Physiological Effects of Winter Rape (Brassica napus var. oleifera) Prehardening to Frost. II. Growth, Energy Partitioning and Water Status during Cold Acclimation

Prehardening of winter rape, i.e. its early growth in a reduced day temperature (+12°C) from emergence to the beginning of cold acclimation at chilling temperatures (the 1^st stage of cold acclimation), has a beneficial influence on frost resistance. In earlier studies it has been demonstrated that during prehardening, plants formed leaf rosettes and increased the photosynthetic efficiency at chilling temperatures. In the present study investigations were carried out on the effect of prehardening on the growth rate of the plants during the 1^st stage of cold acclimation, and the progress of selected physiological processes occurring during this stage and resulting in increased frost resistance. It has been demonstrated that a greater inflow of photoassimilates during the 1^st stage of cold acclimation results in greater increments of the dry mass of prehardened plants. These plants show also a distinct inhibition both of the elongation growth and the rate of expanding new leaves. The acquired energy is thus spent to a greater extent on the processes associated with increasing frost resistance, and not on growth. In prehardened seedlings, during the 1^st stage of cold acclimation, there have been observed in leaves a higher rate of both water content decrease and drop in the osmotic potential of the cell sap and water potential in the tissues. Also an increased accumulation of soluble sugars and free proline was noticed. However, the beginning of these processes was not observed during the prehardening period. Prehardening stimulated the effectiveness of the 1^st stage indirectly through changes leading to the increased amount of available energy and enabling the utilisation of the greater part of acquired energy in the cold acclimation process.     

Relationship between Prehardening, Photosynthetic Activity at Cold Acclimation Temperatures and Frost Tolerance in Winter Rape (Brassica napus var. oleifera). The Consequences for the Reliability of Frost Resistance Estimation under Controlled Conditions

The effect of prehardening (early stage of growth at moderate low temperatures (+12°C) during the day) on the reliability of frost resistance estimation in a controlled environment has been studied on three winter oilseed rape cultivars differing markedly in their field survival rate (Leo, Górczański and Idol). It has been also examined the relationship between the photosynthetic activity during the first stage of cold acclimation and the level of frost resistance observed in investigated cultivars. Presented results demonstrated that prehardening, which increases to a significant degree the effectiveness of the cold acclimation process, also increases the differences in cold hardiness between cultivars, and limits the magnitude of experimental errors made during frost resistance estimation under controlled conditions. In all studied cultivars, prehardening increases significantly the photosynthetic activity during cold acclimation. On the other hand, both in the prehardened and in the non-prehardened plants, no relation has been found between either gas exchange rates or chlorophyll 'a' fluorescence characteristics at low temperatures and cultivar ability for acclimation. Neither the existing differences in photosynthetic activity, nor the degree of photosynthetic apparatus acclimation to cold, which occurs during prehardening, are the factors responsible for the frost resistance variation observed between studied cultivars.     

Winter Hardiness, Frost Resistance and Vernalization Requirement of European Winter Oilseed Rape (Brassica napus var. oleifera) Cultivars within the Last 20 Years

Cultivars of European winter oilseed rape cultivated in the second half of the 1970s and in the mid-1990s were screened for their winter hardiness, frost resistance and vernalization requirement. A strong correlation between winter hardiness and frost resistance in both groups of rape has been noticed. Among oilseed rapes cultivated in the late 1970s, low erucic acid and particularly double zero cultivars were less winter hard than high erucic acid cultivars. Double zero cultivars were characterized by lower frost resistance and lower vernalization requirement. A significant correlation between vernalization requirement and both frost resistance and field survival has also been shown. Frost resistance of the 1990s (double zero) cultivars was higher than that of double low cultivars from the late 1970s. Their vernalization requirement was still small and did not correlate with either frost resistance or winter hardiness. It was concluded that reduction in the content of glucosinolates in the 1970s involved decrease in winter hardiness and vernalization requirement of cultivars. During the following 20 years winter hardiness of double low cultivars has been improved, but vernalization requirements have not changed. As a result no correlation between winter hardiness and vernalization requirement in contemporary canola cultivars has been observed.     

Photosynthetic Acclimation to Cold as a Potential Physiological Marker of Winter Barley Freezing Tolerance Assessed under Variable Winter Environment

Winter‐hardiness is a complex trait limiting cultivation of winter barley (Hordeum vulgare ssp. vulgare) with respect to the regions of temperate climate. In the present studies, we verified whether inexpensive and fast physiological markers characterizing photosynthetic acclimation to cold may provide robust characteristics of winter barley genotypes for improved frost resistance. Freezing tolerance of 28 winter barley varieties and advanced breeding lines were tested for three winters in field‐laboratory experiment and under fully controlled conditions. To increase the environmental variability of freezing tolerance, a part of the plants were also de‐acclimated under semi‐controlled conditions and re‐acclimated in laboratory before freezing tests. After controlled cold acclimation, apparent quantum yield of photosystem II (F_v/F_m) as well as photochemical (q_P) and non‐photochemical (NPQ) coefficients of chlorophyll fluorescence quenching were studied. Field‐laboratory method assessment of freezing tolerance gives distinct and even opposite results in subsequent years. Also de‐acclimation interacted with growth conditions in the field, giving different rankings of genotypes each year. The results obtained suggest that high level of freezing tolerance measured in laboratory, which is connected with photosynthetic acclimation to cold may be not sufficient for the expression of field resistance, especially when winter conditions are not favourable for cold acclimation.     

Photosynthetic Activity and Soluble Carbohydrate Content Induced by the Cold Acclimation Affect Frost Tolerance and Resistance to Microdochium nivale of Androgenic Festulolium Genotypes

The aim of the experiment was to verify whether changes in photosynthetic activity measured by means of chlorophyll fluorescence techniques and soluble carbohydrate level induced during pre-hardening and cold acclimation in androgenic forms of Festulolium are related to their winter hardiness and pathogen resistance. The study was performed on six androgenic genotypes of Festulolium, which differ in their degrees of winter hardiness. The chlorophyll fluorescence parameters and sugar content were measured in the control plants, pre-hardened at 12 °C and cold-acclimated at 2 °C. Cold acclimation at 2 °C, preceded by pre-hardening at 12 °C, induced a decline in maximum PSII quantum efficiency ( F _v/ F _m) and in non-photochemical quenching (NPQ). Exposure to 2 °C also resulted in reduced efficiency of energy conversion in photochemical processes ( q _p). The soluble carbohydrate amount increased in the susceptible genotypes and was associated with a decline in NPQ and current quantum yield of PSII (φ_PSII). In resistant plants, a decrease in the sugar content was observed, which could be explained by their consumption in metabolic processes initiated during cold acclimation. The changes in sugar content were associated with a decline in NPQ and q _p.     

Effect of Completion of Vernalization on Generative Development of Winter Rape (Brassica napus L. var. oleifera) Plants

Germinating seeds and young plants of winter rape var. Górczañski were vernalized for 56–63 days under conditions of 9-hour day, at the temperature 2 and 5 °C and in continuous darkness at the temperature 2 °C. After vernalization the plants grew under conditions enabling to complete vernalization: in a glass-house at the temperature day/night 15/10 °C and in semi natural conditions of open vegetation hall in the period from June till August. After sub-optimal vernalization further growth of the plants at lowered temperature increased its effectiveness (completion of vernalization). Depending on the degree of the vernalization of the plants the completion of their vernalization was both obligatory, i.e. conditioning the acquisition of the ability of generative development, and facultative i.e. accelerating this development. It has been demonstrated that the population of plants of the examined variety is strongly differentiated not only with respect of vernalization requirements in the particular plants, but also what regards the effectiveness of vernalization completion. New observations have been made indicating that the mechanisms controlling the successive phases of generative development, i.e. phase of forming flower buds and the flowering phase are not identical which may be interpreted as indicating that the "flowering factor" is polymorphous.     

Induction of Generative Development of Winter Rape (Brassica napus L. var. oleifera) in Relation to Vernalization Conditions and Age of Vernalized Plants

Germinating seeds and young winter rape plants were vernalized 56–63 days at 5 or 2°C under nine-hour days or in darkness. The highest percentage of generative plants and the most rapid flowering were obtained following the vernalization of young seedlings and germinating seed under conditions of nine-hour day, at 5°C. The least effective induction of generative development followed the vernalization at 2°C in continuous darkness. The vegetation period from the end of vernalization till the beginning of flowering was the shortest when four-week-old plants were vernalized under conditions of nine-hour day, yet the vegetation period from the beginning of germination to flowering was the shortest when seed germinating under conditions of nine-hour day were vernalized. The period was extending as older plants were being vernalized. Data indicating that the optimal temperature for vernalization of older plants is higher than for germinating seed and young seedlings were obtained.     

Comparison of Vernalization Requirements and Frost Resistance of Winter Rape Lines Derived from Double Haploids

Vernalization requirements and cold resistance of 13 lines of winter rape derived from doubled haploids obtained by androgenesis were investigated. The degree of vernalization requirements was examined in two parallel experiments. In the first experiment seedlings aged 2 weeks were vernalized during 63 and 35 days under controlled conditions, at 5 °C. In the second experiment the natural conditions of vernalization were differentiated by sowing the plants at four different dates in spring: March 15th, April 15th, May 15th, and at the latest date excluding vernalization, June 5th. The lines examined revealed differentiation of vernalization requirements that were similar in both experiments; all the lines required a period of exposure to cold before flowering. Cold resistance of lines was estimated in two successive series at −15 °C and −17 °C. Before testing the plants were kept in natural field conditions from the beginning of September until the middle of November. Testing of cold resistance was preceded by hardening under controlled conditions. Considerable differences in cold resistance was found in the forms investigated.
The results obtained do not show any relation between frost resistance and the degree of vernalization requirements, as the line characterized by the strongest winter habit of growth showed low cold resistance, whereas the lines which were closer to spring growth habit showed the highest level of cold resistance; the lines with the least vernalization requirements revealed the highest level of cold resistance. This conclusion can be confirmed by the significance of the correlation coefficients between the various indices defining the frost resistance and the indices of vernalization requirements.     

Temperature Before Cold Acclimation Affects Cold Tolerance and Photoacclimation in Timothy (Phleum pratense L.), Perennial Ryegrass (Lolium perenne L.) and Red Clover (Trifolium pratense L.)

The expected temperature rise in late summer/early autumn can change the conditions for acclimation and affect the winter survival of perennial crops. This study examined the effect of the temperature just before the onset of cold acclimation (pre‐acclimation) on freezing tolerance of timothy (Phleum pratense L.), perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L.) populations (both cultivars and breeding populations) adapted to either northern or southern parts of Norway. Using phytotron experiments, we studied whether increasing pre‐acclimation temperature delays growth cessation, affects photoacclimation and reduces freezing tolerance. Furthermore, we assessed whether these effects were related to the latitudinal adaptation of the plant material. The results showed that a rise in pre‐acclimation temperature decreased both cold acclimation capacity and photoacclimation in these species. This affected the freezing tolerance, which was reduced significantly more in northern‐adapted population of timothy and perennial ryegrass compared with southern‐adapted populations. Red clover was less affected by temperature changes than the grasses.     

甘蓝型油菜抗裂角品种(系)的选与分析

利用随机碰撞测试方法,对229份自交纯合的甘蓝型油菜品种（系）进行了抗裂角指数测定,以期筛选出抗裂角种质。结果表明,抗裂角性状在现有品种（系）中存在广泛变异,变异系数达114．4％。发现了2份抗裂角的品种（系）,占0．9％;较抗的资源占3．93％;处于中间状态的品种（系）占8．73％;易裂角资源占27．07％,极易裂角的品种（系）占59．39％。选择6个品种（系）进行了连续3年的测试,表明抗裂角性状由品种（系）的遗传特性决定,但受环境条件影响;随机碰撞法具有较好的重现性。简单相关分析显示,抗裂角指数与角果密度呈显著负相关,与角皮厚度、角果长度、角果宽度、角喙长度、角粒数呈显著正相关,但相关系数都很小。     

白菜型冬油菜抗寒性与生理生化特性关系

为了了解渗透物质与油菜抗寒能力的关系,本研究以2个白菜型冬油菜陇油6号和天油4号为试验材料,通过冷冻处理,对油菜根部相对电导率和叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、可溶性蛋白、丙二醛(MDA)等一系列生理生化指标进行了检测。结果表明,陇油6号(DQW-1)的抗寒能力强于天油4号,陇油6号和天油4号的SOD和CAT活性、可溶性蛋白含量、MDA含量随着温度的降低均呈现出先上升后下降的变化规律。低温下耐寒性强的陇油6号能保持较高的SOD酶活性、CAT酶活性、可溶性蛋白和较低的MDA含量。因此,SOD和CAT活性、可溶性蛋白和MDA含量在一定程度上能反映白菜型冬油菜的抗寒性。     

白菜型与甘蓝型冬油菜抗寒机理差异的研究

为探究白菜型与甘蓝型冬油菜抗寒机理差异的原因。以8个抗寒性不同的冬油菜品种为材料,采用大田试验和盆栽试验相结合的方法,待油菜长至5~6片真叶时,大田试验进行植物学形态,干物质积累量的测定,盆栽试验按24℃→10℃→5℃→0℃→-5℃→-10℃各48 h依次降温处理后测定生理生化指标。结果表明,白菜型冬油菜冬前生长点洼陷,幼苗匍匐生长,干物质积累主要集中在地下部分,其中白菜型冬油菜地下部鲜质量与地下部干质量较甘蓝型冬油菜平均增加了236.1%,263.0%,说明抗寒性强的冬油菜能够在营养生长阶段将光合有机产物优先运输到地下部,建立庞大的根系,为安全越冬提供代谢能量。随着温度的变化,不同类型冬油菜的生理生化活性有较大的差异,-5℃时陇油7号SOD活性较CK增加了10.7%,0℃时陇油7号CAT、POD活性较CK分别增加了24.7%,28.6%,而0℃时白菜型冬油菜SP含量较甘蓝型冬油菜平均增加了32.3%,-10℃时白菜型冬油菜的SS含量较甘蓝型冬油菜平均增加了71.4%,-10℃甘蓝型冬油菜MDA含量较白菜型冬油菜平均增加了52.8%,这说明抗寒性强的品种在低温条件下能够保护自身免受损伤,其中CAT、POD、SP是抵抗冷害的保护性物质,SOD、SS是抵御冻害的保护性物质。白菜型冬油菜比甘蓝型冬油菜在形态学及生理水平上都具有明显的优势,形态学上的优势使其有利于抵御极端低温天气,提供维持越冬及冬后返青所需的代谢能量;生理水平上,低温胁迫后保护性酶活性、调节性物质含量增加,能够有效地保护细胞膜结构,MDA含量减少,可以缓解低温对冬油菜叶片的伤害,从而保证高越冬率,为北方白菜型与甘蓝型冬油菜抗寒性研究提供理论依据。     

大蒜根系水浸液处理对连作甜瓜光合及荧光特性的影响

摘 要：【研究目的】为更有效的缓解甜瓜连作障碍问题,对甜瓜与大蒜间互作效应的研究在理论和应用上都有重要的意义。【方法】以甜瓜品种“金蜜”为材料,盆栽于连作与非连作土壤中,用大蒜根系水浸液处理幼苗,处理后30天,测定叶绿素含量、气体交换和叶绿素荧光参数。【结果】连作使甜瓜叶片光合色素含量、净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、蒸腾速率（Tr）下降,使甜瓜叶片初始荧光强度（Fo）增加,PSⅡ最大光化学效率（Fv/Fm）、PSⅡ实际光化学效率（ΦPSⅡ）和光化学猝灭系数（qP）下降。大蒜根系水浸液处理连作与非连作甜瓜,均提高叶片光合色素含量、Pn、Gs、Ci、Tr、Fv/Fm、ΦPSⅡ和qP,降低Fo。【结论】甜瓜不适宜连作,大蒜根系水浸液能促进甜瓜生长,缓解甜瓜的连作障碍。     

冷驯化不同阶段茶树DNA甲基化模式的变化

低温胁迫是影响茶树产量、生长发育和地域分布的重要环境因子之一,需要通过冷驯化的诱导来提高其抗寒性。DNA甲基化是植物表观遗传的重要方式,环境胁迫会引起植物DNA甲基化状态的改变。为研究DNA甲基化是否参与茶树的低温响应,本研究利用甲基化敏感扩增多态性技术(MSAP)和高效液相色谱法(HPLC),分析了不同冷驯化阶段茶树基因组DNA甲基化水平及状态变化。MSAP分析结果表明,50对选择性扩增引物在对照、驯化后和脱驯化样品中分别扩增出905、968和970个甲基化条带,总甲基化位点比例分别为50.6%、54.1%和54.2%。与未驯化的样品相比,冷驯化后和脱驯化的样品基因组DNA甲基化水平升高。HPLC的检测结果与MSAP结果类似。进一步分析甲基化模式发现,与对照相比,茶树冷驯化过程中同时发生了甲基化和去甲基化现象,但总体变化趋势表现为甲基化水平的增加。表明茶树在抗寒响应中出现DNA甲基化现象。     

Assessment of Sensitivity to Frost in Ochrus chickling (Lathyrus ochrus (L.) D.C.) by Chlorophyll Fluorescence Analyses

Ochrus chickling ( Lathyrus ochrus (L.) D.C.) is a promising feed legume for rain-fed farming systems in the Mediterranean environments of West Asia and North Africa (WANA) because of its drought tolerance and resistance to broom rape ( Orobanche crenata Forsk.). However, it is highly susceptible to cold and improving Its resistance would further improve its adaptation.
The potential of the chlorophyll fluorescence technique in screening for frost sensitivity in seedlings of five Lathyrus ochrus genotypes and one each of Vicia ervilia (L.) Wild and V. sativa L. was assessed by measuring the rate of rise in induced or variable chlorophyll fluorescence of fully developed leaflets after cold hardening in the open and subsequent exposure to freezing. The method differentiated the highly frost-susceptible L. ochrus genotypes from the more tolerant Vicia species. Testing the technique with nine genotypes of L. ochrus in which the plants were established, cold-hardened and frost-stressed under controlled conditions confirmed its sensitivity even to reveal the narrow inter plant differences that generally exist within a cultivar or genotype to frost. It is therefore considered as a useful screening technique for cold/frost tolerance in L. ochrus.     

Using Digital Image Analysis to Describe Canopies of Winter Oilseed Rape (Brassica napus L.) during Vegetative Developmental Stages

In our experiment digital image processing is used to predict characteristics in a winter oilseed rape canopy. A large series of images was taken in 2002–2003 in close intervals from a measuring area of 1 m². These images were automatically evaluated by a self‐written computer program analysing the red/green/blue colour channels of each pixel. The number of determined green pixels was then related to the total pixel count of the image. Image evaluation helped to determine canopy structure by digital image analysis subjected to several applications, i.e. soil coverage, leaf area index (LAI), dynamics of plant number during vegetative developmental stages including entire winter season. Furthermore, number of plants per m² and position of each plant were determined by image analysis. Results show that all parameters are dynamic during the vegetative developmental stages (germination–beginning of flowering) mainly depending on temperature. During the vegetative developmental stages number of plants varied. Emergence lasted 30 days resulting in large differences in growth and development of individual plants. During winter number of plants decreased due to longer phases of frost. Plant growth indicated by dynamics of LAI alternated with phases of cessation due to low temperatures above zero or frost. Reductions in soil coverage and LAI clearly started at daily mean temperatures below 5 °C. After the analysis, differences in LAI as well as changes in number of plants during the early phase crop development can serve (i) as input parameters to growth models, (ii) to improve canopy reflectance measurements by separating spectral signatures of soil and canopy and (iii) to determine and explain heterogeneities within the canopy.     

Chlorophyll Fluorescence‐Based Studies of Frost Damage and the Tolerance for Cold‐Induced Photoinhibition in Freezing Tolerance Analysis of Triticale (×Triticosecale Wittmack)

Freezing tolerance of 60 breeding lines of winter hexaploid triticale (×Triticosecale Wittmack) was studied in the field‐laboratory experiment. The experiment was repeated over three winters. The survey was also carried out in plants grown and cold‐acclimated in the laboratory. In both the experiments, plant survival analysis and chlorophyll fluorescence‐based studies on energy flows in photosystem II (PSII) (JIP‐test) after freezing of detached leaves were performed. In the laboratory experiment, the temperature of 50 % electrolyte leakage from leaves and the resistance against cold‐induced photoinhibition were additionally investigated. In the case of plants’ cold‐acclimated in the field, determination of the freezing tolerance of PSII gave similar results as the determination of freezing tolerance of whole plants. Both traits were strongly affected by genotype–environmental interactions, but these effects were less visible for PSII characteristics. In the laboratory experiments, a strong correlation between freezing tolerance and the tolerance for cold‐induced photoinhibition of photosynthesis was observed. The possibility of the use of chlorophyll fluorescence‐based techniques for the determination of freezing tolerance in triticale is discussed.     

Effect of Timing and Nitrogen Fertilizer Application on Winter Oilseed Rape (Brassica napus L.). I. Growth Dynamics and Seed Yield

The field experiments conducted on the grey‐brown podzolic soil in the four growing seasons (1998–2001) at Krzeslice Farm, central‐western Poland comprised seven fertilization variants: 80_NF + 80_CAN; 80_CAN + 80_CAN; 80_AN + 80_AN; 80_NF + 50_CAN + 30_CN; 80_CAN + 50_CAN +30_CN; 80_AN + 50_AN + 30_CN (where NF – nitrofos NPK; CAN – calcium‐ammonium nitrate; AN – ammonium nitrate; CN – calcium nitrate) and control (without N) applied in split rates at the beginning of spring regrowth (80 kg N ha^?1), stem elongation (80 or 50) and flower buds visible stages (30). The yielding effect of tested fertilization variants was significant in comparison with the control (2.24 t ha^?1). The highest mean seed yield (3.64 t ha^?1) was collected from 80_AN + 80_AN and 80_CAN + 80_CAN variants. Mean values of 4 years indicate that the second N rate division (80 + 50 + 30) decreased yield, although not significantly in comparison with these two N treatments. Plants grown on these treatments have developed different patterns of growth to yield the seeds. These patterns were characterized by very high crop growth rate during flowering (above 21 g m^?2 day^?1) and negative at maturation (down to ?2.5 g m^?2 day^?1). Plants fertilized with ammonium nitrate (80_AN + 80_AN) reached maximum growth rate earlier (65 days), which lasted longer (20 days) than plants fertilized with calcium‐ammonium nitrate (71 days lasting 17.5 days). Plants grown on the control treatment reached the highest crop growth rate within 79 days (14.8 g m^?2 day^?1), which lasted 15 days.     

Transfer of resistance to race 2 of Plasmodiophora Brassicae from Brassica napus to cabbage (B. oleracea var. Capitata). I. Interspecific hybridization between B. napus and B. oleracea var. Capitata

Summary Interspecific hybridization between Brassica napus L. (2n=38, a₁a₁c₁c₁) and B. oleracea var. capitata L. (2x- and 4x-cabbage; 2n=2x=18, cc and 2n=4x=36, cccc) was carried out for the purpose of transferring clubroot disease resistance from the amphidiploid species to cabbage. Nineteen hybrids with three different chromosome levels (2n=28, a₁c₁c; 2n=37, a₁c₁cc and 2n=55, a₁c₁cccc) were obtained. The F₁ plants were mostly intermediate between the two parents but as the number of c genomes in the hybrids increased, the more closely the hybrids resembled the cabbage parent. All F₁ hybrids were resistant when tested against race 2 of Plasmodiophora brassicae wor. The complete dominance of resistance over susceptibility suggested that the gene(s) controlling resistance to this particular race of the clubroot pathogen is probably located on a chromosome of the a genome in Brassica.Contribution No. J654.     

脯氨酸与植物的抗寒的综述

本文对低温胁迫下,脯氨酸在植物体内的变化、作用机理、代谢与调节及其在植物抗寒育种中的应用方面的研究进行了综述。