Frost tolerance in apricot (Prunus armeniaca L.) receptacle and pistil organs: how is the relationship among amino acids, minerals, and cell death points?

Sprayed biodegradable liquid film improved the freezing tolerance of cv. Cabernet Sauvignon by up-regulating soluble protein and carbohydrate levels and alleviating oxidative damage

Most cultivars of Vitis vinifera L. are very sensitive to cold. As an exogenous protectant, Biodegradable Liquid Film (BLF) is considered to protect winegrapes from low temperatures and dry winds for safe overwintering. This study aimed to reveal the physiological and biochemical mechanisms of BLF regulating the freezing tolerance of wine grapes. Groups of ten-year-old vines (Cabernet Sauvignon) were sprayed with BLF in November 2020 and 2021, or left untreated as a control treatment, and field plant mortality after overwintering were investigated. Branch samples were collected monthly for determination of biochemical indicators. Dormant two-year-old cuttings (Cabernet Sauvignon) were also used for the determination of relative expression levels of key genes. The results showed that the application of BLF reduced the branch semi-lethal temperature in January and February samples compared with control, and reduced the mortality of above-ground parts, branches and buds. The physiological status of shoots was greatly affected by the climatic conditions of the year, but BLF treatment increased the levels of soluble protein and soluble sugar, and also decreased the content of superoxide anion and malondialdehyde at most sampling times. Correlation analysis showed that the differences in freezing tolerance between BLF and no treated overwintering(CK) vines were mainly related to peroxidase activity, soluble sugar, reducing sugar and starch content. Low temperature stress activated the over expression of ICE1, CBF1, and CBF3, especially for 12h. BLF treatment significantly increased the expression levels of CBF1 and CBF3 under low temperature stress. Overall, these results demonstrate that BLF treatment protects vines from freezing damage by upregulating osmo-regulatory substances and alleviating oxidative damage.

Differential thermal analysis reveals the sensitivity of sweet cherry flower organs to low temperatures

The frequency and severity of spring frosts increase during the budburst in many regions of the world as global warming increases. Variability in the freezing resistance of sweet cherry flower organs during the active growing period has been rarely documented, especially in regard to the sepal, pedicel, receptacle, petal, stamen, and pistil organs of flower at the deacclimation stage. The freezing resistance of flower organs of six sweet cherry cultivars was investigated at regular intervals from the first white stage through the full bloom stage using differential thermal analysis (DTA) for 2019-2020. For most of the cultivars, petal and stamen organs of flower exhibited higher freezing resistance than other flower organs. There were significant differences in frost tolerance among cultivars, and 'Van' and 'Wild Genotype' had a lower level of low temperature exotherms or critical temperatures (LT₅₀ values) in both stages, whereas 'Merton Late' was more sensitive to frost than other cultivars. Additionally, an increase in LT₅₀ values in all cultivars was observed with the progression of the budburst. The results in the present study can increase the certainty of decision-making regarding the timing and methods to increase the air temperature in orchards during spring frost events to prevent frost damage. Larger data sets are required to further validate our results, and future efforts should thus be focused on determining the critical temperatures of flower organs using different measurement techniques.