Effect of cold stratification on the temperature range for germination of Pinus koraiensis

Germination at low spring temperatures may offer a competitive advantage for the growth and survival of plant species inhabiting temperate forest ecosystems.Pinus koraiensis is a dominant species in temperate forests of northeastern China.Its seeds exhibit primary morphophysiological dormancy following dispersal in autumn,limiting natural or artificial regeneration:direct seeding and planting seedlings in spring.The aim of this study was to determine the optimum cold stratification temperature that induces germination to increase towards lower temperatures.Seeds from two populations(Changbaishan and Liangshui)were cold stratified at 0,5 and 10℃.Germination to incubation temperatures(10/5,20/10,25/15 and 30/20℃;14/10 h day/night)were determined after 2 and 4 weeks,and 5.5 and6.5 months of cold stratification.After 5.5 months,approximately 68-91%of seeds from both populations germinated at incubation temperatures of 25/15℃and 30/20℃,regardless of cold stratification temperatures.When the cold stratification temperature was reduced to 0℃and the period increased to 6.5 months,germination at 10/5℃significantly improved,reaching 37%and 64%for the Changbaishan and Liangshui populations,respectively.After 6.5 months of cold stratification,there was a significant linear regression between cold stratification temperatures and germination at10/5℃.The range in temperatures allowing for germination gradually expanded to include lower temperatures with decreasing cold stratification temperatures from 10 to 5℃and further to 0℃.

Effects of tallowtree seed coat on seed germination

We measured physiological parameters including water uptake in-vitro embryo germination ratio, and seed coat structure observed by scanning electron microscopy （SEM） to explore the influence of seed coat on the germination of seeds of tallow tree （Sapium sebiferum （Linn） Roxb.）. Tallow tree seeds had good water permeability. We found that germination of cabbage seeds was inhibited when cabbage seeds were soaked in extracted solutions from tallow tree seed coat. Seed coat structure at the side of the radicle appeared to be a barrier to seed germination. We tested methods to break tallow tree seed dormancy. Dormancy of tallow tree seeds was overcome by soaking the seeds in 500 mg·L^-1 or 1000 mg·L^-1 GA3, followed by 100 days of cold stratification.

The coupled effect of light and temperature on dormancy release and germination of Pinus koraiensis seeds

Elucidating the regulatory mechanisms of environmental factors on seed dormancy and germination will provide guidance for tree regeneration.Toward understanding the coupled effect of light and temperature on dormancy release and germination of Pinus koraiensis seeds,we set up three light conditions(L200:200μmol m^(-2) s^(-1),L20:20μmol m^(-2) s^(-1),L0:0μm^(-2) s^(-1))and four storage temperatures[T-5:-5°C(50 days),T5:-5°C(50 days)+5°C(50 days),T25:-5°C(50 days)+5°C(50 days)+25°C(50 days),T15:-5°C(50 days)+5°C(50 days)+25°C(50 days)+15°C(50 days)]using imbibed seeds,then quantified phytohormones gibberellic acid(GA_(3))and abscisic acid(ABA)during the stratification.Germination percentage(G_(P)),mean germination time(T_(M)),and germination value(G_(V))under 25/15°C temperature and the three light conditions were then determined.Phytohormone levels and germination performances were significantly affected by light and temperature.No consistent trend was found between the phytohormone levels and G_(P) caused by light levels.Under the three light conditions,ABA concentrations in the embryo and endosperm decreased as storage temperature shifted from T-5 to T25 and increased from T25 to T15;GA_(3) decreased in nearly all four storage temperatures.G_(P) reached 40–60%in T25 storage without light irradiance.In the three light conditions,G_(P) and G_(V) were higher at T5 and T25 than at T-5 and T15;so T5 and T25 are considered as optimum storage temperatures for dormancy release and germination.At optimum temperatures,light(L200,L20)significantly increased the G_(P) and G_(V) compared with the dark(L0).At L200 and L20,significant negative correlations between G_(V) and the ABA concentrations and positive correlations between G_(V) and GA/ABA in the seed embryo were found.Temperature played a more important role in primary dormancy release and germination;light was unnecessary for primary dormancy release.Light facilitated seed germination at optimum temperatures.The dormancy release and germination of P.koraiensis seeds were controlled by a decrease in ABA concentrations or an increase in GA/ABA induced by temperature variations.

Effects of Different Treatments on Physiological Characteristics of Cephalotaxus sinensis Seeds

Cephalotaxus sinensis seeds can’t germinate even in the appropriate environment. However, numerous studies have showed that cold stratification and gibberellin acid (GA) can break the seed dormancy and promote seed germination effectively. To investigate the effect of cold stratification and different concentrations of exogenous GA3 on dormancy breaking in seeds of Cephalotaxus sinensis, we monitored germination rates and changes in soluble sugar, starch, amylase, soluble protein, free amino acid during cold stratification. The results showed that seeds stratified for 5 months germinated to 12.7%, while those disposed with 200, 400, 600 mg/L of GA3 germinated to 29.2%, 21.7%, and 18.4%, respectively. Free amino acid content was enhanced significantly, whereas soluble sugar content decreased during 45 days and then increased constantly. Additionally, the main reserves such as starch, protein decreased significantly during cold stratification, and cold stratification induced increases in the activities of α-amylase, (α + β)-amylase. The preliminary results show that the combination of GA3 and cold stratification has better effect to break seed dormancy.

Sequential temperature control of multi-phasic dormancy release and germination of Paeonia corsica seeds

Aims The physiological responses during dormancy removal and multi-phasic germination were investigated in seeds of Paeonia corsica(Paeoniaceae).Methods Seeds of P.corsica were incubated in the light at a range of temperatures(10-25 and 25/10℃),without any pre-treatment,after W(3 months at 25℃),C(3 months at 5℃)and W+C(3 months at 25℃followed by 3 months at 5℃)stratification,and a GA_(3)treatment(250 mg·l^(−1)in the germination substrate).Embryo growth,time from testa to endosperm rupture and radicle emergence were assessed as separate phases.Epicotyl-plumule emergence was evaluated incubating the germinated seeds at 15℃for 2 weeks,at 5 and 25℃for 2 months on agar water before transplanting to the soil substrate at 10,15 and 20℃and at 15℃for 2 months on the surface agar water with GA_(3).Important Findings Embryo growth,testa rupture,endosperm rupture(radicle emergence)and growth of the epicotyl were identified as four sequential steps in seeds of P.corsica.Gibberellic acid alone and warm stratification followed by 15℃promoted embryo growth and subsequent seed germination.Cold stratification induced secondary dormancy,even when applied after warm stratification.After radicle emergence,epicotyl-plumule emergence was delayed for ca.3 months.Mean time of epicotyl-plumule emergence was positively affected by cold stratification(2 months at 5℃)and GA_(3).P.corsica seeds exhibited differential temperature sensitivity for the four sequential steps in the removal of dormancy and germination processes that resulted in the precise and optimal timing of seedling emergence.