Properties of chloroplast membrane-bound ferredoxin--NADP + reductase during cold hardening of wheat. No indication of qualitative membrane changes during cold hardening

Kinetic parameters of the chloroplastbound ferredoxin-NADP⁺ reductase from two varieties of wheat (Triticum aestivum), hardy Kharkov 22 MC (winter wheat) and less hardy Rescue (spring wheat), were followed during induction of frost hardiness as a means of examining possible changes in chloroplast membranes during hardening. No changes were found in the Michaelis constants for NADPH and 2,6-dichlorophenol indophenol, inhibition constants for p-chloromercuriphenylsulfonate, and activation energy values of the enzyme in either variety. The data suggest that no qualitative changes occurred in the properties of wheat chloroplast membranes related to ferredoxin-NADP⁺ reductase during cold hardening.     

Winter hardiness in trench celery

A total of 51 red and white commercial varieties of trench celery were grown and examined for winter hardiness at the National Vegetable Research Station. Although some plants of most varieties survived the winter, none showed a commercially useful degree of winter hardiness, in that none were marketable after moderate frost. The red varieties had a significantly better survival than the white varieties. In the first season, single plant selections were made from the varieties having both the highest percentage of winter survival and the best agronomic characters. Although some of the progenies derived from these selected plants by self-pollination showed a small increase in winter survival as compared with their parent varieties when both were grown in the second season, no plants of these progenies were sufficiently hardy to remain marketable after moderate frost. It was concluded that none of the varieties tested showed any promise as a source of winter hardiness to be used in a breeding programme, and that selection for one generation from within these varieties did not improve winter hardiness to a useful extent.     

Cytological Studies on the Cold Resistance of Plants the Changes of the Intracellular Materials of Wheat in the Overwintering Period

In the literature, the information on the correlation between the material changes and the cold resistance of plants is full of contraditions, especially in regard to the changes of the sugar and protein contents in connection with the development of the cold resistance in hardened condition. The present work was undertaken with an attempt to study the changes of the intracellular materials of wheat in the overwintering period with cytochemical methods. The wheat varieties used in this study were the same as used in our previous work (Chien and Wu, 1965), these are, 2 winter varieties (Nungta 183 and Huapei 187), 2 spring varieties (Nanta 2419 and Piyü), and 2 intermediate ones (Pima No. 1 and Pingyaian 50). The plants of the different varieties were cultivated under the same environmental conditions. Samples were collected and fixed at the same time (twice a month from October to March). For making microscopical preparations, the sections of materials for comparative studies were mounted on the same slide, so that they all were subjected to exactly the same treatment. The results obtained are summarized as follows: 1. The starch content in the cells of the tillering nodes increased, as the temperature fell in autumn. The starch grains gradually disintegrated when the plants came in hardened period (late October to mid-November), and completely disappeared in severe winter (January). They were regenerated in mid-February. 2. The soluble sugar gradually increased with the falling of the temperature in late autumn and steadily increased until the temperature approached 0 ℃. However, when the temperature dropped further, the soluble sugar content decreased and finally in March reached the level which it assumed before winter. 3. It was determined by cytochemical reactions that the cytoplasmic proteins and RNA and the nuclear basic proteins increased from late autumn to early winter. The degree of these changes showed apparent difference between the different varieties. Based on the phenomena observed, the authors discussed their correlation with the cold resistance of wheat plants. 4. The fat and lipids were also tested, but there was no indication of the occurrence of these substances in the winter season. The study on the DNA content revealed no correlation of any kind with the development of the wheat hardiness.     

Changes in fatty acid composition of winter wheat during frost hardening

Twelve day old winter wheat seedlings (cvs Kharkov, frost hardy and Champlein, less hardy) accumulated linolenic acid at the expense of linoleic acid during controlled hardening. The change was most pronounced in the roots, where it was not specific to the phospholipid fraction. It was less marked in the leaves, but occurred there mainly in the phospholipids. The lack of differences between fatty acid profiles of the two cultivars rules out the explanation of varietal differences in frost hardiness in winter wheat on the basis of major changes in fatty acid unsaturation.     

Characteristics of the rRNA synthesis taking place at low temperatures in wheat cultivars with varying degrees of frost hardiness

The characteristics and intensity of rRNA synthesis occurring at temperatures around freezing point were examined in connection with frost hardiness in wheat cultivars. The intensity of rRNA synthesis taking place near freezing point showed a close positive correlation with the critical temperature (LT₅₀) characteristic of the frost resistance of the varieties. The quantity of high MW precursors to rRNA appears to be heterogeneous in hardy and non hardy varieties at low temperatures and point primarily to an inhibition in the maturation processes of ribosomes in the final nuclease processing step in non-frosthardy varieties.     

Effect of frost nights and day and night temperature during dormancy induction on frost hardiness, tolerance to cold storage and bud burst in seedlings of Norway spruce

For trees, the ability to obtain and maintain sufficient levels of frost hardiness in late autumn, winter and spring is crucial. We report that temperatures during dormancy induction influence bud set, frost hardiness, tolerance to cold storage, timing of bud burst and spring frost hardiness in seedlings of Norway spruce (Picea abies (L.) Karst.). Bud set occurred later in 12°C than in 21°C, and later in cool nights (7°C) than in constant temperature. One weekly frost night (−2.5°C) improved frost hardiness. Cool nights reduced frost hardiness early, but improved hardiness later during cold acclimation. Buds and stems were slightly hardier in 21°C than in 12°C, while needles were clearly hardier in 12°C. Cold daytime temperature, cool nights and one weekly frost night improved cold storability (0.7°C). Seedlings receiving high daytime temperatures burst buds later, and were less injured by light frost some days after bud burst.     

Stimulation of Phospholipid Biosynthesis during Frost Hardening of Winter Wheat

Lipids were labeled with ³³P during frost hardening of two varieties of winter wheat (Triticum aestivum), hardy Kharkov and much less hardy Champlein. The main labeled compounds were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylglycerol. With time of incorporation the proportion of the radioactivity incorporated into the lipids increased in phosphatidylcholine, especially in Kharkov and at 1 C. During hardening, phospholipid synthesis was greatly stimulated in Kharkov, but much less in Champlein. The proportion of the phospholipids synthesized changed only little with hardening, with a trend towards an increase in phosphatidylcholine. Increased phospholipid synthesis does not seem to be a prerequisite to hardening in winter wheat. However, a high rate of phospholipid synthesis may be required to maintain frost resistance.     

The relative hardening of roots and shoots and the influence of day-length during hardening in perennial ryegrass

The influence of long and short days during the hardening period on the cold hardiness of perennial ryegrass seedlings was studied as was the relative hardiness of roots and shoots. Hardiness was assessed by the electrolyte release method which was a measure of the amount of damage subsequent to low temperature treatment. Long days promoted hardiness in shoots of Pax 0tofte plants and in one case under short days the roots were found to be hardy. Generally roots were less hardy than shoots in Pax 0tofte and S23 plants hardened under long days for 2 wk. When hardened at the fourth leaf stage for 2 wk at + 5 ^oC under long day conditions, Pax 0tofte plants were more hardy than those of S23. The long day effect on hardiness was arrived at more rapidly, there being no difference in hardiness after 3 wk in Pax 0tofte hardened under long or short days, whereas a significant degree of hardening was observed after 1 wk of hardening under long days at – 4 ^oC. The results obtained are discussed in relation to winter kill of grasses in the West of Scotland, and it is considered that root damage is not an important factor in causing winter kill. The promotive effect of long days on hardiness when hardening commences in late autumn is considered an advantage in temperate regions as it may also allow early frosts to be withstood.     

抗寒锻炼中不同抗寒性小麦细胞膜糖蛋白的细胞化学研究

本研究根据植物细胞的特点,修改了在动物和人体细胞方面立的酶标Con A的电镜细胞化学方法,成功地展现了2个不同抗寒性冬小麦品种幼苗在抗寒锻炼和脱锻炼过程中细胞膜系统上糖蛋白的分布动态,显示与Con A连接的标志酶-辣根过氧化物酶活性的反应产物呈颗粒状分散分布在质膜、内质网、核膜及液泡膜的一些部位上,揭示糖蛋白在冬小麦细胞膜系统上的分布似有其特定的位点。经抗寒锻炼后,强抗寒性品种燕大1817细胞内的糖蛋白在内质网和核膜上的分布量明显地增加;同时,几乎所有的胞间连丝通道中都有糖蛋白的分布。脱锻炼后,内质网和核膜上的糖蛋白分布量又减少,胞间连丝通道中的糖蛋白也消失,基本上回复到抗寒锻炼前的分布状态。抗寒性弱的冬小麦品种郑州39-1幼苗在同样的抗寒锻炼和脱锻炼过程中不产生这些明显的变化。这些结果说明,抗寒锻炼中内质网和核膜上糖蛋白分布量的增加,以及糖蛋白输入胞间连丝的动态变化是与植物抗寒力的提高和保持稳定密切相关的。     

Nucleotide sequence and molecular analysis of the low temperature induced cereal gene, BLT4

Summary The nucleotide sequence and derived amino acid sequence of a cDNA clone (BLT4) for a low temperature induced barley gene were determined. This gene, together with a small family of related genes, was shown to reside on chromosome 3. The BLT4 clone has homology with genes in wheat and oats. Its expression was studied in oats and in barley doubled haploid lines segregating for spring/winter habit and for frost hardiness. These analyses show that elevated steady state levels of BLT4 mRNA are produced in shoot meristematic tissue after 3 days low positive temperature treatment. The low temperature response was found in all barley doubled haploid lines and was therefore not associated specifically with either the spring/winter habit or frost hardiness. Elevated levels of BLT4 mRNA were also seen in drought-stressed barley and it is likely that this is a gene encoding a low molecular weight protein that is responsive to dehydrative stresses, such as cold and drought.The EMBL accession number for BLT4 is X56547 H. vulgare cDNA     

The pattern of frost-hardening of leaves of winter cauliflower (Brassica oleracea var. botrytis cv. Clause 30)

The suitability of an electrical conductivity assay of leaf material for determining frost hardiness in winter cauliflower was established. The assay was used to monitor the changes in hardiness of field-grown plants during two seasons at two sites. Levels of frost hardiness were related to mean air temperature over the 7-day period prior to sampling (r = 0.6008, P< 0.001). There was no clear disjunction of any temperature to indicate a threshold temperature of hardening. Dehardening occurred in spring and during mild spells in winter. In the mild regions where this crop is grown commercially it is likely that plants are not fully hardened for much of the winter. This may facilitate curd growth but may put the crop at risk from frost damage.     

小麦幼穗分化及抗寒性杂种优势研究

对６个不同生态类型小麦品种及其完全双列杂交Ｆ１的穗分化特点及抗寒性进行比较研究,结果表明,杂种在穗分化进程上存在明显“倾早现象”：但杂种的抗寒性强弱由其抗寒性强的亲本起主导作用,不同生态类型品种间杂交,有可能选育出幼穗分化早,越冬性好的强优势组织。     

Effect of the 5R(5A) alien chromosome substitution on the growth habit and winter hardiness of wheat

The growth habit, ear emergence time, and frost tolerance of wheat/rye substitution lines have been studied in cultivars Rang and Mironovskaya Krupnozernaya whose chromosome 5A is substituted with chromosome 5R of Onkhoyskaya rye. Hybrid analysis has demonstrated that the spring habit of the recipient cultivars Rang and Mironovskaya Krupnozernaya is controlled by dominant gene Vrn-A1 located in chromosome 5A. Onokhoyskaya rye has a dominant gene for the spring habit (Sp1) located in chromosome 5R. It has been found that the resultant 5R(5A) alien-substitution lines have a winter type of development and ears do not emerge during summer in plants sown in spring. The change in growth habit has been shown to be related to the absence of the rye Spl gene expression in the substitution lines. The winter hardiness of winter 5R(5A) alien-substitution lines has been studied under the environmental conditions of Novosibirsk. Testing the lines in the first winter demonstrated that their winter survival is 20-27%. The possible presence of the frost resistance gene homeoallelic to the known genes Fr1 and Fr2 of the common wheat located on chromosomes 5A and 5D, respectively, is discussed.     

Comparing image (fractal analysis) and electrochemical (impedance spectroscopy and electrolyte leakage) techniques for the assessment of the freezing tolerance in olive

Olive growth and productivity are limited by low temperatures mainly during winter, but sometimes also in spring and fall. The most effective way to avoid these damages in areas subjected to these climatic conditions is to select least susceptible varieties, but the choice of the right method to determine cold hardiness is extremely difficult. The aims of the work were (1) to assess LT₅₀ (lethal temperature at which 50% of damage in plants subjected to low temperatures occurs) of some olive varieties in two seasons (summer and winter) and (2) to assess the reliability of different methods to evaluate cold hardiness. LT₅₀ was determined on 21 different olive (Olea europaea L.) Italian varieties by leaf and shoot electrolyte leakage, shoot impedance spectroscopy and leaf color determination of fractal spectrum. All the experiments were conducted on non-acclimated and cold-acclimated plants. Our results showed that all the three methods were able to detect damages on olive plants after exposure to low temperatures, with leaves appearing more sensitive to cold stress than shoots. Among these methods, fractal analysis could be very useful in assessing cold hardiness of plants on the basis of visible injury, without sophisticated or expensive instruments and in a reliable and cost-effective way, using only a scanning device, a personal computer and dedicated freeware software.     

Overwintering stress of Vaccinium vitis-idaea in the absence of snow cover

A snow manipulation experiment aimed to assess risks of direct freezing injury, freeze-induced dehydration and winter desiccation in the absence of snow cover on lingonberry (Vaccinium vitis-idaea). Frames with sheet-plastic sides and removable lids were used in this experiment for two purposes: to prevent accumulation of snow in mid-winter and to provide extra heat during early spring. Leaves were analyzed for frost hardiness, tissue water content and osmotic concentrations, and photoinhibition (Fv/Fm) during the period from the 10th of February to the 7th of April. The natural snow accumulation was low indicated by a minor difference in minimum temperatures between the frame treatment and naturally snow-covered plots. The heating effect of the frames started gradually at the end of February along with increasing solar elevation angles, and was highest at the beginning of April. Frost hardiness peaked in March as a consequence of cold periods, but it was practically lost by the beginning of April. Tissue water content decreased gradually at first, becoming greatly decreased later due to the extra heat. In accordance, the tissue osmotic concentrations increased first gradually, followed by a dramatic increase. Photoinhibition increased uniformly with increasing solar radiation, but at the end showed a sharp increment within a few days, obviously also indicating the effect of heating. It was concluded that neither lethal freezing stress nor significant freeze-induced dehydration occurred during the experiment. However, plants that overwintered without snow suffered from severe winter desiccation injuries due to the combination of solar heat and frozen soil. Although the desiccation stress was possibly a lethal factor, it was preceded by long-term and continued photoinhibition. It was concluded that during overwintering, chamaephyte species may suffer from both freezing and winter desiccation in the absence of protecting snow cover. However, during mild winters provided by climatic change scenarios, the risk of winter desiccation will be more probable. In relation to the future climate, it was concluded that winter desiccation and photoinhibition may develop gradually during a snowless winter and would, even if they did not reach a lethal level by themselves, possibly reduce frost hardiness.     

Energy state of spring and winter wheat during cold hardening. Soluble sugars and adenine nucleotides

Marked increases were found in the content of total soluble sugars, reducing sugars and ATP in winter wheat ( Triticum aestivum L. cv. Frederick) during cold hardening. The changes in soluble sugars and ATP of spring wheat ( T. aestivum L. cv. Glenlea) grown under similar conditions were less pronounced. The increase in ATP content during hardening of winter wheat was not associated with significant changes in the content of ADP or AMP. The adenylate energy charge did not change during hardening in either cultivar, but it was higher in the winter cultivar under both growth conditions. This difference could be related to the cold hardiness capacity of winter wheat.     

The effect of low temperature on the microtubules in root meristem cells of spring and winter cultivars of wheat Triticum aestivum L

We have studied the response of the interphase and mitotis microtubule arrays in root meristem cells of spring and winter cultivars of wheat Triticum aestivum L. (Moskovskaya 35 and Moskovskaya 39) during cold stress (1 h at 0 degrees C) and acclimation to cold (3-48 h at 0 degrees C). Our data show that interphase microtubules are more resistant to cold than mitotic arrays in both cultivars. During cold stress the density of endoplasmic microtubules increases in interphase cells of winter plants, yet no changes are detected in cells of spring plants. In mitotic cells of both wheat cultivars the density of microtubules within the kinetochore fibers decreases, yet this effect is more evident in the cells of spring plants. During acclimation to cold of both cultivars, we have observed the disorganization of the interphase cortical arrays and the enhanced growth of endoplasmic microtubule arrays, composed of microtubule converging centers. However, the reaction of mitotic microtubule arrays differs in the cells of winter and spring plants. In winter plants, during prophase diffuse tubulin "halo" accumulates first at perinuclear area, followed by the appearance of the microtubule converging centers. In spring plants, we have observed the formation of the prophase spindle, yet later the prophase spindle is not detected. Metaphase cells of both cultivars show similar aberrations of the mitotic spindle, accumulation of abnormal metaphases and the excessive formation of microtubule converging centers. In telophase cells of both cultivars, acclimation induces similar reaction, resulting in the disorganization of the phragmoplast and the formation of multiple microtubule converging centers. The latter are detected in the perinuclear areas of the daughter cells in winter plants and in the cortical cytoplasm of cells in spring plants. Our data point to the common pathways of microtubule response to cold treatment (0 degrees C). The excessive formation of the microtubule converging centers indicates the activation of microtubule assembly during prolonged cold treatment.     

Does the lack of vernalization requirement interfere with winter survival of oilseed rape plants?

Recent studies (Rapacz 1999) have shown that cultivars of spring-type oilseed rape are able to cold-acclimate to the level comparable with winter cultivars, but only after prehardening which results both in the increase of photosynthetic activity and in growth cessation. It is commonly known that under field conditions spring-type cultivars could not survive winter. Present studies were undertaken to explain the reasons for low winter hardiness of spring type rape plants. Six cultivars of spring and two of winter rape were sown in the open-air vegetation room at the end of August. The obtained results indicate that the degree of frost damage in spring-type plants increased in the course of winter and this increase was parallel to elongation of generative shoots observed after periods of warming. Each spring cultivar was completely killed by frost just after its generative shoot reached 15–20 cm, irrespective of its frost resistance level, determined previously under laboratory conditions. In the case of winter cultivars survival rate was consistent with laboratory-estimated frost resistance. It is suggested that spring rape could not survive winter because of its limited ability to prevent shoot elongation during winter at temperatures slightly above 0 °C. It was also found that less efficient photosynthetic electron transport in autumn was observed in these spring cultivars in which the elongation of generative shoots was observed already during the first warm break in winter.     

Influence of Purines and Pyrimidines on Cold Hardiness of Plants. III. Associated Changes in Soluble Protein and Nucleic Acid Content and Tissue pH

When applications of certain purines and pyrimidines enhanced the development or maintenance of cold hardiness, the content of water-soluble, trichloroacetic acid-precipitable protein and nucleic acids and tissue pH were higher in treated plants than in controls. The reverse was generally true when the treated plants were less cold hardy than the controls. In some instances, the purines and pyrimidines increased the content of these nitrogenous constituents in a nonhardy variety to a level equal to that found in untreated plants of a hardy variety.     

Cold hardiness in summer and winter diapause and post-diapause pupae of the cabbage armyworm, Mamestra brassicae L. under temperature acclimation

Cold hardiness and biochemical changes were investigated in winter and summer pupae of the cabbage armyworm Mamestra brassicae at the diapause and post-diapause stages under temperature acclimation. Diapause pupae were successively acclimated to 25, 20 and then 10 degrees C (warm-acclimated group). Pupae at the diapause and post-diapause stages were successively acclimated to 5, 0, -5 and then -10 degrees C (cold-acclimated groups). Supercooling point values in winter and summer pupae remained constant regardless of the diapause stages and acclimated temperatures. Warm-acclimated pupae at the diapause stage did not survive the subzero temperature exposure, whereas, cold-acclimated pupae achieved cold hardiness to various degrees. Winter pupae were more cold hardy than summer pupae, and pupae at the post-diapause stage were more cold hardy than those at the diapause stage. Trehalose contents in winter pupae rose under cold acclimation. Summer pupae accumulated far lower trehalose contents than winter pupae, with the maximal level occurring in winter pupae at the post-diapause stage. Glycogen content remained at a high level in diapause pupae after warm acclimation, whereas it decreased after cold acclimation. Alanine, the main free amino acid in haemolymph after cold acclimation, increased at lower temperatures in both diapause and post-diapause pupae, but the increase was greater in the diapause pupae. These results suggest that cold hardiness is more fully developed in winter pupae than in summer pupae, and cold acclimation provides higher cold hardiness in winter pupae at the post-diapause stage than at the diapause stage.