Comparative Study On Over-summering Ability Of Different Provenances Of Sorbus Pohuashanensis

Sorbus pohuashanensis(Hance Hedl)is a deciduous small tree of Maloideae(Maloideae)of the Rosaceae family,growing in slope or valley forests at an altitude of 900-2500 m.Sorbus pohuashanensis tree is a kind of excellent ornamental and landscape tree which integrates fruit viewing and leaf appreciation.Although it has been widely used in the northeast of China,it has not been used in the landscape construction of the north China plain.Sorbus is naturally distributed in heilongjiang,jilin,liaoning,Inner Mongolia,central and southern gansu,central and western shaanxi,northern shanxi,central and western hebei,shandong and southeastern anhui.In the country of origin,different provenances of Sorbus pohuashanensis have good growth and no obvious injury to the leaves.When transplanted to the north China plain,the performance of catalpa varies.In this paper,10 species of Sorbus pohuashanensis seedlings were used as materials to study the growth and summer performance of Sorbus pohuashanensis seedlings in baoding,hebei province,and to discuss the physiological and metabolic changes of Sorbus pohuashanensis seedlings during summer and the effect of exogenous salicylic acid treatment on the physiological and biochemical indexes of the seedlings.The research results are as follows:(1)The growth and survival rate of Sorbus pohuashanensis from different provenances in baoding,hebei were different.Under the shade condition,the laoshan provenance in shandong had the largest plant height growth(37.22cm),which was significantly higher than other provenances.Under the condition of which were,laoshan mountain in shandong plant full of provenance and shandong taishan provenance growth is 32.49 cm and 24.21 cm respectively,significantly higher than that of hebei west lingshan,the wuling mountain in hebei,Beijing LaPaGouMen provenance,the pangquang ditch nature reserve,shanxi,jilin,Beijing,hebei camel liangshan,mount tai in shandong,shandong laoshan provenance growth in diameter were significantly higher than other provenance,including hebei camel liangshan provenance,highest of 3.35 mm.The ultimate survival rate of taishan provenance was the highest,52%.In addition,it is expected to select the high and fast growing plants from laoshan and taishan provenances.(2)the naturally higher summer temperatures caused heat damage to the Sorbus pohuashanensis plants of different species,which were manifested as loss of water,wilting and yellowing of some leaves,black spots on the leaves,and Browning of the tip of the leaves.At the beginning of August,the heat damage levels reached the highest.The heat damage indexes of the 10 sources of NM,BJL,SDT,JL,SXP,HBX,HBW,HBT,BJ and SDL were 39.58%,55.08%,32.08%,62%,58.69%,57.93%,63%,35.02%,50% and 29%,respectively.JL provenance was the highest(62%).SDL provenance was the lowest at 29%.(3)during the summer from June to August,natural high temperature reduced the net photosynthetic rate,transpiration rate and stomatal conductance of most Sorbus pohuashanensis species,and only SDT species showed an upward trend.From June to July,the net photosynthetic rate of SDT species increased by 1.09 mol·m-2·s-1,an increase of 6.37%.Transpiration rate increased by 0.1mmol·m-2s-1 and 1.33%.The stomatal conductance increased by 12.13%.From June to August,the intercellular carbon dioxide concentration of all kinds of seedlings showed an upward trend.(4)during the summer from June to August,the effects of natural high temperature on the physiological and biochemical indexes of Sorbus pohuashanensis of different provenances were different.Except SXP provenances,the relative conductivity of other provenances showed a rising--rising--declining trend from June to September.SDL soluble sugar was significantly higher than that of all provenances,and HBT was significantly lower than that of all provenances(P<0.05).The free proline of SDT was significantly higher than that of all provenances,the SDL was significantly higher than that of all provenances except SDT,and the lowest HBW provenance was 40.17% lower than that of SDT.In addition,natural high temperature makes SOD content show a rising--falling--rising trend,and makes POD show a declining trend,which reduces FV/FM,FV/F0 and improves ABS/RC.(5)the membership function was used to make a comprehensive evaluation of the natural over-summering ability of 10 species of sorbus pohuashanensis in baoding area,and the sequence was SXP<HBW<HBX<BJ<HBT<BJL<NM<JL<SDL<SDT.(6)exogenous salicylic acid can effectively alleviate the occurrence of heat damage in Sorbus pohuashanensis seedlings,and the appropriate salicylic acid concentration is 2mmol/L.When salicylic acid concentration was 2mmol/L,SOD activity was 540.38 u /g,which was 27.96%,19.48%,13.30% and 22.86% higher than that of control(distilled water),1mmol/L,3mmol/L and 4mmol/L,respectively.POD enzyme activity was 171.27U/g,significantly higher than that of other treatments and controls.The content of free proline was 55.89mg/g,significantly higher than that of other treatments.With the increase of salicylic acid concentration,soluble protein content first increased and then decreased.At 2mmol/L,it reached a maximum value of 67.15 ug /g,which was 18.55% higher than that of CK.Soluble sugar content at 2mmol/L was 6.83mg/g,significantly higher than that in CK treatment(49.78%).It can be seen that salicylic acid treatment can avoid high temperature damage by improving the activity of SOD and POD protective enzymes and increasing the content of free proline,soluble protein and soluble sugar.