| Amomum villosum Lour. is a kind of evergreen perennial herbs in the genus Amomum which belongs to the family of the Zingiberaceae. Its dry ripe fruit is the traditional China medicine (TCM) commonly used in clinic, which has the pharmacological effects of clearing dampness, promoting appetite, warming spleen, preventing diarrhea, regulating qi, calming fetus and so on.A. villosum exists serious fruit dropping phenomenon which greatly affects the production of Amomi Fructus, and dampens the enthusiasm of farmers to grow A. villosum. If we take some effective measures to reduce the amount of dropping fruits, the production of Amomi Fructus maybe increase in some extent, that will be benefit to the development of Amomi Fructus industry.In this paper, the fruit characteristics in different stages and fruit dropping phenomenon of A. villosum were studied, and the laws of fruit growth and development and dropping were obtained. In addition, the fruit dropping mechanism was also investigated. The results showed in this paper can lay a theoretical foundation for formulateing effective measures to reduce the rate of fruit dropping.The results of the study are as follows:1. The law of fruit growth and development of A. villosum was studied.The changing tendency of fruit transverse diameter of A. villosum was slow-fast-slow-steady, and that of longitudinal diameter was fast-slow-steady. During the 0 to 24th day after pollination was the peak period of fruit expanding, and the fruit shape developed from near-cylindrical into subglobose. About 7 days after pollination, fruit thorns could be observed obviously, and it grew to maximum at the 27th day after pollination. The thickness of fruit peel increased to the largest around the 24th day after pollination. But the fruit thorn length and fruit peel thickness both decreased in the later.The increasing curve of fruit weight of A. villosum appeared as S shape, the peak period was from the 12th to 24th day after pollination. Seed mass formed at about the 18th day after pollination, before that, the seeds couldn’t grow together to form a mass. Seed mass weight grew fast in the early stage, and then maintained steadily. The fresh weight ratio of seed mass to fruit increased slowly along with the development of the fruit.The seed of A. villosum swelled quickly from the 12th to 30th day after pollination, and it’s shape developed from the bulb into irregular polyhedron gradually. Besides, the color of seed changed from transparent yellow to tan as time went on. At about the 15th day after pollination, the seed was completely surrounded by membranous aril, and was covered of uneven striations on the surface at about the 18th day after pollination, however, it was smooth before that.The dry weight of 100 fruits and 1000 seeds at the 75th day after pollination were 44.73 g and 11.88 g, but they were 48.59 g and 13.18 g at the 90th day, which were significantly different between both. For the fresh weight of 100 fruits, the content of seed volatile oil and bornyl acetate, there was no significant difference between these two stages. The fresh weights of 100 fruits at two stages were 235.57 and 248.68 g, the volatile oil contents were 2.93% and 3.02%, and the bornyl acetate contents were 0.79% and 0.82%. According to the results above we know that the content of volatile oil and bornyl acetate in A. villosum seeds accumulate steadily at the later stage of growth and development, but the dry weight of fruit may increase to some extent if we delay to harvest reasonably.2. The fruit dropping law of A. villosum was studied.The fruit abscission part is located in the joint of fruit and fruit peduncle. It was found that the abscission layer cells appear to be prolate slightly by microstructure observation, and they are smaller than neighboring cells. Fruit dropping was observed first at the 9th day after pollination, and the peak period occurred from the 12th to 15th day, after the 18th day, the number of dropped fruit reduced drastically. Only few of fruits dropping were observed from the 24th to 90th day. The peak period of fruit dropping was also the stage of fruit growing rapidly. The final fruit dropping rates in 2014 and 2015 were 64.72% and 73.61% respectively.3. The physiological mechanism of fruit dropping in A. villosum was studied.The soluble sugar contents in normal fruits at the day of 12th,15th and 18th after pollination were 0.55%,0.98% and 1.76%respectively. The soluble sugar contents in dropping fruits at the day of 12th and 15th after pollination were 0.46% and 0.8% respectively. The soluble sugar content in normal fruits is higher than that of dropping fruits at the same stage, therefore, normal fruits have stronger nutrition competition ability to ensure the nutritional needs for fruit growing and developing.Cellulase and polygalacturonase activities in dropping fruits were respectively 2.87 and 2.24 times of normal fruits at the 12th day after pollination. In addition, cellulase and polygalacturonase activities in dropping fruits were respectively 1.68 and 1.08 times of normal fruits at the 15th day after pollination. Therefore, hydrolysis enzymes activities were highly correlated to the fruit abscission.There was no difference between normal fruits and dropping fruits in the microelement contents of Zn, Mn, Fe, B and Mo, but the content of Ca in dropping fruits was 32% higher than that in normal fruits at the same stage. It is supposed when the concentration of Ca2+ increases, it may activate the Ca2+-CaM signal system, and induce the plant to produce ethylene, then the hydrolytic enzymes activities are raised, which leads to the fruit abscission.Immunohistochemical results showed that there was no obvious difference between normal fruit peduncle and dropping fruit peduncle in the IAA content, but GA3 and ABA contents of normal fruit peduncle were significantly higher than that in dropping fruit peduncle. Besides, near the fruit abscission part, the IAA content of dropping fruit peduncle was higher than normal fruit peduncle. According to the above results, we guess that the low level of GA3 may trigger the fruit dropping, and the relative balance of GA3 and ABA in fruit peduncle ensures normal development of fruits. After the abscission being initiated, IAA distributing intensively in the fruit dropping part may accelerate the abscission process. |
PDF Full Text Request