Metabolic acclimation to hypoxia in winter cereals : low temperature flooding increases adenylates and survival in ice encasement

Cold hardened seedlings of winter wheat (Triticum aestivum L. em Thell) show an hypoxic hardening response: an exposure to low temperature flooding increases the tolerance of plants to a subsequent ice encasement exposure. Seedlings of winter barley (Hordeum vulgare L.) do not show such a response in similar experimental conditions. During ice encasement, there are general declines in adenylate energy charge (AEC), total adenylates and ATP:ADP ratios in the crown tissues of two winter wheat cultivars, and a winter barley, but rates of decline are faster in the barley. When the ice period is preceded by low temperature flooding of the whole plant, levels of the adenylate components are raised significantly in the wheats, and to a lesser extent in the barley. The survival of plants in ice preceded by flooding is related to the increased initial level of adenylates at the onset of the ice encasement stress, and the maintenance of higher levels of adenylates and ATP in the early stages of ice encasement as a result of accelerated rates of glycolysis. Higher survival of both winter wheat and barley plants during ice encasement in the light is also associated with significantly higher levels of AEC and adenylates in the early stages of ice encasement.     

Temperature Interactions with Growth Regulators and Endogenous Gibberellin-like Activity during Seedstalk Elongation in Carrots

Stecklings (roots) of three cultivars of carrots (Daucus carota L.) were vernalized 10 weeks at 5 C and subsequently grown at each of three greenhouse night/day temperature regimes: high (27/32 C), medium (21/27 C), and low (15/21 C). Floral differentiation occurred first in the easy bolting cv. Scarlet Nantes, intermediate in cv. Danvers 126, and last in cv. Royal Chantenay. Stem elongation arising from the subapical meristematic region always preceded floral differentiation. Extractable gibberellin-like activity in carrot stem apices increased from harvest during the 10-week vernalization period, then remained constant even though floral differentiation and stem elongation occurred during an additional 20-week cold storage period. Low temperature had both an inductive and a direct effect on reproductive development depending on length of low temperature exposure.     

Metabolic and Ultrastructural Changes in Winter Wheat during Ice Encasement Under Field Conditions

The effect of ice encasement on the physiological, metabolic, and ultrastructural properties of winter wheat (Triticum aestivum L.) grown under field conditions was examined by artificially encasing winter wheat in ice during early winter. Cold hardiness and survival of ice-encased seedlings declined less rapidly in Kharkov, a cold-hardy cultivar than in Fredrick, a less hardy cultivar. Ethanol did not accumulate in non-iced seedlings, but increased rapidly upon application of an ice sheet. Lactic acid accumulated in both cultivars during late autumn, prior to ice encasement, and elevated levels of lactic acid were maintained throughout the winter in seedlings from both iced and non-iced plots. The rate of O₂ consumption of shoot tissue of seedlings from non-iced plots remained relatively constant throughout the winter, but declined rapidly in seedlings from ice encased plots. Major ultrastructural changes did not occur in shoot apex cells of non-iced winter wheat seedlings during cold hardening under field conditions. However, the imposition of an ice cover in early January resulted in a proliferation of the endoplasmic reticulum membrane system of the cells, frequently resulting in the formation of concentric whorls of membranes, often enclosing cytoplasmic organelles. Electrondense areas within the cytoplasm which appeared to be associated with the expanded endoplasmic reticulum were also frequently observed.     

Cold-induced accumulation of protein in the leaves of spring and winter barley cultivars

Electrophoretic pattern and quantitative changes in soluble proteins were determined in the leaves of spring and winter cultivars of barley (Hordeum vulgare L., cv. Makouei and cv. Reyhan, respectively) exposed to 4 degrees C for 14 d. Seedlings were grown in a controlled growth chamber for 2 weeks at a constant air temperature of 20 degrees C and then transferred to constant 4 degrees C for 14 d followed by returning to 20 degrees C (cold treatment), or they were maintained throughout at 20 degrees C during the experimental period of 40 d (control treatment). Plants were sampled every 48 h for leaf fresh weight measurements. Total leaf soluble proteins were extracted and their concentration was either determined by a colorimetric method, or size-fractionated on SDS-PAGE. Low temperature-induced increases in protein amount occurred over the second week of exposure to cold treatment irrespective of cultivar: the winter cultivar was 2 d prior in this response. The protein patterns and their density showed differences between-cultivars and between-temperature treatments. A new cold-induced polypeptide was recognized in the leaves of winter barley cultivar on day 22 (8 d at 4 degrees C) compared to the control. This polypeptide was produced earlier over the first 48 h of low temperature in the winter cultivar compared with the spring one, recognizing in the leaves of cold-treated seedling until day 26. This more rapid response to a low temperature by the winter barley cultivar indicates a more sensitive response compared with the spring barley, probably cold-shock protein is a component of this cold-induced response.     

Synthesis of Freezing Tolerance Proteins in Leaves, Crown, and Roots during Cold Acclimation of Wheat

Protein synthesis was studied in leaves, crown, and roots during cold hardening of freezing tolerant winter wheat (Triticum aestivum L. cv Fredrick and cv Norstar) and freezing sensitive spring wheat (T. aestivum L. cv Glenlea). The steady state and newly synthesized proteins, labeled with [³⁵S]methionine, were resolved by one- and two-dimensional polyacrylamide gels. The results showed that cold hardening induced important changes in the soluble protein patterns depending upon the tissue and cultivar freezing tolerance. At least eight new proteins were induced in hardened tissues. A 200 kilodalton (kD) (isoelectric point [pl] 6.85) protein was induced concomitantly in the leaves, crown, and roots. Two proteins were specifically induced in the leaves (both 36 kD, pl 5.55 and 5.70); three in the crown with M_r 150 (pl 5.30), 45 (pl 5.75), and 44 kD (pl > 6.80); and two others in the roots with M_r 64 (pl 6.20) and 52 kD (pl 5.55). In addition, 19 other proteins were synthesized at a modified rate (increased or decreased) in the leaves, 18 in the crown and 23 in the roots. Among the proteins induced or increased in hardened tissues, some were expressed at a higher level in the freezing tolerant cultivars than in the sensitive one, indicating a correlation between the synthesis and accumulation of these proteins and the degree of freezing tolerance. These proteins, suggested to be freezing tolerance proteins, may have an important role in the cellular adaptation to freezing.     

Differences between Dianthus caryophyllus L. cultivar in in vitro growth and morphogenesis are related to their ethylene production

The involvement of ethylene in the vitro development of shoots from nodal segments of two cultivars of carnation (Dianthus caryophyllus L.) was studied. Shoots of cv. Barbaret Antares showed low hyperhydricity in contrast with the high levels showed by cv. Barbaret Tanga when both were cultured in airtight culture vessels. Longer shoots were produced, in both cases, when the rate of gas exchange in the culture vessel was increased by using vented closures, which also prevented hyperhydricity and increased the multiplication coefficient in cultures of Barbaret Tanga.The two cultivars produced ethylene throughout the culture period but, a higher amount was produced during the first, second and fourth weeks in culture by the cultivar more sensitive to ventilation (Barbaret Tanga). Trapping ethylene did not produce any effect on cv. Barbaret Antares but improved the quality of cv. Barbaret Tanga explants, decreasing hyperhydricity and increasing the number of shoots, the length of the main shoot and the multiplication coefficient. These effects were more marked when ethylene was trapped during the first two weeks in culture.     

Response of antioxidant and osmoprotective systems of wheat seedlings to drought and rehydration

Complex study of the effect of soil drought (72 h) and subsequent rehydration for 24 and 48 h on the activities of antioxidant and osmoprotective systems in the leaves of young plants of winter wheat (Triticum aestivum L.) cvs. Ballada (high productivity) and Beltskaya (low productivity) was carried out. Under drought conditions, the content of water in the leaves of cv. Ballada reduced to a lesser degree than in the leaves of cv. Beltskaya. Drought did not affect the rate of leaf growth in cv. Ballada but retarded leaf growth in cv. Beltskaya. Under drought conditions, the content of ascorbate reduced in cv. Beltskaya but was not changed in cv. Ballada; the content of glutathione increased by 19% in cv. Ballada and by 30% in cv. Beltskaya. Under drought conditions, ascorbate peroxidase activity was not changed in cv. Ballada whereas in cv. Beltskaya there was a tendency to its decrease. Glutathione reductase activity in the leaves of cv. Beltskaya increased stronger than in cv. Ballada. Substantial differences between cultivars in the accumulation of reducing sugars and sucrose under water deficit were observed. In both cultivars, drought induced an active proline accumulation. Observed differences in the cultivar responses to water stress evidently indicate differences in the strategy of their adaptation to drought. Drought did not affect the contents of chlorophyll and MDA in both cultivars. The data obtained allow a suggestion that, under conditions of moderate soil drought, the coordinated system of antioxidant defense and osmotic control functioned sufficiently effective; as a result, oxidative stress was not developed in both cultivars. Young plants of both cultivars differing in their responses to water deficit retained the ability to recover after rehydration.     

Resistance to aphids in immature wheat and barley*

Resistance to Sitobion avenue and Metopolophium dirhodum was assessed in the glasshouse by releasing immature aphids on uncovered wheat and barley plants at the tillering stage. Six cultivars of winter wheat were tested with S. avenue and of these cv. Kador was resistant and cv. Maris Huntsman susceptible. Among seven cultivars of barley, cv. CI16145 was more resistant to S. avenue than any other whilst cvs Tyra and Nirakei 10 were the most susceptible, but the cultivars did not differ significantly in the numbers of M. dirhodum on them, although there were ranking differences similar to those observed with S. avenue.     

Evaluation of four grasses for use in phytoremediation of Cs-contaminated arid land soil

Although residue management seems a key factor in residue-mediated weed suppression, very few studies have systematically compared the influence of different residue management strategies on the establishment of crop and weed species. We evaluated the effect of several methods of pre-treatment and placement of winter rye (Secale cereale L.) and winter oilseed rape (Brassica napus L.) residue on seedling emergence under field conditions. For both species two cultivars, differing in allelochemical content, were used. Residues incorporated in the upper soil layer exerted a large inhibitory effect on the establishment of the relatively early emerging lettuce (Lactuca sativa L.) and spinach (Spinacia oleracea L.) seedlings, whereas the inhibitory effect on the slightly later emerging Stellaria media L. seedlings was variable, and often a stimulatory effect on the very late emerging Chenopodium album L. seedlings was observed. Differences between cover crop cultivars were minor. For winter oilseed rape residue, pre-treatment strongly affected the time-course of residue-mediated effects. Finely ground residues were only inhibitory to seedling establishment during the first two to three weeks, whereas cut residues became inhibitory after this period. For winter rye, residue placement was most important. Residue incorporation gave variable results, whereas placement of winter rye residue on top of the soil inhibited the emergence of all receptor species. In conclusion, the optimal residue management strategy for weed suppression depends both on the cover crop species used and the target weed species.     

Solute Accumulation and Compartmentation during the Cold Acclimation of Puma Rye

During cold acclimation of Puma rye (Secale cereale L. cv Puma), the intracellular osmotic potential nearly doubles. During this period, the accumulation of glycinebetaine, proline, and soluble sugars was monitored. The amount of glycinebetaine increased from 290 to 1300 micrograms per gram fresh weight during the 4-week acclimation period. Proline content did not change during the first 3 weeks of acclimation but then increased from 27 to 580 micrograms per gram fresh weight during the next 3 weeks. The total soluble sugar content more than doubled by the second week of cold acclimation, increasing from 11 to 26 milligrams per gram fresh weight. Most of this increase can be attributed to the accumulation of sucrose and raffinose, whose levels increased from 2.4 and 0 to 11 and 5 milligrams per gram fresh weight, respectively. The content of monosaccharides, predominantly glucose, remained at a constant 10 milligrams per gram fresh weight throughout the acclimation period. A comparison of the sugar content of protoplasts versus vacuoles isolated from cold-acclimated leaves revealed that the extravacuolar volume contained monosaccharides, sucrose, and raffinose. Thus, the increased amounts of sucrose and raffinose that occur during cold acclimation are present in compartments external to the vacuole and may contribute to cryoprotection.     

Carbohydrate metabolism of cactus in a desert environment

The concentration of glucan, mucilage, soluble carbohydrates, and malic acid were determined in Opuntia bigelovii Engelm. during a 23-week period. The experiment began during the dry summer by irrigation to stimulate Crassulacean acid metabolism and was followed by 13 weeks of drought. After the 13-week drought period, the plants were irrigated throughout a 10-week period until late December. The maximum level of malic acid determined each day at dawn decreased throughout the drought period and increased after irrigation. High levels of malic acid occurring at dawn are indicative of active Crassulacean acid metabolism. Soluble carbohydrates also decreased during drought and increased after irrigation. Both glucan and mucilage increased slightly for about 9 weeks during the drought period and then began to decrease. Irrigation was accompanied by a further decrease in concentration of glucan and mucilage. Since both glucan and mucilage changed in a similar manner and since their concentrations in the tissue are correlated, it is hypothesized that both function as storage carbohydrates. Whereas glucan is the nocturnal substrate for malic acid synthesis, there are no data to support or refute a similar hypothesis for mucilage.     

Interstrain Competition between Representatives of Indigenous Serotypes of Rhizobium trifolii

The symbiotic characteristics of Rhizobium trifolii strains 1-01 and 2-01 were evaluated both individually and in various combinations on two cultivars (Mt. Barker and Woogenellup) of subterranean clover (Trifolium subterraneum L.). Nodules were observed on day 8 independent of cultivar or strain. Cultivar differences were measured in nodulating efficiency by 1-01 since 54% of the primary nodules were formed on cv. Mt. Barker and only 15% were formed on cv. Woogenellup in the zone above, or 1 cm below, the root tip location at the time of inoculation. The percentage of nodules formed in this zone by 2-01 was similar on both cultivars (31 to 32%). When mixtures of strains 1-01 and 2-01 (230:1 and 1:20) were used to inoculate plants, >90% of the nodules on both cultivars were occupied by the more abundant strain in the inoculum regardless of sampling date (4 or 8 weeks). In contrast, large percentages of nodules on 4-week-old plants of both cultivars exposed to a 5:1 inoculum mixture were doubly occupied (64 and 74%). By week 8 these values had decreased significantly (P ≤ 0.01) and were accompanied by large increases in the percentage of nodules occupied by either strain 1-01 alone (1 to 65%) on cv. Mt. Barker or 2-01 alone (4 to 49%) on cv. Woogenellup. The superior (cv. Mt. Barker) and inferior (cv. Woogenellup) symbiotic performance of plants inoculated with the 5:1 mixture correlated more closely with the 8-week than the 4-week nodule occupancy data. Primary nodule occupancy by 1-01 and 2-01 was significantly influenced by changes in the inoculum ratios of 1-01/2-01 from 5.7:1 to 0.67:1 on cv. Mt. Barker and from 1.9:1 to 0.67:1 on cv. Woogenellup. Despite evidence for extensive proliferation of the inoculant strains on the rhizoplanes, no evidence was obtained for either interstrain antagonism or selective proliferation as a valid reason to explain the outcome of primary nodulation.     

Changes in activity of lysine decarboxylase in winter triticale in response to grain aphid feeding

Changes in lysine decarboxylase (LDC) activity caused by Sitobion avenae (F.) feeding on two winter triticale cultivars (cvs) were studied. The aphid fecundity and values of intrinsic rate of natural increase showed that cv Witon was less susceptible to S. avenae than cv Tornado. The grain aphid feeding on more susceptible triticale caused a decrease in the LDC activity, with exceptions of root tissues after two weeks of the feeding. In case of less susceptible cv Witon reduction of the LDC activity was observed only during initial period of S. avenae feeding. Later the aphid infestation induced activity of the LDC within tissues of cv Witon.     

Changes in Cytokinin Activities and Mass Spectrometric Analysis of Cytokinins in Root Exudates of Rice Plant (Oryza sativa L.) : Comparison between Cultivars Nipponbare and Akenohoshi

Changes in exudation rate and cytokinin activities in the exudates were measured in two varieties of rice (Oryza sativa L.), cv Nipponbare (a Japanese normal cultivar) and cv Akenohoshi (a high-yielding cultivar). The exudation rates of Akenohoshi, the leaves of which remained green for a longer time, were higher than those of Nipponbare after the booting stage. Cytokinin activities in the exudates of Akenohoshi were higher than those of Nipponbare during the ripening period. Cytokinins in the exudates collected during the middle of the ripening stage were analyzed with mass spectrometry using deuterium-labeled standards. trans-Zeatin, trans-ribosylzeatin, and N⁶-isopentenyladenosine were detected as free cytokinins, and zeatin was detected in the hydrolysates of highly polar fractions (“conjugated zeatin”) in the exudates of both cultivars. Conjugated zeatin was the predominant cytokinin in both cultivars. Therefore, we suggest that conjugated zeatin is an important form of cytokinin during the ripening stage. The level of each of the cytokinins in Akenohoshi was higher than that in Nipponbare. Also, we discuss the correlation between the leaf senescence and cytokinin content in root exudates.     

Endosperm acidification and related metabolic changes in the developing barley grain

The starchy endosperm (SE) of the developing grain (caryopsis) of barley (Hordeum vulgare L.) cv Himalaya, as well as that of other barley cultivars examined, acidifies during maturation. The major decrease in pH begins with the attainment of maximum grain dry weight, onset of dehydration, and completion of chlorophyll loss. Acidification is correlated with the accumulation of malate and lesser amounts of citrate and lactate, produced and probably secreted by the pericarp/testa/aleurone (PTA). It is accompanied by large concurrent rises in phosphoeno/pyruvate carboxylase and alcohol dehydrogenase (ADH) activity in the PTA. The activity of seven other enzymes of oxaloacetate and pyruvate metabolism was found to fall or rise only slightly during acidification. Sequential changes in relative amount of ADH isozymes were found in both PTA and SE. The PTA maintained a high respiration rate and adenylate energy charge (AEC) throughout acidification, whereas the SE showed a low respiration rate and rising AEC. The data are consistent with the occurrence of hypoxia in the SE. It is suggested that the above enzyme changes are required for the development of a malate/ethanol fermentation (i.e. a mixed metabolism) in the aleurone layer during maturation.     

Accumulation of Free Proline at Low Temperatures

The accumulation of free proline in the first leaves of barley, Hordeum distichum L., and wheat, Triticum aestivum L., in response to a range of low temperatures was examined with 10-day-old plants. In barley (cv. Prior) no proline accumulated at 8°C or above, but in wheat (cv. Gabo) proline accumulated at 12°C and lower temperatures. In barley, the first leaf survived for 29 days following transfer to 5°C and continued to accumulate proline throughout this period. In contrast, the first leaves of plants maintained at 20°C survived for 13 days only and accumulated no proline. Proline accumulation at low temperature was shown to be light-dependent, both in intact plants and excised leaf sections, and the light requirement could not be replaced by supplying leaf segments with precursors of proline. Proline accumulation in response to water stress was not light-dependent at 20°C but was at 5°C. Inter-specific and intra-specific variation in the extent of accumulation in response to low temperature was also examined. Considerable variation was encountered but there was no clear relationship with geographical distribution or chilling sensitivity for the species and no correlation with accumulation in response to water stress in the cultivars of barley examined.     

Quantifying relationships between rooting traits and water uptake under drought in Mediterranean barley and durum wheat

In Mediterranean regions drought is the major factor limiting spring barley and durum wheat grain yields. This study aimed to compare spring barley and durum wheat root and shoot responses to drought and quantify relationships between root traits and water uptake under terminal drought.One spring barley（Hordeum vulgare L. cv. Rum） and two durum wheat Mediterranean cultivars（Triticum turgidum L. var durum cvs Hourani and Karim） were examined in soil‐column experiments under well watered and drought conditions. Root system architecture traits, water uptake, and plant growth were measured. Barley aerial biomass and grain yields were higher than for durum wheat cultivars in well watered conditions. Drought decreased grain yield more for barley（47%） than durum wheat（30%, Hourani）. Root‐to‐shoot dry matter ratio increased for durum wheat under drought but not for barley, and root weight increased for wheat in response todrought but decreased for barley. The critical root length density（RLD） and root volume density（RVD） for 90% available water capture for wheat were similar to（cv. Hourani） or lower than（cv. Karim） for barley depending on wheat cultivar. For both species, RVD accounted for a slightly higher proportion of phenotypic variation in water uptake under drought than RLD.     

Characteristics of Salt-Tolerant and Salt-Susceptible Cultivars of Barley

Twelve cultivars of barley (Hordeum vulgare L.) from the collection of the Vavilov Institute of Plant Industry, Russian Academy of Agricultural Sciences, were screened by assessing the length of 6-day-old seedlings grown in water culture at 70, 120, and 170 mM NaCl. As a result, two salt-susceptible cultivars, Belogorskii and QB 60.1, and three salt-tolerant cultivars, Elo, Odesskii 115, and Local from Ecuador, were selected, and these cultivars were used in the greenhouse soil-culture experiments. The grain yield of salt-tolerant cultivars was affected by NaCl to a lesser degree than that of the salt-susceptible cultivars. In both cases, soil salinization increased the sodium content in the seedlings as compared to the control plants. Characteristically, salt-susceptible cultivars accumulated more Na⁺ in their shoots than salt-tolerant cultivars; the reciprocal pattern was found in the roots. Soil salinization decreased K⁺ content in the shoots of the salt-susceptible cv. Belogorskii as compared to the control, whereas in the most tolerant cv. Local from Ecuador, the potassium content increased.     

Participation of amino acid decarboxylases in biochemical interactions between triticale (Triticosecale; Poaceae) and bird cherry-oat aphid (Rhopalosiphum padi; Aphididae)

The roles of ornithine decarboxylase, lysine decarboxylase and tyrosine decarboxylase in biochemical interactions of two cultivars of winter triticale (Triticosecale), Tornado and Witon, and bird cherry-oat aphid (Rhopalosiphum padi L.) were determined. Results showed the resistant Witon had higher lysine decarboxylase activity than the susceptible Tornado. There was a significant negative correlation between the density of R. padi populations and lysine decarboxylase activity. Such correlations did not occur for the other decarboxylases. Aphid feeding induced a decrease of lysine decarboxylase activity within both cultivars after one week of infestation and increased its activity after two weeks in the moderately resistant Witon. Ornithine decarboxylase activity was induced in tissues of the susceptible Tornado and inhibited in Witon after two weeks of infestation. Aphid infestations did not change tyrosine decarboxylase activity in Witon, whereas in Tornado it decreased in activity after one day of aphid feeding and then increased after two weeks. It was concluded that of the three enzymes studied, lysine decarboxylase was the most important in the response of winter triticale to infestation by R. padi.