Abstract
Paeonia ostii is an economically important oil crop, which has been widely cultivated in the middle and lower reaches of the Yangtze River in China in recent years. Although P. ostii is highly adaptable to the environment, the prolonged high summer temperature in this region severely inhibits its growth, which adversely affects seed yield and quality. In this study, P. ostii plants were subjected to 20°C/15°C (day/night) and 40°C/35°C (day/night) temperatures for 15 days. The changes in physiological and biochemical indicators of P. ostii under high-temperature stress were initially investigated. The results showed that with the deepening of leaf etiolation, chlorophyll a and chlorophyll b concentration, carotenoid concentration, Soil Plant Analysis Development (SPAD) values and leaf relative water content decreased significantly, while both relative electrical conductivity (REC) and free proline concentration showed an upward trend. Meanwhile, the continuous accumulation of reactive oxygen species (ROS) in P. ostii plants, led to an increased activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX). Moreover, with the extension of the high-temperature treatment, the anatomical structures of P. ostii were destroyed, resulting in a decreased photochemical efficiency of the photosystem II (PSII) reaction center and photosynthesis was inhibited. Taken together, these results provide reference values for understanding the physiological response of P. ostii to high-temperature stress and establish a foundation for further research on the relevant underlying molecular mechanisms.
Highlights
The continuous progression of modern human civilization is accompanied by the burning of a large number of fossil fuels, which increases the concentration of greenhouse gas and has led to global warming [1]
Most P. ostii research is devoted only to cultivation techniques and the production of seed oil [12,13,15], while physiological responses of P. ostii to high-temperature stress have rarely been reported. In this experiment, potted seedlings of P. ostii were studied and we evaluated the physiological response of P. ostii to high temperature, including the plant phenotype, chloroplast pigment concentrations, leaf relative water content, accumulation of reactive oxygen species (ROS), relative electrical conductivity (REC), free proline concentration, antioxidant enzyme activities, photosynthetic characteristics, chlorophyll fluorescence parameters and leaf ultrastructure
The chlorophyll (a + b) concentration of the high-temperaturetreated leaves decreased to 34.50% on day 15; the chlorophyll a and chlorophyll b concentrations decreased to 32.05% and 39.91%, respectively, and showed significant differences in each period
Summary
The continuous progression of modern human civilization is accompanied by the burning of a large number of fossil fuels, which increases the concentration of greenhouse gas and has led to global warming [1]. In 2011, the US Environmental Protection Agency indicated that global temperatures could rise by 2.23–6.63°C by the 21st century [2]. High temperature has been considered a common abiotic stress, that can adversely affect plant growth and development [3]. Plants can rapidly sense changes in environmental temperature and respond quickly [4]. Similar to other abiotic stresses, high temperature can cause leaf curling, leaf folding, and dehydration of plants [5]. The oxidation of proteins, lipids and nucleic acids under high temperatures leads to cellular damage, which is a direct consequence of excessive production of reactive oxygen species (ROS) [6]. High temperature has been the strongest constraint of crop production worldwide [9]
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