Growth trade-offs in Neyraudia reynaudiana in response to different levels of drought stress

The trade-off relationship is an important survival strategy in the plant’s life cycle. This relationship is important in plant growth processes because it helps us to understand the survival strategies in different habitats. In this study, the pioneer plant for soil and water conservation, Neyradia reynaudiana, was subjected to different drought stress treatments using the potting method. The growth differences and material distribution characteristics under different stress treatments were analyzed to explore the growth trade-off of N. reynaudiana under drought stress. The results showed that 1) there was no significant difference in the average plant height under different drought conditions. There was a significant difference (P < 0.05) in the number of leaves between moderate/severe drought stress, and adequate water supply was available only in the middle stage (60 d). A significant difference (P < 0.05) was observed in the number of tillers between severe and mild drought stress and adequate water supply only in the late stage (90 d). There were growth trade-offs between plant height growth and tiller, as well as tall growth and number of leaves, under drought stress conditions. In the initial stage of moderate and mild drought stress (30 days), plants tended to grow tall, and at longer stress times, they tended to grow tillers; in the initial stage of severe drought stress, they also tended to grow tillers. With long stress times, the plant height decreased and the number of tillers and leaves increased. 2) A significant negative correlation was observed between the distribution of water and dry matter in N. reynaudiana. With increasing drought stress, the dry matter ratio of the leaves, stems, roots, and the whole plant gradually increased, and the water content gradually decreased. As drought stress increased, the distribution of water, dry matter, and total biomass in the leaves gradually decreased, whereas that in the stems gradually increased. The proportion of dry matter distributed by the root system gradually increased. 3) Under different drought conditions, there was a trade-off relationship (as one decreases, the other increases) between plant height and tiller growth in terms of resource allocation. Drought resistance and survival probability were improved by increasing the investment in tillers, which reflects the growth strategy and investment trade-off mechanism of N. reynaudiana under drought stress.