RESUMEN
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.
Asunto(s)
Prunus avium , Frío , Análisis Diferencial Térmico , Flores , TemperaturaRESUMEN
To the better management of spring frost problem in the apricot cultivars, evaluation of biochemical changes in flower and/or flower organs during bud break could be one of the key factors. In this study, the relationship between the biochemical metabolites such as amino acids and minerals in the receptacle and pistil organs of two different apricot cultivars (frost-sensitive and frost-tolerant) and their relative effects on the frost tolerance of the cultivars and their organs were investigated during full blooming stage. In both apricot cultivars, it was found that the cell death points (CDP) of flower receptacle (- 6.3 to - 8.4 °C) were at higher temperatures than the CDP of flower pistil organs (- 13.1 to - 14.5 °C). Receptacle organs in flower, therefore, had less tolerance to spring frost damage. In addition, significant differences in mineral and amino acid contents were detected both between apricot cultivars and between the receptacle and pistil organs of the cultivars. Amino acid and mineral contents were lower both in the freezing-sensitive apricot cultivar ("Mihralibey") and the freezing-sensitive organ (receptacle) in comparison with the freezing-tolerant apricot cultivar ("Igdir Salak") and the freezing-tolerant organ (pistil). A significant negative correlation was also observed between the mean CDP values and both amino acid and mineral contents in the receptacle and pistil organs of both apricot cultivars. A negative correlation was found between CDP values and glutamate from amino acids and N, K, and Mg from minerals, and also these were determined that they had positive effects on frost tolerance increase. An important finding from our work revealed that the amount of each mineral and amino acid allocated differently to the receptacle and pistil organs of the apricot cultivars. The understanding of the amino acids and the mineral dynamics may contribute to improving the tolerance of flowers of apricot or other deciduous species to frost damage during spring. In the future, we may conclude that protection strategies such as increasing amino acids and mineral content in the receptacle organ of flowers would be necessary to cope with the negative effects of spring frost.
Asunto(s)
Prunus armeniaca , Aminoácidos , Muerte Celular , Flores , MineralesRESUMEN
Many studies to date on the response of cherry flower buds to frost have focused on visual evaluations by observing tissue browning after frost event in the orchard and laboratory conditions but only little knowledge is available on the consequences of intracellular ice formation on cellular ultrastructure that underlies exothermic reactions during bud burst stages. In this study, the differential thermal analysis (DTA) method was used to investigate critical frost temperatures for the sweet cherry cultivars '0900-Ziraat', 'Erzincan Macar', 'Lambert', 'Vista', 'Stella', and 'Early Burlat' under laboratory-based freeze assays. In the course of our experimental study, frost tolerance or cell death points (CDPs) of flowers of six cherry cultivars were investigated in consecutive phenological stages from the start to the end of blooming, for 2 years. The frost tolerance of flower buds changed according to different developmental stages and cherry cultivars. Our results of frost tolerance tests performed on the cherry blooming stages are rather controversial. Our findings have shown that at the open cluster stage, the frost tolerance of the flower buds is very sensitive (mCDP = -1.18°C for 'Lambert'), while the first white stage has revealed an important increase (mCDP= -9.96°C for '0900-Ziraat') in the frost tolerance of those. Averaged over 2 years, the temperatures causing 50% frost damage for flower buds were -2.08 to -3.76°C at the side green stage, -1.49 to -3.22°C at the green tip stage, -1.18 to -1.98°C at the open cluster stage, -7.92 to -9.96°C at the first white stage, and -6.29 to -9.36°C at the full bloom stage in the range of six cultivars. Based on our test results, '0900-Ziraat' and 'Vista' were regularly classified as frost-tolerant cultivars. The flower buds of 'Lambert' and 'Early Burlat' have been regularly the most sensitive, while 'Erzincan Macar' and 'Stella' were ranked into the group of medium sensitivity. These results can help farmers to estimate possible frost damages on sweet cherry flower buds due to frost events at the investigated phenological stages.
Asunto(s)
Prunus avium , Análisis Diferencial Térmico , Flores , Congelación , TemperaturaRESUMEN
BACKGROUND: This study investigated changes in peroxidase (POX) and polyphenol oxidase (PPO) activities through adventitious rooting in hardwood cuttings of grapevine rootstocks. Three grapevine rootstocks with different propensity to produce adventitious roots were selected: recalcitrant (Ramsey), non-recalcitrant (Rupestris du Lot) and intermediate (99R) cultivars. RESULTS: The averages of root number at 65 days were 96 in Lot, 76 in 99R and 30 in Ramsey. Both enzyme activities characteristically increased before adventitious rooting, regardless of rooting ability of the rootstocks, and then decreased. POX activity increased in Ramsey cuttings at 22 days, in Lot and 99R cuttings at 14 days after planting, and then decreased gradually until 51 days. The highest POX activity was determined in Ramsey rootstock with the highest rooting ability and the lowest activity was determined in the rootstocks with the lowest rooting ability. PPO activity gradually increased in Ramsey rootstock cuttings from 10 days to 22 days, in Lot and 99R cuttings at 14 days, and then decreased until 51 days. A significant correlation was identified between high POX activity and adventitious rooting capability in rootstocks, but the same result was not determined with PPO activity. CONCLUSION: A recalcitrant rooting variety cannot increase POX activity sufficiently before rooting. Therefore applications that could increase POX activity in stem cuttings during rooting may facilitate increased rooting in such rootstocks.