| Artemisia sphaerocephala and A.ordosica are important sand-fixation plants in the north of China. In this study, A.sphaerocephala comes from Dalate Banner (the origin area) of Kubuqi Desert and Wengniute Banner (the aerial seeding area) of Horqin Sandy Land, and A.ordosica from Dalate Banner too. The research focuses on the relationship between phenology and environmental factors, flowering phenology characteristics, quantitative character differences and inflorescence anatomical structure, etc. the main results are as follows:(1) The sprout period of two species was all in the end of February. A.ordosica and A. sphaerocephala of Dalate Banner entered leaf expansion in late April and early May respectively, while A. sphaerocephala of Wengniute Banner in around the middle of May. From sprout period to leaf-expansion period, A. sphaerocephala required longer time. The squaring period of A. ordosica was in the middle of June, the local A. sphaerocephala at the end of July, were approximately40days later than A. ordosica, and the squaring period of A. sphaerocephala from Wengniute Banner was in early August, a week or so later than A. sphaerocephala from the origin. From leaf-expansion period to the squaring period, A.ordosica took more than40days, and the time needed for A. sphaerocephala was twice more than A.ordosica. All the plants entered the first flowering dates after squaring period for about a month. The first flowering dates of A. ordosica and A. sphaerocephala in Dalate Banner began in the middle of July and late August respectively, while A. sphaerocephala’s in aerial seeding area began a week late. About two months later, the fruit mature period was came, A. ordosica in late September and A. sphaerocephala of two area in late October.(2) The main climate factors which influence A.ordosica and A.sphaerocephala were:leaf-expansion period, the sunshine time, rainfall, high temperature and low temperature of ten days. The main climate factors affecting the squaring period were the sunshine time, the low temperature and rainfall of ten days. The first flowering dates connected with sunshine, temperature, but the flowering stage of different years differed less than3days, thus the length of sunshine were the dominant factors. Every factor would have influenced the fruit mature period, but not obviously. In general, the temperature and sunshine are the primary factors effected the phonological phase of two species.(3) According to the2012observation, the onset of A.sphaerocephala population in aerial seeding area started in August30, later than the origin area by5d (August25), while the A.ordosica’s was the earliest (July15); the flowering duration of A.sphaerocephala population in aerial seeding area was14d, and13d in the origin area, between which there were9d overlapping flowering, and A.ordosica had a longer flowering duration of16d. Compared with the2013observations, the flowering phenology and the flowering process of them were similar. They all exhibited a mass-flowering pattern and the flowering frequencies were unimodal. The lifetime of the capitulum of A.sphaerocephala and A.ordosica in Dalate Banner had a highest frequency of6d, while A.sphaerocephala in Wengniute Banner was the highest frequency of4d, and they all had the highest single flower life of1d. A.ordosica in Dalate Banner had the highest flowering synchronization index, but A.sphaerocephala was the lowest in aerial seeding area, obviously lower than that in origin area. The flowering order of the capitulum at secondary inflorescence branches was basically similar. The first flowering positions were all near the base of branches, but the frequency was not high, about8%. The flowering amplitude curves of them were all unimodal, with A.sphaerocephala and A.ordosica in Dalate Banner showing a normal distribution; while it was positive skewness in the aerial seeding area. The flowering onset of A.sphaerocephala in origin area was more concentrated, but final flowering of A.ordosica took a longer time. (4) On the main quantitative traits, A.sphaerocephala’s crown width in Dalate Banner was significantly greater than A.ordosica’s and A.sphaerocephala’s in aerial seeding area (P<0.01). The difference of reproductive shoots length were not significant after they stopping growth, but the A.ordosica vegetative shoots were much longer than A.sphaerocephala (P<0.01). The leaves length at the middle of the stem of A.ordosica (average4.50cm) had no significant difference as compared with the local A.sphaerocephala (4.74cm), but A.sphaerocephala in Wengniute Banner (3.78cm) was significantly lower. As to the leaf width, A.ordosica (4.64cm) was significantly greater than A.sphaerocephala (Dalate Banner2.64cm, Wengniute Banner2.89cm, P<0.01). About diameter of capitulum, A.sphaerocephala in Dalate Banner (2.38mm) and Wengniute Banner (2.46mm) were significantly larger than A.ordosica (2.21mm). The achene of A.sphaerocephala (length2.02mm, width0.94mm) was significantly greater than the A.ordosica(length1.45mm, width0.53mm, P<0.05).(5) As to the primary inflorescence branch length and the secondary inflorescence branch number on the primary inflorescence branch and the diameter of the secondary inflorescence, A.sphaerocephala in Dalate Banner all larger than A.ordosica, but the A.sphaerocephala in these two places had no significant difference. The angle between the secondary and primary inflorescence branches of A.sphaerocephala was more than50°and A.ordosica less than50°,the secondary inflorescence branches of A.sphaerocephala arranged on stems showed a large expanded conical shape and the A.ordosica showed a expanded conical shape, which reflected the growth of flowers shoots could make better use of the space resources.(6) The flower bud differentiation process of A. ordosica and A. sphaerocephala were similar, according to the form of growth cone on shoot tip and flower bud differentiation characteristic, the process could be divided into three periods:floral axis differentiation period, inflorescence differentiation period and flower organs differentiation period. The entire plant flower bud differentiation order was the top first after branching. For a single capitulum, the flower bud differentiation from the periphery to the center was a division and the trend was to the heart. The two kinds of plants had the same capitulum structure. Given the number of flowers, the capitulum edge female flowers of A.sphaerocephala were1-8pieces, more than A.ordosica (2-6pieces), and the central bisexual flowers were4-14pieces, close to the A.ordosica (5-15pieces). |
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