| Plant type is a key factor that determines potential of crop yield, when gramineous grain crop especially plant type breeding of rice has obtained an important achievement, study on plant type breeding in soybean raised the people to pay attention to it. Podding-habits of soybean is one of main characters of plant type, and there is important effects of types of stem termination on adaptability of soybean varieties. So, the types of stem termination is a core problem of plant type design of soybean. Improving and adjusting podding-habits of soybean is beneficial for improvement of plant type, elevation of adaptability, and increase of crop yield. From differentiation of soybean varieties and photoperiod adjustment, anatomical differentiation essence of different types of stem termination soybean varieties, variation law of stem termination development under different photoperiod treatments, effect of long day on the terminal raceme of soybean, regulation rules of AGAMOUS gene among different soybean varieties and under different photoperiod treatments were studied, which would provide theory base of plant type breeding of soybean especially improvement of podding-habits and cultivation and management of soybean.Varieties differentiation of different types of stem termination including Zhonghuang13,Zhonghuang24 and Fengjiao66-12 was studied through morphology and anatomy methods. The results were that determinate (Zhonghuang13 and Fengjiao66-12) and indeterminate (Zhonghuang24 ) soybeans usually produce flower buds, differentiation was that flower buds of determinate soybeans initiated more early than flower buds of indeterminate soybean. When raceme primordium of determinate soybeans had developed, the terminal floral primordium of indeterminate soybean began to produce, leaves of the terminal node was little, and the stem termination could not produce pods in short supply of nutrition. In the process of terminal raceme formation of different types of stem terminaion soybean, initiation time of raceme differetiation played essential fuction. As to determinate soybeans cv. Zhonghuang13 and Fengjiao66-12, there was significant difference in the length of raceme. The results were that long raceme soybean cv. Fengjiao66-12 initiated more early flower buds, and terminal raceme differentiated more rapidly than short raceme soybean cv. Zhonghuang13, which resulted increase of raceme length and flower number in short time. The main cause of different raceme length soybean varieties was determined by initiation time and rate of raceme differentiation.The cause of podding-habits soybean formation was affected not only internal genetic factors, but also external environmental factors. The above three soybean varieties were treated with short-day of 12 h and long-day of 16 h in whole growth period, the different photoperiod treatments changed development process, podding-habits, plant morphogeny, and agronomical characters of different types of stem termination. And by this method photoperiod-sensitive and photoperiod-insensitive soybeans were divided, which is an important meaning at the production and popularization of soybean varieties. the results were that duration from emergence to blooming and duration from emergence to earlier maturity of three soybean varieties were delayed with increase of time of exposure to long day. Through anatomy observation, initiation time of flower buds differentiation among three soybean varieties was more earlier under short day condition than under long day condition, at this point three soybean varieties was sensitive to photoperiod, but they could bloom and seeding under two photoperiod treatments, and had adaptability to different environment. By short-day hastening rate results were analyzed that the blooming time and maturity time of Zhonghuang13 was weaker sensitivity to photoperiod than other two varieties, plant height, node no. at stem, branches, pod no. at raceme, seed no. /plant, seed weight /plant of Zhonghuang13 at maturity were insensitive to photoperiod. Flower no. at raceme of Zhonghuang24 was insensitive to photoperiod, other agronomic traits were sensitive, whereas node no. at stem of Fengjiao66-12 was insensitive to photoperiod. In a word, most agronomic traits of Zhonghuang13 had insensitivity and stability to photoperiod, and Zhonghuang13 was extensive photoperiod adaptability soybean which could be planted at the area of multi-ecotype.To make photoperiod especially importance of long-day for growth and development of short-day crops clear, In the current study, a photoperiod-sensitive and late maturity determinate soybean cv. Zigongdongdou (Maturity Group IX), was used to investigate photoperiod effects on the development of terminal inflorescence (raceme) of soybean, plant type and agronomic traits, with emphasis on the role of long-day in the formation of raceme. The plants were treated with short-day (SD) of 12h for 13 days to induce the initiation of terminal inflorescence, and then moved to 16h long-day treatment (LDT) for 0, 1, 2, 3, 4 and 5 weeks, respectively. After LDT, plants were returned to SD condition. Along with the increment of weeks of LDT, the blooming dates of soybean plants were progressively delayed, and the duration of terminal inflorescence differentiation were distinctly prolonged through anatomical observation, and the length of raceme increased. A positive linear correlation was found between weeks of LDT and the duration from emergence to beginning bloom, and the duration of the terminal inflorescence differentiation, and the length of raceme. In 2-5 wks LDT, inflorescence reversion and floral reversion happened and the rate of reversion increased, with the increment of weeks of LDT, reversion proportion of terminal raceme presented the gradual increment trend, and plant type varied with change of terminal raceme, and agronomic traits tended to increase under long-day condition. The results of the present study indicated that effects of long day on inflorescence development of soybean was acculmulative. In a way, long-day is beneficial for development and yield formation of short-day crop.Function and regulation rule of related genes in the process of stem termination of soybean was unclear at present, by making use of AG cloned by our lab we researched AG expression during the developmental period of soybean stem termination primarily. GmAG is one of AG subfamilies among MADS-box gene family, whose identity is 78% to amino acid sequence of STK (AGL11) by analyzing DNAMAN software. Space-time change of GmAG expression at the stem termination was studied by RT-PCR and RNA in situ hybridization. The results were that GmAG was observed a little at the stem termination and trifoliate leaves primordium in the early growth period, and intensity of GmAG expression increased at the inflorescence meristem and floral primordium, it showed that GmAG played a role in determining traits of inflorescence meristem. With differentiation of floral primordium, GmAG was observed in the carpel and stamen, and GmAG expression was strong in the ovule. It indicated that GmAG is an important function for carple and stamen formation and ovule development as flower organ genes C and D. Different photoperiod treatments effected GmAG expression in some extent, but differentiation was not significant. That intensity of GmAG expression increased for photoperiod-sensitive stem termination under SD condition suggested GmAG accelerated flowering of some soybean. And GmAG was observed a little at reversed shoot tips, which indicated GmAG had a characteristic of transition from shoot apical termination to floral meristems. So, GmAG played a important role in improving floral primordium differentiation, carple and stamen formation and ovule development, and photoperiod signals caused GmAG change in some extent, but detail explanation about the reason of phenomemon need to study further. |
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