Increased Frost Resistance Research Articles

Seasonal Dynamic of Nonstructural Saccharides in a Rhizomatous Grass Calamagrostis Epigeios

Seasonal dynamic of total nonstructural saccharides (TNS) and individual saccharides (starch, sucrose, glucose, fructose, fructans) was followed in rhizomes and stem bases of Calamagrostis epigeios (L.) Roth at two types of meadows communities in the South Moravia (Czech Republic): cnidion and molinion alliances, which differ in their water regime. The TNS were formed mainly by fructans and starch, while glucose, sucrose and fructose were low. The amount of TNS in rhizomes and stem bases of plants from wet cnidion site was higher than in plants from drier molinion site. The seasonal trends of all saccharides were similar in the both sites. During growing season (June to October) the main storage sugar was fructan (18 – 21 % of dry biomass). At the beginning of September the content of fructan decreased to 10 – 12 % and simultaneously the content of sucrose increased from 1 to 3 %. This may increase frost resistance. The content of TNS in the stem bases was lower than in the rhizomes. During winter time the stem bases contained 2 to 2.5 % of sucrose. Plant height and aboveground biomass were also higher in molinion site.

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 1st 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 1st 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 1st 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 1st 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 1st 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.

A phylogenetic analysis of the Eucryphiaceae

A range of characters from modern and fossil species are used to present a phylogeny of Eucryphia Cav. (Eucryphiaceae). Amongst the extant taxa, the Australian species form a monophyletic group, but the South American species are paraphyletic. This, coupled with their present-day distribution and the fossil record, supports the view that Eucryphia had a Gondwanic origin at least 50 million years prior to the disruption of Australia from Antarctica. Although based on a limited data set with only vegetative characters available, the inclusion of the fossil members of Eucryphiaceae has demonstrated several trends that have been inferred to represent a response to the changing climatic conditions of the Cenozoic. These responses have included a general decrease in leaf size, loss of serrate leaf margins and the development of peltiform cuticular extensions on the abaxial leaf surface. These extensions may aid in decreasing transpirational water loss and/or increasing frost resistance.

Carbohydrate content of Eucalyptus gunnii leaves along an annual cycle in the field and during induced frost-hardening in controlled conditions

The annual changes in frost hardiness were studied for three Eucalyptus gunnii genotypes. Frost resistance evaluated on leaf discs by the electrolyte leakage method reached a maximum in the coldest period and a minimum in summer demonstrating winter frost hardening. Genotype 634 exhibited a higher intrinsic resistance than the other genotypes both in the hardened and in the non-hardened stages. Plants of this genotype were also frost acclimated in controlled conditions by a progressive decrease of culture temperature (25 to 0 °C) but the degree of hardening appeared to be lower in these conditions. The carbohydrate patterns in leaves varied with acclimation. In controlled conditions the leaves of genotype 634 exhibited a rise in sucrose, fructose and raffinose concentration up to a temperature of 10 to 7 °C which subsequently decreased. In natural conditions a comparison of the three genotypes allowed us to correlate the higher intrinsic resistance of genotype 634 to a higher soluble sugar content. During acclimation fructose and raffinose changes were also correlated to an increase in cold resistance even though the kinetics of these changes differed in controlled and natural conditions. The starch content was very low in the various genotypes in the different conditions but oligosaccharides such as stachyose and possibly verbascose were detected. The results point out the relationships occurring between increased frost resistance and changes in fructose and raffinose concentration in E. gunnii leaves.

Frost Resistance in .Eucalyptus nitens (Deane & Maiden) Maiden: Physiological Aspects of Hardiness

The effects of photoperiod, temperature regime and differential root and shoot temperatures on frost resistance were examined in both hardening and dehardening Eucalyptus nitens seedlings. Frost resist- ance was primarily determined by measuring the relative loss of electrolytes from frosted leaf discs. This method of assessing frost resistance compares favourably with the frosting of whole seedlings since the critical temperatures producing 50% leaf death in whole seedlings and the leakage of 50% of cellular electrolytes (T50) agreed to within 0.6°C after 14 and 28 days' hardening. Unhardened seedlings had T50 values of - 3.4°C. Seedlings hardening over a 56 day period, at night temperatures of 3°C for 16 h and days of 13-25°C, steadily increased in frost resistance to T50 values of -7.5°C. Reducing the daily amount of hardening temperature from 16 to 8 h produced seedlings that were over 1.0°C less frost resistant at the end of 42 days' hardening. On the other hand, seedlings exposed to a constant 3°C, day and night, suffered considerable water stress and were unable to harden beyond -5.8°C, even after 77 days. Heating seedling roots to between 6 and 18°C throughout the 3°C regime maintained high plant water status but did not confer any increased frost resistance. Rates of dehardening in well hardened seedlings increased with increasing day and 1 or night tempera- ture in the range 6-20°C. Seedlings exposed to 14 h nights at 6.0°C, just 3°C warmer than the hardening temperatures used, were unable to maintain T50 levels of -7.5°C and dehardened by 2.5°C over a 3-week period. The dehardening rate of leaves from seedlings exposed to an air temperature of 18°C day and night was significantly reduced if roots were exposed to 3°C.

PHYSIOLOGICAL INVESTIGATIONS OF LEAF MUCILAGES II. THE MUCILAGE OF TAXUS BACCATA L. AND OF THUJA OCCIDENTALE L.

Seasonal variations of the content of leaf mucilages of Taxus baccQta and Thuja occiden· ttllfs were determined. In Taxus the content is highest during the late winter and early spring and lowest in the summer. In Thuja it is highest in the winter, decreasing during spring and low in the summer months. Under the light microscope . Toxus mucilage was located in the vacuoles of mesophyll ceUs and that of Thu/a in mucilage idioblasts. Temperature txperlments show that slorase of mucilage is not temperature dependent and is not reduced by prolonged darkness. Taxus mucilae at 96% relative humidity it equilibrates to 180%. and at 100% rh to 280 - 300% of its dry weight . From mucilage content and cell volume the mucilage concentration of the vacuoles can be estimated as being higher than S -6%, which must give rise to a remarkable matric potential. It is suggested that the water-binding capacity of the mucilage plays an important role in stabilizing the water relations of the needles. thereby increa sing frost resistance .

Eucalyptus Physiology. III. Frost Resistance.

The effects of different hardening regimes were studied in E. viminalis by varying temperature, light conditions and photoperiod. The role of root temperature in dehardening was investigated in E. grandis. The relationship between leaf glaucousness and frost resistance was reexamined in E. urnigera and in crosses between the glaucous frost-resistant species E. pulverulenta and the green. less-resistant species E. grandis. These studies involved seedlings but adult material was also used when checking the association between frost resistance and G, the growth regulator in E. grandis. Provided that night temperatures were close to freezing, rapid hardening was independent of photoperiod, light source and day/night temperature differentials. No significant relationship between level of frost resistance and intensity of leaf glaucousness was observed in a segregating progeny of E. urnigera. In F2 and backcross progenies between E. pulverulenta and E. grandis, no evidence was obtained for either physiological or genetical links between glaucousness and frost resistance. As in several other Eucalyptus species, low root temperatures delayed rapid dehardening in E. grandis. Increased frost resistance towards the top of E. grandis seedlings was associated with marked ontogenetic increases in G content. The G content of a 2 m sapling was highest in winter when maximum frost resistance had developed. This and other supporting evidence suggests that G has a role in the frost resistance of E. Grandis perhaps by affecting active electron transport properties of membranes. No information of this kind is available for other Eucalyptus species.

EFFECT OF DROUGHT ON FROST RESISTANCE AND FATTY ACID CONTENT OF YOUNG WINTER WHEAT PLANTS

Low soil moisture, both prior to and during freezing, increased frost resistance of 12-day-old winter wheat (Triticum aestivum L.) plants. While frost resistance increased, percentage of linolenic acid decreased in drought-stressed plants (10% of soil water-holding capacity) as compared with controls (40%). This occurred whether drought stress was applied before freezing at 1 °C or at 20 °C. A degree of frost hardening can be achieved in winter wheat by drought stress without low temperature treatment, and without an increase in degree of unsaturation of fatty acids.

Growth Responses of Tall Fescue and Bermudagrass to Leaf Applications of Ancymidol1

AbstractGrowth inhibitors are used for topgrowth control of turfgrasses, but little information exists on associated physiological responses or growth of other plant parts. Therefore, experiments were conducted with ancymidol and an analog to assess their potential as growth retardants and their effects on physiological processes associated with vigor and tolerance to environmental stress.Tall fescue (Festuca arundinacea Schreb.) and bermudagrass [Cynodon dactylon (L.) Pers.] were grown under controlled environment conditions, and regrowth was measured for up to 32 days following application of foliar sprays of inhibitor. Topgrowth of bermudagrass was almost stopped at concentrations of ancymidol above 100 ppm, whereas tall fescue gave a quantitative growth response over the 200 to 600 ppm range. Root weight of treated bermudagrass was less than the control after a 21‐day regrowth period, but not when the growth period was 32 days. Root growth of tall fescue was not affected by treatment. Stubble weight of bermudagrass, which included leaf and stem tissue up to 6 cm above soil level, tended to be increased by treatment. Stubble weight of tall fescue was unaffected. Stolon number and weight were reduced about 50% by treatment of bermudagrass whereas tiller number of tall fescue was increased up to 30%.Concentration of storage carbohydrate was reduced 10 to 20% in stubble and stolons of treated bermudagrass, and 25 to 40% in all tissue of treated tall fescue. This probably occurred because net CO2 exchange per pot was usually reduced by treatments due to decreased leaf area. Net CO2 uptake of both species on a leaf area basis was unaffected. Water use per pot per day was 20 to 25% lower in treated plants.Results suggest that short‐term growth control may be feasible to reduce transpiration. Long term control, such as slowing growth in fall to increase frost resistance, may also be possible. However, in this study storage carbohydrate levels were lower than controls, and thus plants may not be vigorous enough to maintain themselves over long time intervals.

Einfluß einer Vorbehandlung von Weizenkaryopsen durch Quellung und Rücktrocknung vor der Aussaat auf die Temperaturresistenz der Keimlinge und Jungpflanzen

Results are reported concerning the behaviour of wheat plants resulting from caryopses which were pretreated by the method of P. A. Henckel, i. e. soaking in water and redrying before sowing, called pre-sowing treatment. Is is said by Henckel and his coworkers that by such pretreatment hardiness of plants will be induced lasting during their whole development. In numerous experiments we could not confirm this effect. Immediately after presowing treatment the dry caryopses are extremely hardened not only against dryness but also against frost or heat, due to their great water loss. Indeed, all these kinds of hardiness disappear within few days by a new start of soaking combined with development of germlings. Soon it is reached again the degree of hardiness of non-treated controls. Two days old germlings of cv. ‘Qualitas’ (winter wheat) at first exhibited an increased frost resistance, which diminished during promoting development of seedlings. Such a diminution of initial degree of resistance was observed also after longer storage of pretreated caryopses before sowing. In three leaf stage plants of cv. ‘Fanal’ (winter wheat) did not show an increased frost resistance, and the degree of heat hardiness of plants resulting from pretreated and non-treated caryopses did agree entirely, too. By an effective hardening treatment of seedlings by dryness or cold (0°C) the frost resistance increased distinctly. Plants which grown from pretreated caryopses, showed a decreased ability to become hardened against frost or heat in comparison with plants from non-pretreated caryopses. Pre-sowing treatment by Henckels method, therefore, has a negative influence on following treatment of plants to induce hardiness. Our experiments have indicated no signs that after soaking and redrying of caryopses the resulting plants were more resistant against low or high temperatures in comparison with non-treated controls, in so far as plants older than three days were tested. It may be that the increased yields from field experiments reported by Henckel based on special conditions not at all connecting with pre-sowing treatment. Our oppinion is supported by some statements in literature.

Frost resistance of concrete of various strengths under compressive loading

1. In concrete without admixtures a constant compressive stress that does not exceed the fissure-formation limit R f 0 increases the frost resistance two times and more (for thawing in sea water). 2. When the stress increases above R f 0 , the frost resistance of the concrete decreases, and for values δ=0.4 to 0.6 Rpr (depending on the strength of the concrete) becomes smaller than the frost resistance of the non-loaded concrete. 3. The constant compressive stresses in constructions should be limited to the value δ=0.4 to 0.6 Rpr for which the frost resistance does not appear to be lower than the standard, since for higher load levels an increase in the microdestructions of the concrete immediately after the loading is taking place, and this process is accelerated under the action of repeated cycles of freezing and thawing. 4. In very important construction exposed to repeated cycles of freezing and thawing the compressive stresses should not exceed the limit R f 0 . An increase of the stresses is admissible in the initial period provided that a thermal protection system is installed during the first winter. 5. The supplementary stresses which are induced in the concrete during freezing by the difference between the thermal expansion coefficients of the concrete and the reinforcing steel must be taken into account when the values of the compressive stresses are determined. 6. The concrete with air-entraining admixtures has an increased frost resistance in all cases, including when it is under compressive stress, and this permits of accepting higher levels of compressive stresses in structures made of this type of concrete than in those made of concrete without admixtures.

Die physiologie der frostresistenz

Recent results on the physico-chemical properties of a plant cell, related to frost hardiness, e.g., cell permeability, viscosity of cytoplasma, and the osmotic potential of the cell, are briefly summarized. In detail a survey is presented on the metabolic processes casually involved in frost hardiness and which, at very low temperatures or in nonhardened cells, ultimately lead to an irreversible injury of the cell. Thus, the sulfhydril-disulfide hypothesis of Levitt (1956) is mentioned, and the investigations of Heber and Santarius (1964) on the inactivation of phosphorylating systems by temperatures below the freezing point of water as well as the protective action of soluble carbohydrates, amino acids and electrolytes on chloroplasts and mitochondria are discussed critically. From these results it is concluded that the frost resistance of a plant may be regarded as a dynamic phenomenon and that metabolic mechanisms play a mayor role. The consequences in respect to frost protection of crop plants, especially the possibility to increase frost resistance by exogenous application of metabolites, have been outlined.

STUDIES ON THE VARIETAL DIFFERENTIATION OF FROST RESISTANCE OF THE TEA PLANT : VI. The Distribution of Sugars in Cells during Frost Hardening in the Tea Plant with Special Reference to Histochemical Observation by using <14><SUP>C</SUP>-sucrose

Although the protein of the chloroplast and mitochondrial membranes is the weak point against freezing, there is no varietal differentiation of the content and stability of its constituent against freezing. However, there is a clear varietal differentiation of the content of sugars in the tea leaf. Therefore, the present authors elucidated where sugar must be accurnulated in a cell to increase frost resistance according to the biochemical experiments and micro-autoradiographic observations of <14>C-sucrose. From these results, it is evident that sugars are distributed in the cytoplasm of cells in the plant to increase frost resistance.

Growth Regulators and Plant Vitality, Increased Frost Resistance by Application of Plant Growth-Retardant Chemicals

Growth Regulators and Plant Vitality, Increased Frost Resistance by Application of Plant Growth-Retardant Chemicals