Physiological Responses And Cold Resistance Of Five Michelia Species To Low Temperature

In this article,Annual grafting of five Michelia species(Michelia.macclurei Dandy,M.‘Danxia’,M.crassipes Law,M.‘Yuxia’ and M.yunnanensis Franch.ex Finet et Gagn)were used as test material,In this paper,five kinds of annual grafted plants of the genus Michelia were used as test materials,and two methods of natural low temperature stress and artificial low temperature stress were used to study the cold resistance from morphological structure to physiological and biochemical index changes.Concluded as follow:1.During the natural overwintering process,field freezing observation and freezing injury index calculations showed that the freezing injury index of(M.macclurei Dandy(0.000)< M.crassipes Law(0.286)< M.‘Danxia’(0.857)< M.yunnanensis Franch.ex Finet et Gagn(1.143)< M.‘Yuxia’(1.714);The cold-resistance of five Michelia species was ranked as M.macclurei Dandy> M.crassipes Law > M.‘Danxia’ > M.yunnanensis Franch.ex Finet et Gagn>M.‘Yuxia’.2.Comparative analysis of nine leaf structure indexes of five Michelia species in three periods during natural wintering.thickness of Upper epidermis The thickness of Upper epidermis,palisade tissue and spongy tissue ratio,and looseness of palisade tissue were screened by the index change rate combined with principal component analysis,which could be used as morphological indicators for cold resistance evaluation of five Michelia species.The obtained cold resistance was ranked as M.macclurei Dandy> M.crassipes Law > M.‘Danxia’ > M.yunnanensis Franch.ex Finet et Gagn>M.‘Yuxia’.3.The changes in the relative conductivity,malondialdehyde content,and superoxide dismutase activity of five Michelia species during natural overwintering at multiple low temperatures indicated that low-temperature domestication in the early winter could effectively improve the plant’s ability to withstand cooling again in the late winter and even cold spring.The values of membership functions of the five species of Michelia were very similar,and the order of cold resistance was as follows:M.macclurei Dandy> M.crassipes Law > M.‘Danxia’ > M.yunnanensis Franch.ex Finet et Gagn>M.‘Yuxia’.4.Frost damage observation results of artificial low temperature stress showed that the freezing damage to the leaf surface would be obvious when the temperature was lower than-8 ℃ for 2 hours.The frost damage of M.’Yuxia’ was the earliest,and the symptoms were the worst,followed by M.yunnanensis Franch.ex Finet et Gagn,M.‘Danxia’,M.crassipes Law,and M.macclurei Dandy only showed signs of slight freezing damage at-12 ° C,its cold resistance was the strongest.5.The value of membership function of 4 physiological indexes of 5 Michelia species under artificial low temperature stress showed that the cold resistance ability was M.macclurei Dandy > M.‘Danxia’ > M.crassipes Law> M.yunnanensis Franch.ex Finet et Gagn>M.‘Yuxia’.6.According to the relative conductivity fitting Logistics regression equation to calculate the semilethal temperature,The results showed that their cold resistance was ranked as M.macclurei Dandy(-14.362℃)> M.‘Danxia’(-13.255℃)> M.crassipes Law(-11.696℃)> M.yunnanensis Franch.ex Finet et Gagn(-9.086℃)>M.‘Yuxia’(-8.881℃).7.Based on the combination of natural low temperature stress and artificial low temperature stress,the cold resistance of five Michelia species could be ranked as M.macclurei Dandy> M.crassipes Law > M.‘Danxia’ > M.yunnanensis Franch.ex Finet et Gagn>M.‘Yuxia’.