Conclusions
Our results showed that there is an optimal germination time, and it was
late spring in this study, when plants can maximize their growth
potential in relatively favorable conditions. Plants that germinated
earlier in spring used a longer time for vegetative growth and did not
outperform late-spring germinants, probably due to exposure to spring
drought and response to competition. Delaying germination into summer
led to a faster growth, increased leaf allocation, decreased stem
allocation, advanced reproduction and shorter life cycle, but further
delay of germination into late summer led to insufficient reproduction
and incomplete life cycle due to extremely short growth period. In
response to delayed germination, plants may first increase root
morphological traits before enhancing leaf morphological traits, in
order to achieve stable reproductive efforts. They may increase the leaf
allocation by producing more leaves than increasing individual leaf
mass, at the cost of reduced stem allocation, rather than root
allocation. These suggested root plasticity plays a predominant or
fundamental role in plant response to environments, probably
orientating, regulating and determining the responses of above-ground
organs. Therefore, it is more crucial for plants to maintain root
allocation stable, whereas mass allocated to stem or leaves can always
be deliberated and balanced depending on specific situations. In spite
of conspicuous disadvantages, plants with advanced and delayed
germinated were still able to use different strategies to better adapt
to subsequent environments, via modifying a number of allocation and
morphological traits. Plasticity in these traits may play an important
role in determining plant survival and success in face of the
environmental challenges due to inopportune germination timing.