition to diverging results, there is still much to be studied.…”