Seed Polymorphism And Its Ecological Adaptive Strategy In Salsola Bracchita Pall.

In this paper, we observed and compared the characteristics of seeds germination, dispersal, seed longevity, the reproductive out ,the reproductive allocation of four types seeds of Salsola bracchita Pall., and discussed their survival strategies in the extreme environment of Zhungaer desert. The main results were as follow:(1)The fruits and germination, dispersal strategy: We discovered that Salsola bracchita Pall. are actually four different types of fruits (utricles) that differ in shape, size, seed color and external structure. The seed of four different types fruits were germinated in incubators with 12 h photoperiod and 12 h thermoperiods (dark/light) of 5/15℃, 5/25℃, 15/25℃for 20 days. Type A and B fruits can be easily dispersed by wind far distance from the mother plant. The germination percentages of type A and type B seeds are high and quickly at different alternating temperature. Type C fruits has thecal tepals without wings, and distributed nearby the mother plant. The germination percentages of type C seeds at different alternating temperature are all above 80%. Type D fruits also distributed nearby the mother plant. Type D seeds have physiological dormancy because germination is slow and low (< 20%). The scarification on the seed coat of type D seeds can hasten and increase the seed germination percentage and germination index in 3 different alternating temperature.(2) The temperature, time and germination characteristics: The experiments showed that effect of temperature on germination of type A,B and C fresh seeds is significant, indicating the low temperature significant inhibited germination of seeds, The traits would disappear after three types seeds stored for four months. The germination of type A,B and C seeds significant decreased with an increase of time, while the germination of type D seed increased with an increase of time.(3) The wings, the salt and germination characteristics: The experiments showed that the attached winged perianthes inhibited type A and B seeds germination. Winged perianthes formed a mechanical barrier to seed germination, and they required to be removed to enhance germination. The germination of type A,B and C was decreased with an increase in salinity, Increases in NaCl concentration progressively inhibited seed germination. Rate of germination decreased with an increase in salinity. Seeds that were incubated in NaCl solution for 13 d recovered after being transferred to distilled water and the germination percentage of recovery of type A and B seeds was higher than type C seeds. Indicating that the chief influence of high salinity is primarily osmotic to type A and B seeds, but it may be a combination of ion toxicity and primarily osmotic to type C seeds.(4) The size and the reproductive out: The results showed that different individuals have significant difference in plant weight, plant height, the number of branch class and node in its natural population. Four types dispersal units are significant change in the different size plant, The total number of dispersal units increases accompany with the increase of the size of plant. But There are significant changes among the ratio of four types dispersal units (A: B: C: D), which changes from 1:2.780:11.564 :1.857 to 1.506 : 2.663 : 1.052 : 1.(5) The size and the reproductive allocation: There was not significant difference between the mass of mean and the number of four types dispersal units, so these phenotypic traits were not size-dependent. The reproductive allocation of four types f dispersal units were significant change in the different size plant, The type A,B,D and total reproductive allocation increased accompany with the increase of the size of plant, but the type C dispersal units reproductive allocation decreased with the increase of the size of plant.