Duration Of Cold Stratification Research Articles

THE EFFECT OF COLD TREATMENT ON THE GERMINATION OF <i>CARDIOCRINUM CORDATUM</i> VAR. <i>GLEHNII</i> (LILIACEAE) SEEDS

The seeds of Cardiocrinum cordatum var. glehnii are characterized by a complex morphophysiological type of dormancy. There are three mechanisms of germination inhibition: two of them are localized in the embryo and one in the surrounding structures of the seed. To overcome these mechanisms, different temperature regimes for seed stratification are required.It was revealed that the mechanism of inhibition of embryo postdevelopment is removed at higher temperatures of 18–20°C for 1.5 months for stored seeds or 2 months for fresh ones. Optimal rates of embryo development were observed at 9–10°C. At the end of postdevelopment, the embryos in different experimental variants could significantly differ in length. However, the degree of heterogeneity of the sample by embryo length did not affect the germination rate and the final percentage of germinated seeds.@The temperature regime during embryo postdevelopment did not affect the subsequent growth of the embryonic root and seed germination, as well as cold stratification at the beginning of the experiment did not stimulate embryo growth.The development of embryo root was possible only after exposure to cold (0–2°C). It was demonstrated that the energy of seed germination and the germination rate significantly depend on the duration of cold stratification, regardless of the moment of exposure to cold. The longer the cold treatment was, the faster the seed germination. At the same time, not only cold stratification on water, but also dry storage of seeds at 0–2°C accelerated their germination.Under natural conditions, seed germination of C. cordatum var. glehnii occurs in 18–19 months after dissemination. In laboratory experiment, freshly harvested seeds of this species could be germinated in 7–8 months, taking into account that approximately 4 months of warm stratification are required for the further development of the embryo, and 3.5–4 months of cold stratification are required to remove the mechanism of germination inhibition.Differences in the duration and period of exposure to cold, however, did not affect the final percentage of germinated seeds. In almost all variants, the final percentage of germination was high (from 86 to 100%).The results of the experiment indicate that the process of seed germination of C. cordatum var. glehnii is realized in nature under the effect of different durations of temperature influences, which ensures the plasticity in the reproduction of this species in natural conditions.

Does the lag time between radicle and epicotyl emergences in acorns of pedunculate oak (Quercus robur L.) depend on the duration of cold stratification and post-stratification temperatures? Modelling with the sigmoidal growth curves approach

AbstractThe objective of this study was to determine how the current (10–16 weeks) and predicted future (2–8 weeks) length of cold stratification and current and predicted future post-stratification temperatures influence radicle and epicotyl emergence in acorns of Quercus robur. We tested radicle and epicotyl emergence at two temperatures corresponding to the current (15/6°C) and predicted future early autumn and spring temperatures (25/15°C) in Poland. We fitted models to describe and derive parameters for radicle and epicotyl emergences over time. The parameters included maximum percentage, rate of emergences, time to achieve the maximum emergence rate, emergence delay and time to 50% emergence. In most cases, the Gompertz model was the best fit, but in a few cases, the logistic model was the best. Richard's model for most of the cases did not converge. This model, according to both information criteria values, was the best fit for epicotyl emergence at 15/6°C following 8 weeks of cold stratification. Richard's model was also the best fit for epicotyl emergence at 25/15°C following 14 weeks of stratification.. Our results indicate that at temperatures typical for early autumn (15/6°C), the time necessary for radicle emergence from 50% of acorns was longer than that from acorns placed at 25/15°C. Four weeks of cold stratification extended 50% radicle emergence at 15/6°C to 70 d, whereas 12 weeks of stratification shortened the time to 11 d. When the acorns were incubated at 25/15°C, radicle emergence occurred faster than at 15/6°C and the time lag between radicle and epicotyl was shorter.

Physiological epicotyl dormancy and its alleviation in seeds of Yunnanopilia longistaminea: the first report of physiological epicotyl dormancy in China.

Yunnanopilia longistaminea is an endangered monotypic species belonging to Opiliaceae. This edible plant is an important germplasm source with a high economic value in China if propagation were less difficult. Seed dormancy and germination of this species were investigated to improve propagation. Considering seeds have a fully developed embryo and mature and are dispersed in summer, and radicles and epicotyls emerge the following autumn and next spring, respectively, we hypothesized that Y. longistaminea seeds may undergo physiological epicotyl dormancy. Seed moisture content and viability decreased as dehydration occurred. Thus, the seeds may be recalcitrant. The seed germination of this species involves two stages: radicle emergence and epicotyl (shoot) emergence. The optimum temperature was 28 °C and 28 °C/20 °C to radicle emergence. The optimum GA3 solution for the seeds undergoing shoot emergence was 100 mg L−1. The percentages of shoot emergence in seven and 14 days stratification at 5 °C were slightly higher than those in other groups. This study is the first to describe physiological epicotyl dormancy in Y. longistaminea seeds. Under natural conditions, seeds are subjected to Y. longistaminea a autumn → winter → spring temperature. Warm moist conditions and cold stratification can improve radicle emergence and alleviate epicotyl dormancy, respectively. The duration of cold stratification also significantly affects the epicotyl dormancy release of Y. longistaminea. Optimal dormancy breakage methods are warm (28 °C/20 °C) → cold (5 °C) → GA3(100 mg L−1) → warm (28 °C/20 °C).

Seed dormancy and germination changes of snowbed species under climate warming: the role of pre- and post-dispersal temperatures.

Climate warming has major impacts on seed germination of several alpine species, hence on their regeneration capacity. Most studies have investigated the effects of warming after seed dispersal, and little is known about the effects a warmer parental environment may have on germination and dormancy of the seed progeny. Nevertheless, temperatures during seed development and maturation could alter the state of dormancy, affecting the timing of emergence and seedling survival. Here, the interplay between pre- and post-dispersal temperatures driving seed dormancy release and germination requirements of alpine plants were investigated. Three plant species inhabiting alpine snowbeds were exposed to an artificial warming treatment (i.e. +1·5 K) and to natural conditions in the field. Seeds produced were exposed to six different periods of cold stratification (0, 2, 4, 8, 12 and 20 weeks at 0°C), followed by four incubation temperatures (5, 10, 15 and 20°C) for germination testing. A warmer parental environment produced either no or a significant increase in germination, depending on the duration of cold stratification, incubation temperatures and their interaction. In contrast, the speed of germination was less sensitive to changes in the parental environment. Moreover, the effects of warming appeared to be linked to the level of (physiological) seed dormancy, with deeper dormant species showing major changes in response to incubation temperatures and less dormant species in response to cold stratification periods. Plants developed under warmer climates will produce seeds with changed germination responses to temperature and/or cold stratification, but the extent of these changes across species could be driven by seed dormancy traits. Transgenerational plastic adjustments of seed germination and dormancy shown here may result from increased seed viability, reduced primary and secondary dormancy state, or both, and may play a crucial role in future plant adaptation to climate change.

Seed Germination Response to Temperature, Cold Stratification Period, and Gibberellin Treatment in Spiraea fritschiana

To improve the germination of Spiraea fritschiana seeds for mass propagation, we evaluated the effect of a range of temperatures, cold stratification periods, and gibberellic acid (GA₃) treatments on three germination characteristics. Final germination percentage (FGP) increased as the temperature for seed germination increased, up to 30°C, while the mean germination time (MGT) and the mean number of days to 30% germination (T 30 ) decreased when seeds were germinated at 25-30°C. The optimum germination temperature of S. fritschiana seeds is approximately 30°C considering FGP, MGT, and T 30 together. FGP increased with the duration of cold stratification up to a period of 6 weeks, but declined after 8 weeks of cold stratification, as prolonged cold stratification can induce dormancy with a resultant decline in germination. Pretreatment with 6-8 weeks of cold stratification or soaking seeds in distilled water or 500 mg · L -1 GA₃ for 24 h accelerated and increased the germination of S. fritschiana seeds, regardless of temperature. However, further study might be required to evaluate the effect of GA₃ concentrations lower than 500 mg · L -1 on the promotion of germination in S. fritschiana seeds.

Dormancy and germination in Rosa multibracteata Hemsl. & E. H. Wilson

Most of the achenes produced by Rosa multibracteata Hemsl. & E. H Wilson are dormant on maturity and require pretreatment to stimulate germination. To investigate the mechanism of dormancy and to develop effective methods of improving germination, roles of the pericarp, testa, and embryo of R. multibracteata in regulating dormancy were studied by investigating the effect of different pretreatments on germination. The effects of temperature and water stress were also tested with achenes treated by warm plus cold stratification. In freshly harvested achenes, pericarps are permeable and the embryo fully developed, which eliminates the possibility of physical, morphological, or morphophysiological dormancy. Germination percentage remained low (<5%) despite softening the pericarp or even removing it fully. However, fully removing the testa improved germination significantly (39%), indicating the possible presence of germination inhibitors in the testa. Dry storage, scarification with sulphuric acid (H 2SO 4), and warm stratification proved ineffective by themselves but when combined with cold stratification, improved germination and shortened the cold stratification period needed to break dormancy. Dry storage for 68 weeks followed by cold stratification for 16 or 24 weeks resulted in maximum germination (72–79%) among all the treatments. In achenes scarified with H 2SO 4, germination increased with an increase in the duration of cold stratification. Neither gibberellic acid (GA 3) nor ‘smoke water’ (water through which smoke had been bubbled for 2 h) had any positive effect on germination even on seeds that had been mechanically scarified or stratified. Both high temperature and water stress lowered germination in achenes treated with warm plus cold stratification. Our results suggest that R. multibracteata achenes have an intermediate physiological dormancy, and that dry storage for 68 weeks followed by cold stratification for 16 or 24 weeks is the best method for propagating R. multibracteata from seed.

Caryopsis germination and seedling emergence in an inland dune dominant grass Leymus secalinus

Leymus secalinus (Georg.) Tzvel. (Poaceae) is a dominant sand dune grass inhabiting the Mu-Us Sandland, semiarid China. Freshly harvested caryopses (seeds) are in non-deep physiological dormancy (non-deep PD) because of low percentage and slow rate of germination. Experiments were conducted to examine the effects of temperature, cold stratification, caryopsis coat scarification or partial removal of endosperm and sand burial on caryopsis dormancy, germination and seedling emergence. Caryopsis germination was significantly influenced by duration of cold stratification, temperature and their interactions. After 8 weeks of cold stratification, caryopsis germination percentage at 30 °C reached to 90%, equally in light or darkness. Rate and percentages of germination were also hastened and increased by scarifying the caryopsis coat or by artificial removal of different proportions of the endosperm. However, seedling developmental characteristics were significantly influenced by the proportion of the endosperm that remained in the caryopses. Seedling emergence, caryopsis germination and enforced dormancy in sand were significantly affected by sand burial depth. As sand burial depth increased, caryopsis germination and seedling emergence decreased whereas caryopsis enforced dormancy increased. 1–2 cm was the optimal depths for caryopses germination and seedling emergence. Although there were still 30% caryopses germinated at 8 cm, the maximal burial depth for seedling emergence was only 4 cm. The partial germination strategy regulated by non-deep PD, temperature and sand burial ensures that only a few caryopses germinated each time and may reduce risks for seedling survival.

Ein Beitrag zur Kenntnis über die Stratifikation und Keimung von Eschensamen (Fraxinus excelsior L.)

Summary The morpho-physiological dormant seeds of ash ( Fraxinus excelsior L.) were stratified in 2 stages for 10 or 18 weeks respectively at 23°c, followed by cold-stratification at + 4°C. During the warm stratification the morphologically differentiated, but not fully developed embryos started growth; the after-ripening took place during cold-stratification. Prolonged warm stratification increased the percentage of developed embryos and the germination capability enhanced, too. Ageing of the seeds prolonged the necessary period of stratification before the start of germination. Prolonged warm-stratification shortened the necessary duration of cold-stratification. In warm/cold-stratified embryos the content of water-soluble proteins increased to 300 %. During cold-stratification the DNA content in the embryos increased by 200—300 %. The RNA content reached 300 % after 15 weeks. The transfer after the 10th week into the cold is accompanied by a “chilling-shock”, which, however, was not observed after a transfer after the 18th week. The duration of the “chilling-shock” prolonged with increasing age of the seeds.