Micromorphology And Germination Of Peganum Multisectum(Maxim.)bobr. Seed And Its Ecological Adaptive Strategy

Peganum multisectum(Maxim.) Bobr. is a perennial herbaceous plant which belongs to the family of Zygophyllaceae. It was mainly distributed in many desert regions in the northwest of China. The special micromorphology and mucilage of P. multisectum seeds,play an important role in seed dispersal and germination. In this study, the characteristics changes of mucilaginous seed coat before and after wetting were observed by dissecting microscope and scanning electron microscopy. The effects of seed coat ornamentation and mucilage on water uptake, sand adhesion, floatability and germination of seeds were analyzed. The phenomenon of seed dormancy and germinations at different temperatures and drought stress were studied. The main conclusions are as follows:The seed coat ornamentation of Peganum multisectum can produce mucilage, which making the meshes form the closed chambers. After absorbing water, the pellicles became mucilaginous and a lot of bubbles appeared in the mucilage chambers. The mucilage layer and chambers of seed can store much air, which facilitated seed floatation on moving water and further dispersal. Meanwhile, seed coat ornamentation and mucilage can enhance adhesive ability of seed to the soil and other plants, thereby escaping from seeds bareness to maintain seed vigor. The seed coat ornamentation and mucilage can also absorb a large amount of water quickly and hold water, thus maintaining soil seed bank in the harsh desert.Furthermore, the mucilaginous seed coat can delay germination but promote seedlings growth in an unpredictable environment, which increasing the ability of plant establishment.The seeds of P. multisectum with nondeep physiological dormancy phenomenon, and the dormant can be gradually afterripened after storing one month in the laboratory, 4 ℃refrigerator and field conditions. Especially in field conditions, the seed germination rate and the length of young roots increased significantly, which means that the field conditions is more advantageous to break the seed dormancy. Seed dormancy characteristics was beneficial to the choose of seed germination time for P. multisectum. Most of the seeds can germinate in the spring when the weather is warming and rainy, which reduce the probabilities that the seeds germinate under the suitable temperature in winter. Thus, the number of seedlings died due to discomfort environmental conditions would reduced. It’s a kind of adaptive protection strategy.The temperature, PEG osmotic potential and their interaction had significant effect on seed germination of P. Multisectum. Mild drought stress could promote seed germination and seedling growth, but with the gradual increase of PEG osmotic, seed germination gradually suppressed. The difference of response to drought stress for P. Multisectum at different temperature is obvious, and the proper temperatures(25/15℃ and 30/20℃) can mitigate the effects of drought stress on seed germination and improve the drought tolerance of seeds.After drought stress was relieved, seed germination ability has certainly recovered, which means that many seeds are dormant in the harsh environmental condition, but they can fast germinate when condition become appropriate. The response of seed germination can ensure seeds avoid adversity in dry season successfully, which is conducive to the continuation of species.