Study On Growth And Chilling Hardiness In Different Pinus Caribaea Provenances

Pinus caribaea is the main species for industrial raw material.Screening fast-growing cold-resistant provenance of P.caribaea is the focus of current breeding.In this paper,16 provenances from three varieties of P.caribaea(PCH,PC B and PCB)were selected as the research objects and 4 provenances from P.elliottii were chosen as the control group.Provenance stands were set up in Lechang,Luhe and Yangdong in Guangdong respectively.Pot experiments were set up in Guangzhou.To explore the growth and adaptabilityof different provenances of P.caribae,the growth and survival rate of different provenances were observed at seedling stages.Pot experiments were carried out to evaluate the cold-resistant of P.caribaea by monitoring the growth of P.caribaea at seeding stage and the influence of chilling on the growth,phenotypes and the leaf relative conductivity(REC).Toanalyzethe response mechanism of different provenanceinP.caribaea to chilling,the magnesiumproto-porphyrin(Mg-Proto IX),the activities of phenylalanine ammonia-lyase(PAL)as well as the C hl fluorescence parameters were measured at normal temperature and natural low temperature.The main results are as follows:(1)At different sites of the provenance trial forests,the survival rate order of field is as the following: Yangdong>Luhe>Lechang,and the PC B 16 had a higher survival rate and faster growth,especially inLechang which is located at the relatively high latitude.The divergence among provenances was high in PCH.6,7,8,9 provenances showed low surviving rate and slow growth,while 12 and 18 provenances had obviousgrowth advantage.PCCgrew slowly in seedling stage,but 11 from PCB had the highest survival rate.As for the pot trial in Guangzhou,itwas showed that PCHwas the relatively fast-growing taxa,but PCC was relatively slow-growing one,and 16 from PC B showed the growth advantage at the later stage.The results of phenotype observation indicated that PCH sprouting rate were high,which may be the reason of its rapid growth,while Pinus elliottii and PCC had a lowsprouting rate and slow growth.(2)Subjected to chilling in January 2016,P.caribaea suffered chilling injury.The symptoms of chilling injury were shown below: white spots appeared on the needlesof PCH,and the needles of PCC 13 and17 turned purple.However,the PCB 16 and PCC 11 had no obvious chilling injury symptoms.Meanwhile,the needles of P.elliottiibecame reddish-yellow occurring in phenological change.The chilling stresshad affected the growth of P.caribaea.The ranking of the growth of PCH 1,3,9,10 droppedobviously among 16 P.caribaea provenances,while the ranking ofPCC 11 dropped slightly.Compared to normal temperature,the REC of PCH 1、3、6、7 and PCC 11 increased significantly under low temperature,which indicated that the above provenances had been influenced bychilling.(3)In order to explore the difference mechanism of cold tolerance of P.caribaeaprovenances,the further investigation of the physiological indexes related to stress resistance were carried outat normal and lowtemperature.The results showed that the temperature had significantly affected Mg-Proto IX contentsand PAL activities of the tested provenances,and the Mg-Proto IX of experimental materials at the natural low temperature was3.2 times more than that atthe normal temperature.The provenance had a significant effect on the soluble sugar contents and PAL activities,while the interaction effects between temperature and provenance affected PAL activities obviously.At the low temperature,the soluble sugar contents of PCH7,a poor cold-tolerant provenance,was significantly decreased,while the PAL activities of PCB16 and P.elliottiiwere significantly increased.Therefore,the results of physiological indicators were consistent with the cold-tolerantperformance of provenances.(4)The C hl fluorescence parameters were examined in July and August 2016 and February 2017 separately.It was observed that the measured time and species had a significant effect on value of the PSII maximal photochemical efficiency(Fv/Fm)and the PSII actual photochemical efficiency(Fv′/Fm′),while the interaction effect was low.The Fv/Fm and Fv′/Fm′ were higher in February than in July and August;the response models of measured times of two species were opposite in the effective quantum yield(ΦPSII),the photochemical quenching coefficient(qP)and the apparent electron trans portrates(ETR).In contrast,the ΦPSII and qP of PCB 16 were significantly higher than other provenances,while the q P of PCH 3,7,which are poor cold-tolerantprovenances,were significantly lower than the one of other provenances.According to the analysis of the growth at seedling stage and cold-tolerance of P.caribaea provenances,thePCB 16,PCH 12,18 with good and stable growth,and relatively chilling hardiness were obtained,while PCH 1,3,7which cannot stand the cold obviously were selected from 16 P.caribaea provenances.Compared with other provenances within the same species,PCC 11 had a better growth advantage,but it was sensitive to low temperature.Afurther research about thatshoule be carried out.The decrease of the concentrations of the soluble sugar and the ΦPSII,qP and the increase of the content of Mg-Proto IX might be the indicative indexes of the P.caribaeawhen itsuffered low temperature stress.The activity changes of PAL could be the evaluation indexes of cold-resistant of P.caribaeaprovenances.