Effects of water stress and NaCl stress on different life cycle stages of the cold desert annual Lachnoloma lehmannii in China

For a plant species to complete its life cycle in arid and saline environments,each stage of the life cycle must be tolerant to the harsh environmental conditions.The aim of the study was to determine the effects of water stress(water potentials of–0.05,–0.16,–0.33,–0.56,–0.85 and–1.21 MPa)and NaCl stress(50,100,200,300,400,500 and 600 mmol/L NaCl)on seed germination percentage,seedling survival and growth,juvenile growth and plant reproduction of Lachnoloma lehmannii Bunge(Brassicaceae),an cold desert annual that grows in the Junggar Basin of Xinjiang,China in 2010.Results indicated that low water stress(–0.05 and–0.16 MPa)had no significant effect on seed germination percentage.With a decrease in water potential,germination percentage decreased,and no seeds germinated at–0.85 and–1.21 MPa water stresses.Germination percentage of seeds was significantly affected by NaCl stress,and higher germination percentages were observed under non-saline than saline conditions.An increase in NaCl concentrations progressively inhibited seed germination percentage,and no seeds germinated at ≥400 mmol/L NaCl concentration.Non-germinated seeds were transferred from both PEG(polyethylene glycol-6000)and NaCl solutions to distilled water for seed germination recovery.The number of surviving seedlings and their heights and root lengths significantly decreased as NaCl stress increased.About 30% of the plants survived and produced fruits/seeds at 200 mmol/L NaCl concentration.Thus,seed germination,seedling establishment and reproductive stage in the life cycle of L.lehmannii are water-and salt-tolerant,with seedlings being the least tolerant.These tolerances help explain why this species can survive and produce seeds in arid and saline habitats.