The Influence Of Net Wind And Wind-drift Sand On The Physiological Characteristics Of Calligonum Mongolicun Seedling

In this paper,wind tunnels were used to simulate the intensity of different net winds and wind-drift sand stress.The change of chlorophyll fluorescence parameters?photosynthetic capacity?malondialdehyde content?antioxidative enzyme activity and osmotic adjustment substance content of Calligonum mongolicus seedlings after net wind and sandstorm stress were studied.By analyzing the relationship between the physiological characteristics of Calligonum mongolicun with wind and wind-drift sand,the response mechanism of Calligonum mongolicun seedlings to the net wind and wind-drift sand was revealed,which provided a scientific basis for vegetation restoration and ecological environment construction in desert areas.The main conclusions of the experimental study are as follows:?1?With the enhancement of wind-drift sand stress,the Fv/Fm of Calligonum mongolicum seedlings first increased slightly and then decreased.The PSII _maximal efficiency?Fv'/Fm'?slightly increased under mild wind-drift sand stress at high and low steady-state light,and decreased significantly under severe wind-drift sand stress.PSII operating efficiency?Fq'/Fm'?decreases.The photochemical quenching coefficient qP rises first and then decreases under high and low steady-state light.The non-photochemical quenching coefficient?NPQ?remained stable under light and moderate wind-sand current stress under low steady-state light and increased under severe stress;under high light intensity,under mild and moderate stress,the NPQ of Calligonum mongolicum seedlings was lower than that of CK,and increased under severe stress.In summary,mild wind-sand flow stress has slightly increased light use for Calligonum mongolicum seedlings,while moderate and severe wind-sand flow stress significantly reduces the efficiency of light utilization by plants.?2?In the four fitting models of this study,from the comparison of the coefficient of determination,the fitting effect is the optimum for the right-angle hyperbola correction model,and the right-angle hyperbola model is the worst.The right-angle hyperbola correction model can well adapt the photosynthetic variation of Calligonum mongolicum seedlings under different wind speeds,net wind and wind-drift sand stress.The calculation of photosynthetic parameters is also more convenient and close to the measured values than the other three models,but there is a difference between the calculated apparent quantum efficiency AQE and the measured value.This aspect can be calculated using a non-rectangular hyperbolic model.?3?The effects of net wind and wind-drift sand stress on the callus of Calligomum mongolicum were different.Under net wind stress,the Pn of Calligomum mongolicum seedlings showed an“N”shape change;Gs and Tr showed similar trends and showed a steady increase;WUE showed a linear decline.Under wind-drift sand stress,the Pn of Calligomum mongolicum seedlings showed a“W”shape change,and a significant difference was observed between 14m/s and CK;Gs and Tr increased first and then decreased;WUE fluctuates greatly,although it increased but still keep a downward trend.Comparing the trends of Ci and Ls under different treatments,we can see that under net wind stress,the photosynthetic rate of Calligonum mongolicum seedlings is limited by stomata at 5m/s,non-stomatal at 8-11m/s,and under wind-drift sand stress,non-stomatal limitation first appeared,followed by stomatal limitation,mainly non-stomatal limitation.?4?The MDA content of callus of Calligonum mongolicum seedlings underwent net wind stress,and the content of MDA showed a trend of“W”.There was no significant difference among the treatments.Under wind-drift sand stress,the content of MDA decreased first and then increased.The minimum value is reached at a wind speed of 11m/s.Under net wind conditions,chlorophyll a,chlorophyll b,and chlorophyll of Calligonum mongolicum seedlings first increased and then decreased.Under wind-drift sand stress,the changes of chlorophyll a,chlorophyll b,and chlorophyll of Calligonum mongolicum seedlings were more stable than those under pure wind conditions.And the chlorophyll content is lower than the net wind stress.?5?Under the conditions of net wind and wind-drift sand stress,the changes of various protective enzyme activities of Calligonum mongolicum seedlings varied greatly.Under net wind conditions,CAT activity increased under the wind speed stress of 5m/s,8m/s and 14m/s,and decreased under the stress of 11m/s and 17m/s.Under wind-drift sand stress,the activity of CAT decreased as a whole.Under net wind stress,POD of Calligonum mongolicum seedlings decreased under the stress of 5m/s and 8m/s,and increased under the wind speed of 11m/s and 17m/s.Under wind-drift sand stress,POD activity decreased but was greater than CK.No matter whether it is net wind or wind-drift sand stress,the SOD activity of Calligonum mongolicum seedlings showed“N”type changes.Under the net wind,APX decreased overall with stress,and it was relatively stable.Under t wind-drift sand stress,APX peaked at 5m/s and 8m/s and then decreased.When the net wind hits,the pro content increases first and then decreases with increasing stress intensity.The wind-drift sand stress is the same as the net wind stress trend,but the fluctuation range is larger than the net wind.