Studies On Adaptive Evaluation And Photosynthetic Characteristics Of The Shrub Magnolia

M.‘Jane' and M.‘Betty' are a class of the fine Shrubs Magnolia selected by American gardeners through cross-breeding,both flowers and leaves have high ornamental value.In this paper,the two varieties of the Shrubs Magnolia M.‘Jane' and M.‘Betty' introduced from the United States were studied,by observing the botanical characteristics,phenological period,growth and development and stress resistance,and through examining the photosynthesis characteristics to evaluate the adaptability of its introducted in Jinzhong area of Shanxi,and analyze the main physiological and ecological factors affecting its net photosynthetic rate,in order to understand the growth and photosynthetic characteristics of the Shrubs Magnolia,and provide a theoretical reference for its introduction,cultivation and popularization.The results were as follows:1.M.‘Jane' and M.‘Betty' can grow normally in the Taigu area of Shanxi Jinzhong,but the resistance is poor.The surface of leaves is shiny,and the tip of the young leaves is slightly reddish-brown,at autumn,the color becomes yellow or copper red,the leaves of the branches of the year are larger,long is 15~20 cm and wide is 8~10cm,while the leaves of perennial branches are smaller,long is 5~15 cm and wide is 3~8 cm;The cupped flowers are large,purple outside the petals,pink white inside,the petals edge of M.‘Jane' is smooth,but the M.‘Betty' is slightly distorted;Compared with M.liliflora,the periods of flowering,leafexpansion and defoliation of M.‘Jane' and M.‘Betty' are relatively late,the average is 14 d,20 d and 4 d,respectively;M.‘Jane' and M.‘Betty' have a slower growth rate,with the fastest growth rate in May;M.‘Jane' and M.‘Betty' have poor resistance,the leaves are prone to anthrax,the incidence rates are 30% and 50% respectively,during the winter,the branches are easy to freeze,Mortality rate of 5%.2.The annual changes in the net photosynthetic rate of M.‘Jane' and M.‘Betty' are both “double peak” curves.The net photosynthetic rates of M.‘Jane' and M.‘Betty' showed the first and second peaks in June and August respectively,and the peaks of net photosynthetic rate in June were 5.72 ?mol·m-2·s-1 and 5.78 ?mol·m-2·s-1 respectively,Compared with in June,the peaks of M.‘Jane' and M.‘Betty' in August increased by 28.50% and 21.33%,respectively,therefore,M.‘Jane' and M.‘Betty' have stronger photosynthesis ability in August than in June.3.The diurnal variation of net photosynthetic rate of M.‘Jane' and M.‘Betty' in different months showed a “double peak” curve: The diurnal variation of Pn of M.‘Jane' and M.‘Betty' in different months showed a “double peak” curve with obvious mid-depression,which all are mainly caused by non-stomatal factors;in June and August,the Pn of M.‘Jane' and M.‘Betty' exhibited positive correlations with Stomatal Conductance(Gs)(P<0.05),the Pn of M.‘Jane' exhibited positive correlations with Photosynthetic affecting radiation(PAR)in June(P<0.05),the Pn of M.‘Jane' and M.‘Betty' exhibited positive correlations and significantly positive correlated in August with Transpiration rate(Tr),respectively.4.By fitting light response curve and analysing parameter of M.‘Jane' and M.‘Betty' shows that M.‘Jane' and M.‘Betty' belongs to shade-tolerant plants.By comparing the light response fitting curves of M.‘Jane' and M.‘Betty',in June and August,the maximum net photosynthetic rate(Amax)is 8.41~9.37 ?mol·m-2·s-1,light compensation point(LCP)is 34.99~44.81 ?mol·m-2·s-1,light saturation point(LSP)is 188.49~226.51 ?mol·m-2·s-1,and chlorophyll a/b(Chl a/b)is 2.29~2.55,they all met the plant's negative shade value,and the apparent quantum yield of M.‘Jane' and M.‘Betty' in June and August is 0.046~0.054,which are slightly higher than the apparent quantum yield 0.03~0.05 of general plants under natural conditions,indicating that the Shrub Magnolia has strong ability to use low light,so it can be judged that the Shrub Magnolia belongs to shade-tolerant plants.5.The correlation analysis of chlorophyll content,specific leaf weight and net photosynthetic rate.The chlorophyll content and specific leaf weight of M.‘Jane' and M.‘Betty' increased with the growth of leaves.in June,The chlorophyll content,specific leaf weight of M.‘Jane' and M.‘Betty' exhibited positive correlations(P<0.05)and significantly positive correlated(P<0.01)with pn,respectively.In August,There was no significant positive correlation between chlorophyll content,specific leaf weight and net photosynthetic rate in M.‘Jane' and M.‘Betty' leaves.6.Both M.‘Jane' and M.‘Betty' are vulnerable to intense light and high temperatures.In June and August,the maximum photochemical efficiency Fv/Fm of M.‘Jane' and M.‘Betty' were less than 0.834,indicating that the leaves were exposed to intense light and high temperature in June and August;compared with June,In August,relative quantum efficiency of PS? photochemistry(?PS?)increased by 120.00% and 87.50%,respectively,electron transport rate(ETR)increased by 120.27% and 83.62%,respectively,and photochemical quenching(q P)increased by 35.29% and 43.18%,respectively,but,non-photochemical quenching(NPQ)decreased by 48.60% and 9.72%,respectively,indicating that,in August,The photosynthetic ability of M.‘Jane' and M.‘Betty' is stronger than that in June.In summary,M.‘Jane' and M.‘Betty' can bloom normally in Shanxi Jinzhong,but the resistance is poorer;M.‘Jane' and M.‘Betty' have strong ability to use low light and belongs to shade-tolerant plants;M.‘Jane' and M.‘Betty' are vulnerable to intense light and high temperature;therefore,when introducing The Shrubs Magnolia,the control of pests and diseases and winter protection measures should be done well,it also should be shaded,mixed with trees,or combined with sprinkler irrigation in the summer,in order to improve the introduction success rate of The Shrubs Magnolia.