Natural flooding is one of the major factors affecting vegetation
dynamics in many regions of the world. The
Flooding Pampa Grasslands (Argentina) are frequently exposed to flooding
events of diverse intensity and
duration, some of which Leontodon taraxacoides, an exotic dicot.
frequent in these grasslands, seems to
survive. Its responses to four different water depths (0, 1, 7 and 13 cm)
were studied. The results indicate that
plants in conditions of total submergence (depth of 13 cm) did not survive.
In less severe flood conditions,
increases in the leaf insertion angle resulted in the maintenance of a
large proportion of the total leaf area above
the water. Differences in leaf length and a decrease in the width and the
proportion of lobes per leaf were also found
under partial submergence conditions (depth of 7 cm). Root and leaf aerenchyma,
present in unflooded
plants, showed a significant increase in flood conditions. In spite of
the anatomical and morphological
responses, total biomass and leaf area were severely affected by water
depth. Control plants allocated more biomass
to reproductive organs, while partly submerged plants allocated more to
leaves and less to reproductive organs.
Mature L. taraxacoides plants presented a wide range of plastic
adjustment as a survival strategy in soil
anaerobiosis, and appear to be able to survive short spring floods in a
vegetative state; in contrast, they might not
tolerate total submergence conditions imposed by more intense and long-lasting
floods.