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Abstract
An international seminar on Plant Cold Hardiness was held at the Saint Paul campus of the University of Minnesota on November 2-4, 1977. This meeting was jointly sponsored by the National Science Foundation and the Japan Society for the Promotion of Science under the auspices of the U.S.—Japan Cooperative Science Program as well as the College of Agriculture, University of Minnesota. Seventy scientists representing 13 states and Washington, D.C., Canada, Colombia, Iran, Japan, Mexico, New Zealand, Norway and Poland attended the meeting, which was held to review current research, to discuss research priorities, to foster collaborative projects, and to consider how recent research findings might be applied to increasing food production.
The seminar focused on the fundamental biological processes of freezing survival in plants. Six consecutive sessions dealt with freezing stress, membranes, cold acclimation, supercooling, plant survival/breeding for cold resistance, and cryopreservation/cryoprotection. The subject matter encompassed horticultural and agronomic food crops, and forest species. Specific information can be obtained from the list of participants cited
Abstract
Tubers of potato (Solarium tuberosum L.) ranging from 6.9 to 18.6% total amino acids, on a dry weight basis, were analyzed by 6 methods which determine protein content: 1) total amino acids minus free amino acids determined by column chromatography, 2) Kjeldahl N × 5.7, 3) Kjeldahl N × 5.7 minus free amino acids determined by column chromatography, 4) Kjeldahl N × 5.7 minus ninhydrin determined free amino acids, 5) ninhydrin total minus ninhydrin free amino acids, and 6) Folin-Lowry analyses. The results of the latter 5 methods were correlated to the data of method 1 (column chromatography). All of the methods, except 4, had correlation coefficients above the 99% level of significance. When compared to the data obtained from column chromatography, methods 6 and 4 gave low, while method 3 gave approximately equal protein values. Method 2 is excellent for determining total tuber amino acids, (r = 0.96**) and is the method of choice for screening large numbers of tubers for protein, (r = 0.92**). Kjeldahl N × 5.7 correlates high with tuber protein, because there is a high correlation between tuber free and protein bound amino acids, (r = 0.74**). However, Kjeldahl N × 5.7 gives high tuber protein values. Based upon their correlation coefficients, methods 2, 5 and 6 are applicable for screening, but their individual shortcomings must be considered when interpreting results from tubers.
Abstract
The viability of apple blossom buds after test freezing was quantitatively estimated by the technique of electrical conductivity combined with visual observation. A sharp increase in the percent of leaching always indicated freezing injury to the blossom. This technique can provide not only a quantitative estimation of freezing injury but it can detect small differences in the cold tolerance existing between species.
Abstract
The freezing resistance of leaf, crown, and root tissues was determined for nonhardened and cold-hardened cultivars of perennial rye (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), and red and chewings fescues (Festuca rubra L. and F. rubra var. commutata Gaud.). The nonhardened leaf and crown tissues of all the cultivars studied survived temperatures below –9.8°C. After acclimating at 5° under short days for 6 weeks or longer, the maximum increase in hardiness was in ‘Wintergreen’ (chewings fescue) which survived –27°. The cold-acclimation behavior of ‘Wintergreen’ was studied at acclimating temperatures of 0° and 5°. Both the leaf and crown tissues had at least 2 stages of acclimation, in which an acclimating temperature of 5° was conducive to the initial stage, followed by a lower acclimating temperature (0°) for the second stage.
Abstract
Seven experimental selections and one commercial cultivar of potato (Solanum tuberosum L.) were grown in moderate (22/18°C, day/night) and cool (11/7°, day/night) regimes to determine the influence of temperature on potato tuber nitrogen, amino acid, and nucleic acid levels. Tubers from low temperatures had higher percentages of rRNA and lower levels of alpha-keto acids. Moderate and cool grown tubers of the same genotype exhibited slightly different gel electrophoretic banding patterns in 88% of the samples, evidence that tuber protein composition was altered. Glutamate, from HCl hydrolysates, was higher in cool grown tubers. Most cool grown tubers were higher in Kjeldahl nitrogen, due in part to higher levels of glutamate family amino acids, i.e. glutamate, proline and arginine. The free amino acids, histidine and arginine were higher in the cool grown tubers. The essential amino acid scores of leucine, isoleucine, lysine, threonine and valine and the amino acid patterns of methionine were significantly lower in the cool grown tubers; consequently, the cool grown tubers were nutritionally inferior per unit of tuber nitrogen.
Abstract
Several tuber-bearing Solanum species with different levels of frost hardiness and different capacities for cold acclimation were studied for the interrelationship of freezing and heat tolerance after cold and heat acclimation. Cold acclimation could increase the frost hardiness in some species as previously reported, but except for S. commersonii it did not change the heat hardiness in species studied. Heat acclimation, on the other hand, could increase the heat hardiness in all tested species without affecting their frost hardiness. There is no systematic relationship between freezing and heat tolerance and no correlation in heat hardiness between the controls and the heat acclimated plants. The results indicate that the mechanisms of cold and heat acclimation in the potato appear to be independent of each other.
Abstract
Water stress and short day treatments increased the frost hardiness and the water saturation deficit (WSD) of stems of red-osier dogwood (Cornus stolonifera L.) plants grown for 21 days at controlled temperatures, photoperiods, and water supply. Potted plants were watered either to the point of saturation (control) or with lesser amounts (98, 60, or 30 ml/pot per day). Hardiness and WSD were proportional to the level of water stress. The greatest increase in hardiness (from −3 to −11°C) occurred in die 38 ml treatment during the first 7 days. Prolonging water stress, for an additional 14 days, induced little additional hardiness. There was no increase in the hardiness (−3°C) or WSD of control plants grown under long days (14 hours). Control plants grown at short days (10 hours) increased in hardiness from −3 to −6.5°C and WSD increased from 7.5% to 18.2% in 21 days. Water stress or short days caused significant increases in hardiness and WSD, but a combination of the 2 treatments caused no further increase in hardiness or WSD.
Abstract
Potato plants (Solarium tuberosum L. cv. Irish Cobbler) which were intermittently misted fixed more 14CO2 than nonmisted plants. Most of the 14C was found in the sugar fraction with the greatest activity translocating to the top of the plant. The highest 14C in the nonvolatile organic acid fraction was found in the leaf which was fed 14CO2. The radioactivity of the free amino acid fraction was highest in tubers of misted plants, but was highest in the 14CO2 fed leaf of the nonmisted plants.
Abstract
Inheritance and selection of heat tolerance were investigated in common bean (Phaseolus vulgaris L.). Parental, F1, backcross, and F2 populations from the crosses PI 271998 × BBL 47, PI 271998 × 80 BP-6 and 5BP-7 × BBL 47 were used in the inheritance study. Parental, F2, F3 and backcross populations of the cross PI 271998 × BBL 47 were used to estimate selection gain. Plants were evaluated for heat tolerance by the conductivity method after 32 days in the growth chamber at 20°/15°C (day/night) and acclimation at 37° for 24 hr. The joint scaling test indicated that the additive-dominance model was adequate to explain heat tolerance in crosses PI 271998 × BBL 47 and 5BP-7 × BBL 47. The major variation for tolerance for these 2 crosses may be controlled by a small number of genes. The additive-dominance model was inadequate for PI 271998 × 80BP-6, however, and epistasis was present. Narrow sense heritability estimates ranged from 2.9% to 24.0%, indicating relatively small additive effects. Broad sense heritability estimates ranged from 0.0% to 21.6%, suggesting sizable environmental effects. Realized heritability from selection for tolerant F2 plants was 7.9%. These estimates perhaps represent the lower limit of heritability for heat tolerance. The conductivity method could be considered for evaluating heat tolerance in a breeding program but should be more effective in screening F3 families than individual F2 plants.
Abstract
Quantitative changes in 4S, ribosomal and tenaciously bound RNA occurred in response to various combinations of temp and photoperiod. Short days accompanied by low temp (SD/LT) elicited an increase in ribosomal RNA, whereas RNA decreased with time in a long day, high temp (LD/HT) regime. Plants exposed to a LD/HT regime had reduced levels of RNA even after 5 or 9 days of pretreatment in a SD/LT environment. It appears that the quantitative variations of RNA in the SD/LT and LD/HT regimes are due primarily to RNA synthesis rates rather than to changes in ribonuclease activity. Temperature had a marked influence on ribosomal RNA level in potato plants while the response to photoperiod was not as great.