<b>‘Desiccation tolerance of <i>Rhamnidium elaeocarpum</i> Reissek (Rhamnaceae) seeds

Abstract

ABSTRACT. This study aimed to investigate the desiccation tolerance of Rhamnidium elaeocarpum Reissek seeds through physiological and biochemical alterations. Fruit were collected from the municipality of Jaupaci, Goias State, Brazil, when the water content of their seeds had a 37% wet basis (w.b.) and the seeds were subsequently kept in a drying oven with air circulation at a temperature of 35ºC until a water content was reached of 20 to 12% (w.b.). The following parameters were evaluated: germination, germination speed index, emergence, emergence speed index, electrical conductivity and respiration rate. Furthermore, the electrophoretic profile of the isoenzymes: catalase, peroxidase and esterase, the enzymatic activities of endo-β-mannanase and α-amylase and the electrophoretic analysis of heat-resistant proteins were performed. A higher germination speed and respiratory rate was obtained for seeds with a water content of 12% w.b., and the activity of catalase isoforms was more pronounced in seeds with a higher degree of dehydration, which was in contrast to peroxidase, showed decreased activity. The seeds contained heatresistant proteins of low molecular weight that ranged from 48.7 to 13.2 kDa. We found that the acquisition of drying tolerance in R. Elaeocarpum Reissek seeds is associated more with catalase than with esterase and peroxidase.Keywords: drying, germination, isoenzymes, respiration rate, heat-resistant proteins.Tolerância à dessecação em sementes de Rhamnidium elaeocarpum Reissek (Rhamnaceae) RESUMO. O trabalho teve como objetivo investigar a tolerância a dessecação em sementes de Rhamnidium elaeocarpum Reissek por meio de alterações fisiológicas e bioquímicas. Os frutos foram coletados no município de Jaupaci, Estado de Goiás, quando as sementes apresentavam teor de água de 37% base úmida (b.u.), sendo em seguida mantidas em estufa de secagem com circulação de ar à temperatura de 35ºC até alcançarem os teores de água de 20 e 12% (b.u.). Foram avaliados os seguintes parâmetros: germinação; índice de velocidade de germinação; emergência; índice de velocidade de emergência; condutividade elétrica; taxa respiratória; perfil eletroforético das isoenzimas: catalase, peroxidase e esterase; atividade enzimática de endo-β-mananase e α-amilase e análise eletroforética de proteínas resistentes ao calor. Maior velocidade de germinação e taxa respiratória foi obtida para sementes com teor de água de 12% b.u. A atividade das isoformas de catalase foi mais pronunciada em sementes com maior grau de desidratação em relação à peroxidase que diminuiu sua atividade. As sementes apresentaram proteínas de baixo peso molecular resistentes ao calor, variando de 48,7 a 13,2 kDa. A aquisição de tolerância à secagem em sementes de R. elaeocarpum Reissek é mais associada à enzima catalase do que às enzimas esterase e peroxidase.Palavras-chave: secagem, germinação, isoenzimas, taxa respiratória, proteínas resistentes ao calor.

Behavior of Esterase, Peroxidase, Protein Profile and Growth Parameters of Zea maize and Vicia faba Cultivar under Heat Stress

“…These results are in accordance with those of Mohamed & Abdel -Hamid (2013).These new protein bands may be the HSPs or the enzyme of the antioxidant systems which plays very important role in providing tolerance against oxidative burst which is in conformity with the observation made by Singh & Khurana (2016). Another approach to understand the molecular basis of heat stress tolerance is to identify stress induced changes in the protein expression (Bita &Gerats, 2013 andSilva et al 2015).…”

“…One band which has Rf 0.02 was present in all treatments (monomorphic bands). In addition, two unique bands were detected in the tolerant genotype (Giza 92) under heat stress treatment (Silva et al, 2015) Three types of modifications are observed in the protein patterns of two organs of Vicia faba cv. Assuit 95/2 and Zea maize cv.…”

“…Peroxidase activity in the tolerant genotypes of cotton (Giza 85 and Giza 92) increased under heat stress treatment (40°C). Peroxidases are hemecontaining oxidoreductases that participate in a number of metabolic processes, such as regulation of cell elongation, lignifications, cross linking of cell wall structural proteins and phenolic oxidation (Kumar et al, 2012 andSilva et al 2015). Seven bands of esterase electrophoretic patterns were observed among the profile of all treatments.…”

Physiological and biochemical changes during desiccation tolerance loss in millet (<i>Pennisetum glaucum</i> L.) seeds

“…CAT enzymatic expression was higher for seeds with a 3 mm radicle (Figure 3), indicating higher oxidative stress. Silva et al (2015) concluded that the presence of CAT might be associated with the acquisition of desiccation tolerance in Rhamnidium elaeocarpum seeds. Their results indicated an increase in the content Acta Scientiarum.…”