Photoperiod-and temperature-mediated control of the ethylene response and winter dormancy induction in Prunus mume

Plant dormancy is essential for perennial plant survival.Different genotypes of Prunus mume,including Eumume group and Apricot Mei group,undergo leaf senescence and dormancy at different times.In order to verify the cold resistance of P.mume,freeze resistance evaluation was carried out.Our results showed that Apricot Mei group had a stronger freezing tolerance than Eumume group and that leaf senescence and dormancy of Apricot Mei group occurred at an earlier period before winter.Based on phenotypic data in response to seasonal climate change,the significant candidate regions were selected using GWAS.Furthermore,through KEGG pathway and qRT-PCR analyses,we found that the ethylene-related genes,including PmEIL(Pm002057)and PmERF(Pm004265),were significantly upregulated in‘Songchun’Mei(Apricot Mei group)and downregulated in‘Zaohua Lve’Mei(Eumume group).Ethylene-related genes expression models showed that ethylene may be indirectly involved in the induction of dormancy.The PmEIL and PmERF genes were the core genes of the ethylene signal transduction pathway and were regulated by the exogenous ACC or PZA compounds.For non-dormant or weekly dormant perennial plants,application of ACC was able to induce plant dormancy and thus enhance cold/freeze tolerance.Overall,the expression of the major ethylene genes played a significant role in dormancy induction and freezing tolerance in P.mume;accordingly,application of ACC and PZA compounds were an effective approach for enhancing cold/freeze of tolerance of woody plant.

Effect of Photoperiod Treatments on Dormancy Induction and Changes in Correlated Respiratory Rate of Nectarine Peach Bud

The responses of dormancy induction to illumination and the characteristics of respiratory rate were studied with the nectarine peach bud in this article. The trial was conducted with nectarine （Prunus persica var. nectariana cv. Shuguang） and involved three treatments： a short day treatment （8 h）, a long day treatment （16 h）, and the normal condition as the control. The dormancy status was determined with the growth of shoot and the sprouting ability, and the respiratory rate was mensurated with oxygen electrode. Short day treatment could induce the growth stopping of peach shoots ahead, promote the development of dormancy, and induce buds into dormancy with 21 d previous to control. Long day treatment postponed the growth stopping and the induction and development of dormancy. The respiratory rate decreased according to the development of dormancy induction. The minimum respiratory rate appeared about 7 days after the start of dormancy induction. Bud respiratory rate increased during this period and then declined and remained at low level during dormancy period. Long day reduced buds respiratory rate slightly. Short day could induce dormancy obviously, and long day postponed dormancy induction. The changes of respiratory rate were correlated with the development of dormancy induction, and the bud respiratory rate was also affected by photoperiod.

Effect of Photoperiod on Key Enzyme Activities of Respiration in Nectarine Buds During Dormancy Induction

Shuguang （Prunus persica var. nectariana cv. Shuguang） nectarine was used to study effects of photoperiod on key-enzyme activities of respiration during dormancy induction. The dormancy status was determined with sprouting ability. Spectrophotometry was used to investigate activities of phosphohexose isomerase （PGI）, malic dehydrogenase （MDH）, and glucose-6-phosphate dehydrogenase （G6PDH）. The results revealed that short day （SD） treatment promoted dormancy induction while long day （LD） treatment postponed the process. During dormancy induction, PGI activities declined, MDH activities changed little, and G6PDH activities increased both in flower buds and leaf buds. PGI activities and MDH activities in SD treatment were lower than control, and G6PDH activities were higher, which was opposite with LD treatment. The changes of respiratory key-enzyme activities were adjusted by photoperiod and correlated with the development of dormancy induction.

Effects of Photoperiod on Alternative Respiration Pathway in Nectarine Flower Buds During Dormancy Induction

Characteristics of dormancy induction and alternative respiration pathway （also known as cyanide-resistant respiration） of nectarine flower buds in different photoperiods were studied to determine the function of photoperiod and alternative respiration pathway in dormancy induction. Oxygen-electrode system and respiratory inhibitors were used to measure total respiratory rates and rates of alternative respiration pathway. The results showed that total respiration rate （Vt） in flower buds showed to be double hump-shaped curves. Short day raised, brought the first-hump of Vt forward and delayed the second-hump, while long day delayed the whole curve. The capacity （Vast） and activity （pValt） of SD and LD changed synchronously and both showed to be double hump-shaped curves. Short day made the first climax of Vast and pValt existed much earlier, while long day increased their rates significantly. The length of day had little effects on the later period climax. Long day also increased the contributions of altemative respiration pathway in total respiration rate （pValt/Vt）. The changes in alternative respiration pathway were correlated with the induction of dormancy and adjusted by photoperiod. Short day promoted dormancy induction of nectarine trees, while long day delayed it.

Photothermal controls of vegetative dormancy in Poa secunda

Background:Summer vegetative dormancy is a desirable trait in cool-season grasses when they are interplanted with annual crops.Sandberg bluegrass(Poa secunda J.Presl.)shows summer dormancy,but the environmental cues that control dormancy remain unknown.Methods:A controlled environment study using temperature and day length combinations of 32.2℃/15 h,26.6℃/14 h,21.1℃/13 h,and 15.5℃/12 h was conducted with P.secunda accessions PI232347,PI639272,and PI232348,and‘Audubon’red fescue as a nondormant control to determine the optimum treatment for dormancy induction.A second study using treatments of 26.6℃/14 h,21.1℃/13 h,and 15.5℃/12 h was conducted to determine the thresholds for dormancy release.A third study used a factorial experiment with two temperatures(32.2℃ and 15.5℃)and two day lengths(15 and 12 h)to differentiate between temperature and day length effects on dormancy induction.Results:Of the four temperature and day length combinations,all except for 15.5℃/12 h resulted in dormancy by the end of 6 weeks,with 32.2℃/15 h inducing dormancy in only 17 days.Of the three treatments for dormancy release,15.5℃/12 h broke dormancy the fastest in all accessions and released the most number of plants from dormancy.Considerable variation existed between accessions for the speed of dormancy release in the 21.1℃/13 h and 26.6℃/14 h treatments.The third study showed that temperature is the primary inducer for summer dormancy,while longer day length may promote dormancy under inductive temperatures.Conclusions:This study identified the optimum photothermal for induction and release of summer dormancy in P.secunda,which will help future studies in elucidating the mechanism of summer dormancy.