Abstract: Ephemeral plants are important plant groups in temperate deserts. Studies on their growth, reproduction, and resource allocation will help understand the life strategies of ephemeral plants. In this study, we examined phenological characteristics, growth dynamics and seed output of Veronica biloba L., an ephemeral plant species inhabiting the Junggar Desert. The results showed that: (1) V. biloba emerged on March 19 and entered reproductive growth at the four-leaf stage (32 d). Its development rhythm was fast, and life cycle was short (only 62 d). (2) The cotyledon turned yellow and fell off at full fruit stage, and the survival time lasted for 49 d. Root length increased rapidly in the seedling stage and stopped expanding in the reproductive stage. Root system was shallow. With the growth and development of plants, aboveground biomass increased rapidly, and belowground biomass increased slowly. The root-shoot ratio decreased gradually from 3.1 in seedling stage to 0.091 in fruit ripening stage. (3) Biomass of mature plants varied greatly (0.0126-0.2269 g), with a coefficient of variation of 0.8. There was a power function allometric relationship between the biomass of reproductive organs and vegetative organs, belowground biomass and total biomass. With the increases of total biomass, root-shoot ratio was negatively correlated with total biomass, the seed biomass linearly increased, but the reproductive allocation ratio remained at a relatively stable level (30.7%). The resource allocation strategy enables plants of all sizes to achieve a steady proportion of seed yield, which has important ecological implications to maintain population renewal and propagation of ephemeral plants.

Key words: phenology, growth dynamics, reproductive output, reproductive allocation