Effects of Drought and Rehydration on the Physiological Responses of Artemisia halodendron

Abstract

Artemisia halodendron is a widely distributed native plant in China’s Horqin sandy land, but few studies have examined its physiological responses to drought and rehydration. To provide more information, we investigated the effects of drought and rehydration on the chlorophyll fluorescence parameters and physiological responses of A. halodendron to reveal the mechanisms responsible for A. halodendron’s tolerance of drought stress and the resulting ability to tolerate drought. We found that A. halodendron had strong drought resistance. Its chlorophyll content first increased and then decreased with prolonged drought. Variable chlorophyll fluorescence (Fv) and quantum efficiency of photosystem II (Fv/Fm) decreased, and the membrane permeability and malondialdehyde increased. When plants were subjected to drought stress, superoxide dismutase (SOD) activity degraded under severe drought, but the activities of peroxidase (POD) and catalase (CAT) and the contents of soluble proteins, soluble sugars, and free proline increased. Severe drought caused wilting of A. halodendron leaves and the leaves failed to recover even after rehydration. After rehydration, the chlorophyll content, membrane permeability, SOD and CAT activities, and the contents of the three osmoregulatory substances under moderate drought began to recover. However, Fv, Fv/Fm, malondialdehyde, and POD activity did not recover under severe drought. These results illustrated that drought tolerance of A. halodendron resulted from increased enzyme (POD and CAT) activities and accumulation of osmoregulatory substances.

Physiological Responses of Agriophyllum Squarrosum and Setaria Viridis to Drought and Re-watering

“…Its content is therefore closely related to the carbon xation e ciency of photosynthesis and, because photosynthate provides the energy source for metabolic responses, plays an important role in the drought resistance of plants. Chlorophyll uorescence is often used to analyze plant photosynthesis and photosynthetic physiology under stress 1 . Fm is the uorescence output when the reaction center of PSII is completely closed, and therefore re ects the maximum electron transfer through PSII 41 .…”

“…In mid-July 2019, one hundred and twenty pots of each species were randomly separated into three water treatments: plants were watered to 60 to 65% of eld capacity (the control), 40 to 45% of eld capacity (moderate drought, MD), 20 to 25% (severe drought, SD) of eld capacity. The severity was de ned based on the physiological responses of A. halondendron to soil water in a previous study [1]. From 17 to 20 July, we regulated soil water content within the speci ed range based on the weight of soil in each pot.…”

“…Thus, dryland ecosystems respond rapidly to precipitation changes 14 . Many studies have shown that plants under stress produce high levels of reactive oxygen species (ROS), which results in increased membrane permeability (due to peroxidation of membrane lipids), protein inactivation, and even death 1,15 . The accumulation of ROS in plants also activates a protective system of antioxidant enzymes, with increased activities of antioxidant enzymes such as catalase, superoxide dismutase (SOD) and peroxidase, which scavenge excess ROS to maintain a balance between an active oxygen metabolism and reducing the damage to cell membranes caused by ROS 16,17 .…”

“…The effects of drought are intricate due to the different combinations of environmental characteristics with plant characteristics, including species differences 1,18 . Mafakheri et al 19 reported that the chlorophyll a, chlorophyll b, and total chlorophyll content of three chickpea (Cicer arietinum) cultivars decreased dramatically under drought stress, that chlorophyll uorescence in olive decreased, and that the decreased chlorophyll uorescence in Brassica rapa resulted directly from a failure to recover from drought after rehydration 20 .…”

“…To supply some of the lacking knowledge, we designed the present study to explore the responses of a pioneer species and a climax species to drought using a pot experiment. The dominant species A. halodendron has been previously studied 1 . In the present study, we studied the pioneer species A. squarrosum and the climax species S.viridis to reveal their physiological responses to drought, with the goal of revealing their adaptions to an extreme desert environment and to support the restoration of desert vegetation in a degraded sandy land.…”