不同黑莓品种的抗冻性分析

采用电导法测定了7个黑莓（Rubusspp．）品种及1个树莓品种（对照）经冷冻处理后电解质渗出率的变化,并用二项式和Logisties方程对测定数据进行了拟合。结果表明,经0℃至～35℃的冷冻处理后,7个黑莓品种枝条的电解质渗出率大多高于对照;黑莓品种‘Young’枝条的电解质渗出率相对较小。二项式的拟合度高于Logistics．方程,二项式拟合结果表明,供试黑莓品种的抗冻性均低于树莓品种‘Reveille’,其中黑莓品种‘Young’的抗冻性较强,LT50为-31．0℃;黑莓品种‘Brazos’和‘Arapaho’的LT50分别为-19．4℃和-19．9℃,抗冻性较弱。     

桂花开花进程中花瓣色素、可溶性糖和蛋白质含量的变化

以软叶丹桂(O smanthus fragrans‘Ruanye Dangu i’)、柳叶银桂(O.fragrans‘Liuye Y ingu i’)和四季桂(O.fra-grans‘Sijigu i’)3个桂花品种为试材,研究了桂花不同品种开花和衰老过程中的花瓣色素、可溶性糖和蛋白质等的变化。结果表明:(1)从初花期到盛花期再到衰老期,类胡萝卜素和花青素的含量先升高再下降,与花瓣颜色深浅变化一致,表明不同时期花色的变化主要由色素的含量变化所引起。(2)3个桂花品种花瓣的含水量、可溶性糖和可溶性蛋白质的含量均呈下降趋势,而花期较长的软叶丹桂比柳叶银桂和四季桂降幅要低,而柳叶银桂和四季桂之间差异不显著。     

基于生理指标与籽粒产量关系的小麦品种抗冻性分析

以20个冬小麦品种为材料进行盆栽试验,对其在低温胁迫条件下功能叶超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性,丙二醛（MDA）、可溶性蛋白、可溶性糖含量以及籽粒产量、千粒重和籽粒形态性状进行测定.结果表明：拔节初期麦苗经-4 ℃低温胁迫后,不同品种冬小麦籽粒形态性状和产量性状均发生变化,绝大多数小麦品种籽粒长宽比、圆度和不育小穗数均增加,籽粒等效直径和面积及千粒重和籽粒产量均下降.通径分析表明,拔节初期低温处理后,功能叶SOD活性和可溶性糖含量是影响籽粒产量的主导因素,其中SOD活性对籽粒产量的直接影响较大,直接通径系数为-0.578.以籽粒产量下降的百分数作为小麦抗冻性评价的标准,可将20个小麦品种划分为3类：强抗冻类型的济麦19、济麦20、良星99、山农1135、山农8355、泰山23、泰山9818、汶农6号和烟农21,弱抗冻类型的临麦2号、潍麦8号、烟农19和淄麦12号,而其余7个品种属中度抗冻类型.苗期综合评价值（D值）与籽粒产量下降的百分数之间呈显著负相关(r=-0.512*),说明小麦苗期抗冻性强有利于获得较高的籽粒产量.苗期是小麦抗冻性鉴别选择的重要时期.     

钙与钙调素对柑橘原生质体抗冻性的影响

钙与钙调素对柑橘原生质体低温锻炼过程中抗冻力的获得有影响。加钙残余螯合剂或钙调素（ChM）拮抗剂TFP,能明显抑制柑橘原生质体抗冻性的表达。钙离子载体A23187可提高未经低温锻炼的原生质体抗冻力,但该作用在钙调素拮抗剂TFP参入下则减弱,表明原生质体抗冻力的表达受钙和钙调素的调节。     

低温锻炼过程中柑桔原生质体抗冻性的变化

在低温锻炼过程中,柑桔原生质体抗冻性逐步提高,至第１２ｄ达最大,随后缓慢降低。同一品种胚性愈伤组织的原生质体的抗冻性比叶肉原生质体强。     

甜杨6-磷酸葡萄糖脱氢酶在抗冻性低温诱导中的作用

对-20℃低温锻炼及脱锻炼过程中甜杨(Populus suaveolens)幼苗的G6PDH、SOD和POD活性、MDA含量和半致死温度(LT50)进行了测定和分析.结果发现,低温锻炼在一定程度上提高了幼苗6-磷酸葡萄糖脱氢酶(G6PDH)、SOD和POD活性,降低了MDA含量和幼苗半致死温度(LT50).另外,将幼苗放回常温(脱锻炼)2 d能引起幼苗的G6PDH、SOD和POD活性的显著下降,并使LT50和MDA含量的迅速回升.结果表明,低温锻炼中G6PDH活性的增加有助于SOD和POD活性的提高,进而对幼苗的LT50和MDA含量的降低有明显的促进作用,G6PDH可能参与了SOD和POD活性的调节和抗冻性的低温诱导.     

低温锻炼过程中柑桔原生质体抗冻性的变化(简报)

在低温锻炼过程中，柑桔原生质体抗冻性逐步提高，至第12d达最大，随后缓慢降低。同一品种胚性愈伤组织的原生质体的抗冻性比叶肉原生质体强。     

黄淮海地区不同冬春性小麦抗冻能力及冻害指标Ⅰ.隆冬期不同冬春性小麦抗冻能力比较

通过两年室外盆栽和室内人工控制试验,建立了不同冬春性小麦品种死苗率与低温的定量关系,确定了隆冬期不同冬春性小麦品种死苗率达10%、20%和50%的临界低温以及抗冻能力密度.结果表明： 强冬性小麦品种抗冻能力最强,半致死温度最低（燕大1817为-21.5 ℃,京411为-21.2 ℃）,其次是冬性品种（农大211为-21.1 ℃,农大5363为-20.3 ℃）和弱冬性品种（郑366为-18.5 ℃,平安8号为-18.4 ℃）,春性品种抗冻能力最弱（郑9023为-15.4 ℃,偃展4110为-14.7 ℃）.当温度降低到冬小麦冻害发生临界温度后,温度每降低1 ℃,弱冬性小麦（郑366和平安8号）死苗率增量最大,分别增加16.8%和25.8%,冬性小麦（农大211和农大5363）死苗率分别增加14.7%和18.9%,强冬性小麦（燕大1817和京411）死苗率分别增加15.4%和13.1%,春性小麦（郑9023和偃展4110）死苗率分别增加13.8%和15.1%,说明冻害发生后若持续降温,弱冬性品种遭受冻害风险更大.     

不同小麦品种对低温胁迫的反应及抗冻性评价

以济麦19、济麦21、济南17等15个冬小麦品种为材料,对其在低温胁迫条件下功能叶和叶鞘超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性、丙二醛(MDA)含量与可溶性蛋白含量等生理指标进行测定,以功能叶各项指标的抗冻系数作为衡量抗冻性的指标,利用主成分分析、聚类分析对其抗冻性进行综合评价。低温胁迫条件下,不同冬小麦品种起身拔节期功能叶和叶鞘中SOD活性、POD活性和CAT活性均不同程度地上升,MDA含量和可溶性蛋白含量均下降。通过主成分分析和聚类分析,将15个冬小麦品种划分为3类:济麦19、山农8355属强抗冻类型;山农664、泰山9818、济麦21、济麦22、烟农24、烟农19、烟农21、汶农6号、鲁麦21、济南17属中度抗冻类型;其余3个品种(泰山23、聊麦18、临麦2号)属弱抗冻类型。     

高寒山区牧草根中丙二醛、渗透调节物、多胺季节动态与抗冻力关系研究

温带地区的高山多年生草本植物可在－３０℃组织结冰状况下生存,然而人们并不了解其抗冻的生理机理。本研究目的拟通过测定自然生境下生长的４种高寒山区禾本科牧草（无芒雀麦（Ｂｒｏｍｕｓ ｉｎｅｒｍｉｓ Ｌｅｙｓｓ．）、花雀麦（Ｂｒｏｍｕｓ　 ｓｉｎｅｎｓｉｓ　 Ｋｅｎｇ．）、垂穗披碱草（Ｅｌｙｍｕｓ ｎｕｔａｎｓ Ｇｒｉｓｅｂ．）、草地早熟禾（Ｐｏａ ｓｐｈｙｏｎｄｙｌｏｄｅｓ　 Ｔｒｉｎ．）根中渗透调节物、膜脂过氧化产物、多胺含量季节变化,以了解他们与牧草抗冻的关系。结果表明,在晚秋（９月１～１５日）牧草根中ＭＤＡ含量增高,尔后下降,冬季保持恒定。总碳水化合物（ＴＮＣ）,可溶性糖、脯氨酸、可溶性蛋白质含量随晚秋气温下降而增加,在１１月达到最高,尔后下降,且持续到翌年春季。随晚秋气温下降从９月到１１月根中多胺含量迅速增加,４种牧草平均增加１８０％,其中亚精胺（Ｓｐｄ）占多胺含量的５３％。在１１月牧草根中多胺几乎完全消失。上述物质在晚秋入冬增加正好与牧草抗冻锻炼时间相吻合,因而是植物抗冻适应的重要生理响应和植物越冬的低温保护物质。他们在降低细胞冰点、防止细胞结冰引起的膜机械伤害,抑制膜脂过氧化保护膜稳定性方面具有重要作用。     

The relationship between freezing resistance and fatty acid composition of yeasts

Abstract The relationship between freezing resistance and cellular long-chain fatty acid composition of 18 selected yeast strains was studied. All strains produced a series of saturated and unsaturated evennumbered fatty acids ranging from 14 to 20 carbons in length. The majority of the freeze-resistant yeasts were found among fermentative species with a content of oleic acid above 40%.     

Simulation of in situ freezing damage of the photosynthetic apparatus by freezing in vitro of thylakoids suspended in complex media

Chloroplast thylakoid membranes were isolated from leaves of unhardened and cold-acclimated spinach (Spinacia oleracea L.). For freezethaw treatment, the membranes were suspended in complex media composed to simulate the solute concentrations in the chloroplast stroma in the unhardened and hardened states of the leaves. In particular, high concentrations of amino acids were applied for simulating the hardened state. After frost treatment, photosynthetic activities and chlorophyll fluorescence parameters of the thylakoids were tested to determine the degree of freezing damage. The results revealed a pattern of freezing injury similar to that observed upon frost treatment of thylakoids in situ. A major manifestation of damage was the inhibition of photosynthetic electron transport. Uncoupling of photophosphorylation, which is the dominating effect of freezing of thylakoids suspended in binary solutions (e.g., containing one sugar and one inorganic salt), was also visible but less pronounced in the complex media. Thylakoids obtained from cold-acclimated leaves did not exhibit an increased frost tolerance in vitro, as compared with thylakoids from unhardened plants. The results, furthermore, indicated a strong protective effect of free amino acids at the concentrations and composition found in chloroplasts of hardened leaves. The presence of inorganic salts in the complex media slightly stabilized rather than damaged the membranes during freezing. It is concluded that inactivation of thylakoids in situ may be understood as the destabilizing action of the combined solutes surrounding the thylakoids, occurring when solute concentration is raised due to freezing of water.Abbreviations Chl chlorophyll - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - Hepes 4-(2-hydroxyethyl)-1-piper-azineethanesulfonic acid - PSI photosystem I - PSII photosystem II     

Effect of freezing and thawing on the distribution of lysosomal hydrolases in leaves of Solanum tuberosum L.

Density-gradient ultracentrifugation techniques showed that freezing and thawing of potato leaves resulted in a change in the density of subcellular particles containing acid phosphatase and acid ribonuclease (RNase). Gel filtration experiments were used to characterise the molecular forms of the hydrolases associated with the various cell fractions. Freezing and thawing promoted a release of a portion of the complement of acid phosphatase and RNase from the lysosomes to the supernatant fluid fraction of cell homogenates. The freezing treatment appeared to activate latent lysosomal RNase.     

Effects of salicylic acid and cold on freezing tolerance in winter wheat leaves

The effects of salicylic acid (SA) (0.01, 0.1 and 1 mM) and cold on freezing tolerance (freezing injury and ice nucleation activity) were investigated in winter wheat (Triticum aestivum cv. Dogu-88) grown under control (20/18 °C for 15, 30 and 45-day) and cold (15/10 °C for 15-day, 10/5 °C for 30-day and 5/3 °C for 45-day) conditions. Cold acclimatisation caused a decrease of injury to leaf segments removed from the plants and subjected to freezing conditions. Exogenous SA also decreased freezing injury in the leaves grown under cold (15/10 °C) and control (15 and 30-day) conditions. Cold conditions (10/5 and 5/3 °C) caused an increase in ice nucleation activity by apoplastic proteins, which were isolated from the leaves. For the first time, it was shown that exogenous SA caused an increase in ice nucleation activity under cold (15/10 and 10/5 °C) and control conditions. These results show that salicylic acid can increase freezing tolerance in winter wheat leaves by affecting apoplastic proteins.     

The role of ABA in freezing tolerance and cold acclimation in barley

The role of ABA in freezing resistance in nonacclimated and cold‐acclimated barley ( Hordeum vulgare L.) was studied. Eleven nonacclimated cultivars differed in their LT₅₀, ranging from −10.8 to −4.8°C. Sugars, free proline, soluble proteins and ABA were analyzed in nonacclimated cultivars and during cold acclimation of one cultivar. There was an inverse correlation between LT₅₀ and both ABA and sucrose contents. Exogenous ABA caused a decrease in the freezing point of leaf tissue in the cultivar with the lowest level of endogenous ABA, but not in the cultivar with the highest level, suggesting that ABA in the latter may be near the optimum endogenous level to induce freezing tolerance. Plants of cv. Aramir treated with ABA or allowed to acclimate to cold temperature increased their soluble sugar content to a similar level. The LT₅₀ of leaves of cold‐acclimated cv. Aramir decreased from −5.8 to −11.4°C, with biphasic kinetics, accumulating proline and soluble sugars with similar kinetics. The biphasic profile observed during cold acclimation could be a direct consequence of cryoprotectant accumulation kinetics. ABA and soluble protein accumulation showed a single step profile, associated mainly with the second phase of the LT₅₀ decrease. Thus, a significant increase in endogenous ABA is part of the response of barley to low temperature and may be required as a signal for the second phase of cold acclimation. Endogenous ABA contents in the nonacclimated state may determine constitutive freezing tolerance.     

Evolution of freezing susceptibility and freezing tolerance in terrestrial arthropods

Arthropods have evolved various adaptations to survive adverse seasons and it has long been discussed why some arthropods are freezing-susceptible and some are freezing-tolerant. However, which mode of frost resistance came first during the course of evolution? A commonly held opinion is that no choice of strategy has been offered in evolution, because each species of arthropod may have its own evolutionary and natural history, leading to cold-hardiness. Freezing tolerance is more frequent in holometabolous insect orders and partially used by certain vertebrates, like some terrestrially hibernating amphibians and reptiles. Supported by phylogenetic, ontogenetic and ecological arguments, we suggest here that freezing tolerance is more recent than freezing susceptibility in the course of arthropods evolution. In addition, we observe that three basic modes of freezing resistance in insect species exist in the field: (i) permanent or year-round freezing-susceptible species, (ii) alternative or seasonal freezing-susceptible/freezing-tolerant species, (iii) permanent or year-round freezing tolerant species.     

Stress-induced expression of cyclophilins in proembryonic masses of Digitalis lanata does not protect against freezing/thawing stress

Using proembryonic masses (PEMs) of Digitalis lanata Erh., it was demonstrated that cold, hormonal or osmotic stress, which increased freezing tolerance during cryopreservation, induced an increasing level of two peptidyl-prolyl-cis/trans-isomerases (PPIases). The difference in pI (9.2 ± 0.2 and 9.5 ± 0.2, ±SD; n = 3) allowed the separation of the two enzymes by free-flow isoelectrophoresis. Both were inhibited by cyclosporin A and thus belong to the cyclophilin family of PPIases. The enzymes differed slightly in their substrate specificity and their relative molecular masses of 18038 ± 4 Da (D. lanataCyp18.0) and 18132 ± 3 Da (D. lanataCyp18.1). Both cyclophilins were blocked N-terminally. Partial internal amino acid sequences from the two cyclophilins, with a length of 34 amino acids, displayed 82% sequence identity to each other. Pretreatment of PEMs with abscisic acid, sorbitol or a combination of both substances led to a 270 ± 30% elevation of the total cytosolic cyclophilin concentration determined with a cyclophylin affinity sensor. During the first 4 d of pretreatment, the total PPIase activity was enhanced up to 230 ± SD% compared with the control culture. The lag phase between maximal PPIase concentration after 4 d of pretreatment and maximal effect of freezing tolerance after 10 d of pretreatment indicated that increasing levels of cytosolic PPIases may be necessary to overcome the stress induced by hormones and osmotica during pretreatment but not to protect against freezing/thawing stress. Received: 17 September 1998 / Accepted: 29 January 1999