Drying peanut seed using air ambient temperature at low relative humidity

The moisture content of peanut kernel (Arachis hypogaea L.) at digging ranges from 30 to 50% on a wet basis (w.b.). The seed moisture content must be reduced to 10.5% or below before seeds can be graded and marketed. After digging, peanuts are cured on a window sill for two to five days then mechanically separated from the vine. Heated air is used to further dry the peanuts from approximately 18 to 10% moisture content w.b. Drying is required to maintain peanut seed and grain quality. Traditional dryers pass a high temperature and high humidity air stream through the seed mass. The drying time is long because the system is inefficient and the high temperature increases the risk of thermal damage to the kernels. New technology identified as heat pipe technology (HPT) is available and has the unique feature of removing the moisture from the air stream before it is heated and passed through the seed. A study was conducted to evaluate the performance of the HPT system in drying peanut seed. The seeds inside the shells were dried from 17.4 to 7.3% in 14 hours and 11 minutes, with a rate of moisture removal of 0.71% mc per hour. This drying process caused no reduction in seed quality as measured by the standard germination, accelerated ageing and field emergence tests. It was concluded that the HPT system is a promising technology for drying peanut seed when efficiency and maintenance of physiological quality are desired.

Seed anatomy and germination of Phoenix roebelenii O'Brien (Arecaceae)

The objective of this study was to investigate the morphology, anatomy and germination behaviour of Phoenix roebelenii seeds. Biometric data were obtained by measuring 100 seeds extracted from recently harvested fruits and air-dried for one day. Four replications of 50 seeds each were previously treated with Vitavax-Thiran and then put to germinate in Sphagnum sp. in plastic trays at room temperature. Morphological details of the seeds were documented with the help of a scanning electronic microscope and then drawings were made with the help of a clear camera coupled to a stereomicroscope. Permanent lamina containing embryo sections were prepared to study its anatomy. The mean dimensions of the seeds were: length of 10.32mm, width of 5.21mm and thickness of 3.91mm. The weight of one thousand seeds was of 151.1g and the mean number of units.kg-1 was 6,600. Germination started between 27 and 58 days after sowing. The seeds are of the albuminous type, the endosperm is hard and the embryo (which is not clearly differentiated) occupies a lateral and peripheral position. During seed germination, seedling protrusion begins with the opening of an operculum, through which the cotyledon petiole is emitted with the embryonic axis at its tip. The portion of the cotyledon petiole that remains inside the seeds acts as a haustorium for the absorption of nutrients from the endosperm. The plumule emerges through a rift in the posterior part of the cotyledon. Secondary roots are observed to grow from the anterior part of the primary root.

Germination, initial growth and cotyledon protein content of bean cultivars under salinity stress

Excess salts in the root zone inhibit water uptake by plants, affect nutrient uptake and may result in toxicities due to individual salts in the soil solution. Excess exchangeable sodium in the soil may destroy the soil structure to a point where water penetration and root aeration become impossible. Sodium is also toxic to many plants. Beans (Phaseolus vulgaris L.) are consumed as protein source in northeastern Brazil, although little is known about common bean cultivar tolerance to salinity. The germination of bean cultivars under salt stress was studied. The cultivars 'Carioca' and 'Mulatinho' were submitted to germination test in a germinator at 25ºC, at the Seed Analysis Laboratory of the Brazilian Agricultural Research Corporation unit in the Semi- Arid region (Embrapa Semi Árido), Petrolina, Pernambuco State. These seeds were germinated on "germitest" papers imbibed in distilled water or in 10, 50, 100 e 200 mol.m-3sodium chloride (NaCl) solutions. At the first and second counts of the germination test, normal seedlings were counted, measured, weighed and dried, supplying data for vigor, total germination, fresh matter weight and dry matter weight and seedlings length. Total protein was quantified in cotyledons at 3, 6 and 9 days after sowing. The results indicated that the NaCl content influenced seed germination and concentrations above 50 mol.m-3 decreased germination and seedling growth.

Desiccation tolerance and DNA integrity in Eugenia pleurantha O. Berg. (myrtaceae) seeds

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were submmited to drying in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. It was observed DNA degradation in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Desiccation tolerance and dna integrity in Eugenia pleurantha o. berg. (Myrtaceae) seeds

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were dried in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. DNA degradation was observed in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Changes in gene expression during drying and imbibition of desiccation sensitive Magnolia ovata (A. St.-Hil.) spreng. seeds

Seeds of Magnolia ovata were dried to different water contents to assess the viability and transcript abundance of genes related to seed development, cell cycle, cytoskeleton and desiccation tolerance.The expression of development, cell cycle and cytoskeleton relative genes (ABI3, CDC2-like and ACT2) alone could not explain the germination behaviour of M. ovata seeds in relation to drying damage. Irrespective of their initial water content, the seeds performed in the same way during the initial period of germination and the deleterious effects of desiccation only occurred in later stages. Expression of PKABA1, sHSP17.5 and 2-Cys-PRX did not show a relationship with desiccation. However, the expression patterns of PKABA1 and sHSP17.5 suggested the participation of these genes in protective mechanisms during the imbibition of M. ovata seeds.

Physiological and enzymatic alterations in papaya seed during storage

This study was done to evaluate the physiological and enzymatic alterations in papaya (Carica papaya L.) seeds during storage period. Seeds were extracted from mature fruits of Formosa group papaya hybrid Tainung 01. The sarcotesta was removed by rubbing the seeds on a wire screen under running water and then dried to the moisture content (MC) of 5, 8 or 11% The seeds were packed in multilayer paper bags, polyethylene bags, aluminum foil pouch and metallic canisters and stored for 15 months under laboratory conditions. Seeds were evaluated, at three month interval, for MC, germination, and the activity of acid phosphotase (AP) and malate dehyrogenase (MDH) was evaluated with the use of amide gel (12%) electrophoresis. The fresh seeds had post-harvest dormancy, which was broken after six month storage. Independent of the package type, the seeds could be stored for 12 months with 8 or 11% MC under ambient conditions. There was no association between seed deterioration and alterations in AP and MDH activity.

Partial characterization of genes from the embryonic axis of Melanoxylon brauna Schott. (Leguminosae-Caesalpinioideae) seeds

The objective of this study was to partially characterize some genes involved in the desiccation tolerance of the embryonic axis of Melanoxylon brauna seeds subjected, or not, to oven fast-drying. Seeds were initially dried rapidly in an oven at 40 ºC, 50 ºC, 60 ºC, 70 ºC, and 80 °C, for 24, 48 and 72 h and then subjected to germination tests and moisture content determination. Degenerate primers were designed for 19 genes. The CDNA was used as a template for PCR amplifications using the degenerate primers, and the PCR products obtained were purified, cloned and sequenced. The seeds showed a gradual reduction in percent germination with increasing temperature and drying time. Nucleotide sequences of the cloned fragments related to genes CAT1, SPS1, Abi5, Transk and PM25 were obtained. The similarity analysis with the sequences deposited in databases revealed similarities with genes CAT1, SPS1, Transk and PM25 from other plant species. The nucleotide sequences obtained from the respective genes will be used for designing specific primers for gene expression analyses during seed germination in order to understand the causes for loss of physiological quality of Melanoxylon brauna seeds.