Study On The Transpiration Of Greenhouse Grapes In Cold Regions Of Northeast China And Its Response To Influencing Factors

Facility fruit trees have become the main production form and agricultural economic source of facility agriculture in Northeast China.However,the current research on the water demand law of the fruit trees in the facility and its influencing factors are still not perfect.Especially in the northeast region,where the climate is cold,the temperature have a large difference between day and night,and the environment changes under the conditions of the facility is unique,so sap flow and transpiration changes are more complicated.In order to find out the relationship between the characteristics of fruit sap flow and its influencing factors under the facility environment in the cold regions of Northeast China.And using the wrapped stalk flow meter,TDT soil moisture sensor,the time domain reflectometer and the meteorological automatic monitoring system dynamically to monitor the tree fluid flow,grape soil moisture status and meteorological data continuously.The mathematical and analytical methods were used to analyze the daily and monthly variation of grape sap flow,transpiration characteristics and response to environmental factors.Detailed and chaptered conclusions are follows:（1）The daily sap flow rate showed a trend of single peak changes,intraday peak values occurred between 10:30-13:00,the peak values reached 406.32 g?h-1 at the most vigorous August.The variation of transpiration of grapes during the whole growth period showed obvious seasonal variation characteristics.The transpiration of the grape during the whole growth period was the most severe in July and August,the maximum daily transpiration exceeded 4 mm?d^-1,while the average daily transpiration in October is only 0.79 mm?d^-1.（2）The positive correlation between grape sap flow rate and PAR、VPD、VT were significant（P<0.01）,and the negative correlation between sap flow rate and RH（P<0.01）.The main influencing factors of instantaneous flow rate and daily transpiration were PAR and VPD.At month scale,the most important influence factor changes between PAR and VT.The main influencing factors of sap flow during the whole growth period were PAR and VT,however,the coefficient of determination would decrease as the study time scale increases.The results showed that in different meteorological factors and sap flow,the time lag varied obviously,there was a significant time lag between sap flow rate and PAR,VPD.PAR’s start-up time and stop time were ahead of the sap flow,the peak time were behind sap flow,the longest time lag of PAR was 1.5 hour.VPD lagged behind the flow fully.（3）During the whole growth period,the transpiration of the grape ranged from 126.14-210.52mm,and the maximum transpiration was reached under the W3（The upper and lower limits of irrigation water respectively account for 90%and 80%of the field water capacity）condition.At different stages of growth period,the sap flow rate showed a single peak change trend,under the treatment of water treatment W2（The upper and lower limits of irrigation water respectively account for 90%and 65%of the field water capacity）and W3,the sap flow rate under high nitrogen treatment(N3,521.74 kg hm^-2)was significantly higher than that of medium nitrogen treatment(N2,347.82 kg hm^-2)and low nitrogen treatment(N1,248.56 kg hm^-2).However,under W1（The upper and lower limits of irrigation water respectively account for 90%and 55%of the field water capacity）,with the addition of nitrogen,the sap flow rate would decrease.This indicated that when the soil moisture content was too low,the addition of nitrogen could inhibit grape transpiration.（4）PAR was the key meteorological factor controlling sap flow under different water and N conditions that explained 85.7%-92.8%of variation in sap flow rate.Under water treatment,the correlation betweenthe sap flow and four meteorological factors was better than nitrogen treatment.There was evident hysteresis loops in the relationships between SFR and PAR（cunter clockwise rotation）under different water and N conditions.The time of maximum sap flow rate was either occurred before maximum PAR.Under W1N3 treatments,sap flow rate was the least sensitive to PAR compared to other treatments.And because of the particularity of the greenhouse environment,the cycle diagram between PAR and SFR appeared as a twist.