The Study On The Pod And Seed Development And Determination Of Seed Optimum Harvest Time Of Vicia Cracca

Vicia cracca is a perennial legume plant and one of the most common fodder plants in northern China. It is a wild high-quality forage widely grown mostly for hay, green forage, silage and grain. However, V. cracca seed production is a major problem because of pod shatter at plant maturity. Pods are fragile at harvest time and seed loss can negatively impact yield. Harvesting too early may result in low yield and poor seed quality, whereas harvesting too late may result in shattering and reduced seed yield. Many agriculture methods have been used to apply in production. Unfortunately, many of these methods are difficult to apply in production, while in others seed loss is not effectively prevented. Researchers have focused on determining optimum harvest time to avoid seed loss. Thus the aim of this research was to study the development of pod and seed and determine the optimum harvest time of Vicia cracca to resolve the problem in production.The experiment was conducted at Ecosystem Field Station of the Institute of Grassland Science at Songnen Grassland in China (44°40′N 123°44′E, 167 m above sea level). V. cracca plants were sown in 2003. Field and laboratory experiments were conducted from 2005 to 2007. Flowers were tagged in early August at peak anthesis. Tagged pods were harvested at 3-day intervals beginning 9 days after peak anthesis (DAPA) and continuing until 42 DAPA. Pod and seed morphological characters, pod and seed physiological characters and seed quality were determined from 2005 to 2006. Seeds were harvested and evaluated seed salt and alkaline resistance in 2006; The rate of pod shatter was recorded and measure the indexes related to pod shatter in 2005 and 2006 during seed maturity; In 2007, we measured the physiology indexes and the rate of hardseededness. The results were showed as followed:1. The result of the development of pod and seed of V. cracca showed that pod and seed color and sizes were significant different from other sampling dates from they loss green (from 36 to 42 DAPA). Seed dry weight and thousand seed dry weight reached the highest from 30 to 42 DAPA. Pod and seed moisture contents were lowest from 33 to 42 DAPA. The results of standard germination test, accelerated aging test and cold test showed that the percentage germination, germination rate, embryo length and germination vigor were highest from 33 to 42 DAPA. The electrical conductivity was lowest from 27 to 42 DAPA.2. The result of adversity test showed that percentage germination, germinatin energy, germination rate, radical length and germination vigor were higher from 33 to 42 DAPA than other sampling dates. Adversity resistance was higher from 33 to 42 DAPA than other sampling dates. And the seed of the same sampling date in salt resistance was higher than alkaline resistance;3. The result of the rate of hardseededness in different sampling dates showed that hardseeded seeds occurred at 36 DAPA. The morphological and physiological indexes were significant different from other sampling dates. A strong negative correlation was found between seed moisture content and percentage of hard seed during seed development. The hardseeded seed occurred at 24 DAPA and a strong negative correlation was found too between seed moisture content and percentage of hard seed when seed dried for about 1 month.4. The results of the pod shatter in different sampling dates during seed maturity showed that the rate of pod shatter was 0 from 6:00 to 8:00 and from 16:00 to 18:00 in one sunshiny day. The rate of pod shatter was nearly 0 in the whole cloudy day. A strong negative correlation was found between the rate of pod shatter and humidity, pod moisture content. A strong positive correlation was found between the rate of pod shatter and air temperature, pod wall temperature. However, there was no correlation between the rate of pod shatter and other indexes in a cloudy day. The partial correlation result showed that there was no correlation between the rate of pod shatter and the indexes of circumstance factors.The optimum harvest time of V. cracca in different sampling dates was from 36 to 42 DAPA. The optimum harvest time of V. cracca during harvest time was 6:00～8:00 and 16:00～18:00 in one sunshiny day and every time was optimum in a cloudy day.Pod and seed color and sizes could be dependable and rapid indicators providing a simple way for seed producers to judge optimal harvest time. Pod and seed moisture contents were more accurate than seed dry weight and thousand seed weight relatively. Germination time, percentage germination, germination rate, embryo length and germination vigor could not be the accurate indicators. Electrical conductivity and growing degree days could not be the accurate indicators too.