Logit models were used to analyze freeze-survival data of apple (Malus domestica Borkh.). The effects of hardening and dehardening treatments and two treatment durations on lethal temperature were studied using two cultivars. The major benefits of logit models were 1) the form of the sampling variation in the qualitative response variable was taken into account, 2) the lethal temperatures could be estimated with confidence intervals, and 3) the effects of treatments could be interpreted and compared easily using odds ratios. The momentary frost resistance estimates for `Antonovka' and `Samo' were –46 and –43C, respectively. Dehardening at 14C raised the lethal temperature by 12 to 15C, whereas hardening at –15C did not affect the frost resistance of either cultivar.
Seasonal cold hardiness of red raspberry (Rubus idaeus L.) canes was measured by freeze-induced electrolyte leakage test and visual rating of injury. Leakage data were transformed to percentage-adjusted injury values and related to lethal temperature by graphical interpolation and by the midpoint (T50) and inflection point (Tmax) estimates derived from three sigmoid (the logistic, Richards, and Gompertz) functions. Tmax estimates produced by Richards and Gompertz functions were corrected further using two different procedures. The 10 leakage-based hardiness indices, thus derived, were compared to lethal-temperature estimates based on visual rating. Graphical interpolation and Tmax of the logistic or T50 of the Gompertz function yielded lethal-temperature estimates closest to those obtained visually. Also, Tmax values of the Gompertz function were well correlated with visual hardiness indices. The Richards function yielded hardiness estimates deviating largely from visual rating. In addition, the Richards function displayed a considerable lack of fit in several data sets. The Gompertz function was preferred to the logistic one as it allows for asymmetry in leakage response. Percentage-adjusted injury data transformation facilitated curve-fitting and enabled calculation of T50 estimates.
Temperature is a limiting factor for plant growth. Warm-season turfgrasses can experience winter-kill when grown in the “transition zone.” On the other hand, when properly cold-acclimated, these same plants can withstand otherwise lethal temperatures. As part of our investigations into the biochemistry and molecular biology of cold acclimation in bermudagrass, total RNA from crowns (rhizome buds) isolated at different timepoints before and after chilling temperature exposure, was isolated by salt-buffer/phenol extraction, followed by LiCl precipitation and DNAse treatment. Differential display reverse transcriptase polymerase chain reaction (DD-RT-PCR) was performed using specific-(dT11NN) or variable-(dT12VN) anchor primers (where V = dA, dG and dC and N = dA, dG, dC or dT) for first strand cDNA synthesis by RT. The ss-cDNAs were converted to double stranded molecules and PCR amplified using a randomly chosen 10-mer primer paired with the same anchor primer used for cDNA synthesis. The dCTP32 labeled cDNAs were fractionated on non-denaturing polyacrylamide gels. Individual bands exhibiting differential expression between treated and nontreated samples were identified for reamplification, cloning, sequencing and further characterization of the differential nature of their expression by reverse northern hybridization and RT-PCR. Only those excised bands able to be reamplified using the anchor:10-mer pair were selected for cloning. To date, 90 variable-anchor:10-mer or specific-anchor:10-mer pairs have been screened. Of these, ≈27 have exhibited possible differential expression with one or more bands. Nucleotide (and deduced amino acid) sequence information was used to search on-line databases for similarity/homology with previously reported gene or protein sequences.
Abstract
Florets of overwintering azalea, Rhododendron spp., were found to avoid cold injury by prevention of ice formation in the floret tissues. When crystallization did occur it was invariably lethal. The temperatures at which florets froze were readily identified from the recorded cooling curves of individual florets during controlled cooling tests since an exotherm occurred at the moment of ice crystallization. Depending upon cultivar and temperature, exotherms were observed between −15 and −43°C during midwinter. Each excised intact floret produced only 1 exotherm. In contrast there were 3 exotherms in cooling curves of hardened stem sections. The 3rd exotherm which occurred between −37 and −42° in midwinter appeared to coincide with the exact lethal temperature for stems.
Previously, we reported recovery of plants from “Near-Lethal” (NL) (Sub-Lethal) stresses was dependent on stage of development and post-stress environment Dormant plants exposed to NL-heat, freezing, and hydrogen cyanamide either died or were severely injured when stored at 0°C or recovered at 23°C and natural condition. This study reports on the changes in the evolution of metabolic heat in dormant red-osier dogwood (Cornus sericea L.) stem tissues after beat stress. Heat stress (51°C for half an hour) was followed by one of two post-stress environment (PSE) (0° or 23°C dark condition). Isothermal measurements of the heat of metabolism of the tissues were taken after 0, 1, 2, 5, 7 and 11 days of PSE. A significant reduction of metabolic heat generation occured in heat stressed plants at 0°C PSE from one to 11 days of incubation as compared to the non-stressed tissues. At 23°C PSE, no significant differences of heat generation between stressed and non stressed tissues were found within 7 days of incubation. The rate of metabolic. heat measured by decreasing temperature scanning microcalorimetry (21° to 1°C) were lower in beat stressed tissues. Arrhenius plots of metabolic heat rate gave a linear slope for non-stressed tissues and a complex slop for NL-stressed tissues at lower temperatures. Energy of activation (Ea) between 1°-8°C were 15.45 and 83.882 KJ mol-1 for NL-heat and non-stressed tissues, respectively.
Abstract
Roots of sour orange (Citrus aurantium L.), ‘Carrizo’ citrange [C. sinensis L. (Osbeck.) × Poncirus trifoliata L. (Raf.)] and ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)] seedlings were exposed to various high temperatures for 20 minutes and heat injury was determined by electrolyte leakage procedures, microscopic examination, and visual observations. Temperatures at the midpoint of sigmoidal curves fitted through electrolyte leakage data for excised roots were 51.6° ± 0.5°C, 52.5° ± 0.7°, and 53.5° ± 0.5° for ‘Carrizo’ citrange, sour orange, and ‘Swingle’ citrumelo rootstocks, respectively. Electrolyte leakage results with excised roots were supported by microscopic examination and visual observations of whole plants.
assumed to correspond to the temperature at which the supercooled water in the bud crystalizes and the buds become critically injured through freezing. These LTE measures can provide estimates of the temperatures that would cause lethal cold damage in the
injury can reduce yields. Freeze tolerance, more generally referred to as “cold hardiness,” is measured by lethal temperature on specific plant tissues such as floral buds, xylem, or phloem. In fruit crops, freezing temperatures (<0 °C) can affect
increase of lethal temperature (loss of cold hardiness) per day (slope, °C·d −1 ). The results suggest that the worst scenario is a freezing night after warm days. High temperatures during warm days not only increase the rate of bud development but also
under each root module when RZT fell below the desired setpoint. The RZT treatments were imposed from 5 DAP until 28 DAP. The +11 °C (35 °C) root zone temperature treatment during the first growth cycle proved to be lethal to wheat after 17 d (22 DAP