| In the process of vegetation restoration,drought is an important factor that restricts the growth and development of plant seedlings.It may occur in any period of plant growth,especially in the seedling stage.Plants have strict water requirements and are an important stage of plant growth and development.Therefore,in the process of seedling growth,reasonable and effective irrigation measures play a crucial role in the growth and development of plants and the improvement of yield.In order to explore the response mechanism in the cork oak seedling in dry defense system,this test is to the seedlings of Quercus variabilis as the experimental material,using pot experiment method,a control,mild,moderate water stress,the stress of each 0 d,7 d and 14 d,28 d and 21 d,the 7 d after watering test studies the growth of the seedlings of Quercus variabilis index,root morphology,moisture index,chlorophyll content,photosynthesis,osmotic regulation substances and the change of the index such as antioxidant enzyme activity.The main conclusions are as follows(1)With the increase of drought stress level,dry weight of stem and leaf gradually decreased with the deepening of stress degree.Under the treatment of T2,it was 84.96%and 82.81%of CK group,respectively.The higher the drought stress gradient was,the smaller the dry weight of stem and leaf was.Plant height,base diameter and leaf number also decreased gradually with the increase of drought stress level,which were significantly different from CK under the treatment of T2.(2)In the late period of drought stress,the total root length and root tip number of quercus cork seedlings were significantly higher than that of the control group(P<0.05).After rehydration for 7 days,each treatment group recovered to the control level,with a certain compensation effect.The total root area increased first and then decreased with the strengthening of drought stress.After 7 days of rehydration,the two treatment groups were still significantly lower than the CK group(P<0.05).The total root volume of seedlings decreased significantly under different degrees of drought stress(P<0.05),and T2 decreased the most.The total root volume of the three treatment groups reached the maximum value at 21 d of stress,but the total root volume of the T1 and T2 treatment groups was still significantly lower than that of the control group.The total root volume of T1 and T2 treatment group was significantly lower than that of CK group,and decreased with the enhancement of drought stress gradient.After rehydration for 7 days,the total root volume under T1 and T2 treatment was significantly lower than that under CK group(P<0.05),and the control level was not recovered.This indicates that quercus variabilis seedlings can increase the number of root growth to adapt to drought stress(3)under each drought treatment,the relative water content and leaf water potential of quercus variabilis seedlings decreased with the extension of drought time,and decreased with the strengthening of drought gradient.At 14 d of drought stress,the relative water content of leaves under T1 and T2 treatment decreased sharply(P<0.05),and at 28 d of drought stress,the relative water content of leaves was only 2.01%of the control Leaf water potential decreased sharply at 7 d under drought stress,and the decrease was greater under T2 treatment.After rehydration,the relative water content and leaf water potential of the leaves returned to the control level.It showed strong drought tolerance of quercus variabilis seedlings.(4)the content of chlorophyll(Chl a,Chl b and Chl t)decreased gradually with the deepening of drought degree,and the T2 treatment decreased by 47.55%,40%and 82.7%,respectively,compared with the control after 28 days of drought stress(P<0.05).The net photosynthetic rate,transpiration rate and stomatal conductance of quercus variosa seedlings decreased gradually.After rehydration,both treatment groups returned to the control level.With the extension of drought time and the deepening of drought stress gradient,water use efficiency(wue)decreased first,then increased and then decreased.After rehydration,both T1 and T2 treatment groups did not return to the control level.(5)the activity of SOD,POD and CAT increased first and then decreased with the extension of drought time.The activity of SOD,POD and CAT reached the maximum at 21 d of drought stress,and the POD content increased by 2.63 times compared with the control(P<0.05).After rehydration,all three indexes returned to the control level.The content of MDA in the leaves of quercus variabilis variabilis seedlings increased with the increase of drought stress.At 28 d of stress,the results of T1、T2 were 63.36%and 154.54%higher than those of CK treatment group,and the difference between each treatment group and CK group was significant(P<0.05).After rehydration for 7 days,T1、T2 treatment in quercus variabilis variabilis leaves could be restored to the control level.In summary,that cork oak has a strong drought resistance(6)the contents of osmotic regulators such as soluble sugar,soluble protein and free proline gradually increased with the extension of drought stress time and the increase of drought stress level,and the increase range of T2 was always greater tha n that of T1 group.During drought stress for 28 days,soluble sugar and soluble protein content reached the maximum value under each treatment(P<0.05),while during drought stress for 21 days,the content of free proline increased by 2.5 times compared with that of the control group(P<0.05).After rehydration,all the indexes were restored to the control level,indicating that quercus variabilis has strong drought tolerance and recovery ability under drought stress. |
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