Study On Fresh Jujube Photosynthetic Physiological Characteristics And Fruit Quality Of Different Varieties

Chinese date has a long history of cultivation in China and has important ecological and economic value.Yulin is one of the main production areas of red dates in China,but in recent years,there have been problems such as variety decline,which has led to difficulties in the development of the jujube industry.Introducing fresh jujube varieties is of great significance in promoting the upgrading and transformation of the jujube industry.in view of this,This study employed the GFS-3000/P portable photosynthesis measuring system to investigate the diurnal variations of photosynthesis-related indicators（the key indicators include net photosynthesis rate Pn,intercellular carbon dioxide concentration Ci,transpiration rate Tr,and stomatal conductance Gs）,in four fresh jujube cultivars（Puyang Tangzao,Leng Baiyu,Zao Cuimi,and Jin’Ai No.4）at four growth stages（bud stage,flower and fruit stage,fruit growth stage,and fruit ripening stage）under natural conditions.The study aimed to analyze and compare the relationship between different ecological factors and diurnal variations of photosynthesis and to explore the correlation between photosynthetic physiological characteristics and fruit quality,providing a theoretical basis for promoting excellent fresh jujube cultivars in the Yulin region.The results of the study are presented below.（1）The four types of fresh dates have varying characteristics in their photosynthetic diurnal variations across four different periods.The net photosynthetic rate（Pn）all exhibit a“double peak”trend,with the first peak appearing at 10:00 and the second at 15:00,with the first peak significantly greater than the second.A clear“noon break”phenomenon is observed,where Pn decreases significantly,and the upper crown layer shows a greater Pn than the lower crown layer,as well as one-year-old branches having a greater Pn than three-year-old branches.As for intercellular carbon dioxide concentrations（Ci）,all four types of fruits show a valley at 9:00 and reach their peak at 14:00,and the Ci ranks in descending order for the four different parts are:lower crown layer>three-year-old branches>one-year-old branches>upper crown layer.Transpiration rate（Tr）also follows a“double peak”trend,with the upper crown layer greater than the lower,and three-year-old branches greater than one-year-old branches.Stomatal conductance（Gs）follows a similar pattern,with the upper crown layer greater than the lower,and one-year-old branches and three-year-old branches close to each other,and both greater than the upper crown layer.Finally,water use efficiency（WUE）shows an increasing order from the lower crown layer to the upper,and one-year-old branches and three-year-old branches have similar values.（2）For all four varieties during flowering,fruit growth,and fruit maturation stages,the net photosynthetic rate（Pn）showed a highly significant positive correlation with photosynthetically active radiation（PAR）and transpiration rate（Tr）（P<0.01）.Relative humidity（RH）and intercellular CO₂ concentration（Ci）were common influencing factors for the net photosynthetic rate during leaf expansion in all four fresh date palm varieties,while temperature（Ta）and Ci were common influencing factors during the same period.During fruit growth,Ta,Ca and Ci showed a common influence on the net photosynthetic rate in all four varieties,while during fruit maturation,Ta,Ca,RH and Ci were common influencing factors.During the ripening period,the net photosynthetic rate of Puyang Tangzao showed a significantly positive correlation with total sugar and Vc content（P<0.01）.The net photosynthetic rate of Jin’Ai No.4 showed a significant positive correlation with Vc content（P<0.05）,while the net photosynthetic rate of Leng Baiyu showed a significant positive correlation with single fruit weight and total sugar（P<0.05）and an extremely significant positive correlation with Vc content（P<0.01）.Furthermore,the net photosynthetic rate of Zao Cuimi showed a significant positive correlation with total sugar and Vc content during the ripening period（P<0.05）.（3）The four fresh jujube varieties were ranked in descending order of single fruit quality as follows:Zao Cuimi>Leng Baiyu>Jin’Ai No.4>Puyang Tangzao.Zao Cuimi had the highest fruit hardness,followed by Leng Baiyu,Jin’Ai No.4,and Puyang Tangzao had the lowest.Leng Baiyu had the highest Vc content among the four varieties.The total sugar content was ranked in descending order as Puyang Tangzao>Zao Cuimi>Jin’Ai No.4>Leng Baiyu.Total acid content was ranked in descending order as Zao Cuimi>Jin’Ai No.4>Leng Baiyu>Puyang Tangzao.The soluble solid content was ranked in descending order as Leng Baiyu>Jin’Ai No.4>Zao Cuimi>Puyang Tangzao.The highest solid-acid ratio was 73.54 for Leng Baiyu,and the lowest was 58.47 for Zao Cuimi.The highest sugar-acid ratio was 107.54 for Puyang Tangzao,and the lowest was 54.56 for Jin’Ai No.4.Jin’Ai No.4 had the lowest appearance score,while Leng Baiyu had a higher score than Puyang Tangzao,but the difference between the two was not significant.Puyang Tangzao had the highest taste score with 56.71points,followed by Leng Baiyu with 56.61 points,and Jin’Ai No.4 had the lowest taste score.Leng Baiyu had the highest fruit skin thickness score,followed by Puyang Tangzao,and Zao Cuimi had the lowest score.Leng Baiyu had the highest overall score with 95.05 points,followed by Puyang Tangzao with 93.26 points,and Jin’Ai No.4 had the lowest overall score of 87.57 points.The highest comprehensive evaluation score was for Leng Baiyu,followed by Puyang Tangzao,and the lowest was for Jin’Ai No.4.In conclusion,the photosynthetic capacity and fruit quality of Leng Baiyu jujube and Puyang tangzao were better than that of Zao Cuimi and Jin’Ai No.4,so they were more suitable for introduction and cultivation in Yulin area.