The Effect Of Sowing Time On The Physiological Characteristics And Quality Formation Of Safflower From Different Producing Areas

Safflower has rich medicinal value and has been widely used in clinical treatment.With the gradual discovery of its medicinal value,the market demand for safflower is constantly expanding,and the supply-demand imbalance is becoming more and more apparent.Reasonable cultivation measures can improve the yield and quality of safflower,and sowing time is an important factor in achieving high-yield and high-quality safflower.Reasonable sowing time can effectively improve the utilization efficiency of climate resources such as light and temperature,and fully tap the production potential of safflower.Therefore,in this study,two safflower varieties,"Baihong 1"and"Yunnan landrace",were used as experimental materials,and six sowing dates were set,including autumn sowing,including October 15th（B1）,October 25th（B2）,November 4th（B3）,and spring sowing,including February 18th（B4）,February28th（B5）,and March 8th（B6）.The photosynthetic characteristics,physiological characteristics,yield formation factors of different safflower treatments were observed,the content of medicinal components in safflower was detected,and the effect of sowing time on the physiological characteristics and quality formation of safflower was analyzed.The suitable sowing time for high-yield and high-quality production of different safflower varieties was screened,and a scientifically formulated safflower cultivation technology was developed to enhance the yield and medicinal value of safflower.The main research results are as follows:1.Different sowing dates and varieties all affect the photosynthetic characteristics of safflower to varying degrees.The photosynthetic characteristics of safflower showed a trend of first increasing and then decreasing with the changes in seedling stage,branching stage,and flowering stage,with branching stage being the highest.The net photosynthetic rate of safflower during each growth stage was in descending order from branching stage,flowering stage to seedling stage.The net photosynthetic rate of"Yunnan landrace"was higher overall than that of"Baihong 1",and under different sowing dates,the net photosynthetic rates of both varieties showed a trend of first increasing and then decreasing with the delay of sowing dates.Under the treatment of sowing date B2,the photosynthetic characteristics of safflower were generally higher than those under other sowing dates,with the net photosynthetic rate of"Baihong 1"at branching stage reaching 28.38μmol CO₂·m^-2·s^-1 and that of"Yunnan landrace"at branching stage reaching 29.03μmol CO₂·m^-2·s^-1.This indicates that suitable sowing dates can effectively improve the photosynthetic characteristics of safflower.2.There are certain differences in chlorophyll fluorescence parameters among different sowing dates and varieties.With the changes in seedling stage,branching stage,and flowering stage,Fv/Fm,q P,NPQ,ETR,and Y（II）all showed a tendency of first increasing and then decreasing,reaching a high level at branching stage.This indicates that the branching stage is the fastest growth stage for safflower.During each growth stage,the indices such as Fv/Fm,q P,ETR,and Y（II）showed a trend of first increasing and then decreasing with the delay of sowing dates,reaching their highest values under the treatment of sowing date B2.On the other hand,NPQ showed a trend of first decreasing and then increasing with the delay of sowing dates,with varying degrees of differences between treatments.This indicates that suitable sowing dates can improve the light energy conversion efficiency and potential activity of PS II,reduce heat dissipation,and promote photosynthetic efficiency.The chlorophyll fluorescence parameters of"Yunnan landrace"are higher overall than those of"Baihong 1".3.The total chlorophyll content showed a trend of first increasing and then decreasing with the delay of sowing dates,and according to different growth stages,it showed a trend of branching stage>flowering stage>seedling stage.This indicates that in the branching stage,safflower is in the stage of rapid growth,and the synthesis rate of chlorophyll is at its fastest level.With the delay of sowing dates,the total chlorophyll content showed a trend of first increasing and then decreasing,reaching its highest value at sowing date B2.The total chlorophyll content of"Yunnan landrace"was slightly higher than that of"Baihong 1".The content of soluble protein showed a trend of first increasing and then decreasing with the delay of sowing dates,with the highest value at sowing date B2,and a trend of varying degrees of first increasing and then decreasing with the change of seedling stage,branching stage,and flowering stage.The content of soluble protein reached its highest value at the branching stage,and there was not much difference between"Yunnan landrace"and"Baihong 1".The content of malondialdehyde and conductivity showed a trend of first decreasing and then increasing with the delay of sowing dates,with the lowest value at B2.4.There are differences in traits such as plant height,stem diameter,and number of primary branches among safflower plants of different sowing dates and varieties.With the delay of sowing dates,the plant height and number of primary branches of"Baihong 1"showed a gradually decreasing trend,with sowing date B1 being the highest,but the difference between B1 and B2 was not significant.The stem diameter showed a trend of first increasing and then decreasing with the delay of sowing dates,with B2 being the thickest and significantly higher than the other treatments.The plant height of"Yunnan landrace"showed a gradually decreasing trend with the delay of sowing dates,and the difference between B1 and B2 was not significant.The stem diameter and number of primary branches showed a trend of first increasing and then decreasing with the delay of sowing dates,with the B2 sowing date having the thickest and most primary branches.The top fruit ball diameter and top fruit ball seed number of"Baihong 1"and"Yunnan landrace"were the best at the B2 sowing date,showing a trend of first increasing and then decreasing with the delay of sowing dates.The single plant grain weight and dry weight of the stigmas were both the best at the B2sowing date.The single plant grain weight and dry weight of the stigmas of"Yunnan landrace"were significantly higher than those of"Baihong 1".5.There are differences in medicinal ingredients such as flavonoids,polysaccharides,HYSA,and chlorogenic acid in"Baihong 1"and"Yunnan landrace"under different sowing dates,and they show different degrees of difference.With the delay of sowing dates,each index showed a trend of first increasing and then decreasing,and reached the highest value at the B2 sowing date,and the overall performance among the treatments was significantly higher for autumn sowing than for spring sowing.The flavonoid content of"Baihong 1"was higher than that of"Yunnan landrace",but the polysaccharide content was slightly lower than that of"Yunnan landrace"."Yunnan landrace"had higher HYSA and Kaempferol contents than"Baihong 1".