Effects Of Cold Stratification Research Articles

Taiwanese montaneSambucus chinensisseeds require warm stratification, contrasting with other congeneric temperate members

AbstractMany temperate plant genera, likeSambucus, have species with range disjunctions among North America, Europe and/or Asia. Cold stratification (sometimes in combination with warm stratification) is the primary mechanism to break seed dormancy in these species. For some of these genera showing Northern Hemispheric disjunctions, members also occur in subtropical or tropical regions, mostly confined to higher elevations where climate and vegetation differ from those in northern latitudes. We made two hypotheses concerning germination for the subtropical TaiwaneseSambucus chinensis: (1) seeds from populations exposed to warm temperatures would require warm stratification, and (2) seeds from populations exposed to cold temperatures need cold stratification. We investigated the germination (including embryo growth) of non-stratified seeds over a range of temperatures and tested the effects of cold stratification and of gibberellins GA3and GA4on germination. The amount and timing of germination among populations varied substantially in response to temperature treatments. Seeds from all populations of this species required warm temperatures for dormancy break and germination, regardless of environmental conditions. As such, the majority of seeds had non-deep simple morphophysiological dormancy, which, until now, has not been reported in any members ofSambucus. The seed characteristics of the subtropicalS. chinensisare different from those of temperate members of the genus in which cold stratification is the predominate treatment to overcome dormancy.

Effects of cold stratification and dry storage at room temperature on seed germination of eight desert species from the Hexi Corridor of China

Aims We investigated seed germination of eight desert plant species of the Hexi Corridor of China following cold-wet stratification and dry storage at room temperature to better understand seed germination and dormancy characteristics and how these species are adapted to their habitat. Methods Seed viability and initial germination percentage of Glycyrrhiza uralensis, Sphaerophysa salsula, Peganum multisectum, Zygophyllum fabago, Nitraria tangutorum, Lycium ruthenicum, Salsola ruthenica and Asterothamnus centrali-asiaticus were determined. Then seeds of these species were divided into four groups (I, II, III and IV) and stored in a refrigerator ((4 ± 1) °C, moist), cold room in winter ((–5 ± 1) °C, moist), outdoor in winter ((–26 – 10) °C, moist) and room temperature ((20 ± 1) °C, dry) for 60 d. Germination was determined under a constant (20 °C) and an alternating temperature regime (25 °C / 10 °C) with 12 h photoperiod (light/dark) for 30 d. Two main germination indices including germination percentage and T50 (half germination time) were recorded. Data were analyzed by one-way ANOVA and the least significant difference test (LSD) at 5% level. Important findings There were three types of seed responses to cold-wet stratification: germination percentage increased, no change, or decreased. Germination percentage of seeds of P. multisectum and Z. fabago significantly increased following cold-wet stratification of 4 °C and –5 °C, and partially increased following –26 – 10 °C. Germination percentage of seeds of L. ruthenicum significantly increased following 4 °C, –5 °C, –26–10 °C and dry storage at room temperature, with germination of 90%–100%. Seeds of P. multisectum, Z. fabago and L. ruthenicum have slight physiological dormancy. Germination of seeds of N. tangutorum, G. uralensis and Sphaerophysa salsula slightly changed following three cold-wet stratification. Seeds of Salsola ruthenica with non-dormancy (germinated to 84% before storage) decreased their germination following cold-wet stratification of 4 °C, whereas no change occurred at –5 °C, –26 – 10 °C. In addition, the response of germination to incubation temperature varied with species.

Lipolytic activity and chilling requirement for germination of some almond cultivars

Traditionally, cold stratification for three weeks is commonly used for almonds (Prunus amygdalus Mill.) seeds germination. In this study, the effect of cold stratification in two almonds varieties: ‘‘Achaak’’ a Tunisian cultivar and ‘‘Tuono’’ an Italian cultivar was tested. The study revealed, for the first time, that only the Tunisian cultivar ‘‘Achaak’’ was able to start up its germination after 16 h of imbibition, at 26°C without any previous chilling. In these conditions, (i) hypocotyl elongation was not affected compared to the Controls, suggesting that the cold requirement of a seed is an adaptation to climatic factors; (ii) the ability of germination of 5-year-old Achaak seeds was not totally affected; (iii) the partially purified lipase showed a true neutral activity, detected at the 3-day-old germinating step. This is the first published data regarding the almond lipase identification.

Effects of cold stratification and sulphuric acid pre-treatments on germination of pomegranate (Punica granatum L.) seeds in greenhouse and laboratory conditions

This study was carried out to determine the effects of some pretreatments including soaking in concentrated (98%) H2SO4 for 10, 20, 30, 40 and 50 min and cold stratification (at 4±1°C) for 15, 30, 45 and 60 days followed by soaking in H2SO4 for 10, 20, 30, 40 and 50 min on seed germination and to investigate how to overcome dormancy of Punica granatum L. seeds. The seeds were sown in polyethylene pots in the greenhouse and sown at 22±1°C under darkness in laboratory conditions. The statistical approach was a randomized complete block design with three replications. Germinated seeds were observed periodically during 50 days to determine germination percentages and germination rates. Soaking in H2SO4 for 30 min with cold stratification for 45 days gave the highest germination percentage (60.7%) in the laboratory while, the highest germination percentage (85.5%) was obtained from soaking in H2SO4 for 40 min with 30 day cold stratification pre-treatment although there were not any significant differences for germination percentages between pre-treatments in the greenhouse. In addition, the best germination rate (21 days) was obtained from the seeds which were soaked in H2SO4 for 30 min with 45 day cold stratification and soaked in H2SO4 for 40 min with cold stratification for 45 days pre-treatments in the greenhouse. Key words: Dormancy, germination, pre-treatment, Punica granatum, seed.

Effect of cold stratification, scarification and hormones on germination of dimorphic seeds of Atriplex centralasiatica under saline conditions

1 Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 286 Huaizhong Road, Shijiazhuang, 050021 P.R. of China (E-mail: W. Li: wqli@ms.sjziam.ac.cn; X. Liu: xjliu@ms.sjziam.ac.cn) 2 Plant Science Center, RIKEN, Institute of Physical and Chemical Research, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan (E-mail: a-hanada@riken.jp) 3 Institute of Sustainable Halophyte Utilization, University of Karachi, Karachi-75270, Pakistan (E-mail: ajmalk@uok.net.pk)

Geographic Variation in Germination Traits in Melia azedarach and Rhaphiolepis umbellata

Some plant species traits may not be uniform across populations distributed across a wide latitudinal range. This study examined intraspecies variation in the effects of cold stratification on the germination of seeds of two widespread trees, Rhaphiolepis umbellata (Rosaceae) and Melia azedarach (Meliaceae), collected from the subtropical Ogasawara Islands (southern seeds) and the temperate Japan mainland (northern seeds). Under the no-treatment control, the southern seeds germinated faster in R. umbellata and achieved a higher germination percentage in M. azedarach. The regional differences in germination performance were reduced by cold stratification. It was reasonable that these germination traits increase fitness under each climate region. Because the remote Ogasawara populations are sufficiently isolated to have developed some distinct characteristics, even common, widespread species may have important conservation value where they exist within insular biota.

Understanding the germination of bulbils from an ecological perspective: a case study on Chinese yam (Dioscorea polystachya)

Bulbils serve as a means of vegetative reproduction and of dispersal for many plants; this latter aspect making them analogous to seeds. However, germination of bulbils may differ considerably from seeds due to dissimilar anatomical structures and perhaps environmental cue perception. The few laboratory studies done on bulbils suggest that their germination is similar to that of seeds in the same habitats and to vegetative buds of winter-dormant plants. The present study is the first to examine how bulbil germination is controlled in nature in relation to dispersal (before vs. after winter of the same cohort) and to ambient temperatures. Under laboratory conditions, temperature and light requirements for root and shoot emergences from bulbils of Dioscorea polystachya collected in September, 2005, February, 2006 (produced in 2005) and July, 2006 were determined. Effects of cold stratification and dry storage for releasing dormancy were tested on September and July bulbils. The phenology of dormancy release and of root and shoot emergences and the persistence of bulbils in soil were followed over time under field conditions. Although a low percentage of bulbils collected in July or in September produced roots, but no shoots, in the laboratory and field, these roots died within approx. 1 month. Regardless of collection date, cold stratification markedly increased root and shoot emergences. Bulbils sown outdoors in October produced roots and shoots the following March and April, respectively. The soil bulbil bank is short lived. Bulbils of D. polystachya are similar to seeds of many temperate plants being mostly dormant when dispersed in summer or autumn and overcoming dormancy with cold stratification during winter. Adaptively, bulbil germination primarily occurs in spring at the beginning of a favourable period for survivorship and growth.

Effects of cold stratification and sulphuric acid pretreatments on germination of three provenances of smoke-tree (Cotinus coggygria Scop.) seeds in greenhouse and laboratory conditions

This study was carried out to determine which pre-treatments should be preferred to overcome dormancy problems of Cotinus coggygria seeds which were collected from three different provenances. Pre-treatments applied to the seeds were submersion in concentrated (98%) sulphuric acid (10, 20, 30, 40 and 50 min) and submersion in sulphuric acid (10, 20, 30, 40 and 50 min) followed by cold stratification (15, 30, 45 and 60 days). The seeds were sown in polyethylene pots in the greenhouse and sown at 22 ± 1°C under darkness in laboratory conditions. The statistical approach was a randomized complete block design with 3 replications. Germinated seeds were observed periodically for 50 days to determine germination percentages and germination rates. Submersion in H2SO4 for 50 min with cold stratification for 15 days gave the highest germination percentage (88.1%) in the laboratory while, while the highest germination percentage (70.2%) was obtained from submersion in H2SO4 for 10 min with cold stratification for 30 days pre-treatment in the greenhouse. The analyses also revealed that the seeds collected from Ardanuc resulted in the highest germination percentage value (44.6%) in the laboratory among the provenances. The highest germination percentage (53.2%) sown in the greenhouse conditions was determined from the seeds collected in Artvin.

Effects of cold stratification and sulphuric acid pretreatments on germination of three provenances of smoke-tree (Cotinus coggygria Scop.) seeds in greenhouse and laboratory conditions

This study was carried out to determine which pre-treatments should be preferred to overcome dormancy problems of Cotinus coggygria seeds which were collected from three different provenances. Pre-treatments applied to the seeds were submersion in concentrated (98%) sulphuric acid (10, 20, 30, 40 and 50 min) and submersion in sulphuric acid (10, 20, 30, 40 and 50 min) followed by cold stratification (15, 30, 45 and 60 days). The seeds were sown in polyethylene pots in the greenhouse and sown at 22 ± 1°C under darkness in laboratory conditions. The statistical approach was a randomized complete block design with 3 replications. Germinated seeds were observed periodically for 50 days to determine germination percentages and germination rates. Submersion in H2SO4 for 50 min with cold stratification for 15 days gave the highest germination percentage (88.1%) in the laboratory while, while the highest germination percentage (70.2%) was obtained from submersion in H2SO4 for 10 min with cold stratification for 30 days pre-treatment in the greenhouse. The analyses also revealed that the seeds collected from Ardanuc resulted in the highest germination percentage value (44.6%) in the laboratory among the provenances. The highest germination percentage (53.2%) sown in the greenhouse conditions was determined from the seeds collected in Artvin.

Lipid mobilization, gluconeogenesis and ageing-related processes in dormant walnut kernels during moist chilling and warm incubation

AbstractTo understand the beneficial effects of cold conditions during the alleviation of dormancy of walnut (Juglans regiaL.), lipid mobilization, gluconeogenesis and changes related to ageing were compared in dormant kernels incubated in the cold and under deteriorating warm conditions. Stratifying kernels at 5°C for 30 d enhanced their germination capacity, whereas warm-incubated (27°C) kernels turned rancid after 20 d and had reduced germination. Kernel imbibition was sufficient to bring about lipid mobilization, irrespective of temperature of incubation. Although imbibed kernels displayed high isocitrate lyase activity, starch and soluble sugar accumulation occurred only under cold conditions. Deteriorative 64 kDa fatty acyl-ester hydrolase activity declined in cold-stratified kernels. Cold treatment also led to reduced lipid peroxidation and hydrogen peroxide in kernels. The activity of NADP+-isocitrate dehydrogenase, an NADPH-generating enzyme, declined in warm-incubated kernels. Thus, warm-incubated kernels undergo ageing associated with oxidative stress, but there are beneficial effects of cold stratification in preventing deteriorative ageing-related processes. Imbibition is sufficient to allow lipid mobilization to occur in dormant walnut kernels, although cold stratification accompanied by gluconeogenesis is essential for kernel germination.

Germination requirements of the alpine endemic Silene elisabethae Jan: effects of cold stratification, light and GA3

Summary Silene elisabethae Jan (Caryophyllaceae) is a narrow endemic plant species that occurs in calcareous grasslands of the Southern Italian Alps, and is protected by National and Regional Red Lists (IUCN). Seed germination requirements of this species were studied for the fi rst time with the aim of producing appropriate germination protocols for use in ex situ conservation. Seeds were collected from three populations and sown on agar in the laboratory. Increasing durations of cold stratifi cation resulted in an increase in germination from 20 to 90%. In addition, GA3 could substitute for a cold stratifi cation requirement resulting in 90 to 100% germination in the absence of chilling. All populations germinated to higher levels in the light than dark, and populations from the coldest collection site germinated better at low temperatures, suggesting adaptation of seed germination behaviour to the local microclimate. Our results indicate that seeds of S. elisabethae exhibit non-deep physiological dormancy and that light plays an important role as a germination cue.

Effects of cold stratification, sulphuric acid, submersion in hot and tap water pretreatments in the greenhouse and open field conditions on germination of bladder-Senna ( Colutea armena Boiss. and Huet.) seeds

This study was carried out to determine which pre-treatments should be preferred to overcome dormancy problems of Colutea armena seeds which were collected from three different provenances. Pre-treatments applied to the seeds were submersion in concentrated (98%) sulphuric acid for 30 min, floating in hot water (100°C) followed by continual cooling for 24 h in the same water, soaking in tap water (20 ± 1°C) for 24 h and cold stratification for 20, 40 and 60 days. The seeds were sown in polyethylene pots in the greenhouse and in seedbeds under open field conditions. The statistical approach was a randomized complete block design with three replications. Germinated seeds were observed periodically during 70 days to determine germination percentages and germination rates. The highest germination percentages (52.2, 56.7 and 60.5%) were obtained in seeds which were submersed in sulphuric acid for 30 min and sown in the greenhouse for all three provenances. The best germination rates for provenances of Kopruba
ý and Derinkoy were 14 and 16 days which were determined in seeds soaked in sulphuric acid for 30 min and sown in the greenhouse. On the other hand, the best germination rate (12 days) of provenance of Salkýmlý was determined in seeds which were floated in hot water (100°C) followed by continual cooling for 24 h in the same water and sown under open field conditions.

Effect of cold exposure on seed germination of 58 plant species comprising several functional groups from a mid-mountain Mediterranean area

The effects of cold stratification on seed germination of 58 species from a Mediterranean area in central—eastern Spain were studied. The area is subject to fires and has a very continental climate, with long winters (187 frost days during the year). Differences in germination among species taking into account their phylogeny were studied by dividing them according to their life form (chamaephytes, hemicryptophytes), post-fire regeneration strategy (non-sprouters, sprouters), and geographical distribution range (Iberian Peninsula endemics, Mediterranean, widely distributed species). Treated seeds were stratified at 5 °C for 4 weeks, then incubated, along with the control seeds, at 15 °C for 6 weeks. Most species were not affected by cold stratification, and in the cases where they were, germination was generally lower after stratification, not higher. In general, germination percentages were low, which shows that stratification by itself was not able to break seed dormancy. Functional groups differing in their post-fire regenerative strategy or distribution range showed differing responses. Sprouters and endemic species from the Iberian Peninsula were negatively affected by stratification treatment. This is interpreted as a mechanism to stop germination after winter, preventing plants from late germination in spring, which would leave them facing summer drought without a deeply developed root system.

Germination of Dimorphic Seeds of the Desert Annual Halophyte Suaeda aralocaspica (Chenopodiaceae), a C4 Plant without Kranz Anatomy

Suaeda aralocaspica is a C4 summer annual halophyte without Kranz anatomy that is restricted to the deserts of central Asia. It produces two distinct types of seeds that differ in colour, shape and size. The primary aims of the present study were to compare the dormancy and germination characteristics of dimorphic seeds of S. aralocaspica and to develop a conceptual model of their dynamics. Temperatures simulating those in the natural habitat of S. aralocaspica were used to test for primary dormancy and germination behaviour of fresh brown and black seeds. The effects of cold stratification, gibberellic acid, seed coat scarification, seed coat removal and dry storage on dormancy breaking were tested in black seeds. Germination percentage and recovery responses of brown seeds, non-treated black seeds and 8-week cold-stratified black seeds to salt stress were tested. Brown seeds were non-dormant, whereas black seeds had non-deep Type 2 physiological dormancy (PD). Germination percentage and rate of germination of brown seeds and of variously pretreated black seeds were significantly higher than those of non-pretreated black seeds. Exposure of seeds to various salinities had significant effects on germination, germination recovery and induction into secondary dormancy. A conceptual model is presented that ties these results together and puts them into an ecological context. The two seed morphs of S. aralocaspica exhibit distinct differences in dormancy and germination characteristics. Suaeda aralocaspica is the first cold desert halophyte for which non-deep Type 2 PD has been documented.

Cold stratification, light and high seed density enhance the germination of Ottelia alismoides

The effects of cold stratification, light and seed clustering in petri dish on Ottelia alismoides seed germination were investigated. The seeds required light and an extended cold period in order to germinate, but neither treatment alone was effective. Seed germination significantly increased with length of the 4 °C cold stratification period. Freshly collected seeds failed to germinate while a 5-month period at 4 °C yielded 29 ± 9% germination in the light, but none in the dark. Treatment with sodium nitroprusside, a nitric oxide source, failed to promote germination in the light or dark. Seeds of O. alismoides showed an unusual and significant positive response to aggregation. Germination in the light, after 5-month 4 °C cold stratification, was stimulated to almost five-fold in the dishes that were more densely sown with seed (20 seeds versus 200 seeds). Likewise, clustering seeds in dense aggregations stimulated germination significantly. Germination more than quadrupled with an increase from 1 to 50 seeds per cluster (200 seeds per dish), reaching a value of 72 ± 4%. Linear regression analysis shows the correlation between seed cluster density (no. per cluster) and germination rate (%) was highly significant ( R 2 = 0.85, P = 0.000). The extended cold stratification requirement is probably an over-wintering device. The mechanism of the density-dependent stimulation is unclear.

Germination ecology of Central Asian Stipa spp: differences among species, seed provenances, and the importance of field studies

Stipa-species are wide-spread in Central Asia, but sexual reproduction in the dry steppes is rare. To facilitate conservation and restoration of these important rangelands, we studied germination characteristics of three common Mongolian Stipa-species under field- and lab conditions. Seeds of Stipa krylovii, Stipa gobica and Stipa glareosa were sown at the study site in Southern Mongolia over two consecutive years during which period tests were carried out to ascertain whether competition or herbivory are the main constraints of seedling establishment. In addition, we tested germination and seed viability in the laboratory under two different temperature regimes (20/10°C and 8/4°C), as well as the effect of cold-stratification. The lab experiments also included S. krylovii seeds originating from three climatically different provenances. None of the three Stipa-species seedlings emerged during the first 2 years of the field study. However, after an unusually intense rain event in the third year, 3% of S. krylovii, 0.6% of S. glareosa and 0.1% of S. gobica seeds germinated in the study plots. The factors ‘sowing-year’ and ‘vegetation’ significantly affected seedling emergence, whereas grazing had no effect at all. Under laboratory conditions a high percentage of viable seeds of S. gobica and S. glareosa germinated at both incubation temperatures, and cold-stratification had no effect on germination or viability. Germination of S. krylovii seeds required warmer temperatures and cold-stratification had a positive effect. Such evidence for dormancy was more pronounced in seeds from the moister, northern provenances. Germination of Stipa-species in the field is rare and only possible under exceptionally moist conditions. Conservation should thus concentrate on steppe conservation rather than on restoration. Where artificial reseeding is necessary, differences among species and also among different seed provenances should be taken into account.

Effects of cold stratification, sulphuric acid, submersion in hot and tap water pretreatments on germination of bladder-senna (Colutea armena Boiss. & Huet.) seeds

Effects of cold stratification, sulphuric acid, submersion in hot and tap water pretreatments on germination of bladder-senna (Colutea armena Boiss. & Huet.) seeds

Germination Techniques for Common Lambsquarters (Chenopodium album) and Pennsylvania Smartweed (Polygonum pensylvanicum)

A laboratory bioassay was conducted to describe the effects of cold stratification and solid matrix priming (SMP®) on the germination response of common lambsquarters and Pennsylvania smartweed seeds. Treating seeds of common lambsquarters with a combination of cold stratification and SMP resulted in 78% germination compared with 13% in control seeds. Analogous treatments of Pennsylvania smartweed seeds resulted in 22% germination compared with 1% for control. Improved germination of common lambsquarters and Pennsylvania smartweed seeds suggested that the combination of cold stratification and SMP treatments have potential for improving seed germination in other weed species that exhibit high levels of seed dormancy.

Ecophysiology of seed germination of wild Dahlia coccinea (Asteraceae) in a spatially heterogeneous fire-prone habitat

Dahlia coccinea grows on fire-prone xerophilous shrubland, on a lava field located in Mexico City. Two kinds of experiments were performed to test the role of fire and environmental heterogeneity on germination. The first experiment tested the effect of environmental conditions (constant and alternating temperatures, cold stratification and light). The second one tested the effects of fire and high temperatures (dry and moist heat) on germination. Seeds of Dahlia were indifferent to light. The seeds showed physiological dormancy, which was lost by after-ripening or by gibberellins. During simulated fires, dry seeds tolerated high temperatures of short duration and also withstood prolonged exposure to 60 °C. Dry heat treatment reduced the mechanical restriction for embryo growth in dormant seeds. Ash and prolonged exposure to moist heat inhibited germination. Exogenous gibberellins reversed the deleterious effects of prolonged exposure to moist heat. The effect of cold stratification was related to the seeds' physiological stage and to light conditions; stratification in the dark reduced germination. Seeds of D. coccinea could tolerate, evade, or be slightly favored by the effects of low intensity fires occurring in their habitat. Seed responses to treatments suggest that the spatially heterogeneous lava field could provide a wide variety of micro-sites where physiological dormancy could be broken and during fires seeds could maintain their viability and subsequently germinate and/or develop a seed bank.

The effects of light quality, nitrate concentration and presence of bracteoles on germination of different fruit types in the heterocarpous Atriplex sagittata

Summary We investigated the effect of light quality, nitrogen supply, fruit size and age on germination of the three types of fruit produced by Atriplex sagittata. Regardless of fruit type, seed germination was significantly reduced in the dark. Light quality had no significant effect on germination of seeds from fruit types A and B, both of which are dormant, but seeds from fruit type C, which are non‐dormant, germinated better in green light (low photon flux and red : far‐red ratio, simulating conditions in the canopy) than in white light. Optimum nitrate concentration differed between seed types but, for all, germination was reduced at the highest concentration used. The effects of cold stratification and its interaction with light and nitrogen effects were also studied. Strong interactions between stratification and light were found in all seed types but other interactions were less frequent. Three size classes of type C fruit showed similar final germination percentages but large seeds germinated more slowly. The effect of seed age was highly significant: over a 3 year period, the germinability of dormant seeds (types A + B) increased while that of non‐dormant seeds (type C) fell. The salt concentration in bracteoles of freshly ripened fruits was too low to mediate an inhibitory effect on germination. Moreover, the first autumn rain would be sufficient to remove all the salt from bracteoles. Differences between fruit types in depth of dormancy, and in response to the quality of light and to nitrate concentration in the soil, allows A. sagittata to respond to the spatial and temporal variation in environmental conditions encountered by this annual of disturbed habitats.