Submergence of forage legumes: Lotus species show better tolerance than Trifolium and Melilotus species due to their superior recovery after stress

Abstract

Climate change is leading to increased heavy rainfall, making plant submergence in flood-prone pastures more common. Forage legumes play a vital role in boosting herbage production and quality, especially when grown with grasses in low nitrogen input areas. However, their tolerance to complete submergence and subsequent recovery remains poorly understood. This study evaluated eight forage legumes after 5 or 10 days of complete submergence: (1)Lotus tenuis; (2) Lotus corniculatus; (3) Lotus japonicus; (4) Trifolium repens; (5) Trifolium fragiferum; (6) Trifolium pratense; (7) Trifolium michelianum; and (8) Melilotus albus. We assessed physiological and growth traits related to tolerance and recovery. All species survived except M. albus and T. michelianum. For the six surviving species, growth parameters linked to recovery were more prominent in Lotus species than in Trifolium species. Lotus species maintained higher biomass, improved stomatal conductance, and increased chlorophyll concentration in young leaves, along with a quicker recovery of PSII efficiency. In contrast, T. pratense showed the least tolerance and recovery, indicating its unsuitability for waterlogged areas. L. tenuis emerged as the most promising species for submergence tolerance, with L. corniculatus also showing potential, particularly in areas prone to short-term flooding.