Neither advanced nor delayed germination is optimal for performance –
dynamic morphological plasticity in response to germination timing in
Abutilon theophrasti (Malvaceae)
Abstract
How plants respond to germination timing via morphological plasticity is
not well documented, in spite of its importance for understanding plant
strategies in dealing with natural environmental challenges of
complicacy, especially in the perspective of the entire life cycle of
plants. To address this issue, we conducted a field experiment with
Abutilon theophrasti by growing plants in four periods, as four
germination treatments (GT1~GT4), before measuring a
number of mass and morphological traits on them at three (or four)
growth stages (EX, I~III). Results the optimal
germination time for A. theophrasti was late spring, as plants that
germinated in this period achieved the maximum total mass, with the
highest stem and reproductive allocation and the lowest leaf allocation,
among plants of all germination treatments. 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. Results
suggested plants that germinated within the optimal period can maximize
their growth potential in relatively favorable conditions. 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 plasticity in a number of allocation and
morphological traits. Root plasticity may play a predominant or
fundamental role in plant response to environments, or it is crucial to
maintain root allocation stable, while stem or leaf allocation can often
be sacrificed depending on specific situations.