Molecular Plant Breeding 2025, Vol.16, No.1, 44-54 http://genbreedpublisher.com/index.php/mpb 44 Research Report Open Access Physiological Responses of Four Hedera Plants to High Temperature Tolerance TingZhang1 , PingLi 2, JialiWei 2 1 Shanghai Engineering Research Center of Sustainable Plant Innovation, Shanghai Botanical Garden, Shanghai, 200231, China 2 Shanghai Key Lab of Bio-energy Crops, College of Life Science, Shanghai University, Shanghai, 200444, China Corresponding email: zhangting@shbg.org Molecular Plant Breeding, 2025, Vol.16, No.1 doi: 10.5376/mpb.2025.16.0005 Received: 25 Dec., 2024 Accepted: 30 Jan., 2025 Published: 08 Feb., 2025 Copyright © 2025 Zhang et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Zhang T., Li P., and Wei J.L., 2025, Physiological responses of four Hedera plants to high temperature tolerance, Molecular Plant Breeding, 16(1): 44-54 (doi: 10.5376/mpb.2025.16.0005) Abstract Ivy is an important horticulture plant for three-dimensional urban greening, and heat stress is one of the important environmental factors limiting the normal growth of ivy. Studying the physiological response of ivy to high temperature stress will be of great significance for screening suitable varieties of ivy and increasing the diversity of urban three-dimensional greening landscape. Two-year cutting seedlings of four ivy varieties were cultured in an artificial climate incubator (20 ℃, 16 h light / 8 h dark) for two weeks, and then treated at 40 ℃ for 7 days. The morphological changes and physiological indexes, such as heat injury index, chlorophyll content, chlorophyll fluorescence parameters, MAD, proline content, CAT activity and SOD activity, were recorded at 0, 1, 3, 5 and 7 days. The heat resistance and heat resistance mechanism of the test materials were comprehensively evaluated through the membership function method. The results showed that the heat resistance of the four ivy species was ‘Sark’>‘Ingelise’>‘Wonder’>‘Golden Ivalace’. The chlorophyll content, maximum photochemical quantum yield (Fv/Fm) and apparent quantum transfer efficiency (ETR) of the four ivy species decreased with the increase of heat stress duration. While the content of MDA continued to increase, and the increase of MDA in heat tolerant varieties was smaller than that in heat sensitive varieties. However, the proline content, CAT activity and SOD activity increased first and then decreased. The peak value of proline content in heat tolerant varieties was later than that in heat sensitive varieties, and the SOD and CAT activities in heat tolerant varieties were significantly higher than those in heat sensitive varieties (P<0.05). Keywords Hedera; Heat stress; Physiological indicators; Heat resistance; Membership function 1 Introduction Ivy is a perennial evergreen vine belonging to the Araliaceae family and the Hedera genus. It can grow by climbing, creeping, and hanging due to its well-developed aerial roots and good spreading ability of branches. It is an excellent material for urban three-dimensional greening. At present, there are over 500 species and varieties of ivy in the world, most of which are distributed in Europe. Among them, the British ivy (Hedera helix L.) is the largest population in the ivy genus. Ivy belongs to the shade loving plant, and its most suitable growth temperature is 18 ℃~20 ℃. It is cold resistant (Metcalfe, 2005) and afraid of extreme heat. It usually grows extremely slowly or stops growing above 30 ℃, and is prone to pest infestations and even wilting at 35 ℃ and above. In the hot summer, high temperature becomes one of the important environmental factors affecting the normal growth of ivy. There are many types of ivy with diverse leaf colors and shapes, but there are less than 10 commonly used varieties in urban greening in China. Therefore, screening heat-resistant ivy varieties and exploring the heat resistance mechanism of ivy are of great significance for enriching the diversity of three-dimensional greening plants and improving the heat resistance of ivy. At present, research on the abiotic stress physiology of ivy mainly focuses on drought, low temperature, heavy metal, and salt stress, with little research on its high temperature stress. For example, drought stress can lead to an increase in the relative permeability of the plasma membrane and proline content of silver edge ivy (Zhang et al., 2015), and a significant decrease in the average and maximum net photosynthetic rate (Pn) of ivy leaves under drought conditions (Xia et al., 2010). Spraying 5 mg/L abscisic acid under low temperature stress can enhance the activity of antioxidant enzymes in Chinese ivy and alleviate the damage caused by low temperature stress (Xiong et al., 2022), while Rehm et al. (2014) found in spring in Switzerland that adult leaves of English ivy in forests are
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