Cornus Stolonifera Michx Research Articles

Modeling the Vegetative Maturity of Red-osier Dogwood1

Abstract A computer model was developed to predict autumn vegetative maturity, end of summer dormancy of red-osier dogwood (Cornus sericea L. syn. Cornus stolonifera Michx.). Empirical equations were developed from growth chamber data and applied to results obtained from lath house grown plants. The model required input parameters of 2-hourly temperatures and daylengths. From the data daily phototemperature values were determined. The empirical model over-estimated the time to maturity of the lath house grown plants by only 4 days, perhaps indicating the need for a more precise measure of the critical photoperiod.

The Relationship between Vegetative Maturity and the First Stage of Cold Acclimation1

Abstract Red-osier dogwood (Cornus stolonifera Michx.) plants were grown outdoors in a lathhouse to study the relationship between vegetative maturity and the first stage of cold acclimation. Both microscopic observations and electrical impedance ratios used to measure damage of frozen stem sections verified the close association of the onset of the first stage of cold acclimation and vegetative maturity. The relationship of these processes to dormancy development is discussed.

Seasonal changes in the major ash constituents of leaves and some woody components of trembling aspen and red osier dogwood

Concentrations of N, P, K, Ca, and Mg were determined at monthly intervals over the growing season in the leaves, twig bark, and twig wood of Populus tremuloides Michx. (trembling aspen) and in the leaves and stems of Cornus stolonifera Michx. (red osier dogwood) in southern Ontario. Concentrations of N, P, and K in the leaves of both species decreased from May to August. Levels of Mg and Ca increased. Nutrient changes in aspen twigs during the May to September period, with the exception of magnesium, followed the reverse direction to those in the leaves. Seasonal changes in all of the nutrients in twigs were very small. Seasonal nutrient variability in red osier stems was also slight, but concentrations of Mg and Ca showed a July peak, and K showed a peak in June. N and P declined from early spring to midsummer but by September in dogwood the levels had returned to the April values.

Water Relations, Stomatal Behavior, and Root Conductivity of Red Osier Dogwood during Acclimation to Freezing Temperatures

Red osier dogwood (Cornus stolonifera Michx.) was artificially acclimated by exposing plants to 8-hour short days (SD) and low (15/5 C) temperatures for 54 to 63 days. Several factors including transpiration rate, stomatal resistance, and root conductivity were correlated so that the rate of water loss in acclimating plants was higher during the first 30 to 40 days of the acclimation sequence. Six days after transferring plants to SD conditions, the stomatal resistance (r(8)) decreased significantly below the r(8) of the 16-hour long day (LD) control plants at the same temperature. Transpiration rate increased by approximately 20 to 30% in the plants transferred to SD. After the initially higher transpiration rate and greater stomatal opening, the stomates closed tightly during the last 2 weeks of acclimation and the transpiration rate of the SD plants dropped to well below the LD control plants. By the end of the acclimation sequence, root conductivity to water uptake was two to three times lower in the SD plants. Leaf xylem water potentials were similar or slightly lower in the plants kept under SD conditions during the first 5 to 7 weeks of the acclimation sequence. During the last 10 to 15 days of acclimation when the stomates closed, SD leaf water potential rose significantly above the plants in the LD conditions. During acclimation, stem water content decreased by 40 to 50%. Changes in tissue hydration can be indirectly related to plant hardiness and may be affected by alteration of stomatal resistance, transpiration rate, and root conductivity during acclimation.

Ethephon-induced Defoliation and Delay of Spring Growth in Cornus stolonifera Michx.1

Abstract The effectiveness of (2 chloroethyl)phosphonic acid (ethephon) in inducing defoliation and in delaying spring bud growth of red-osier dogwood was related to the time of application. Plants treated with ethephon before they matured were not effectively defoliated. Mature plants were effectively defoliated and ethephon’s effectiveness increased progressively at subsequent treatment dates. Ethephon treatments applied on September 29, October 6 and 13, delayed spring bud break by 7, 5, and 3 days respectively. Hand defoliation on the same dates induced identical delays in spring growth.

The Relationship of Vegetative Maturity to Rest Development and Spring Bud-break1

Abstract Rest period, the transition between summer and winter dormancy, and vegetative maturity were studied in red-osier dogwood (Cornus stolonifera Michx.) in Oregon. Maximum rest occurred in late October and early November when 180 days were required for growth resumption under favorable growing conditions. The transition between summer dormancy (correlative inhibition of lateral buds) and winter dormancy (onset of rest) occurred in early September, 21 days before maturity, 49 days before natural leaf abscission, and 56 days before maximum rest. Lateral buds of plants defoliated prior to this transition grew within 10 days while buds of plants defoliated after that date did not resume growth until spring. Vegetative maturity was achieved in late September. Plants defoliated after that time overwintered without apparent injury. Spring regrowth was normal in mature plants, but bud-break was delayed as much as 10 days as a result of defoliation the previous autumn. Vegetatively immature plants defoliated before late September died outright or sustained varying degrees of stem dieback. Natural leaf abscission occurred in late October, 49 days after plants were vegetatively mature. The extent of stem dieback was inversely related to stage of maturity, a relationship that provides a useful means of quantitatively expressing when, and to what extent, plants are mature.

Induction of Frost Hardiness in Stem Cortical Tissues of Cornus stolonifera Michx. by Water Stress

A decrease of protein, RNAs, and starch, and an increase of sugar were observed in 3-day water-stressed red osier dogwood plants (Cornus stolonifera Michx.) when the frost hardiness increased from -3 to -6 C. As the frost hardiness increased to -11 C after 7 days of treatment, the starch continuously decreased, however, the proteins and RNAs increased with a continuous increase of sugar. Further water stress treatment had little effect on the changes of these chemicals. Control plants in short days showed similar gradual biochemical changes in patterns. From the results of frost hardiness increases, the pattern of biochemical changes, and the mechanism of the increased freezing resistance, it appears that the water stress and short days accomplished essentially the same physiological end(s) in inducing frost hardiness in red-osier dogwood.

Induction of Frost Hardiness in Stem Cortical Tissues of Cornus stolonifera Michx. by Water Stress

Water supply and day length were varied in cold hardiness studies of red osier dogwood plants (Cornus stolonifera Michx.). The frost killing temperature, the content and freezing of stem cortical tissue water along with soil moisture content and tension were evaluated. Seven days of water stress in long and short day photoperiod regimes caused a rapid decrease in soil moisture content and plant water potential. During the same period, the frost hardiness increased from -3 to -11 C. Further water stress treatment had little effect. Control plants in short days showed only a gradual decrease in plant water potential and only gradually increased in frost hardiness while control plants in long days were unchanged. Freezing studies using nuclear magnetic resonance showed that increased hardiness in water-stressed plants resulted from both an increased tolerance of freezing and an increased avoidance of freezing, the latter resulting from higher solute concentration in the tissue solutions. The short day controls also showed similar changes; however, the changes were smaller over the 21 days of the study.

NaCl and twig dieback along highways and cold hardiness of highway versus garden twigs

The timing and amount of stem damage and bud kill, along with the Cl content of twigs, were observed over one or two winters in Fraxinus pennsylvanica Marsh, Cornus stolonifera Michx, Malus sp. cv. Hopa, Salix pentandra L., and Syringa vulgaris L. growing along Minnesota highways. Depending on species and the year, damage occurred between January and May.Cold hardiness was compared for highway- and garden-grown Syringa vulgaris L. and Fraxinus pennsylvanica Marsh. Hardiness was assessed as percentage of xylem and cambial browning and percentage of bud kill after exposure to test temperatures between −45 and +4 °C. In November, hardiness was the same, but from mid-December into March, highway twigs showed more damage than garden twigs at the same test temperatures. The differences between highway and garden twigs coincided in time with differences in twig Cl.

Light Intensity Effects on Redosier Dogwood1

Abstract Plants of Cornus stolonifera Michx were grown in shade frames providing 100%, 75%, 53% and 27% natural light Plants with 75% light grew the most and plants with 27% light grew the least as indicated by plant height and weight. Other treatments produced intermediate growth responses.

Nuclear Magnetic Resonance of Water in Cold Acclimating Red Osier Dogwood Stem

The pulsed and continuous-wave nuclear magnetic resonance of water in cold-acclimating red osier dogwood (Cornus stolonifera Michx) stem showed reduced relaxation times and increased line width. The reduction of relaxation times suggests an over-all restriction in the motional characteristics of the water. The increased line width is not related to a molecular property of the water, but is useful in estimating the initiation of cold acclimation. Biphasic relaxation characteristics may be related to partitioning of the water at the cellular level. The liquid water content of the stem was a weak function of temperature between -25 and -55 C, corresponding to approximately 0.15 gram of water per gram of dry stem. The quantity of unfrozen water at subfreezing temperatures was not strongly dependent on the degree of cold acclimation. It is concluded that the ability of dogwood to survive low temperatures depends on its ability to tolerate diminished quantities of liquid water.

Water Permeability and Cold Hardiness of Cortex Cells in Cornus stolonifera Michx.—A Preliminary Report

The relationship of freezing resistance to water permeability of cortex cells was studied in stems of red osier dogwood (Cornus stolonifera Michx.). Permeability was estimated by determining the diffusion flux of tritiated water from cortex slices previously equilibrated in tritiated water. Energy of activation and diffusion time comparisons of tritiated water flux from living cortex slices and slices killed by immersion in liquid N(2) verified that intact membranes of uninjured cortex cells limited water flux.Water permeability of living phloem and cortical parenchyma cells increased during the initial (photoperiodically induced) phase of cold acclimation. This accompanied an increase in hardiness from -3 to -12 C. Little if any further increase in permeability was noted during subsequent acclimation to below -65 C.Permeability measurements on nonhardy cortex samples yielded consistent results, but measurements on samples from hardy twigs were often difficult to reproduce. This unexplained variability precludes specific conclusions, but the tritiated water diffusion flux technique may provide an alternative to traditional plasmolytic techniques in studying water permeability in woody plant tissues.

Changes in Water Relations of Cornus stolonifera During Cold Acclimation1

Abstract Stomatal resistance of leaves, water absorption through roots, and water content of stem internodes was evaluated during cold acclimation of red-osier dogwood (Cornus stolonifera Michx.). Four weeks of short-days at 20/15°C resulted in a significant reduction in stem water content. This reduction was related to water lost from pith cells as this tissue senesced sequentially in successively younger internodes from the stem base to its apex at autumn growth cessation. A 1.5 fold decrease in relative stomatal resistance of leaves and a 3.5 fold increase in resistance to water flow though roots at 0.15 bars tension occurred prior to hardening to -12°C. Additional hardening to -40°C resulted in a 28 fold increase in resistance to forced water flow through roots and equalization of water content in all internodes. Thereafter, water content remained constant but stems continued to harden to temperatures below -65°C. Comparison of resistance to forced water flow through living and dead roots from hardy and tender plants suggested there was a decrease in the permeability of root cells to water during the initial (-12°C) stage of acclimation. Root surfaces became suberized, as acclimation progressed, giving rise to an additional barrier to water uptake in roots of very hardy plants (-45°C). It seems likely that the decrease in hydration of overwintering stems during cold acclimation results from a decreased stomatal resistance and increased root resistance to water movement.

The Influence of Sugars on Growth and Cold Acclimation of Excised Stems of Red-osier Dogwood1,2

Abstract Excised Cornus stolonifera Michx. stems cultured axenically in a liquid medium were acclimated to cold when subjected to short photoperiods and low temperatures. Foliate explants acclimated effectively and defoliated ones did not when they were cultured on White's medium which contained 0.083 M sucrose. Several other concentrations of sugars (0, 0.01, 0.1, and 0.5 M glucose and 0, 0.01, 0.05, and 0.1 M sucrose) did not enhance cold acclimation of foliated explants. The exogenously supplied sugars reduced stem growth, promoted leaf abscission, and enhanced the development of typical autumnal red coloration in leaves and stems. The highest sugar concentration (0.5 M glucose) caused death of the explants. While a minimal level of photosynthate (sugar) is almost certainly required for the active metabolic phases of cold acclimation in hardy woody species, our studies provided no evidence that sugars bear a direct causal relationship to cold acclimation.

Factors Affecting Electrical Impedance of Internodal Stem Sections

A sample holder was designed and built to facilitate measuring the magnitude and phase angle of the electrical impedance of internodal stem sections from Cornus stolonifera Michx. A nonpolarizing, electrically conducting manganese dioxidecarbon paste used between the stem sample and the electrodes of the sample holder allowed measurement of impedance at frequencies from 50 hertz to 500 kilohertz without electrode polarization or electrical interference. The impedance magnitude was linearly dependent on the sample length, but this dependence was minimized by computing a normalized impedance magnitude. The normalized impedance magnitude (Z(nf)) was calculated using the impedance magnitude (Z) at any specified frequency (f) and the impedance magnitude at 500 kilohertz (Z(500 khz)) in the following formula: Z(nf) = (Z - Z(500 khz))/Z(500 khz). The normalized impedance magnitude was sensitive to injury produced by boiling and peeling the sample. Electrical impedance measurements on the bark and wood separately demonstrated that they have different electrical properties.

Relationship of Electrical Conductance at Two Frequencies to Cold Injury and Acclimation in Cornus stolonifera Michx.

The ratio of electrical conductance measured at two frequencies can be used to predict the cold hardiness of stem sections of Cornus stolonifera Michx. during the first stage of cold acclimation. Electrical conductance at 50 hertz divided by electrical conductance at 100 kilohertz gave a better estimate of hardiness than measurements at either frequency alone. The observed increase in the electrical conductance ratio as hardiness increased is consistent with an increase in membrane permeability. After plants were exposed to nonlethal frost, hardiness increased rapidly, and the relation between the conductance ratio and hardiness changed. This change indicates that ice crystallization induces a significant physiological alteration in the plants. Contrary to expectations, stem sections exposed to lethal temperatures could not consistently be separated from sections exposed to nonlethal temperatures by electrical conductance ratio measurements made immediately after thawing.

A Translocatable Cold Hardiness Promoter

Hardy woody species which cold acclimate late or slowly are often injured by early autumn frosts. Adapted hardy species characteristically stop growing and acclimate to some extent prior to autumn frosts. In nature this first stage of acclimation appears to be induced by shortening photoperiods in a number of woody species (4, 23, 24). Because growth cessation is associated with cold acclimation in woody plants, a considerable amount of work has been done to determine whether growth retarding chemicals can induce cold acclimation in the absence of inductive photoperiods. The growth retardants tested have been found to have only slight and often inconsistent effects on hardiness (7, 8, 13, 15). Such findings have stimulated interest in elucidating the effective endogenous system(s) which induce acclimation in hardy species (7, 8). Several researchers have recently reported that short-day-induced leaves are the source of translocatable hardiness promoting factor(s) (4, 5, 10). The existence of such a factor(s) is of practical interest because it (they) may prove to be a relatively simple compound(s) which could be applied exogenously to induce acclimation in the absence of inductive environmental stimuli. There is, as yet, no evidence to indicate whether or not the promoting factor(s) is genotype specific. A considerable amount of research has been done on the environmental control of cold acclimation (1, 4, 10, 24), the natural patterns of acclimation (4, 22), and the metabolic changes associated with acclimation (14) in red-osier dogwood (Cornus stolonifera Michx.). In nature, acclimation usually proceeds in two distinct stages which appear to be induced by short days and low temperatures (4, 21, 22), respectively. Climatic races collected from various sites in North America were found to differ greatly in the timing and rate of cold acclimation when they were grown in a uniform environment field plot in Minnesota (18). In the field at St. Paul, Minnesota (45° North latitude), a clone from Dickinson, North Dakota (47° North latitude), was found to begin cold acclimating as much as 8 weeks earlier in the autumn than a clone from Seattle, Washington (47° North latitude) (20). Both races eventually acclimate to below -196 C, but the Seattle race is often injured severely by the first frost in the autumn at St. Paul. The influence of gibberellic acid and abscisic acid on cold acclimation has been studied in the hardy tree, Acer negundo (8). Based on these results, Irving has suggested that abscisic acid may be the hardiness promoting factor (6).

Patterns of Variation Among Climatic Races of Red‐Osier Dogwood

Red—osier dogwood (Cornus stolonifera Michx.) clones were collected from 21 locations in the natural range of the species and grown in a uniform plot at St. Paul, Minnesota, to determine the extent and nature of geographic variation. Significant variations in plant form and growth rate were noted. Genetic influence among the climatic races was apparent in autumnal phenological events such as onset of rest, change of bark color, and leaf abscission. These events were related to provenance features such as winter minimum temperatures, length of growth season, and to a lesser extent to latitude. The time at which cold hardening began in the autumn differed among clones, but no differences were noted in the ultimate degree of hardiness in midwinter. Spring bud break and flowering occurred at about the same time in all clones, while the loss of red bark color varied. Controlled environment and field tests indicated that photoperiod was the prime factor triggering autumn phenomena, while temperature was most important in the spring.

Cold Acclimation in Cornus stolonifera under Natural and Controlled Photoperiod and Temperature

Seasonal changes in the cold resistance of the living bark of red-osier dogwood (Cornus stolonifera Michx.) were characterized. Concomitant observations were made of dormancy, bark pigmentation, rest period, and leaf abscission. Cold acclimation proceeded in two steps during autumn and ultimately reached a level below -125 F. Plants subjected to decreasing photoperiod and temperature in controlled environment chambers were also induced to acclimate to below -100 F. Plants subjected to decreasing photoperiod alone did not appreciably acclimate to cold, while those subjected to decreasing temperatures alone acclimated only slightly. When a rest period induced by short days preceded exposure to gradually decreasing temperatures, the cold acclimation was rapid and substantial. Cold-acclimated plants maintained a high degree of cold resistance long after the chilling requirements for breaking the rest period had been satisfied. Of the visible phenological changes observed, red bark pigmentation was correlated most closely with cold acclimation.