Life history characteristics of bi-seasonal germinated plants of ephemeral Descurainia sophia

Descurainia sophia is an annual ephemeral plant with a bi-season germination strategy in autumn and spring. The study of its life history traits is helpful in understanding the life history adaptation strategies of ephemeral plants. This study compared the phenological traits, growth dynamics, biomass allocation, and reproductive output of spring-germinated plants (SGP) and autumn-germinated plants (AGP) of Descurainia sophia in Junggar Desert. Results showed: 1) Descurainia sophia exhibits the phenomenon of spring/autumn germination. The time from germination to the end-of-life history of AGP (250 d) was significantly longer than that of SGP (100 d). Spring is the rapid growth period, and the flower budding stage and full blooming stage of AGP and SGP are synchronized. 2) The plant height, root length, aboveground biomass, and underground biomass of AGP were significantly higher than those of SGP. The root length and underground biomass of the two species showed a slow growth trend with the phenological process, and the plant height and aboveground biomass showed an accelerated growth trend as the plant entered reproductive growth. 3) The root/shoot ratio of SGP was significantly higher than that of AGP. The root-shoot ratio of SGP and AGP decreased from 0.38 and 0.31 at the emergence stage to 0.11 and 0.09 at the maturation stage. 4) Plants invest in vegetative organs (leaves and roots) before mid-April, after which they enter reproductive growth, and the biomass allocation ratio of stems and reproductive organs gradually increases. The biomass distribution ratio of stems of AGP was higher than that of SGP, and the distribution ratio of fruits of SGP was higher than that of AGP. 5) The fruit number, seed number, and seed biomass of AGP were higher than those of SGP, and there was no significant difference in seed reproductive allocation. The germination strategy of Descurainia sophia in spring and autumn ensures that its seed germination behavior is dispersed in time and space and can prevent competition between its sibling offspring, which is of great significance for maintaining population stability and expanding population renewal.