Chilling Injury in Cucumber Leaves in Relation to Temperature

An Arrhenius plot of the respiration rate of cucumber leavesshows a break at 12°C; below this temperature Q₁₀ is 5.7.Leaves can survive exposure to 10°C for a week, but if chilledat 8°C for 3 d they show some loss of fresh weight and leakelectrolytes when immersed in water. At 5°C there is a markedloss of water leakage of electrolytes within a few hours.     

Initiation and Development of Chilling Injury in Leaves of Chilling-Sensitive Plants

Based on author’s own and literature data, possible mechanisms of initiation, development, and reparation of cell damages in chilling-sensitive plants during and after chilling are reviewed. A conception of initiation and development of chilling injury, based on a key role of oxidative stress, is put forward. Possible mechanisms of structural and functional changes in cells of chilling-sensitive plants subjected to chilling stress are discussed.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 608–613.Original Russian Text Copyright © 2005 by Lukatkin.     

Overproduction of Photosynthetic Electrons is Associated with Chilling Injury in Green Leaves

Employing the non-invasive techniques of infra-red gas analysis and pulse amplitude modulated chlorophyll fluorometry, we determined the partitioning of photosynthetic electrons between photosynthetic carbon reduction and other reductive processes resulting in the formation of active oxygen species (AOS) in intact green leaves. This we studied in plant species that are adapted to two different agro-climatic conditions, namely the warm plains (76°36E, 9°32N) and the cool mountains (1 600 m a.s.l.) in the south Indian state of Kerala. Ground frost and low temperature were more harmful to those species adapted to the warm plains than the ones adapted to the cool mountains. Exposure to low temperature decreased leaf photosynthetic carbon assimilation rates and quantum yield of photochemical activity in species naturally adapted to the warm plains. High irradiances further aggravated the harmful effects of low temperature stress possibly by overproducing AOS. This resulted in severe peroxidative damage as inferred by the accumulation of malondialdehyde (MDA) in the leaves.     

Mechanism of Chilling Injury in Sweet Potatoes

1. 1. Both amounts of lipid phosphorus and acid-insoluble nitrogen in the mitochondrial fraction from chilling-injured sweet potatoes (var. Okinawa 100) were larger than in the fraction from healthy sweet potatoes. The N-amount appeared to be increased more by chilling-injury than the P-amount.

2. 2. Sweet potato, a tropical plant, showed lower value of the degree of unsaturation of fatty acids in mitochondrial fraction than white potato, a temperate-zone plant.

3. 3. The amount of unsaturated fatty acids of C₁₆, C₁₈ and C₂₀ as percentage of the total fatty acids was higher in mitochondrial fractions from chilling-injured sweet potatoes (var. Okinawa 100 and var. Norin 1) than in mitochondrial fractions from healthy sweet potatoes. However, in the case of white potato mitochondrial fraction no detectable difference was observed between storage at 0~1°C and at 10~14°C.

     

夜间低温胁迫后外源SA对恢复中黄瓜幼苗光合特性的影响

为明确低温胁迫后恢复过程中水杨酸(SA)对植物光合特性的影响,以黄瓜品种‘津研四号’幼苗为材料,通过沙培试验,研究了外源SA对夜间5℃低温胁迫后常温(25℃)恢复中黄瓜幼苗叶绿素含量、光合速率、叶绿素荧光参数、气体交换参数等的影响。结果显示:(1)与喷施清水处理相比,外源SA处理显著促进了夜间低温胁迫后的常温(25℃)恢复效果,显著提高了恢复速度和水平,表现在黄瓜幼苗叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)显著升高,黄瓜幼苗净光合速率在恢复6h时达到对照水平的82.18%。(2)外源SA还明显加快了恢复过程中黄瓜幼苗叶片最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)及非循环电子传递速率(ETR)的恢复,提高了非光化学猝灭系数(NPQ)值,增强了幼苗自身光保护能力。(3)外源SA也促进了黄瓜幼苗叶片表观量子效率(AQY)和羧化效率(CE)的恢复,它们在恢复2d时分别达到对照水平的92.59%和90.62%。研究表明,在夜间低温胁迫后的常温恢复过程中,外源SA可有效地促进黄瓜幼苗光合作用的恢复,增强其对低温环境的适应能力。     

Amelioration of Chilling Injuries in Cucumber Seedlings by Abscisic Acid

Exposure of cucumber seedlings (Cucumis sativus L.) to chilling temperature resulted in injuries such as increased leakage of cellular materials, loss of water and wilting. In addition, the development of the seedlings after the exposure to chilling was impaired. Abscisic acid applied to the seedlings prior to chilling significantly ameliorated these injuries.     

持续低温弱光对黄瓜叶片气体交换、叶绿素荧光猝灭和吸收光能分配的影响

持续常温弱光(25℃/18℃,l00umol m-2 s-1)、低温弱光(12℃/12℃,100 umol m-2 s-1和7℃/7℃,l00μmolm-2s-1)均导致黄瓜生长减慢或停滞、叶绿素含量、气孔导度和净光合速率、光合电子传递速率下降以及胞间CO2浓度上升.常温弱光和12℃弱光处理对光系统II的最大光化学效率Fv/Fm无显著影响,而7℃弱光处理导致Fv/Fm的可逆性下降.常温弱光和7℃、12℃弱光处理均导致了光化学反应速率的降低以及天线热耗散和反应中心过剩能量的增加.在胁迫后,12℃弱光0比7℃弱光更有利于植株光合功能的恢复.     

种子的吸胀冷害和吸胀伤害

概述了喜温植物种子吸胀冷害和吸胀伤害的表现及其在细胞溶质渗漏、呼吸代谢和细胞结构等方面的特点,并讨论和了吸胀冷害的机理。     

Characterization of alpha-Galactosidase from Cucumber Leaves

Two forms of alpha-galactosidase (alpha-d-galactoside galactohydrolase, E.C. 3.2.1.22) which differed in molecular weight were resolved from Cucumis sativus L. leaves. The enzymes were partially purified using ammonium sulfate fractionation, Sephadex gel filtration, and diethylaminoethyl-Sephadex chromatography. The molecular weights of the two forms, by gel filtration, were 50,000 and 25,000. The 50,000-dalton form comprised approximately 84% of the total alpha-galactosidase activity in crude extracts from mature leaves and was purified 132-fold. The partially purified 25,000-molecular weight form rapidly lost activity unless stabilized with 0.2% albumin and accounted for 16% of the total alpha-galactosidase activity in the crude extract. The smaller molecular weight form was not found in older leaves.The two forms were similar in several ways including their pH optima which were 5.2 and 5.5 for the 50,000- and 25,000-dalton form, respectively, and activation energies, which were 15.4 and 18.9 kilocalories per mole for the larger and smaller forms. Both enzymes were inhibited by galactose as well as by excess concentrations of p-nitrophenyl-alpha-d-galactoside sub-strate. K(m) values with this substrate and with raffinose and melibiose were different for each substrate, but similar for both forms of the enzyme. With stachyose, K(m) values were 10 and 30 millimolar for the 50,000- and 25,000- molecular weight forms, respectively.     

Physiological and Biochemical Studies of Chilling Injury in Bananas

The physiological changes in green bananas (cv. Sin-zun), which are very sensitive to chilling injury, were studied during and after exposure to low temperatures (4±1°C, 6±0.5°C) for various periods. While the fruits injured by chilling did not fail to produce CO₂ and ethylene, the pattern of both CO_2- and ethylene production in these chilled fruits (9 and 15 days at 6°C) after transfer to 20°C was not normal. The contents of acetaldehyde and ethanol in chilled fruits, both in peels and pulps, increased with the advance of chilling, injury. There was an accumulation of α-keto acids in the peels of chilled fruits. Only half the conversion of ¹⁴C (fed as succinic acid-1, 4-¹⁴C) to citric acid and isocitric acid was observed in chilled tissues as compared with healthy ones; the activity of citrate synthase in banana peels appears therefore to be inhibited by chilling injury. A histological study of the tissues showed that the browning substances (polyphenols) present in chilled fruits accumulate around the vascular tissues.     

果胶酶与桃果实冷害的关系

桃果实在８℃以下贮藏奶容易干化发绵、不能软化,甚至褐变。这种被称为絮败的冷害特征。与交质的异常代谢有关。果胶酯酶（ＰＥ）和多聚半乳糖醛权酶（ＰＧ）活性的异常导致果胶质不能正常卫解。文章介绍果胶酶与桃果实冷害的关系、桃果实ＰＧ基因克隆及其ＲＮＡ和蛋白质分析的研究进展,并对桃果实冷害发生机理研究中存在的问题作了讨论。     

Estimation of Chilling Sensitivity and Injury in Gloxinia Leaves by the Thermal Hysteresis of NMR Relaxation Times of Water Protons

Thermal hysteresis of longitudinal relaxation times (T₁) ofwater protons in leaf tissues of gloxinia was investigated bypulse nuclear magnetic resonance (NMR) spectroscopy. The profilesof T₁ hysteresis during a slow cool-warm cycle (20 to 0?C) variedwith the degree of chilling injury. General trends of T₁ changesupon warming were as follows: (1) a small increase of T₁ wasobserved when no chilling injury occurred or the degree of injurywas minor, (2) a large increase of T₁ occurred when injury increased,(3) a large decrease of T₁ occurred from the earlier stage ofwarming when serious injury occured. The sum of T₁ ratio (theratio obtained from the difference between the T₁ value in thecooling process and that of the wanning process for eight stepsof cool-warm cycle, divided by the former) reflecting T₁ increaseor decrease during the warming process was related to varietaldifference and seasonal changes of chilling sensitivity. Therefore,T₁ hysteresis can be used as a diagnostic tool in detectingthe chilling sensitivity and the degree of chilling injury. (Received August 27, 1986; Accepted February 24, 1987)     

The Effects of Chilling Temperature on Photosystem II of Cucumber

Chilling (1 ℃ or 5℃, 16 h) treatment inhibited PSⅡ but not PSⅠ of photosynthesis in cucumber, a chilling sensitive plant. Oxygen evolution, variable fluorescence, and DCIP photoreduction were inhibited significantly, and the latter two could be recovered to the control level by adding artificial electron donors. These results suggest that chilling temperature damages PSⅡ of cucumber only on the oxidizing side and does not affect its reaction center.     

多胺与枇杷果实冷害的关系

应用薄层－荧光法测定多胺含量研究其与枇杷（Ｅｒｉｏｂｏｔｒｙａ ｊａｐｏｎｉｃａ Ｌｉｎｄｌ．ｃｖ．Ｄａｈｏｎｇｐａｏ）果实冷害的关系。果实在℃下贮藏时,精胺（ＳＰＭ）和亚精胺（ＳＰＤ）含量逐渐下降,但ＳＰＭ在２周后迅速回升并于第３周时达到高峰,随后又迅速下降,ＳＰＭ在３周后反弹上升。腐胺（ＰＵＴ）含量在前２周缓慢上升,２周后迅速积累并于第３周时形成高峰,随后也迅速下降,贮藏３周后的果实出现明显产     

Polyamine Changes and Chilling Injury in Cold-stored Loquat Fruits

Free polyamine levels (spermine (SPM), spermidine (SPD), and putrescine (PUT)) were determined using thin-layer chromatography and fluorometric method in loquat (Eriobotrya japonica Lindl. cv. Dahongpao) fruits stored at 1℃ and 12℃ and in postharvest SPM treated fruits stored at 1℃ respectively to investigate the relationship between changes in polyamines and chilling injury. In the loquat fruits stored at 1℃, SPM level decreased gradually in the first two weeks, then increased sharply and reached a peak value after three weeks, thereafter it decreased rapidly. SPD level decreased steadily during the first three weeks and increased significantly afterwards. PUT level evolved in a similar way as the SPM level did except that it increased slowly in the first two weeks. The fruit showed symptom of chilling injury manifested as flesh leatheriness after three weeks. However, no significant increase and decrease of these three polyamines was detected during storage at the nonchilling temperature (12℃). The SPM-treated fruits maintained high levels of SPM and SPD and remained low level of PUT during storage at 1℃, and no symptom of chilling injury was observed. These results suggested that the increase in SPM level in response to chilling exposure might serve as a defense mechanism against chilling injury while the accumulation of PUT could be a cause of the stress-induced injury and the increase in SPD level could be a consequence of this kind of stress.     

Accumulation of Putrescine during Chilling Injury of Fruits

Putrescine (Put) increased 68% in lemon (Citrus limon (L.) Burm. f. cv Bearss) flavedo, 39% in grapefruit (C. paradisi Macf. cv Marsh) flavedo, 49% in grapefruit juice, and 149% in pepper (Capsicum annuum L. cv Early Calwonder) pericarp when fruits were stored at chilling temperatures. In lemon flavedo, the coefficient of correlation (r²) between Put concentration with severity of chilling was 0.90 and Put levels almost doubled; the injury index going from 1 to 2 units. Pepper pericarp, which was the most chilling-sensitive tissue tested (injury index going from 1 to 3.8 units), showed the greatest difference in Put accumulation (166 to 413 nanomoles per gram fresh weight) between storage temperatures of 7.2 and 1°C. The least difference (338 to 470 nanomoles per gram fresh weight) was found in grapefruit flavedo between storage temperatures of 15.5 and 4.4°C; the injury index going from 1 to 1.3 units.