Effects of Red and Far Red Light on the Initiation of Cold Acclimation in Cornus stolonifera Michx

Red and far red light distinctly influence the initial phytochrome-mediated phase of cold acclimation in red-osier dogwood (Cornus stolonifera). Under controlled conditions, short days and end-of-day far red light exposure after long days promote growth cessation, cold acclimation, and subsequent cold hardening of dogwood stems in response to low temperature. Nuclear magnetic resonance absorption spectra of the water in internode stem sections imply that the short day-induced phase of cold acclimation involves a change in tissue hydration, at least in part, due to a substantial reduction in bulk phase water as a result of senescence and loss of water from the pith. Seasonal responses to light and an attempt to induce early acclimation under natural conditions with end-of-day far red light are discussed.     

Cold resistance in Antarctic angiosperms

Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Cariophyllaceae) are the only two vascular plants that have colonized the Maritime Antarctic. The primary purpose of the present work was to determine cold resistance mechanisms in these two Antarctic plants. This was achieved by comparing thermal properties of leaves and the lethal freezing temperature to 50% of the tissue (LT50). The grass D. antarctica was able to tolerate freezing to a lower temperature than C. quitensis. The main freezing resistance mechanism for C. quitensis is supercooling. Thus, the grass is mainly a freezing‐tolerant species, while C. quitensis avoids freezing. D. antarctica cold acclimated; thus, reducing its LT50. C. quitensis showed little cold‐acclimation capacity. Because day length is highly variable in the Antarctic, the effect of day length on freezing tolerance, growth, various soluble carbohydrates, starch, and proline contents in leaves of D. antarctica growing in the laboratory under cold‐acclimation conditions was studied. During the cold‐acclimation treatment, the LT50 was lowered more effectively under long day (21/3 h light/dark) and medium day (16/8) light periods than under a short day period (8/16). The longer the day length treatment, the faster the growth rate for both acclimated and non‐acclimated plants. Similarly, the longer the day treatment during cold acclimation, the higher the sucrose content (up to 7‐fold with respect to non‐acclimated control values). Oligo and polyfructans accumulated significantly during cold acclimation only with the medium day length treatment. Oligofructans accounted for more than 80% of total fructans. The degrees of polymerization were mostly between 3 and 10. C. quitensis under cold acclimation accumulated a similar amount of sucrose than D. antarctica, but no fructans were detected. The suggestion that survival of Antarctic plants in the Antarctic could be at least partially explained by accumulation of these substances is discussed.     

Photoperiodic Responses of Brassica campestris cv. Ceres

The photoperiodic responses of Brassica campestris L. cv. Ceres were investigated to determine the suitability of this plant for further studies on the spectral require ments for floral initiation. This is a long-day plant, sensitive to one inductive photocycle on the fourth day from germination. The flowering response increased with the length and intensity of a single period of supplementary light used to extend an 8-hour daylength and was greatest at 25°C. Application of nitrates retarded floral initiation by about two days under short day conditions, but did not affect the re sponse to one long day. Gibberellic acid induced earlier floral initiation under short day conditions. The photoperiodic response was little affected by omitting the main light period immediately before or after the supplementary light, as long as the intensity of supplementary light was greater than 5000 lux. Short interruptions (5–10 minutes) of a single 16-hour dark period with high energy red or far-red radiation did not promote flowering. When given continuously during a single 16-hour dark period, far-red radiation was more effective in flower promotion than an equal energy of red.     

Cold acclimation induces freezing tolerance via antioxidative enzymes, proline metabolism and gene expression changes in two chrysanthemum species

Cold acclimation is necessary for chrysanthemum to achieve its genetically determined maximum freezing tolerance, but the underlying physiological and molecular mechanisms are unclear. The aim of this study was to discover whether changes in antioxidative enzymes, proline metabolism and frost-related gene expression induced by cold acclimation are related to freezing tolerance. Our results showed that the semi-lethal temperature (LT₅₀) decreased from ?7.3 to ?23.5 °C in Chrysanthemum dichrum and ?2.1 to ?7.1 °C in Chrysanthemum makinoi, respectively, after cold acclimation for 21 days. The activities of SOD, CAT and APX showed a rapid and transient increase in the two chrysanthemum species after 1 day of cold acclimation, followed by a gradual increase during the subsequent days and then stabilization. qRT-PCR analysis showed that the expression levels of some isozyme genes (Mn SOD, CAT and APX) were upregulated, which was consistent with the SOD, CAT and APX activities, while others remained relatively constant (Fe SOD and Cu/Zn SOD). P5CS and PDH expression were increased under cold acclimation and the level of P5CS presented similar trends as proline content, indicating proline accumulation was via P5CS and PDH cooperation. Cold acclimation also promoted DREB, COR413 and CSD gene expression. The activities of three enzymes and gene expression were higher in C. dichrum than in C. makinoi after cold acclimation. Our data suggested that cold-inducible freezing-tolerance could be attributed to higher activity of antioxidant enzymes, and increased proline content and frost-related gene expression during different periods.     

Induction of freezing tolerance in spinach is associated with the synthesis of cold acclimation induced proteins

Spinach (Spinacia oleracea L. cv Bloomsdale) seedlings cultured in vitro were used to study changes in protein synthesis during cold acclimation. Seedlings grown for 3 weeks postsowing on an inorganic-nutrient-agar medium were able to increase their freezing tolerance when grown at 5°C. During cold acclimation at 5°C and deacclimation at 25°C, the kinetics of freezing tolerance induction and loss were similar to that of soil-grown plants. Freezing tolerance increased after 1 day of cold acclimation and reached a maximum within 7 days. Upon deacclimation at 25°C, freezing tolerance declined within 1 day and was largely lost by the 7th day. Leaf proteins of intact plants grown at 5 and 25°C were in vivo radiolabeled, without wounding or injury, to high specific activities with [³⁵S]methionine. Leaf proteins were radiolabeled at 0, 1, 2, 3, 4, 7, and 14 days of cold acclimation and at 1, 3, and 7 days of deacclimation. Up to 500 labeled proteins were separated by two-dimensional gel electrophoresis and visualized by fluorography. A rapid and stable change in the protein synthesis pattern was observed when seedlings were transferred to the low temperature environment. Cold-acclimated leaves contained 22 polypeptides not found in nonacclimated leaves. Exposure to 5°C induced the synthesis of three high molecular weight cold acclimation proteins (CAPs) (M_r of about 160,000, 117,000, and 85,000) and greatly increased the synthesis of a fourth high molecular weight protein (M_r 79,000). These proteins were synthesized during day 1 and throughout the 14 day exposure to 5°C. During deacclimation, the synthesis of CAPs 160, 117, and 85 was greatly reduced by the first day of exposure to 25°C. However, CAP 79 was synthesized throughout the 7 day deacclimation treatment. Thus, the induction at low temperature and termination at warm temperature of the synthesis of CAPs 160, 117, and 85 was highly correlated with the induction and loss of freezing tolerance. Cold acclimation did not result in a general posttranslational modification of leaf proteins. Most of the observed changes in the two-dimensional gel patterns could be attributed to the de novo synthesis of proteins induced by low temperature. In spinach leaf tissue, heat shock altered the pattern of protein synthesis and induced the synthesis of several heat shock proteins (HSPs). One polypeptide synthesized in cold-acclimated leaves had a molecular weight and net charge (M_r 79,000, pI 4.8) similar to that of a HSP (M_r 83,000, pI 4.8). However, heat shock did not increase the freezing tolerance, and cold acclimation did not increase heat tolerance over that of nonacclimated plants, but heat-shocked leaf tissue was more tolerant to high temperatures than nonacclimated or cold-acclimated leaf tissue. When protein extracts from heat-shocked and cold-acclimated leaves were mixed and separated in the same two-dimensional gel, the CAP and HSP were shown to be two separate polypeptides with slightly different isoelectric points and molecular weights.     

Characteristics of Cold Acclimation and Deacclimation in Tuber-bearing Solanum Species

The effect of temperatures on cold acclimation and deacclimation in foliage tissues was studied in Solanum commersonii (Oka 4583), a tuber-bearing potato. The threshold temperature for cold acclimation was about 12 C. In a temperature range of 2 to 12 C, the increase in hardiness was dependent on the acclimating temperature; the lower the acclimating temperature, the more hardiness achieved. A day/night temperature of 2 C, regardless of photoperiod, appeared to the optimum acclimating temperature for the Solanum species studied. A subfreezing temperature hardened plants less effectively. The maximum level of hardiness could be reached after 15 days of cold acclimation. However, it took only 1 day to deacclimate the hardened plants to a preacclimation level when plants were subjected to a warm regime from cold. The degree of deacclimation was dependent on the temperature of the warm regime.     

The Role of Light in Cold Acclimation of Hedera helix L. var. Thorndale

The role of light in cold acclimation of Hedera helix L. var. Thorndale appears to differ from that reported for winter annuals. Although light greatly enhances the degree of hardiness attained, cold acclimation is not obligatorily linked to a light requirement. Photoperiods, varying from 8 to 24 hours, received during the cold acclimation period were equally effective in promoting maximum hardiness. Relatively low light intensities and short photoperiods stimulated maximum hardiness, and proportional increases in hardiness in response to increased photoperiods were demonstrated only in stems of prestarved plants. Exclusion of CO₂ and high concentrations of photosynthetic inhibitors decreased hardiness, but in no instance was hardiness reduced to the level of the dark control. The data are only compatible with a photosynthetic role of light if it is assumed that only a small portion of the total photosynthates are required to elicit maximum hardiness. Alternatively, the light stimulation which was elicited by low light intensities, short photoperiods, in the absence of CO₂, and in the presence of photosynthetic inhibitors, may be a light signal similar to a phytochrome response.     

Action and interaction of red and far-red radiation on lipoxidase metabolism of squash seedlings

Lipoxidase, in the cotyledons of squash (Cucurbita moscata) seedlings grown in the dark, reached its peak activity on the fifth day and then declined to its lowest activity on the eighth day. Under continuous irradiation, the rate of enzyme disappearance was accelerated by red (655 mμ) and was retarded by far-red (735 mμ) radiation. Acceleration of enzyme disappearance caused by red light was reversed repeatedly by far-red light in seedlings that received an initial exposure to red radiation. These responses were independent of the duration of irradiation at each of the alternating wavebands. No change was observed when the white light was administered either 24 hours before or 24 hours after the red, far-red treatment.

The lipoxidase system of the seedlings given an initial exposure to far-red radiation also responded reversibly to alternating far-red, red extended exposures, but it failed to respond reversibly when short exposures were employed. Similarly, no change occurred in these seedlings when either pre- or post-treatment with the white light was applied.

These results demonstrate that the capacity of lipoxidase to act reversibly depends primarily on the duration of exposure and on the kind of light (red or far-red) to which the seedlings were exposed initially. In spite of these variations, lipoxidase metabolism can be considered an additional biochemical manifestation of red, far-red reaction that operates in the photomorphogenesis of plants.

     

Effect of Low-intensity Red and Far-red Light and High-intensity White Light on the Flowering Response of the Long-day Plant Lemna gibba G3

The long-day plant Lemna gibba L., strain G3 exhibits a relatively low sensitivity to short, white-light interruptions given during the dark period of a short-day cycle. However, the plants are fairly sensitive to low-intensity red light treatments given during a 15-hour dark period on the third day of a 2LD-(9L:15D)-2LD-7SD schedule. Far-red light is almost as effective as red light, and attempts to reverse the red light response with subsequent far-red light treatments have not been successful. Blue light proved to be without effect. When plants were grown on a 48-hour cycle with 15 minutes of red light every 4 hours during the dark period, the critical daylength was reduced from about 32 hours to slightly less than 12 hours.

Continuous red light induced a fairly good flowering response. However, as little as 1 hour of white light each day gave a significant improvement in the flowering response over that of the continuous red light control. White light of 600 to 700 ft-c was more effective than white light of 60 to 70 ft-c. The white light was much more effective when divided into 2 equal exposures given 8 to 12 hours apart. These results suggest an increase in light sensitivity with regard to flower induction about 8 to 10 hours after the start of the light period.

     

Mass spectrometric approach for identifying putative plasma membrane proteins of Arabidopsis leaves associated with cold acclimation

Although enhancement of freezing tolerance in plants during cold acclimation is closely associated with an increase in the cryostability of plasma membrane, the molecular mechanism for the increased cryostability of plasma membrane is still to be elucidated. In Arabidopsis, enhanced freezing tolerance was detectable after cold acclimation at 2 degrees C for as short as 1 day, and maximum freezing tolerance was attained after 1 week. To identify the plasma membrane proteins that change in quantity in response to cold acclimation, a highly purified plasma membrane fraction was isolated from leaves before and during cold acclimation, and the proteins in the fraction were separated with gel electrophoresis. We found that there were substantial changes in the protein profiles after as short as 1 day of cold acclimation. Subsequently, using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS), we identified 38 proteins that changed in quantity during cold acclimation. The proteins that changed in quantity during the first day of cold acclimation include those that are associated with membrane repair by membrane fusion, protection of the membrane against osmotic stress, enhancement of CO2 fixation, and proteolysis.     

Contrasting types of photoperiodic response in the control of dormancy

Abstract The effect of night-break or day-extension treatments with red (R) and/or far-red (FR) light were examined in the control of dormancy and extension growth in Weigela florida and Picea abies. Dormancy in Weigela (as assessed by the continued production of new leaves) was completely prevented by a 30 min night-break treatment with R: the effect of R was prevented by a subsequent exposure to 30 min FR. A day-extension treatment for 8.25 h with R or with R+FR also completely prevented dormancy, irrespective of whether it was given before or after a short day (SD) in sunlight. There was no significant difference between any dayextension treatment, nor between day-extension treatments and a night-break with R. Dormancy in Picea (as assessed by the maintenance of shoot growth) was also delayed by a night-break with R but less effectively than the most effective day-extension. A day-extension treatment for 9 h with R light was more effective when it preceded than when it followed a SD in sunlight. The addition of FR in the second but not in the first 9 h of a 17 h photoperiod increased its effectiveness. It is concluded that the mechanisms of the control of dormancy must differ in the two species. A day-extension for 16 h with light from tungstenfilament lamps increased stem elongation in Weigela when compared with an R night-break. This resulted from an increase in internode length and there was no significant difference between the two treatments in their effect on leaf production.     

Floral Inhibition of Biloxi Soybean During a 72-hour Cycle

The inhibitory effect of light interruptions given during the photophobe phases of a 72-hour cycle was studied with Biloxi soybean [Glycine max (L.) Merr.]. The basic 72-hour cycle consisted of 8 hours of light followed by 64 hours of darkness and was repeated 7 times. Supplementary white light treatments given at the twenty-fourth and/or forty-eighth hour of the cycle (photophil phases) promoted the flowering levels of the controls and kept light treatments given at the most inhibitory points from inhibiting flowering completely. Such supplementary light treatments did not affect the time of maximum sensitivity to light interruptions. When 30-minute light breaks were used, maximum inhibition occurred at the 16-, 43-, and 63-hour points. The duration of the light breaks affected the time of maximum inhibition when given during the second photophobe phase. The time of maximum inhibition occurred earlier with 4-hour light breaks than with either 3-minute or 2-hour light interruptions.

Three-minute red light interruptions produced essentially the same effect as 3-minute white light interruptions. Such treatments inhibited flowering completely in the first photophobe phase, inhibited flowering to only a small degree in the second photophobe phase, and inhibited flowering to an intermediate degree in the third photophobe phase. Far-red light interruptions strongly inhibited flowering in the first photophobe phase, especially when given early in the dark period. Three minutes of supplementary white light given at the twenty-fourth or forty-eighth hour of the cycle partially overcame the inhibitory effect of far-red light. Four hours of supplementary white light at these times completely overcame the far-red inhibition.

     

Effect of photoperiod and cold acclimation on survival of mice in cold

Male albino mice (Swiss-Webster) were raised at 5 °C under short (8L:16D) and long (16L:8D) light periods. All mice were housed in groups of three to five individuals in plastic mouse cages (16 × 12 × 28 cm) until 42 days of age with food and water ad libitum and cold exposed to ?40 °C between 10:00 am and 4:00 pm to determine survival time or time until loss of righting response occurred (CT min). Under short photo-periods, survival time was 49.3 ± 4.4 min and under long photoperiods it was 38.7 ± 1.9 min (P < 0.05). A second group of mice was maintained from birth at thermoneutral temperature (22 °C) under constant darkness, short day lengths (4L:20D), or constant light in the same fashion as mentioned above. When exposed to ?20 °C survival time was found to be 80.0 ± 5.0 min for the animals kept in constant darkness, 61.1 ± 2.3 min for animals raised in short photo-periods (4L:20D) (P < 0.01), and 52.4 ± 2.3 min for mice raised in constant light (P < 0.05). After 30 min mean rectal temperature was 32.1 ± 0.47 °C for constant-darkness animals, 30.5 ± 0.43 °C for short-day animals (P < 0.02), and 28.5 ± 0.74 °C for animals raised in constant light (P < 0.05). After 60 min mean rectal temperatures for constant-dark, 4L:20D, and constant-light animals were compared and body temperature was found to be 23.7 ± 1.6, 17.3 ± 1.5 (P < 0.01), and 12.8 ± 0.87 °C (P < 0.05), respectively. From these data, it is obvious that photoperiod influences cold resistance at both cold and thermoneutral acclimation temperatures although when considered individually, cold acclimation enhances cold survival to a greater degree than does reduced light exposure.     

High-light-like photosynthetic responses of Cucumis sativus leaves acclimated to fluorescent illumination with a high red:far-red ratio: interaction between light quality and quantity

This study evaluated the photosynthetic responses of Cucumis sativus leaves acclimated to illumination from three-band white fluorescent lamps with a high red:far-red (R:FR) ratio (R:FR = 10.5) and the photosynthetic responses of leaves acclimated to metal-halide lamps that provided a spectrum similar to that of natural light (R:FR = 1.2) at acclimation photosynthetic photon flux density (PPFD) of 100 to 700 μmol m^?2 s^?1. The maximum gross photosynthetic rate (P _G) of the fluorescent-acclimated leaves was approximately 1.4 times that of the metal-halide-acclimated leaves at all acclimation PPFDs. The ratio of quantum efficiency of photosystem II (Φ_PSII) of the fluorescent-acclimated leaves to that of the metal-halide-acclimated leaves tended to increase with increasing acclimation PPFD, whereas the corresponding ratios for the leaf mass per unit area tended to decrease with increasing acclimation PPFD. These results suggest that the greater maximum P _G of the fluorescent-acclimated leaves resulted from an interaction between the acclimation light quality and quantity, which was mainly caused by the greater leaf biomass for photosynthesis per area at low acclimation PPFDs and by the higher Φ_PSII as a result of changes in characteristics and distribution of chloroplasts, or a combination of these factors at high acclimation PPFDs.     

Cold Acclimation of Hedera helix: Evidence for a Two Phase Process

The light-enhanced production and accumulation of sugars is only one step in the process of cold acclimation in Hedera helix L. var. Thorndale (English ivy). Applications of 2,4-dinitrophenol to plants with different portions exposed to light and dark indicated that the mere presence or accumulation of the light-generated promoters did not invoke an increase in hardiness. Kinetics of cold acclimation during alternating periods of light and dark also indicate that the light stimulation of cold acclimation is only a partial component of the total process. Incubation on 50 mm solutions of sucrose can replace the light requirement. A second phase which can proceed in the dark is thought to result in the production of proteins which, due to an altered composition or configuration, have a greater capacity to bind sugars. This is evidenced by the fact that protein from cold acclimated tissue exhibited a higher sugar-binding capacity than protein from nonacclimated tissue. Furthermore, the two phases can proceed independently of each other, but only upon complementation of the products of the two phases is an increase in cold hardiness manifested.     

Evaluation of Polyamine and Proline Levels during Low Temperature Acclimation of Citrus

The polyamines (PA) putrescine (Put), spermidine (Spd), and spermine (Spm) were measured during 3 weeks exposure to cold hardening (15.6°C day and 4.4°C night) and nonhardening (32.2°C day and 21.1°C night) temperature regimes in three citrus cultivars: sour orange (SO) (Citrus aurantium L.), `valencia' (VAL) (Citrus sinensis L. Osbeck), and rough lemon (RL) (Citrus jambhiri Lush). The changes in PA were compared to the amount of free proline, percent wood kill and percent leaf kill. A 2- to 3-fold increase in Spd concentrations were observed in hardened RL, SO, and VAL leaves compared to nonhardened leaves. Spermidine reached its highest level of approximately 200 nanomoles per gram fresh weight after 1 week of acclimation in both SO and VAL leaves, while RL spermidine content continued to increase up to the third week of acclimation. Spm levels in acclimated VAL and RL leaves increased 1- to 4-fold. However, SO leaves Spm content decreased with acclimation. Putrescine levels in SO and VAL increased 20 to 60% during the first 2 weeks of acclimation then declined after 3 weeks. RL putrescine content was not affected by cold acclimation. The data presented here provided direct relationship between increased Spd concentration and citrus cold hardiness. Free proline was 3- to 6-fold higher in acclimated than in nonacclimated trees. Results also demonstrate that in acclimated versus nonacclimated citrus trees the absolute amount rather than the ratio of increase in free proline is more important in predicting their ability to survive freezing stress.     

The role of antioxidant defense in freezing tolerance of resurrection plant Haberlea rhodopensis

Haberlea rhodopensis Friv. is unique with its ability to survive two extreme environmental stresses—desiccation to air-dry state and subzero temperatures. In contrast to desiccation tolerance, the mechanisms of freezing tolerance of resurrection plants are scarcely investigated. In the present study, the role of antioxidant defense in the acquisition of cold acclimation and freezing tolerance in this resurrection plant was investigated comparing the results of two sets of experiments—short term freezing stress after cold acclimation in controlled conditions and long term freezing stress as a part of seasonal temperature fluctuations in an outdoor ex situ experiment. Significant enhancement in flavonoids and anthocyanin content was observed only as a result of freezing-induced desiccation. The total amount of polyphenols increased upon cold acclimation and it was similar to the control in post freezing stress and freezing-induced desiccation. The main role of phenylethanoid glucoside, myconoside and hispidulin 8-C-(2-O-syringoyl-b-glucopyranoside) in cold acclimation and freezing tolerance was elucidated. The treatments under controlled conditions in a growth chamber showed enhancement in antioxidant enzymes activity upon cold acclimation but it declined after subsequent exposure to −10 °C. Although it varied under ex situ conditions, the activity of antioxidant enzymes was high, indicating their important role in overcoming oxidative stress under all treatments. In addition, the activity of specific isoenzymes was upregulated as compared to the control plants, which could be more useful for stress counteraction compared to changes in the total enzyme activity, due to the action of these isoforms in the specific cellular compartments.Supplementary informationThe online version contains supplementary material available at 10.1007/s12298-021-00998-0.