Study On Bi-seasonal Flowering And Fruit Set Characteristics And Its Ecological Adaption Of Two Species Tamarix In Xinjiang

This text was spread around the flowering characteristics, pollination biology, fruit set characteristics and the difference of seeds germination in the two kinds of florescences. It proceeded from the characteristics on bi-seasonal flowering and fruit set for Tamarix arceuthoides and T. ramosisima to discuss the adaptative mechanism of bi-seasonal flowering and fruit set characteristics to desert environment .The main results as follows:The florescence was different between the two Tamarix in spring and summer flowering period. The flowering time, florescence position, size and flower number were different. But at the level of single flower, there was insignificant difference in floral design and flowering dynamic. The spring flowering period with shorter and centralized properties was typical"mass-flowering pattern". The whole flowering period was less than 20 days with more florescence (flowers). However, the summer flowering period lasted longer time from early June to early September, which was called"extended -flowering pattern".The whole flowering period was visited by a great deal of insects. The visiting insects were divided into four kinds: Bees, Flies, Beetles and Butterflies. Bee(sApis indica and Bracohidae)and Flies (Syrphidae) were major spring visitor, while Bracohidae and Beetles were major summer visitor.Fruit set and seed set of spring flowering period was much higher than summer under natural conditions. The bagging experiments showed that, the fruit set of natural pollination was highest, and the ftuit set of net bags and paper bags were successively to bring down for two Tamarix. But ftuit set of net bags in summer flowering period was higher than that of spring.The two species Tamarix seeds in different flowering periods were very small and light with the characteristics of fast germination. There was no significant difference at external morphological characteristics. The final germination of two flowering periods seeds were not significant different at four thermoperiods——5/15℃, 5/25℃, 15/25℃and 25/35℃. But the speed of seed germination was affected by temperature, the lower thermoperiod inhibited germinate, while higher thermoperiod speeded up germinate.Both two Tamarix seeds were not affected by lower NaCl salinity (below 0.2mol/L), conversely which could hasten seeds germination. With the increment of salinity, the inhibitory extent for germination was increased till no germination completely. Both two Tamarix seeds of summer flower had stronger salt-tolerant germination. Seeds which were germinated in NaCl solution for 8 days recovered after being transferred to distilled water, except for that the T. arceuthoides summer seeds had lower recovered germination percentage in 0.60mol/L NaCl solution (less than 10%), but the others seeds couldn't recovered germination, bacause the seeds were losed vigor death by high salinity of NaCl solution. T. arceuthoides and T. ramosisima flowered and fruited consecutively, producing a large number of seeds and owning special germination strategy. It may be the most important characteristic of adaption to desertification environmental of frequently severe disturbance. It's also one of the important reasons of keystone species and widespread species in arid desert ecosystem.