CONICET | Buscador de Institutos y Recursos Humanos

The morphological and physiological responses of willows to flooding have been characterized, but less is known about their responses during the post - flooding period. After the end of the stress episode, plants may modify some traits to compensate for biomass loss. The aim of this work was to analyze the post - flooding responses of willow under two different depths of floodwater. The hypothesis was that the physiological responses in the post - flooding period will be different according to the floodwater depth. Cuttings of clone Salix matsudana NZ692 were planted in pots in a greenhouse. The experiment started when the plants were 2 months old with the following treatments: control (C, watered to field capacity); plants flooded 10 cm above soil level (F10) and plants flooded 40 cm above soil level (F40). The flooding treatment lasted for 30 days and was followed by a recovery period of 28 days (post-flooding period).During the post-flooding period, photosynthetic rate and total leaf area were significantly higher in F40 than in C and F10 treatment. However, the relative growth rate in height was not significantly different between the treatments. This could be because flooding increased root mortality, and in the post flooding period the root to shoot ratio was still significantly lower in F40 compared with C and F10. It is likely that part of the carbohydrates in F40 were used to develop new roots to compensate for the losses, instead of increasing the growth in height. In addition, F40 had a lower number of xylem vessels with higher diameter compared with C treatment, but this did not affect significantly the xylem hydraulic conductivity.From our results, it is clear that the depth of the floodwater not only causes different responses during flooding. The effects persist into the post flooding recovery period, affecting the growth and physiology of willows once the stress episode has ended.