The strategies of plants germinating in the optimal time
Our results showed plants that geminated in late spring performed the best in total mass and reproduction among all treatments, and they had the highest stem mass and allocation, and the lowest leaf allocation. It is reported that early emergence can improve the performance and survival of plants (Abe et al., 2008; Afonso et al., 2014; Bianchi et al., 2019; Cogoni et al., 2013; Verdu´ & Traveset, 2005), due to the profits from a long growing season for growth and reproduction (Donohue et al., 2010; Stratton, 1992). Meanwhile, the climate and soil conditions in late spring should also be more favorable for rapid biomass accumulation, making them less likely to expose to environmental hazards than those germinated in earlier time of spring. Consequently, they can optimize performance in relatively more favorable environmental conditions, leading to an extensive vegetative growth and improved reproduction. In this term, plants that germinate early can have a strong competitive advantage over those germinate late, especially at high population densities (Miller et al., 1994; Orrock & Christopher, 2010). The planting density applied in this study was a little high (plants were sown with an inter-plant distance of 10 cm), which may cause some extent of competition, inducing additional stem elongation, especially for those germinated earlier in spring and late spring and when they grew to larger plant sizes.
The timing of germination determines the environmental cues plants expose to, such as day length, temperature and water availability, which influence the responses of life history traits (Huang et al., 2016; Wilczek et al., 2009). Plants can perceive and transmit the signals of changing photoperiod and temperature (Zhou et al., 2005), to promote time emergence, growth and reproduction to coincide with favourable conditions (Andrés & Coupland, 2012; Blackman, 2017). It suggests they are able to judge the environmental changes by these signals, and determine which strategy to use in dealing with the circumstances indicated by the environmental cues. Consequently, when they did not germinate within the optimal period, plants may still be able to adjust their growth strategy in exposure to unfavorable conditions due to advanced or delayed germination.