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.     

Influence of Warm Intervals on the Effects of Vernalization and the Composition of Phospholipid Fatty Acids in Seedlings of Winter Wheat

Excised embryos of winter wheat were submitted to a different number of vernalization (2 °C) and devernalization (20 °C) cycles of different lengths. In all treatments sum of cold and warm intervals was 50 and 10 days, respectively. The influence of different temperature conditions of seedling growth on the effectiveness of vernalization and correlations between effectiveness of vernalization and final content of phospholipid fatty acids were analyzed.
All indexes of generative development of plants (length of vegetative phase, % of generative plants, number of side shoots) showed the most effective was uninterrupted vernalization beginning immediately after excision of embryos. Increasing the number of 2 ° C/20 °C cycles rapidly depressed effectiveness of vernalization, which reached the minimum with the 8.3 days at 2 °C and 2 days at 20 °C cycle and then improved again as cycles became shorter and more numerous.
Correlations between indexes of generative plant growth and indexes describing composition of fatty acids in seedlings showed that from 50 % to 60 % of variability in the composition of phospholipid can be associated with changes in the degree of generative induction. A higher degree of generative induction was associated with a higher share of < 16, 16: 0 and 18:2 acids and a lower share of 18: 3 acid and also with a lower value of the 16: 0/< 16 ratio of phospholipids.
The relation between the generative induction of plants and the composition of phospholipid fatty acids may however be blurred when induction proceeds under conditions of alternate short spells of vernalization and devernalization temperatures.     

Observations of Effects of Partial Vernalization in Winter Rape Plants Grafted Onto Generative Stock

Winter rape plants vernalized under natural conditions were used as stock for grafting apical and subapical parts of rape seedlings vernalized at 5 °C in light during different periods ranging from 0 to 10 weeks. Acceleration of generative development in both kinds of grafts occurred already after 3 weeks of their vernalization, i.e. after cold treatment of insufficient length to induce flowering in plants developing independently. Effectiveness of vernalization — measured by acceleration of flowering in grafts was highest from 3rd to 5th week of cold treatment and then it declined. Processes occurring during an early stage of vernalization, though insufficient to allow independent generative development, become manifest in grafts made on vernalized stock. This allows investigations of very early stages of vernalization processes inaccessible to observation by other methods.     

Effect of Temperature and Photoperiod on the Development of Lupinus albus L. in a Controlled Environment

An experiment to determine the effect of temperature and photoperiod on Lupinus albus under controlled environmental conditions was carried out, using the three Lupinus albus genotypes 'Tifwhite', 'Esta' and 'Kiev', and three temperature (10/20, 18/28 and 20 °C continuously) and two photoperiod (8 and 16 h daylength) regimes, in all combinations. Half of the seeds were vernalized for 21 days at 4 °C to alleviate the obligate vernalization requirement of Tifwhite. Although Esta and Kiev do not have obligate vernalization requirements, they were influenced by this vernalization period. Observations included the duration of the period from planting to seedling emergence, the duration of the period from planting to the beginning of flowering and the duration of flowering. The vernalization treatment accelerated plant development in all genotypes. The period from planting to emergence was shorter under the higher temperature regime. For all genotypes, the period from planting to flowering was shorter under the longer photoperiod, the same trend as would be expected for long-day plants. Duration of flowering periods were, in contrast to pre-flowering periods, shorter for all genotypes at cooler temperatures. The results of this study confirm that photoperiod does contribute to the growth period from planting to flowering in L. albus and that this species does behave as a long-day plant.     

The Effectiveness of Vernalization of Immature Embryos of Winter Wheat var. Grana as Related to Age and Exogenous Phytohormones

Starting from the 10th day after pollination, immature embryos of winter wheat var. Grana were isolated and then vernalized for 4 to 8 weeks on Murashige and Skoog nutrients containing BAP (0.5 or 2 mg/dm³), NAA (0.5 or 2 mg/dm³), or GA₃ (5 or 20 mg/dm³). Vernalized seedlings were cultivated in a greenhouse and the number of days to the heading of individual plants as well as the percentage of plants capable of generative development were estimated. The lower limit of size for 50 % survival of embryos strongly depended on the phytohormone used: from 0.9 mm in control, 1.1 mm in nutrient containing BAP, 1.2 mm for NAA, up to 1.7 mm in nutrient with GA₃. Exogenous GA₃ was lethal for embryos younger than 18 days but induced elongation of older embryos. Embryos isolated 2.5 to 4 weeks after pollination showed minimal requirements for the length of vernalization. BAP increased the percentage of heading plants originated from the youngest embryos. GA₃ improved partial vernalization, strongly increasing the percentage of heading plants, but did not change the time from the end of vernalization to heading. It has been postulated that GA₃ increases number of plants capable of overcoming the threshold of induction of generative development but does not accelerate the flowering process. Hormonized plants showed no deformation of generative development. As the effectiveness of vernalization increased, the heading of plants was faster but they were shorter, forming spikes with a smaller number of spikelets and producing fever lateral shoots. The very young embryos probably have in reserve sufficient amounts of auxins and gibberellins and therefore exogenous GA₃ decreases their viability or even exerts a deleterious effect. However, as the embryos' ageing, gibberellin starvation develops. This being especially pronounced during vernalization. The de novo synthesis or activation of gibberellins takes place during the second stage of vernalization. This is why exogenous hormone improves the effectiveness of partial vernalization, though it is not possible to substitute by gibberellins the vernalization requirements of immature embryos.     

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.     

Effects of Low Temperature Treatment at Seedling Stage on Soybean Growth, Development and Final Yield

The after effect of continuous and variable chilling temperatures acting periodically for 7 days at seedling stage (day/night: 2/2°C, 5/5°C, 15/2°C, 15/5°C, 15/15°C and control–22/18°C) on growth, development and final yield of soybean cultivar Polan and Progres were investigated. The temperature decrease lengthened the duration of the vegetation period before flowering for both cultivars, which allowed compensation for the reduced–as an effect of chilling–rate of daily increments in the leaf area and the dry weight of the above-ground parts of the plants. The most important symptom of chilling treatment was a considerable increase in the number of axillary branches after flowering, which caused an increase in the dry weight of plants. The subsequent reaction of the growth of leaves to chilling at seedling stage was, after flowering, variety dependent. The area of leaves bigger at Polan or similar to control at Progres ensured good seed filling in an increased number of pods developed on axillary branches. Chill-induced delay in plants development allowed the avoidance of low temperature occurring during flowering in this experiment. This chilling during flowering was one of the reasons of worse-pod setting and reduction of seeds per pod number at control plants.     

Effects of Temperature on the Alkaloid Content of Seeds of Lupinus angustifolius Cultivars

Three experiments were conducted to investigate the effects of high temperatures during seed filling on the alkaloid content of narrow-leaf lupin cultivars. Six cultivars of Lupinus angustifolius were grown in field experiments under different weather conditions in four subsequent years. A high content of alkaloids was found in the seeds harvested in 2006, in which the growing season was characterized by high ambient temperatures during seed filling. A second experiment was performed in the green house at different temperatures (10, 20 and 30 °C) using one cultivar in 2006. This experiment confirmed the results of the field experiments as higher temperatures resulted in a higher alkaloid content of the seeds. In a third temperature stress experiment, three cultivars were grown under long day conditions at day/night temperatures of 30 °C/16 °C and 20 °C/16 °C in growth chambers in comparison with an outdoor control at mean temperatures of 15.5 °C. Like in the other experiments, the seed alkaloid content increased with rising temperature. From these results, it may be concluded that the seed alkaloid content is strongly influenced by the temperature during initiation of flowering up to pod ripening. This has to be taken into account e.g. in trials for cultivar release in which the alkaloid content is a knock-out criterion.     

The Effect of Cold and Sucrose Concentration on its Uptake and on the Respiration Rate of Isolated Embryos of Winter Wheat

Both at 5°C and 20°C the sucrose concentrations between 8–14 % appear to be optimal from the point of view of dry mass accumulation by the seedling. The metabolic efficiency was also the highest for these concentrations of sucrose.
At both temperatures the hydration of the seedlings was strongly dependent on sucrose concentration in the nutrient, diminishing, respectively, from about 6 to about 2 and from about 10 to about 2 mg H²O × mg DW⁻¹ Such low values of the seedling hydration, however, caused only a 10–20 % decrease of their dry weight. Within the range of the applied sucrose concentration (2–20 %) its beneficial – trophic interaction prevails over the negative – osmotic interaction.
At 5°C, as compared with 20°C, a drop in the seedlings hydration was observed, which appears to be the general response of plants to low temperature of growth.
An analysis of the 24-hour respiration rate of the seedlings when grown at 5°C seems to reveal the occurrence of a process requiring additional metabolic energy and, probably, associated with the vernalization process.
A method of leveling the temperature dependent hydration of the seedling is proposed to enable the selection of high-temperature control in the investigations of the biochemical mechanism of frost hardening and vernalization.     

Drought Stress Effects on Seed Yield, Yield Attributes, Growth, Cell Membrane Stability and Gas Exchange of Synthesized Brassica napus L.

Drought stress effects on leaf gas exchange, cell membrane stability, seed yield and yield attributes of synthesized Brassica napus L. cv. Bangla kale and Bangla cabbage were compared. Drought stress treatments were imposed at early vegetative, late vegetative and flowering stages by withholding watering. Bangla cabbage produced greater pods/plant, larger seed size, greater total dry matter/plant, seeds/pot, and 17% greater yield than Bangla kale. The seed yield in plants stressed at early vegetative, late vegetative and flowering stages were 59, 74, 88% lower respectively, than watered plants. Drought stress reduced leaf photosynthesis by 67 to 97%. Bangla cabbage had 68% greater photosynthesis and 56% greater stomatal conductance than Bangla kale under stress at flowering stage. Leaf temperature was 1 to 2°C higher in stressed plants than watered plants. The cell membrane stability (CMS) increased up to 83% at flowering stage under stress compared to 21% under watered conditions. Although Bangla cabbage had high seed yield, yield attributes and photosynthesis under stressed conditions at flowering stage, its CMS values were lower than those of Bangla kale.     

郑麦9023春化基因VRN-1的组成及表达

以郑麦9023叶片为材料,利用序列特异性PCR扩增技术克隆了春化基因VRN-1,并通过0~2℃冰箱模拟春化处理0、10、20和30 d,对该基因在一叶期至九叶期叶片中的表达进行了分析。PCR分析表明,VRN-1基因在郑麦9023的A和D基因组中均为隐性,在B基因组中为显性,基因等位类型为vrnA1VrnB1vrnD1。在克隆VRN-A1、VRN-B1和VRN-D1基因序列的基础上,设计了3个等位基因的特异引物,并利用该特异引物进行半定量RT-PCR分析。结果显示,在未经春化处理的条件下,一叶期VRN-A1和VRN-D1均未检测到表达,而VRN-B1已有较低水平的表达;从三叶期开始,3个等位基因都有较高水平的表达,并一直持续至开花期。在春化处理10、20和30 d条件下,VRN-1的3个等位基因在一叶期就出现较高水平的表达,并保持至开花期。     

Physiological Effects of Winter Rape (Brassica napus var. oleifera) Prehardening to Frost. I. Frost Resistance and Photosynthesis during Cold Acclimation

The objective of the research was to define the changes in photosynthetic activity induced by prehardening and to determine their involvement in frost tolerance of winter rape.
Prehardening of winter rape, consisting of keeping the plants at + 12°C during the light periods from sprouting until the beginning of the 1st stage of cold hardening, contributed to increasing its effectiveness. After 42 days of hardening at + 2°C the resistance of the prehardened plants equalled that attained by winter rape in the most favourable seasons of vegetation in the field. Prehardening stimulated the efficiency of photosynthesis at chill temperatures (+ 2–5°C). Differences in photosynthetic efficiency, like those in frost resistance, increase with successive weeks of hardening. They also concern the leaves already developed at the hardening temperature. A prehardened photosynthetic apparatus is less susceptible to the progress of photoinactivation taking place when the seedlings are kept at + 2°C. It also demonstrated greater activity even during the first hour of hardening or in the newly expanding leaves, and also at higher temperatures, most probably because of the more efficient progress of the dark, processes. The described changes in the functioning of the photosynthetic apparatus induced by prehardening were thus qualitatively very similar to those observed during long-term growth at + 5°C. already described in the literature.     

Effects of Temperature and Photoperiod on Days to Flowering, Yield and Yield Components of Lupinus albus (L.) under Field Conditions

A better understanding of the agronomic importance of planting date and the influence of cold temperatures and photoperiod during germination and plant growth may lead to better management strategies for cultivation of the sweet white lupin (Lupinus albus). The effects of planting date (temperature and photoperiod) were determined on the number of days to flowering, yield and yield components of four early to medium and one late sweet white lupin genotype in a field trial at Potchefstroom, South Africa, planted during February 1996 to January 1997. Moisture stress was avoided through regular irrigation. Duration of the developmental phases planting date to emergence, emergence to floral initiation, initiation to first flower, duration of flower and days to physiological and harvest maturity was related to field measurements of temperature and photoperiod. Differences in the main determinants of yield, i.e. seeds per pod, pods per plant, single seed mass (SSM), plant and pod height and yield, were measured. Results showed that both temperature and photoperiod influence the growth and development of the Lupinus albus genotypes ‘Esta’, ‘Hantie’, ‘Tifwhite’, ‘Kiev’ and ‘LAL 186’. Temperature influences include the effect of vernalization at seedling emergence. Minimum grass temperatures under 5 °C at emergence are effective for vernalization. However, after grass temperatures at emergence increased again from June to December, to gether with an increase in the photoperiod length, ‘Tifwhite’ as well as the other genotypes still flowered earlier, confirming that these cultivars are long‐day plants, which is in accordance with controlled‐environment data. Cool vernalizing temperatures thus not only influence obligate vernalization requiring genotypes such as ‘Tifwhite’, but also influence the non‐obligate genotypes studied. Plan‐ting date had a significant influence on pods per plant, single seed mass (SSM) and seed yield. In all trials laterplanting, from June to November, decreased SSM and seed yield. The highest seed yield of 1.5 t ha^?1 was obtained for the 10 June planting date and the lowest average yield of 0.450 t ha^?1 for the 5 November planting date.     

Methods for evaluation of soybean chilling tolerance at the reproductive stage under artificial climatic conditions

Several evaluation methods for soybean chilling tolerance at the reproductive stage were examined under artificial climatic conditions. Comparisons were made on plants in control and treated plots using three cultivars differing in the level of chilling tolerance. In all methods, plants were grown at 22/17°C (day/night) until first flowering, and then transferred to growth chambers at 24/17°C for control and 15/15°C for chilling treatment, respectively. A method, in which plants were grown at 20/16°C after 4 weeks of the different temperature treatments, proved comparable to the conventional one, in which chilling tolerance at the flowering stage is evaluated using natural and artificial conditions. Another method, in which the plants in chilling treatment plots were grown at 15°C until maturity, also proved usable to evaluate genotypic differences in chilling tolerance independently of maturity time.     

Effect of Temperature Hardening on Growth, Carbohydrate and Protein Levels in Three Grain Crops

The effect of seedling pretreatment at different temperature levels and periods of exposure on growth, pigments, carbohydrates and proteins was studied in three grain crops; sorghum, wheat and barley at different stages of growth. Greater shoot-dry weights were obtained in sorghum with exposure for 15 hrs at 40 °C in the flowering, in wheat for 2 hrs at 10 and 40 °C in the fruiting and in barley for 15 hrs at 0 °C in the flowering stage. Increased root-dry weights were achieved by wheat with exposure for 4 and 15 hrs at all levels even at 0 °C in the flowering and for 15 hrs at 40 °C in the fruiting stage. Chl_a and Chl_b were more responsive in sorghum to higher temperature pretreatments than either wheat or barley. In sorghum the temperature extremes (0 and 50 °C) had resulted in a substantial reduction of Chl_a, and Chl_b in the fruiting stage. Lower and higher temperature-pretreatments had resulted in total available carbohydrate reduction in shoot and root of sorghum and wheat at the early stage, but the reverse was true later in flowering. In contrast, lower and higher temperature pretreatments had increased shoot-protein in sorghum and wheat in the vegetative and in sorghum in the flowering stage. Root-protein was more responsive to low temperature-pretreatments in sorghum and barley during the fruiting stage.     

Methods for the Selection of Low-Temperature Tolerant Mutants of Chrysanthemum morifolium Ramat. by Using Irradiated Cell Suspension Cultures

In order to improve mutant selection procedures, 5000 plantlets were regenerated in three different harvests (flush A, B and C) from X-irradiated (15 and 20 Gy) and non-irradiated cell suspensions of Chrysanthemum morifolium cv. ‘Parliament’. After screening under suboptimal energy condition (12°C greenhouse temperature, winter low-light), a total of 95 early flowering plants were selected. These plants flowered at least as early as a low-temperature tolerant (LTT) mutant E₂, used as a reference. The percentage of early flowering variants was highest among plants obtained from calli, X-irradiated with 15 Gy and regenerating relatively late (flush B). It appeared that the applied selection method (e.q. harvest) had a large impact on the number of early plants obtained.     

The Effect of Seed Vernalization and Irradiation on Growth and Photosynthesis of Field Bean Plants (Vicia faba L. minor) and on Nitrogenase Activity of Root Nodules

The effect of seed vernalization (2–3°C; 36 days) and irradiation intensity during vegetation of field bean upon growth and maximum leaf photosynthesis (P_max) as well as specific (SNA) and total nitrogenase activity (TNA) of root nodules was investigated. The measurements were performed at the initial stage of pod development of varieties with undetermined (cv. Nadwiśański) and determined (cv. Tibo) growth habit. In comparison with plants in shading, those which grew in full irradiation produced larger leaf area and more dry weight, achieving higher P_max values. Stimulation of leaf area enlargement and dry weight increase, especially in respect to the dry weight of underground parts had a positive and significant effect upon TNA value. Accumulation of dry weight was higher in vernalized than non-vernalized plants, but only in the case of cv. Nadwiślański, in full irradiation conditions. In the case of plants grown in poorer irradiation conditions TNA values were about 68 % (cv. Nadwiślański) and 54 % (cv. Tibo) lower, due to significant limitation of root nodules. TNA value of vernalized cv. Nadwiślański plants was 66 % higher in comparison with non-vernalized plants. However, the effect was visible only in full irradiation conditions, due to simultaneous greater intensity of root nodules production and higher SNA value. A positive effect of vernalization could also be observed in the decrease of a negative correlation between dry weight of root nodules and SNA in both varieties.     

Effect of Cold Hardening on Growth and Essential Oil Content of Mentha piperita L.

Divisions of running rhizomes of peppermint plants were planted in loamy clay soil in the experimental farm of National Research Centre, Dokki, Cairo, Egypt. After 21 days, the plants were exposed to low temperature 4, 7°C for 6, 9 and 12 days in controlled chamber before transplanting to large pots in winter season. Three cuttings were taken from the plants of different treatments during the season after 4, 7 and 10 months from transplanting. Representative samples of 6 replicates from each treatment were taken for the determination of vegetative growth and oil content in the leaves and branches.
The results obtained indicated that the highest fresh and dry weight of leaves and branches was recorded in the second cutting, however, it markedly decreased in the third one. The highest favourable effect of cold hardening on vegetative growth was observed at 4°C for 12 days exposure in the second cutting. The percentage of volatile oil in the leaves recorded the highest values in treatment of 7°C for 6 days in the second sampling date. Cold hardening either at 4°C or 7°C resulted in pronounced increase in the essential oil yield produced by the plant with the superiority of 4°C for 12 days which recorded the highest value.
It can be concluded from the obtained results that hardening peppermint plants with low temperature, particularly 4°C for 12 days before transplanting improved plant growth and considerably increased the volatile oil content in plant leaves and branches.     

Effect of Soil Temperature on the Carbohydrate Status in the Potato Plant (S. tuberosum L.)

Seed tubers of the variety Ostara were raised in growth chambers of 16°C air temperature continuously. The vessels were placed in a water bath of automatic temperature regulation so that soil temperatures of 16°C and 28°C could be maintained. Four weeks after emergence the plants were treated with ¹⁴CO₂ and 24 hours later the plants were harvested. Three more treatments and time harvests followed in two weeks intervals. C-14 activity was determined in soluble carbohydrates, in insoluble carbohydrates, and in non extractable residues respectively of the various plant parts in order to obtain information about the translocation of assimilates in the plant.
While the plants at 28°C soil temperature reduced the soluble sugar levels to 50% up to 70 days after emergence, the plants at 16° brought it down to 33% much faster. — The C-14 activity in insoluble carbohydrates amounted to only 50 % in the plants at 28°C while at 16°C it was more than 2/3 (Tables 1 and 2). — The C-14 activity in non extractable residues is much less at 28°C than at 16°C (Tables 3 and 4). — The starch weight reaches only 30% of the value obtained at lower temperature 70 days after emergence (Table 5). — At the higher temperature starch is also increasingly transferred to the tubers but to a much lesser extent and not from the stems and stolons (Table 6).
Possible causes, particularly the role of phytohormones, and consequences are discussed.     

Molecular examination and genotype diversity of vernalization sensitivity and photoperiod response in old and modern bread wheat cultivars grown in Iran

Understanding the genetic factors governing developmental patterns and flowering time in breeding materials is required for the development of new wheat varieties for a specific environment. Iran is among the largest wheat producers in the arid and semi-arid regions of the Middle East and North Africa. The wheat germplasm grown in Iran is either developed nationally or is introduced from the CIMMYT global wheat program. For decades, the wheat breeding program in Iran focused on generating new varieties better able to grow in the predominant Iranian climatic conditions such as humidity at the reproductive stage, high temperature during reproductive stages (terminal heat stress), moderate temperature during the cropping season, and high probability of frost damage during early stages of growth. There have also been sub-programs aimed at developing drought and salinity-tolerant wheat cultivars in Iran. Knowledge of cultivars’ growth habits in Iran is currently limited to flowering in spring-sown nurseries. We identified allelic diversity in loci involved in vernalization response (Vrn) and photoperiod sensitivity (Ppd) in 60 bread wheat cultivars developed in Iran, CIMMYT, or ICARDA. This study revealed that the spring growth habit observed in most of the cultivars is conferred by a combination of recessive vrn-A1 and dominant Vrn-D1, Vrn-B1, and/or Vrn-B3 loci. This implies that most of the cultivars have minimal vernalization requirements for overwintering. Perhaps cold winters, even in the southern regions of Iran, provide sufficient vernalization conditions for cultivars possessing the recessive vrn-A1 allele. The germplasm investigated in this study revealed no evidence indicating selection for or against any specific Vrn and Ppd allele in our wheat breeding program.