Impacts of drought stress on the morphology, physiology, and sugar content of Lanzhou lily ( Lilium davidii var. unicolor )

Water shortage is a key environmental factor that negatively effects plant growth. Lanzhou lily ( Lilium davidii var. unicolor ) is a perennial herbaceous drought-tolerant crop widely used as a food and medicine in China. The effects of drought stress on plant growth, osmotic pressure, and secondary metabolite content differ. Here, we investigate alterations in basic physiological processes and in the accumulation of osmolytes by Lanzhou lily under drought stress. Plants were grown at three drought intensities, being irrigated at 5, 15, and 25 day intervals (either throughout the study or during specific growth stages). Water stress markedly decreased plant height and leaf length. With increasing drought stress, the chlorophyll content, bulb weight, and contents of soluble sugars, polysaccharides, and fructose decreased. In contrast, the proline, glucose, and trehalose contents increased under severe drought stress. In addition, glucose and trehalose contents differed significantly under drought stress at different growth stages, whereas other indicators differed significantly only under drought stress throughout the growth period. Our results demonstrate that Lanzhou lily may adapt to drought stress in different growth stages were different. During the shoot stage, the adaptation strategy was to reduce the growth of aboveground part to sustain the underground parts, but during the bulbs expansion stage Lanzhou lily appears to adapt to drought stress by consuming nutrients from underground bulbs to sustain the growth of the aboveground parts and complete the plant's life cycle and by changing osmotic regulation and the levels of secondary metabolites to improve resistance to drought stress.