| Magnolia wufengensis L.Y.Ma et L.R.Wang was first discovered in 2004 Magnoliaceae Magnolia genus Magnolia genus,because of the color red has a very high ornamental value and scientific value.In the cultivation process will suffer from waterlogging,including flooding and other issues.In this study,waterlogging and growth changes of Magnolia officinalis were studied using pot flooding and root box observation,aiming to provide a theoretical basis for its controlled cultivation.The main conclusions are as follows:(1)With the prolongation of waterlogging stress,the relative increase of plant height and ground biomass of Magnolia seedlings gradually decreased,and the height increase of seedlings decreased by 40.48%,52.38%,50.00%and 54.17%,respectively.The growth volume was reduced by 7.14%,42.86%,49.68%and 71.43%respectively compared with the control.The shape of the seedling leaves gradually turns yellow and wilting,and finally it becomes dark and shedding.After the waterlogging treatment,the seedlings were partially dead after 11 days and 15 days of waterlogging,and the survival rates were 85%and 55%,respectively.The soluble protein content of seedling leaves increased gradually,which was 58.95%,35.01%,32.19%and 47.62%higher than the control.The contents of chlorophyll a,chlorophyll b,and total chlorophyll were gradually decreased,and the differences between treatments were not significant.The photosynthetic parameters of seedlings were significantly reduced.The MDA content in the leaves of the affected seedlings increased significantly during the whole period,which was 6.38%,19.05%,40.12%and 100.95%higher than the control.In the protective enzyme system,the three enzyme activities increased in the early stage and gradually decreased in the later stage.This experiment found that seedling height,ground diameter,biomass and other growth indicators of Magnolia seedlings were significantly inhibited under waterlogging conditions at different times,but plants could adjust the allocation of various biomass,maintain cell osmotic balance,and increase Mechanisms such as protective enzyme activity adapt to waterlogging adversity,can maintain growth within a certain tolerance range and have the potential for recovery.(2)After the waterlogging was relieved,the growth status of Magnolia seedlings was restored,and the relative increase of seedling height,ground diameter,and above-ground biomass began to increase,and the biomass of leaves,stems,and roots of the seedlings that had been flooded for 4 days was dry.The weight increased by 21.84%,10.33%,and 19.93%,respectively.The dry weight of seedlings treated with waterlogging for 7 days increased by 37.98%,3 1.93%,and 44.12%,respectively,compared with the stress immediately after stress relief.The treated leaves with a short waterlogging time began to return to normal,and the severely damaged treatment leaves fell off;the survival rates of the 11 and 15 days seedlings flooded at the end of recovery were 25%and 0%,respectively.During the recovery period,the content of soluble protein in leaves gradually decreased and then gradually increased.The waterlogging treatment on the 4th and 7th days of flooding was reduced by 14.11%and 11.34%respectively when compared with that on just released.The contents of chlorophyll b and total chlorophyll decreased first and then increased slowly.They were significantly lower than the net photosynthetic rate,transpiration rate,stomatal conductance,and intercellular C02 concentration.The four indexes treated with flooding were higher than those immediately after stress relief.Increased 38.55%,15.95%,24.58%and 40.37%.The activities of the three protective enzymes were almost the same during the recovery period,and gradually decreased and remained stable.Studies have shown that the longer the flooding time is,the less effective the restoration effect is.When the stress time is 11 days,the seedlings of Magnolia sativa have lost their ability to recover.When the duration of the stress exceeds 15 days,all of Magnolia seedlings die.(3)During the root box observation,the root growth of Magnolia seedlings in the normal environment conformed to the S-shaped curve,and the trend of the number of roots,root length,root depth,and root width was similar.The average root number growth rate was 0.46 pieces/d.The average growth rate of root length was 1.43cm/d.The increase of seedling root depth was greater than the root width.The average growth rates were 0.42cm/d and 0.25cm/d,respectively.Under waterlogging stress,the root growth of the seedlings was inhibited.The number of roots,root length,root depth and root width were all significantly lower than those of the control.The average growth rates were reduced by 36.96%,37.76%,45.24%,and 40%,respectively,compared with the control.The growth rate will gradually decrease with the extension of stress time,and negative growth will occur when the root system is affected.The effect of leeches on the lateral growth of roots was greater than that of vertical growth. |
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