| Leymus chinensis (Trin.) Tzvel. is a perennial rhizomatous species of the family Poaceae. It has high forage value and good palatability, and also tolerant to cold extremes, drought conditions, and salt-alkaline soils. So this plant is an important perennial grass that widely distributed in northeast China, and also an ideal grass for rangeland use in arid and semiarid regions. However, under nature conditions, the spike rate and seed production of L.chinensis is very poor, which block the needs of forage production and ecological construction. In present study, we explored the differentiation process of the young spike, compared the apical meristem differentiation in reproductive and vegetative shoots, and investigated the relationship of birth time, number, development and spike formation traits next year of various buds and daughter shoots. The results showed that:(1) For the grass after regreening but before spiking data, SAM differentiation was observed in the early stage, elongation stage, single ridge stage, double ridge stage and subsequent stages simultaneously. For the vegetative shoots that were measured after spiking, SAM differentiation was observed only in the early stage, elongation stage and single ridge stage but not in the double ridge stage or subsequent stages. For grass that grew in a greenhouse through the winter, new leaves developed continuously, increased in stem length and had no spiking, and SAM differentiation was observed only in the early stage, elongation stage and single ridge stage. Only grass experiencing SAM differentiation in the double ridge stage can head. The study also determined that low winter temperature played an extremely important role in the spiking of L. chinensis.(2) The number of daughter shoots formed by all kinds of buds has a close relationship with precipitation last month and this month. The output quantity of daughter was directly influenced by precipitation from July to September and the precipitation also indirectly affected the output quantity next month. This means that high precipitation can enhance output of daughter shoots this month and next month. However, drought conditions decreases it. Under high precipitation conditions, axillary daughter output by axillary buds starts in early July, and this time is earlier than the output time of rhizome buds, which starts in late July. Most axillary daughter shoots and rhizome buds output in August, and the termination time is late October. At the beginning time of daughter shoot output, axillary daughter shoot took up 90% of the total daughter shoot. During the fastigium of daughter shoot, axillary daughter shoot took up nearly 80% of the total daughter shoot. During the termination time of daughter shoot output, axillary daughter shoot took up nearly 70% of the total daughter shoot. During the late growing season, the proportion of buds, daughter shoot and rhizome buds, rhizome daughter shoot were different based on different year. However, little changes was found in the proportion of axillary buds and axillary daughter shoot, and the number of axillary buds was lower than axillary daughter shoot.(3) Leaf ages and plant hight of daughter shoots with different come up out of land time are great differed, the earlier birth of daughter shoot, the bigger of leaf age and plant hight; the later birth of daughter shoot, the smaller of leaf age and plant hight. After September, no obvious change was found in leaf and plant height of L. chinensis daughter shoots. The differentiation stage of daughter shoot with same leaf age contained early stage, elongation stage and single ridge stage, but have no double ridge and the subsequent differentiation stage. The proportions of differentiation stage of different leaf stage are also different. The bigger of leaf age, the larger of proportion in single stage. The smaller of leaf age, the larger of proportion in early stage.(4) The spike plants mainly come from the daughter shoots produced on nutrition stage after ripe during last growing season, only a little come from overwintering buds. The spike formation ability next year of axillary daughter shoot is significantly higher than rhizome daughter shoot in the same stage. The earlier birth of the axillary daughter shoot, the greater of spike formation ability. No obvious change was found in the spike formation ability next year between different come up out of land time. Axillary daughter shoot had the largest contribution for spike formation, the spike plants were mainly come from axillary daughter shoot last growing season.The number of daughter shoots formation in August-September is largest, and the height of daughter shoots which come up out of land before September is higher than that after September, as a result, these daughter shoots had the largest contribution for spike formation. A part of the daughter shoots of various leaf ages could spike next year. Shoots of overwinter buds after regreening could also spike, but the spike rate was very low. However, due to the large number of the overwinter buds, their contributions to spike formation of L. chinensis. could not be neglect.In present study, we systematic studied L. chinensis. from daughter shoot to spike plant, clarified that both of the overwinter buds and daughter shoots had contributions to spike formation next year. SAM differentiation was observed at most in single stage at the end of growing season, the shoots could spike only when experienced low temperature in winter. The contributions to spike formation next year not only affected by the spike ability of daughter shoot but also affected by the number of daughter shoot. Above results show that the spike and seed production of L. chinensis. can be controlled, nitrogen and water application in optimal periods can enhance spike rate and seed production next year. |
