Physio-Biochemical Responses of Sweet Cherry Leaf to Natural Cold Conditions.

Trees of the sweet cherry cultivar 'Grace Star' (Prunus avium L.) were exposed to low temperatures without frost for two consecutive nights under natural conditions 36 d after flowering, to study the effects on the physiological properties and metabolic status of leaves. The response was studied by measuring chlorophyll fluorescence and gas exchange parameters and by analyzing chloroplast pigments (i) immediately after exposure, (ii) 24 h and (iii) 48 h later. The first exposure at 2.4 (±0.2) °C and a minimum of 0.8 °C elicited more changes than the second exposure at 4.9 (±0.3) °C and a minimum of 2.4 °C. After the first exposure, the maximum quantum yield of PS II (Fv/Fm), effective quantum efficiency of PS II, net photosynthesis (PN), stomatal conductance (gs), transpiration, and intercellular CO2 concentration were significantly lower, and after the second exposure, the content of chlorophyll b, total chlorophyll, ß-carotene, and lutein were lower. The content of antheraxanthin and zeaxanthin was higher immediately after both exposures, and that of antheraxanthin was also higher 24 h later. Recovery took longer in trees that were exposed twice. Fv/Fm recovered within 48 h, but the de-epoxidation state of the xanthophyll cycle pool, PN, and gs did not reach the level of controls, indicating that the stress effect lasted several days which is probably sufficient to cause fruit drop and reduce yield.

Summer pruning of sweet cherry: a way to control sugar content in different organs.

BACKGROUND: Sweet cherry trees (Prunus avium L.) of the cultivar Grace Star were pruned either in dormancy or in summer. The response was studied by analyzing the sugar content in different organs (flower bud, leaf, and fruit) at three sections of the canopy (inner, outer, and upper) using high-performance liquid chromatography. The effect of summer pruning was evaluated by measuring photosynthetic photon flux density (PPFD) and leaf chlorophyll content (SPAD). RESULTS: In this study, the timing of pruning had a significant effect on sugar content in flower buds, leaves, and fruit. Trees pruned in summer had higher glucose, fructose, sorbitol, and sucrose content in flower buds, higher glucose and fructose contents in leaves, and lower fructose, sorbitol, and total sugar content in fruit than in trees pruned at dormancy. Higher average PPFD and lower SPAD values were measured in the inner canopy of trees pruned in summer. All measured parameters were influenced by position in the canopy. The lowest fructose and sorbitol contents in the flower bud, the lowest content of glucose, fructose, sorbitol, total sugars and the highest SPAD values in the leaf, while less dark and lighter fruit were measured in the inner part of the canopy. CONCLUSION: Summer pruning affects sugar distribution in the tree by altering irradiation conditions within the canopy. Our results suggest that summer pruning is an effective technological measure to improve sugar content in the buds. A strong, well nourished flower bud is a good indication of high fruit production next season. © 2021 Society of Chemical Industry.

The Effect of Water Supply on Sweet Cherry Phytochemicals in Bud, Leaf and Fruit.

The influence of a water supply on the content of phytochemicals (sugars, organic acids, hydroxycinnamic acids, flavonols, flavanols and anthocyanins) in the bud, leaf and fruit of sweet cherry (Prunus avium L.) was studied in two growing seasons. In addition, the shoot length, yield efficiency and fruit weight were determined. The trees of the cultivar 'Regina' on Weiroot 72 or Gisela 5 rootstocks were either irrigated or non-irrigated. Irrigated trees received, in addition to rainfall, an amount of water equal to 100% of evapotranspiration, while non-irrigated trees received only rainwater (40% less). An analysis of phytochemicals was performed using high-performance liquid chromatography combined with electrospray ionization mass spectrometry. Irrigated trees had a higher content of total sugars in leaf and bud, higher content of total organic acids in the fruit, and lower content of total hydroxycinnamic acids, total flavonols and flavanols in the leaf and fruit. Irrigated trees also had higher shoot length, fruit weight and lower yield efficiency. The content of phytochemicals in bud and leaf was not affected by rootstock, but the fruit phytochemical composition, shoot length and yield efficiency were. The content of phytochemicals in the bud and leaf was influenced by the presence or absence of fruits. Our results show that irrigation, rootstock and the presence of fruits had an influence on the composition of phytochemicals in sweet cherry.

Response of chloroplast pigments, sugars and phenolics of sweet cherry leaves to chilling.

The aim of the present study was to evaluate the effect of post-flowering chilling of sweet cherry (Prunus avium L.) on the content of biochemical parameters in the leaf (chloroplast pigments, sugars and phenolics). The effect of chilling was investigated in two experiments. Potted 2-year-old trees of cv. 'Grace Star' and 'Schneiders' were exposed to one, two or three consecutive overnight chillings at an average air temperature of 4.7 °C (Experiment I), but in the following year only trees of 'Grace Star' were chilled at 2.2 °C (Experiment II), 3 to 7 weeks after flowering. The analysis of the biochemical parameters was performed by high performance liquid chromatography combined with electrospray ionization mass spectrometry. Chilling at 4.7 °C caused little or no stress, while 2.2 °C induced more intense stress with increased zeaxanthin, sugar and phenolic content in leaves, while exposure of trees to higher temperatures and closer to flowering showed no changes. Two or three consecutive overnight chilling periods increased the phenolic content and enhanced the accumulation of zeaxanthin in the leaves. Sucrose, sorbitol, fructose, total sugar, and total flavonoid content in leaves increased within 48 h after chilling. Zeaxanthin epoxidized within 24 h after one and 48 h after one and two consecutive overnight chillings.

Sugars and organic acids in plum fruit affected by Plum pox virus.

BACKGROUND: Plum pox virus (PPV) causes severe economic losses in stone fruit production, but little is known about its effect on plum fruit composition. In this study, the influence of PPV on sugars and organic acids was evaluated in a susceptible plum (Prunus domestica L.) cultivar. RESULTS: PPV infection significantly affected the content and composition of sugars and organic acids. The composition of necrotic tissue was modified the most. A short-time infected tree yielded fruit with similar sugar composition to fruit from a healthy tree, but the decline of organic acids was faster. Prematurely ripened symptomatic fruit had reduced fruit weight and low sugar content. CONCLUSION: Infected trees of the studied cultivar produce fruit of inferior quality. Fruits are not suitable for processing, especially when most of them exhibit visual symptoms of PPV infection. © 2016 Society of Chemical Industry.

Effect of Plum pox virus on chemical composition and fruit quality of plum.

The quality of fruit from PPV (Plum pox virus)-infected plum (Prunus domestica L.) trees was investigated during the last 3 weeks of ripening using healthy tree (T3), tree with short-term infection (T2), and tree with long-term infection (T1). The pomological variables (presence of necrosis on fruit, color of fruit, color of flesh, firmness, soluble solids content, and fruit weight) and composition of nutritive compounds (sugars and organic acids) and bioactive compounds (phenolics: anthocyanins, flavonols, and hydroxycinnamic acids) were evaluated. The results indicated that the PPV infection modified the ripening process (the most in T1) and the composition of nutritive and bioactive compounds in the healthy-looking part of the fruit. Long-term infected tree (T1) yielded fruit with the poorest pomological traits and with the most modified composition of nutritive and phenolic compounds. The short-term PPV infected tree also produced fruit with significantly altered phytochemicals composition, although the pomological traits had not changed significantly.

Phytochemicals in fruits of two Prunus domestica L. plum cultivars during ripening.

BACKGROUND: Plums are a rich source of nutritive and bioactive compounds. The objective was to evaluate the impact of fruit tissue (flesh and peel), ripening stage and cultivar on the composition of phytochemicals in plums (Prunus domestica L.) and to analyse the relation between total antioxidant activity (TAA) and the measured variables. RESULTS: The content of total sugars and total organic acids was higher in flesh but total phenolic content (TPC) and TAA was statistically higher in plum peel. The composition of sugars depended on fruit tissue, ripening stage and the cultivar. Ripening and fruit tissue affected the composition and concentrations of organic acids. TPC of 'Haganta' peel increased during ripening but there was no significant time trend for 'Jojo' peel and flesh of both cultivars. The composition of phenolics in peel depended on the cultivar, but in flesh on the cultivar and ripening. Ripening resulted in increased total anthocyanins and TAA in peel. TAA(peel) was positively correlated with TPC(peel) , total anthocyanins(peel), cyanidin 3-glucoside(peel) and peonidin 3-rutinoside(peel) in the cultivar 'Haganta'. CONCLUSION: The composition of phytochemicals in P. domestica fruit depends on fruit tissue, ripening stage and the cultivar. Peel contributes to the TAA on average 20 times more than flesh.

Sweet cherry pomological and biochemical characteristics influenced by rootstock.

Fruits of Lapins sweet cherry (Prunus avium L.) from 12-year-old trees on different rootstocks (F 12/1, Maxma 14, Piku 1, Edabriz, Gisela 5, Gisela 195/20, Weiroot 13, Weiroot 158, and Weiroot 72) were analyzed for pomological (fruit weight, % flesh of fruit weight, soluble solids content, titratable acidity, and firmness) and biochemical parameters (individual sugars, organic acids, and phenolic compounds) considering yield. For the first time, two procyanidins have been identified in sweet cherries using HPLC/MS: procyanidin B2 and procyanidin dimer (gamma(max) = 275 nm; [M - H](-) at m/z 577 and MS(2) fragments at m/z 425, 407, and 289). There were no significant differences between rootstocks in average yield per tree, except for Piku 1 (19.7 kg) with significantly the highest and Gisela 5 with significantly the lowest average yields per tree (7.7 kg). Significant differences in the measured parameters were ascertained among fruits of Lapins derived from different rootstock. Growing Lapins on Weiroot 72 and Edabriz resulted in high soluble solids content and fruit firmness. The lowest fruit firmness was measured on fruits from Weiroot 13, F 12/1, Gisela 195/20, and Maxma 14 trees. Fruits from Gisela 5 contained the lowest concentrations of glucose, fructose, sorbitol, sucrose, and citric acid, while fruits from F 12/1 contained the highest values of glucose, fructose, and shikimic acid. The content of phenolic compounds was the highest in fruits from Weiroot 72 tree, but the highest concentrations of procyanidin B2 and procyanidin dimer were ascertained in fruits from the Edabriz tree. Fruits from Weiroot 72 contained significantly higher concentration of phenols, bioactive compounds, compared to that in fruits from F 12/1. The content of individual and total anthocyanins did not differ significantly among rootstocks.