Effect Of Regulated Water Deficit On Photosynthetic Characteristics, Yield, And Quality Of Edible Sunflower In The Cold Irrigation Area Of Hexi Oasis

An experimental study was carried out in the cold irrigation area of Hexi oasis on the changes of growth dynamics,water consumption characteristics,photosynthetic characteristics,yield,water use efficiency and quality of edible sunflower under the condition of film deficit reduction irrigation.According to the characteristics of water demand in different growth stages of edible sunflower,the experiment took full irrigation CK?75%⁸5%FC?as the control,maintained the middle growth stage as full irrigation,and carried out mild?65%⁷5%?,moderate?55%⁶5%?,severe?45%⁵5%?water deficit regulation in seedling stage of edible sunflower,and mild and moderate water deficit regulation in mature stage,that is,seedling stage mild—mature stage?mild T1,moderate T2?,seedling moderate—mature stage?mild T3,moderate T4?,seedling severe—mature stage?mild T5,moderate T6?.The show that:1)Drip irrigation under mulch can obviously improve the water and heat condition of soil root system.The rise and fall of atmospheric temperature has a significant effect on the surface temperature of soil.The deeper the soil layer is,the smaller the variation of soil temperature is,and the lag phenomenon is obvious.Among them,the variation of temperature in 0-10cm depth of soil layer is 21.54?,which reaches the maximum at the end of seedling stage and the beginning of budding stage,which is 33.56??Drip irrigation is beneficial to keep the soil temperature stable.The average daily ground temperature at 10cm of the control CK in seedling stage and mature stage is 0.5¹.33?and 0.58¹.38?lower than water deficit respectively.?2?The mild,moderate and severe water deficits at the seedling stage can significantly?P<0.05?inhibit the growth of edible sunflower plant height,leaf area index and aboveground dry matter weight.Compared with the control CK,the plant height decreases by 12.18%¹3.12%,20.11%²0.72%and 29.03%²9.78%,the decrease in leaf area index was 20.11%²2.75%,32.80%³3.86%and 43.39%⁴4.97%,and the decrease in aboveground dry matter weight was 13.71%¹4.02%,,25.13%²6.01%and 33.25%³3.54%,respectively.The mild water deficit adjustment at seedling stage was significantly increased by 10.10%¹1.92%compared with the control CK stem thickness.The severe water deficit at seedling stage was significantly reduced by 21.30%²2.32%and 29.34%²9.82%compared with the control CK disk diameter and root dry weight,respectively.Compared with the control CK,the mild and moderate water deficits in the mature stage had no significant?P>0.05?effect on the plant height and root dry weight of edible sunflower;Compared with the control CK,the mild and moderate water deficits in the mature stage had no significant effect on the plant height and root dry weight of edible sunflower;compared with the control CK,the mild water deficits in the mature stage had no effect on the leaf area index and dry weight of the ground had no significant effect;the mild water deficit during the mature period was significantly higher than that of the control CK edible sunflower stem diameter and diameter by 7.81%and5.94%,respectively.?3?After irrigation,the soil moisture content of different water deficit treatment decreased with the increase of water deficit degree,and the peak value tended to be flat.Compared with other water deficit treatments,the control CK had the largest soil moisture content and the steepest peak value,which was relatively large in the whole growth period of edible sunflower.Compared with CK,the water deficit treatment of the water consumption,water intensity and water consumption modulus of sunflower in seedling stage were significantly reduced?P<0.05?,with the decrease of 10.10%⁴6.08%,10.68%⁴6.60%and 7.57%³4.58%respectively;compared with CK,the water consumption,water intensity and water consumption modulus in mature stage were significantly reduced by 27.77%³0.29%,27.78%³0.34%and 15.45%²%3.45%respectively.?4?Severe water deficit at seedling stage and moderate water deficit at maturity stage decreased net photosynthetic rate,stomatal conductance and transpiration rate significantly?P<0.05?.Compared with the control CK,the severe water deficit deficits at seedling stage were 40.30%⁴5.98%,43.99%⁴7.37%,38.20%⁴2.10%;the moderate water deficit deficits at mature stage were 14.23%³2.07%,15.98%⁵1.23%,10.02%²8.45%.Compared with the control CK edible sunflower leaves,the severe water deficit at seedling stage was significantly reduced by 3.41%⁶.83%,43.38%⁴4.98%,32.48%³2.66%,16.01%.Compared with the control CK,the net water assimilation rate and specific leaf weight at the seedling stage were significantly increased by 19.19%²2.62%and 19.50%²2.82%,respectively.The moderate water deficit during the maturity period was significantly reduced by 8.05%²7.60%,5.84%¹4.49%,10.43%²0.17%and 18.79%³4.55%,respectively,compared with the control CK leaf daily volume,crop growth rate,specific leaf area and net assimilation rate.Compared with CK,the leaf weight of moderate water deficit increased by 8.40%²4.79%.?5?The yield of seedling stage of mild water deficit regulation and mature stage of mild water deficit regulation?T1?was the highest(4223 kg·hm^-2),which was0.98%higher than CK.There was no significant?P>0.05?difference.The yield of seedling stage of moderate water deficit regulation and mature stage of mild water deficit regulation?T3?was 4145 kg·hm^-2,which was 0.88%lower than CK.There was no significant difference.T1 treatment had the largest single-disk grain weight and 100-grain weight,which were 2.42%and 3.76%higher than T3 treatment,respectively,and there was no significant difference.The control CK water use efficiency and irrigation water use efficiency were the lowest,9.04 kg/hm²·mm and14.77 kg/hm²·mm respectively.The water use efficiency and irrigation water use efficiency of The water use efficiency and irrigation water use efficiency of moderate water deficit treatment at the seedling stage and mild water deficit treatment at the mature stage were the largest,which were 10.07 kg/hm²?mm and 17.33 kg/hm²?mm,respectively,compared with the control CK,which was significantly higher than11.39%?17.33%?P<0.05?,compared with mild water deficit treatment at the seedling stage and mild water deficit treatment at the mature stage increased significantly by7.36%and 8.18%respectively.?6?Too much or too little irrigation will significantly affect the quality of edible sunflower.The contents of crude fat and crude protein were the lowest in seedling stage of severe water deficit regulation and in mature stage of moderate water deficit regulation,which were 29.56%and 18.41%respectively.Crude fat and crude protein contents of moderate water deficit treatment at the seedling stage and mild water deficit treatment at the mature stage were the highest at 37.23%and 23.68%,respectively,and their crude fat and crude protein contents were significantly increased by 10.84%and 14.90%compared with the control CK?P<0.05?,compared with the severe water deficit adjustment at seedling stage and the moderate water deficit adjustment at the mature stage increased significantly by 25.95%and 28.63%respectively.The economic benefit of mild water deficit at the seedling stage and mild water deficit at the mature stage is the largest,which is 4.25%higher than that of the control CK;Severe water deficit at seedling stage and moderate water deficit at mature stage has the smallest economic benefit,which is significantly reduced by15.23%compared with the control CK.?7?The water production function of edible sunflower was constructed and analyzed by Jensen and Blank model.The water sensitivity index of flowering stage and bud stage was the largest,followed by the filling stage,the mature stage was smaller,and the seedling stage was the smallest.Therefore,it is necessary to fully irrigate?75%⁸5%?in the two critical periods of water demand and grouting to ensure high quality and high yield of edible sunflower.