Plantain (Plantago lanceolata L.) leaf elongation and photosynthesis rates are reduced under waterlogging.

Plantain (Plantago lanceolata L.) has been identified by the New Zealand dairy sector as an option for reducing nitrogen losses from grazed pastures. However, there is growing concern over its poor persistence. Reports have suggested that plantain doesn’t tolerate waterlogged soils, however there is little scientific evidence to support those claims. Thus, this study aimed to investigate the impact of waterlogging on plantain growth and survival. In a glasshouse, three water treatments were applied to plantain plants in pots: control (optimal watering), wet (soil at field capacity), and waterlogged (water table 5cm below the surface) for 39 days, before 27 days under control watering. Leaf elongation and photosynthesis were measured during the experiment. The mean leaf elongation rate of waterlogged plants was 37% lower than control plants during the stress period, but not significantly different than control plants during the recovery period. Waterlogging reduced the rate of photosynthesis in plantain leaves by 15% on average in comparison with control watering during the stress period, however waterlogged and control plants had a similar mean photosynthesis rate during the recovery period. The results show that plantain growth and photosynthesis were significantly limited under waterlogging, however the rapid recovery of these processes following the removal of stress suggests that important physiological functions remained in-tact under waterlogging, possibly due to a tolerance mechanism. These findings suggest that while waterlogging may cause limitations for plantain growth, there is no evidence to suggest that it could cause irreversible damage to plants and thus prevent their recovery.