Seed Dormancy, Germination And Life History Traits Of Two Ephemeral Species

Iris tenuifolin Pall. and Turgenia latifolia (L.) Hoffm. are two ephemeral species distributed in fixedor stable sand dunes and grassland zone of northern Xinjiang，respectively. The former is a perennial andearly-spring flowering species with high ornamental value and the later is one species of annual weedswith serious harm. The primary aim of this study is to explore seed dormancy and germination of twospecies, and analyze the effects of germination time, water and plants density on life history of Turgenialatifolia. The main results are as follows:(1) Seeds of I. tenuifolin have water-permeable seed coats, and seeds are soft and appear fullyimbibed after120h. The embryo is underdeveloped in fresh matured seeds, but it begins to grow inautumn and develope fully before the radical emergence. Fresh matured seeds do not germinate underincubated condition in light and darkness at four temperature regims. With the prolong of storage time, thegermination percentage of seeds after removal of seed coats increases significantly in darkness at20/10℃,suggesting the seeds of this species have morphophysiological dormancy(MPD). GA3has no effect onseed germination and embryo growth, indicating the seeds have deep MPD.14%of the seeds cangerminate after they are buried in soil for three years, revealing the seeds of this species can formpersistent soil seed bank.(2)72%of T. latifolia seeds germinated in the autumn under natural temperatures condition, and therest seeds germinate in the next spring. This indicated that T. latifolia is a facultative winter annual. Theembryo in fresh matured seeds was underdeveloped and their germination percentage was verylow(≤20%)under incubated condition in light and darkness at four temperature regims, but it increasesignificantly after the storage of12weeks at20/10or25/15℃. This indicates high temperature is requiredfor loss of physiological dormancy(PD). The morphological dormancy of seeds can be released at5/2℃.GA3can promote seed germination effectively. All these results suggest seeds of T. latifolia have nondeepcomplx MPD. (3) The life cycle of the autumn germinated plants of T. latifolia is longer than that of the springgerminated plants significantly, and the total biomass, branch numbers and fruit numbers of the former arealso bigger than that of the later significantly; Flowering time, fruiting time and withering dates of theautumn germinated plants are earlier than that of the spring germinated plants. However, the growth rate ofthe spring germinated plants is faster than that of the autumn germinated plants, and the duration ofvegetative growth is shorter than that the autumn germinated plants. In the situation of same germinationtime and same density, the growth rate and total biomass of T. latifolia plants are bigger under wateringtreatment than under no watering treatment. In the situation of same germination time and same wateringtreatment, the height, branch numbers, fruit numbers and total biomass of T. latifolia plants are also biggerat low density than at high density. All these results indicate that the effect of germination time, soil watercontent and plants density on growth, development and reproduction of T. latifolia are different.