Lotus tenuis seedlings subjected to drought or waterlogging in a saline sodic soil

• Lotus seedlings are highly tolerant to water stress from deficit to waterlogging.
• Lotus seedlings tolerate salinity and regulate Na+ concentration in tissue.
• Lotus establishes early associations with AM fungi and Rhizobium.
• Lotus seedlings acquire early imprints to respond better to future stress episodes.

The growth response of Lotus tenuis seedlings to drought and waterlogging in a saline-sodic soil, the mobilization of Na+ in tissue, and the association with native AM fungi and Rhizobium bacteria were studied by means of two experiments under controlled conditions.In the first experiment, we tested the effect of the duration of waterlogging on seedlings very early after sowing, when they had the two cotyledons totally expanded and, in the second experiment, we tested the effect of water stress on seedlings of different growth stages, at a wide range of water availability in the soil, from deficit to water excess L. tenuis seedlings were able to deal with the intensity of water stress at very early growth stages. They established symbiotic associations with AM fungi and Rhizobium bacteria and regulated Na+ concentration in plant tissue to prevent leaf injury. The seedling strategy consisted in decreasing the shoot:root ratio under water deficit and increasing the shoot:root ratio under water excess.Lotus seedlings are highly tolerant to the combination of water and salt stress from early stages in their development and early plant establishment in adverse soil conditions is an important ability of L. tenuis seedlings to grow and survive longer within a grassland ecosystem.