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.

Drying and germination of cupuassu (Theobroma grandiflorum (willd. Ex Spreng.) K. Schum.) seeds

The objective of this study was to verify the effect of drying on germination of cupuassu (Theobroma grandiflorum (Willd. ex Spreng) K. Schum.) seeds. Desiccation was in forced air oven, with temperature ranging from 23 to 33ºC. Sowing was carried out at 0.5cm of depth in plastic trays in sand and sawdust mixture (1:1), previously sterilized in hot water (100ºC), during 2h. Seeds were left to germinate in a laboratory with no temperature and relative humidity control, under natural light. It was quantified the seed moisture content, in four replications of 10 seeds; the germination percentage, performed during 30 days, with daily counts of the number of germinated seeds; the germination speed index; and number of days to the germination onset. The experimental design was completely randomized with four replications of 25 seeds. The reduction of moisture content from 58.6 to 37.8% did not affect seed germination and germination speed index; however, they were affected when moisture content was reduced to values below 30.7%. It was observed that only when moisture content was 16.1% seeds demanded more days to begin germination. Cupuassu seeds are classified as recalcitrant and they can be desiccated up to 37.8% with no reduction on germination.

Performance of different drying methods and their effects on the physiological quality of grain sorghum seeds (S. bicolor (L.) Moench)

This experiment viewed to evaluate the physiological quality of grain sorghum seeds as well as to determine the respective drying curve of each of three drying methods. The seeds harvested at 18.9%, 18.1%, and 18.2% of moisture content were submitted to the following drying methods : a) under natural conditions, b) an intermittent dryer in which the combustion of firewood was the source of caloric energy, and c) a stationary dryer in which the source of caloric energy was the burning of liquefied petroleum gas. The experimental design was a completely randomized one with 25 repetitions of one hundred seeds each. The water contents and weight of one thousand seeds were evaluated. Seeds physiological quality was evaluated by germination and vigor tests. Seed drying rates were of 0.11, 1.25, and 0.55 percent points per hour (pph -1) for the natural, intermittent and stationary drying methods, respectively. The intermittent treatment permits the highest loss of water in the shortest period of time, and germination and vigor remaining unchanged.

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.