| In this paper,We studied the changes of physiological indexes such as growth,photosynthetic characteristics,chlorophyll content and soluble sugar content of Quercus mongolica seedlings under different water conditions.We analyzed and compared with the anatomical structures of the roots and stems of Q.mongolica seedlings,Finally,we can provide a theoretical basis for the afforestation and drought-resistant breeding of Q.mongolica.1.Under the sufficient water supply condition,the growth rate of seedling height and the growth rate of ground diameter were the highest,which were 29.51% and 49.65% respectively.Under the stress of drought,the growth rate of seedling height and the growth rate of ground diameter decreased.Under the condition of FC and 70%FC moisture,the seedling height growth rate decreased greatly,which were 9.17% and 10.29%,respectively.The growth rate of ground diameter was mainly showed significant drop in the 15% FC moisture condition.Drought also has a tendency to increase the growth of the side branches of Q.mongolica.2.In the early stage of drought treatment,the content of chlorophyll a and chlorophyll b and the content of carotenoids in leaves of Q.mongolica were the highest.With the persistence of drought,the contents of chlorophyll a and chlorophyll b were significantly higher under 70% FC water conditions than other treatments,in addition,the differences between other treatments were not significant.During droughts of 2,4,6,and 8 weeks,the difference of soluble sugar content in the leaves of Q.mongolica were not significant,but the soluble sugar was content decreased,and it decreased significantly in the early stage of drought.The soluble sugar content of Q.mongolica leaves treated with 70% FC water condition was highest All the time,They were 108.86 mg?g-1,89.04 mg?g-1,73.30 mg?g-1 and 67.69 mg?g-1,at 2 weeks,4 weeks,6 weeks and 8 weeks respectively.which were higher than the control 16.07 mg?g-1,10.93 mg?g-1,6.42 mg?g-1 and 6.31 mg?g-1,respectively.3.The net photosynthetic rate and WUE of seedling leaves of Q.mongolica responded to the changes of seedling under drought stress.In the early stage of drought,the diurnal variation trend of photosynthesis of Q.mongolica leaves in each treatment was very similar,and the photosynthetic rate was the highest from 8 am to 10 am in the morning.In the middle and late stage of drought,under the water conditions of FC,70%FC and 40 FC,the photosynthetic rate of Q.mongolica seedlings in the morning was higher than that of the control.However,under the water conditions of 15%FC,the photosynthetic rate significantly decreased,and the photosynthetic rate was the highest at 8 o 'clock in the morning,which were 5.34 ?mol?m-2?s-1 and 8.76 ?mol?m-2?s-1,they were decreased to 5.22 ?mol?m-2?s-1 and 2.22 ?mol?m-2?s-1.In the early stage of drought,the water use efficiency of Q.mongoliana seedlings decreased significantly.The highest water use efficiency of CK was 15.74 ?mol?mmol-1,and the lowest was 40%FC was 5.15 ?mol?mmol-1,which was 10.59 ?mol?mmol-1 lower than the control group.In the middle of drought,the highest water use efficiency of CK was 5.57 ?mol?mmol-1,and the lowest water use efficiency of 40%FC was 3.30 ?mol?mmol-1,which was 2.27 ?mol?mmol-1 lower than that of the control group.In the later stage of drought,the highest water use efficiency of CK was 6.14 ?mol?mmol-1,and the lowest water use efficiency of 40%FC was 4.11 ?mol?mmol-1,which was 2.03 ?mol?mmol-1 lower than the control group,it was extremely significant different from the control.There was no difference between different drought treatments.4.Under the condition of continuous drought,the shoot diameter of Q.mongolica decreased.Under CK,FC,70%FC,40%FC and 15%FC moisture condition,the diameter of shoots were 2450.60 ?m,2457.75 ?m,2373.98 ?m,2302.09 ?m and 2056.39 ?m,respectively.15% FC is significantly different from CK and FC,and is significantly different from 70% FC.The width of the pith of the shoots widened with the deepening of the drought.The pith widths of CK,FC,70%FC,40%FC and 15%FC were 531.02 ?m,632.79 ?m,764.05 ?m,823.03 ?m and 902.67 ?m,respectively.In the case of water reduction,the increase of Q.mongoliana pith,may be a way to resist the drought,increase the ratio of pith,to store water,to maintain their own survival.The distribution of stem catheters showed that the large catheters decreased gradually with the increased of the drought degree,While the small catheters increased with the increase of the drought degree,suggesting that Q.mongoliana could adapt to the water shortage condition by increasing the rate of catheters with smaller pore size under the drought stress,which may be the mechanism to resist embolism.To sum up,drought can reduce the growth of Q.mongoliana seedling height,and severe drought can reduce the growth of ground diameter.Under the condition of 70%FC water,chlorophyll,soluble content and photosynthetic rate of Q.mongoliana seedlings were higher in the morning,Suggesting that mild drought might be beneficial to seedling growth and development.Drought also increased the width of the pith and the number of catheters with smaller apertures. |
PDF Full Text Request