Iranian Journal of Seed Research

Extended Abstract
Introduction: Seeds, like other materials, are hygroscopic and exchange moisture with their surroundings. The changes in the moisture of seeds during storage depend on their hygroscopic nature and this feature plays an important role in determining the seed quality and longevity. Furthermore, studying the hygroscopic characteristics if seeds can be useful in seed storage studies as well as in commercial applications such as drying and seeds processing. Therefore, in this study, the relationship between seed moisture content and relative humidity in seed of rapeseed cultivars was studied.
Material and Methods: In this study, the relationship between the ambient relative humidity and seed moisture content of three rapeseed cultivars at 10, 20 and 30 °C was investigated using hygroscopic equilibrium curves. Therefore, water desorption and absorption curves were studied separately. Water absorption and desorption curves were obtained by drying the seeds at 1% relative humidity and seed hydration at 100% relative humidity, respectively, followed by transferring the seeds to different relative humidities at different temperatures and finally determining the equilibrium moisture content of the seeds. It should be noted that glycerol and sulfuric acid solutions were used to creation different relative humidity. Finally, the relationship between seeds moisture content against the relative humidity was quantified by fitting the D’Arcy-Watt equation.
Results: The results indicated that the seeds moisture content varied in cultivars and temperatures at different relative humidities. Also, there was a difference between water desorption and absorption curves in all cultivars and temperatures; desorption curves were generally higher than water absorption curves. The greatest difference among the cultivars regarding seed moisture content was observed at 100% relative humidity, and this difference was less severe at lower relative humidities. Also, the highest seed moisture content of rapeseed cultivars was observed at 20 °C and 100% relative humidity, and the lowest seed moisture content was recorded at 30 °C and 1% relative humidity.
Conclusions: According to the results, it was found that the relationship between seed moisture content and relative humidity followed a sigmoidal function, and this relationship would also vary depending on cultivar and temperature. There was also a difference between the adsorption and desorption curves, which is called "hysteresis", and showed that the seed moisture content at a constant relative humidity was generally higher in the state of dehydration compared with that in the state of hydration. Due to this event, desorption curve is situated higher than the absorption curve.

Highlights:

1. Response to hygroscopic equilibrium curves in seeds of different rapeseed cultivars was compared.
2. Sulfuric acid and glycerol solutions were used to create different relative humidity.

Extended Abstract
Introduction: Tubers are considered as the most important vegetative organs in reproduction of purple nutsedge, as one of the most troublesome weeds worldwide. Therefore, it is great of importance to investigate the properties of the tuber response to the surrounding environment such as absorption and loss of water. Water uptake is the first step in the sprouting process, though the pattern of water uptake by purple nutsedge tubers has not been documented. Loss of water in tubers is one of the potent factors in reducing their ability to sprouting. Three separate experiments were carried out to investigate the absorption and loss of water content of purple nutsedge tubers.
Material and Methods: In the first experiment, the tubers were placed in a water bath at temperatures of 10, 20, 30, and 40 ° C. Then, the weight of the tubers was measured at different times (24 till 3600 minutes). The water uptake percentage of tubers at different temperatures was studied by fitting the Peleg model. In the second experiment, the initiation day of sprouting was investigated at constant temperatures of 10, 20, 30, and 40 ° C. In the third experiment, water loss and sprouting percentage of tubers were evaluated in two conditions refrigerator (4° C) and room (22 to 25 ° C).
Results: The results showed that the initial water content of tubers was 42% and absorbed 10% extra water after being immersed in water. The water uptake behavior was based on the Peleg model at two stages: (1) rapid uptake (less than 420 minutes (7 hours), and (2) a low uptake with a gentle slope afterward. In the Peleg model, the parameters K₁ (minutes *.%weight ^-1) and K₂ (%^-1) are water absorption rate and water absorption capacity, respectively. The K₁ parameter was negatively against temperature. The highest and lowest values were 49.56 and 28.55 at 10 and 40 ° C, respectively. On the other hand, the trend of the K₂ was constant (0.1) at 10-30 °C but was 0.08 at 40 °C. The two-parameter Hyperbola model was superior to the Peleg and predicts the highest water absorption and time to 50 percent water absorption parameters. The results showed that sprouting of purple nutsedge tubers at 10, 20, 30, and 40 °C occurred after 14.44, 6.57, 3.24, and 3.12 days, respectively. Keeping the tubers in the room (22-25 °C) and refrigerator (4 °C), sprouting stopped after 3 and 9 months, respectively. The time required for 50% reduction of sprouting in the room and refrigerator was estimated to be 1.3 months (39 days) and 5.12 months (154 days), respectively. The time required for 50% loss weight of tubers in the room and refrigerator was 1.981 months (59 days) and about 6 months (180 days), respectively. Overall, weight loss (water loss) up 11.85%, resulted in 50% reduction in tuber sprouting.
Conclusion: Maximum water uptake in tubers occurred in less than 420 minutes (seven hours) at all temperatures. Slow sprouting in tubers at low temperatures is not associated with an obstacle in water absorption. Tubers lost half of their sprouting ability by losing water about 12%. On the other hand, the results show that the tubers at cool temperatures (4 °C) lose their water and sprouting capacity less than the ambient temperature (22 to 25 °C).

Highlights:
1- Determination of water absorption pattern on purple nutsedge tubers.
2- Effect of storage location in reducing water and sprouting ability of purple nutsedge tubers.

Extended abstract
Introduction: The seeds of agricultural products are constantly subjected to impact forces from machines from the moment they are harvested to the time they are transferred into storage. Improper design and performance of machines in each of these stages can cause mechanical damage to seeds. Mechanical damage caused by free fall on the seed of agricultural products, which occurs during different stages of harvesting, transportation and other processes, causes a decrease in their quality and an increase in waste. This study aimed to evaluate the amount of mechanical damage caused to chickpea seeds due to the impact of free fall.
Materials and methods: The experiment was conducted as a factorial in the form of a completely randomized design with three replications. The factors included drop height (3, 6, 9 and 12 m), the contact surface (concrete, plywood, metal (iron) and seed-on-seed) and seed moisture content (10, 15, 20 and 25 %).  The studied traits or the amount of damage to the seeds included the measurement of seed deterioration by the accelerated aging method (loss in germination percentage in the accelerated aging test) and the measurement of electrical conductivity.
Results: The results of the analysis of variance showed that all three factors (drop height, the contact surface and moisture content) had significant effects at p<0.01 on the loss in germination percentage in the accelerated aging test and changes in electrical conductivity of chickpea seeds. In terms of loss in germination percentage, the highest damage to seeds occurred in the metal contact (41.96%) and the least in the seed-on-seed treatments(29.71%). Also, the highest amount of electrical conductivity was related to the seeds dropped on the metal (36.09 μS cm^-1g^-1) and the lowest was related to seed-on-seed contact (21.68 μS cm^-1g^-1). As the drop height rose from 3 to 12 m, the loss in germination and electrical conductivity of seeds increased from 27.74 to 48.08% and from 18.72 to 40.47 μS cm^-1g^-1, respectively. Increasing the moisture content of chickpea seeds from 10 to 25% causes a decrease in the amount of damage to the seeds in terms of electrical conductivity (from 38.40 to 21.18 μS cm^-1g^-1). However, the damage was in the form of loss in germination percentage during the accelerated aging test (from 29.22 to 42.88 %).
Conclusion: The findings of this study revealed that the movement of chickpea seeds and the subsequent free fall had a notable impact on their latent damage, leading to a decrease in germination rate and alterations in electrical conductivity. Therefore, it is recommended to minimize fall height and prevent seeds from hitting hard surfaces during seed processing and transportation to mitigate the damage.

Highlights:

1. Seed deterioration tests using accelerated aging and electrical conductivity can be used as appropriate criteria to measure the mechanical damage to chickpea seeds.
2. When designing machines that come into contact with the seeds, it is important to choose surfaces made of soft materials to minimize the destructive effects of the seeds falling from greater heights.
3. The moisture content during the processing and transportation of the seeds should be at an optimal level of around 15%.