Abstract
The aim of this study was to evaluate physiological responses to short-term heat stress in the leaves of traditional (Bistrica) and modern (Toptaste) plum cultivars. In this study, detached plum leaves were incubated at 25 °C (control) and 40 °C (stress). After 1 h of exposure to heat (40 °C), chlorophyll a fluorescence transients were measured, and several biochemical parameters were analyzed. Elevated temperature caused heat stress in both plum cultivars, seen as a decrease in water content (WT), but in the leaves of the cultivar Bistrica, an accumulation of proline and phenols, as well as an accumulation of photosynthetic pigments, suggest the activation of a significant response to unfavorable conditions. Conversely, in the leaves of Toptaste, a significant accumulation of malondialdehyde (MDA) and an activation of guaiacol peroxidase (GPOD), all together with a decreased soluble proteins content, indicate an inadequate response to maintaining homeostasis in the leaf metabolism. The impact of an elevated temperature on photosynthesis was significant in both plum cultivars as reflected in the decrease in performance indexes (PIABS and PItotal) and the maximum quantum yield of PSII (Fv/Fm), with significantly pronounced changes found in Toptaste. Unlike the traditional plum cultivar, Bistrica, in the modern cultivar, Toptaste, short-term heat stress increased the minimal fluorescence (F0) and absorption (ABS/RC), as well as Chl b in total chlorophylls. Additionally, the inactivation of RCs (RC/ABS) suggests that excitation energy was not trapped efficiently in the electron chain transport, which resulted in stronger dissipation (DI0/RC) and the formation of ROSs. Considering all presented results, it can be presumed that the traditional cultivar Bistrica has better tolerance to heat stress than the modern cultivar Toptaste. The cultivar, Bistrica, can be used as a basis in further plum breeding programs, as a source of tolerance for high temperature stress.
Highlights
Global climate changes strongly influence plant production worldwide
The lipid peroxidation, measured as MDA content as an indicator of stress severity, was significantly decreased in the leaves of the cultivar Bistrica exposed to the elevated temperature (11.76%), while in the stressed leaves of the cultivar Toptaste, the MDA content was significantly increased compared to the control for 9.21% (Figure 1c)
The presented results demonstrated significant differences between the plum cultivars in response to short-term heat stress
Summary
Global climate changes strongly influence plant production worldwide. Plum orchards are exposed to high temperatures, affecting fruit quality and yield. Cultivars with a better tolerance for elevated temperature will be the only choice in plum production worldwide because plum production is limited to field plantations. Studies on the physiological responses to high temperature and other stressors between traditional, i.e., autochthonous and modern fruit cultivars are rare. A few studies have showed that traditional fruit cultivars have better physiological responses, i.e., tolerance to drought than modern ones [1,2]. As the main source of assimilates translocated in fruit, leaves are critical tissue in unfavorable environmental conditions. Photosynthesis is considered to be one of the most heat
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