Campomanesia adamantium (Cambess.) O. Berg seed desiccation: influence on vigor and nucleic acids

The aim of this study was to evaluate the sensitivity of Campomanesia adamantium seeds to desiccation by drying in activated silica gel (fast) and under laboratory conditions (slow). To assess the sensitivity of the seeds to desiccation, we used drying with silica gel and drying under laboratory conditions (25 °C), in order to obtain seeds with moisture content of 45, 35, 30, 25, 20, 15, 10 and 5%. The physiological potential of the seeds after desiccation was evaluated by measuring primary root protrusion, percentage of normal seedlings, germination seed index, seedling length, total seedling dry mass, electrical conductivity and DNA and RNA integrities. The C. adamantium seeds were sensitive to desiccation and to a reduction in moisture content to 21.1% or less by desiccation using silica gel, and to 17.2% or less by desiccation under laboratory conditions; impairment of the physiological potential of the seeds was observed at these low moisture content levels. The integrity of the seed genomic DNA was not affected after drying seeds in the two methods. However, drying in silica gel to 4.5% moisture content and drying under laboratory conditions to 5.4% moisture content resulted in the loss of seed RNA integrity

Re-induction of desiccation tolerance after germination of Cedrela fissilis Vell. seeds

This work aimed to characterize the re-induction of desiccation tolerance (DT) in germinated seeds, using polyethylene glycol (PEG 8000). Cell changes were investigated through cytological assays (cell viability and transmission electronic microscopy) as well as DNA integrity during loss and re-establishment of DT. The loss of DT was characterized by drying germinated seeds with different radicle lengths (1, 2, 3, 4 and 5 mm) in silica gel, decreasing the moisture content to ten percentage points intervals, followed by pre-humidification (100% RH / 24 h) and rehydration. To re-induce DT, germinated seeds were treated for 72 h with PEG (-2.04 MPa) and PEG (-2.04 MPa) + ABA (100 µM) before dehydration. Germinated seeds did not tolerate desiccation to 10% moisture content, irrespectively of the radicle length. However, when incubated in PEG, those with 1 and 2 mm long radicle attained 71% and 29% survival, respectively. The PEG+ABA treatment was efficient to re-establish DT in seeds with 1 mm long radicles (100% survival). The ultrastructural assays of the cells of germinated seeds with 2 and 5 mm length confirmed the obtained physiological results. Germinated seeds of C. fissilis constitute a useful tool for desiccation tolerance investigations

Effect of storage in overcoming seed dormancy of Annona coriacea Mart. seeds

The aim of this study was to evaluate the effect of pre-treatments on overcoming dormancy of A. coriacea seeds. Seeds were processed and stored in polyethylene bags at temperatures of at -18°C (42% RH), 5°C (34% RH), 15°C (60% RH) and 25°C (34% RH), during 0, 30, 60, 90, 120 and 150 days. After storage, seeds were immersed in 350 mg.L−1 gibberellic acid for 144 hours. Sowing was carried out in plastic bags containing Red Latosol + Bioplant®. Moisture content, emergence percentage, emergence speed index, length and dry mass of seedlings, were evaluated. The experimental design was completely randomized in a factorial with four replications of 50 seeds each. The seed storage at 5°C and subsequent immersion in gibberellic acid was efficient to reach high percentage, emergence speed and plant growth. A. coriacea seeds showed non-deep simple morphophysiological dormancy wherein the physiological component can be overcome after the seeds are storage at 5°C for a maximum period of 53 days and subsequent immersed in exogenous GA (350 mg.L−1 for 144 hours)

Teste de deterioração controlada em sementes de niger (Guizotia abyssinica (L.f.) Cass.)

O niger (Guizotia abyssinica (L.f.) Cass.) é uma espécie oleaginosa promissora para a produção de biodiesel; entretanto, possui poucas informações a respeito da avaliação do potencial fisiológico de suas sementes. Assim, objetivou-se adaptar a metodologia do teste de deterioração controlada para avaliar seus efeitos sobre as sementes de niger. Foram utilizados seis lotes de sementes, inicialmente caracterizados quanto ao grau de umidade, porcentagem de germinação, primeira contagem de germinação, índice de velocidade germinação, tempo médio de germinação, porcentagem de emergência, índice de velocidade de emergência, tempo médio de emergência; estande inicial de plântulas e crescimento inicial de plântulas. No teste de deterioração controlada as sementes tiveram o conteúdo de água ajustado para 16, 20 e 24%, sendo então submetidas a temperatura de 41°C por períodos de 24 e 48 h. Após o período de deterioração, as sementes foram submetidas ao teste de germinação e procedeu-se a avaliação aos 7 d após a semeadura, contabilizando-se a porcentagem de plântulas normais. O delineamento experimental utilizado foi o inteiramente casualizado com quatro repetições de 50 sementes. O teste de deterioração controlada é eficiente para a avaliação do potencial fisiológico das sementes de niger e correlaciona-se positivamente com o teste de emergência de plântulas, sendo a combinação de 16% de teor de água das sementes e 24 h de exposição a mais adequada para a avaliação do potencial fisiológico das sementes de niger. ABSTRACT Niger (Guizotia abyssinica (L.f.) Cass.) is a promising oilseed species for biodiesel production; however, there is no much information about physiological evaluation of their seeds. The objective of this work was to adapt a controlled deterioration test methodology for niger seeds. Six niger seed lots were used, initially characterized for seed water content, germination percentage, germination first count, germination speed index, mean germination time, emergence percentage, emergence speed index, mean emergence time, initial stand, and seedlings length. In the controlled deterioration test, seed water content was adjusted to 16, 20 and 24% before they were treated to 41°C for 24 and 48 h. After the deterioration period, seeds were subjected to the germination test and proceeded the evaluation at 7 d after sowing, counting the normal seedling percentage. It used the randomized design with four repetitions of 50 seeds. The controlled deterioration test was efficient to evaluate the niger seed physiological potential and it correlated positively with the seedling emergence test. It is recommended the combination of 16% of water content and 24 h of time exposure to evaluate the physiological potential of niger seeds

Drying and reduction in sensitivity to desiccation of seeds of Alibertia edulis: the influence of fruit ripening stage

ABSTRACT The intense environmental degradation in tropical regions suitable for agriculture has decreased native forest populations of plants with important fruits and medicinal properties. Alibertia edulis is a native tree from the Brazilian Cerrado. Knowledge about the effects of drying and storage on the physiological behavior of its seeds may aid in its sustainable exploitation and conservation. The goal of the present study was to determine which fruit ripening stage results in A. edulis seeds with higher tolerance to desiccation, and to investigate the effectiveness of polyethylene glycol (PEG) induced osmotic stress in combination with abscisic acid (ABA) in increasing seed desiccation tolerance during storage. Seeds were dried in activated silica gel (fast) or under ambient conditions (slow). Seeds originating from mid-ripe or fully ripe fruits exhibited better physiological performance than those obtained from green fruits. Slow drying resulted in seeds with high physiological potential. Seeds may be stored for up to 180 days without losing viability when treated with -0.73 MPa PEG without ABA