Molecular Plant Breeding 2025, Vol.16, No.1, 44-54 http://genbreedpublisher.com/index.php/mpb 47 Figure 2 Changes of maximum photochemical efficiency Fv/Fm (A) and photosynthetic electron transfer rate ETR (B) of ivy leaves under high temperature stress The MDA content of four ivy plants showed an increasing trend with the duration of high temperature stress (Figure 3A). On the first day of high temperature stress, compared with the control, there was no detailed change in the MDA content of the four ivy varieties. However, as the duration of high temperature stress increased, the MDA content of the four ivy varieties continued to increase and the trend of change was roughly the same. By the 7th day, the MDA content of ‘Sark’ and ‘Ingelise’ increased by 67.9% and 71.7% respectively, with a significantly lower growth rate than ‘Golden Ivalace’ (107.0%) and ‘Wonder’ (128.7%). The Proline content in the leaves of four types of ivy showed a trend of first increasing and then decreasing after being subjected to high temperature stress, and the peak time of different varieties varied (Figure 3B). When high temperature stress was not applied, the proline content in the leaves of the tested ivy was relatively low. As the duration of high temperature stress prolongs, the proline content in the leaves gradually accumulates, and the degree of accumulation varies among different varieties. Figure 3 Effect of high temperature stress on malondialdehyde (A) and proline (B) contents in ivy leaves The proline content in the leaves of ‘Sark’ and ‘Ingelis’ reached its highest level on day 5 of high temperature stress, which was 5.93 and 3.41 times that of the control, respectively, and then decreased; The proline content in the leaves of ‘Wonder’ and ‘Golden Ivalace’ reached its highest level on the third day of high temperature stress, which was 3.81 and 3.46 times that of the control, respectively, and then began to decrease.
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