Morpho-anatomical changes and physio-biochemical responses of Carex siderosticta under water stress.

Abstract

Carex siderosticta Hance is an advantageous understory and lawn greening resource due to its strong environmental adaptability and ornamental value, but extreme climates render soil moisture a key growth-limiting factor. Thus, this study explored the response strategies of C. siderosticta to drought and flooding via pot water control and double-pot flooding simulations. Results showed that all the water stresses significantly inhibited the growth of C. siderosticta with increasing stress intensity; leaf and root biomass, water content and root activity decreased gradually, and root architecture parameters such as root length and root surface area decreased concomitantly. At the photosynthetic level, the photosynthetic pigment contents decreased, net photosynthetic rate (A_n), stomatal conductance (g_s), and transpiration rate (T_r) declined in a stress-dependent manner, while intercellular carbon dioxide concentration (C_i) increased correspondingly. In terms of physiological metabolism, osmoregulatory substances, including soluble sugar (SS), soluble protein (SP) and proline (Pro) accumulated continuously, and the malondialdehyde (MDA) content increases, which in turn activates the antioxidant system, leading to elevated activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) as well as increased contents of ascorbic acid (ASA) and glutathione (GSH). Anatomically, differential adaptive strategies were developed: under drought stress, the thickness of the leaf blade and epidermal cells decreased, and leaf bulliform cells shrank to reduce water loss; the root xylem vessel diameter was optimized to improve water transport, and the cortex thickness increased to enhance water conduction and absorption capacity. Under flooding stress, aerenchyma developed to alleviate hypoxia stress. This synergistic response involving morphology, physiology and anatomy is the key mechanism enabling C. siderosticta to tolerate both water deficit and water excess simultaneously. Relying on the synergistic strategy of morphological plasticity adaptation, physiological metabolism regulation and anatomical structure specialization to cope with water stress, this species not only exhibits excellent drought and waterlogging tolerance but also serves as a high-quality groundcover resource for water-saving greening in arid and semi-arid regions. It is also suitable for landscape construction and ecological restoration in areas with highly variable precipitation and frequent drought‒flood alternations, thus providing crucial support for water-saving and stress‒resilient greening efforts under the context of climate change.