Effects of Short-Term High Temperature on Gas Exchange in Kiwifruits (Actinidia spp.)

Abstract

Climate changes occurring today require detailed research of the effects of increasing temperatures on photosynthesis in different species and cultivars. Temperature variability is a crucial determinant of the yield and quality of plants, particularly when high-temperature episodes coincide with their growth and fruit development. The effect of high temperature (HT) on higher plants primarily concerns photosynthetic functions, but the sensitivity of photosynthesis to high temperature is not well-understood in kiwifruits. In this study, we designed a new environmental monitoring system to evaluate the effects of environmental factors on the photosynthetic physiology of different kiwifruit species and cultivars. A significant positive correlation was determined between the main photosynthetic indices of kiwifruits, such as transpiration rate and net photosynthetic rate. The net photosynthetic rate of commercial kiwifruit cultivars was strongly inhibited when the temperature exceeded 44.5 °C, and the leaves of kiwifruits were irreversibly damaged when the temperature increased to 52 °C. Kiwifruit cultivars with different ploidy levels (diploid, tetraploid and hexaploid) were found to be sensitive to high temperature, whereas tetraploids had higher HT resistance and hexaploids had the highest net photosynthetic rate. Further research showed that the HT tolerance of kiwifruits existed not only between species but also among cultivars. A. eriantha had the highest net photosynthetic rate at more than 44.7 °C, but those of A. deliciosa and A. arguta declined sharply as the temperature exceeded 43.5 °C. As a result, it was determined that high temperatures have important effects on the photosynthetic activities of kiwifruit plants with different ploidy levels, and that these effects can significantly change their development according to how they differ among different species/cultivars.

Quantification of Phenological, Physiological, and Morphological Response of Kiwifruit Varieties under Rainfed Conditions

“…During the 2019-2020 and 2020-2021 study periods at two locations, the morphological, and physiological parameters of different kiwifruit varieties varied, but the differences were minor as compared to those differences that were observed for phenology. Similar results were reported by Li et al [122], who concluded that hightemperature resistance varieties should be used in the future to have good morphological and physiological traits. Furthermore, Zhong et al [123] explored the growth and physiological responses of four kiwifruit genotypes to salt stress and evaluated the tolerance using PCA.…”

Response of Dahlia Photosynthesis and Transpiration to High-Temperature Stress

“…Under high-temperature stress, plants reduce the leaf temperature by regulating the transpiration rate (Tr) and stomatal characteristics [13], while stomatal opening is positively correlated with Gs and Tr [14]. Plants exhibit avoidance or acclimation mechanisms under short-term high-temperature conditions [15], and the Tr, stomatal opening, and Gs increase with increasing temperature [16]. Under long-term high-temperature conditions, plants prevent excessive water loss by reducing stomatal opening or even closing the stomata, resulting in reduced leaf water potential, Tr, and Pn [17,18] and thus protecting plants from high-temperature stress.…”

Editorial to the Special Issue “Eco-Physiological and Molecular Basis of Stress Tolerance in Plants”

“…However, the degree of HT-stress-induced reduction varied among different cultivars; thus, it is important to understand the physiological and molecular regulation of photosynthesis under HT stress. In a study, Li and his colleagues examined the physiological basis of HT-stress-induced reduction in photosynthesis in kiwifruit [ 10 ]. They found that a temperature exceeding 44.5 °C was detrimental to kiwifruits; nonetheless, kiwifruit cultivars with different ploidy levels (diploid and hexaploid) were found to be sensitive to HT stress, while tetraploids showed relatively higher HT tolerance, suggesting a positive correlation between polyploidy and variation in HT-induced reduction in photosynthesis [ 10 ].…”