| In China,thick-skinned muskmelon is one of the main melon crops cultivated in facility,which is juicy and tasty,rich in nutrition and has good economic benefits.In recent years,with the domestic and foreign markets to the thick-skinned muskmelon demand increases significantly,the quality of the product requirements are more and more high.Calcium is one of the essential medium elements for plants,which plays an important role in the growth and development of plants and the formation of fruit quality.Therefore.it is of great significance to study the effect mechanism of calcium on sugar metabolism in leaves and fruits of muskmelon and to explore reasonable methods of topdressing calcium fertilizer for current soil cultivation of muskmelon.In this experiment,the melon variety’Nongda 103’ was used as the experimental material.The plants were treated with 5 different concentrations of calcium chloride(0,5,15,25 and 35mmol/L)for 2 times,with an interval of 7 days,from the seedling stage(three leaves period)and the fruit growth stage(the day when the female flowers bloom).The effects of exogenous calcium on the growth and development of muskmelon seedlings were studied by measuring the dynamic changes of plant growth index,chlorophyll content,net photosynthetic rate,plant dry matter weight,strong seedling index,MDA content and antioxidant enzyme activity.The effects of exogenous calcium on sucrose metabolism and fruit quality of muskmelon were investigated by measuring the contents of carbohydrate substances in leaves and fruits at fruiting node,sucrose metabolism enzyme activity,fruit quality and yield,etc.The main results were as follows:1.Different concentrations of calcium chloride treatment have different effects on the growth of thick-skinned muskmelon seedlings.Compared with the control.15mmol/L calcium chloride treatment could significantly increase the plant height,stem diameter.leaf area and root activity,and significantly increase the chlorophyll content and net photosynthetic rate of leaves of muskmelon,thus promoting the growth and development of muskmelon seedlings.The index of strong seedlings was 35.52%,45.39%and 39.45%higher than that of the control group at 5d,10d and 15d.2.Different concentrations of calcium chloride treatment at the seedling stage of muskmelon has different effects on the antioxidant enzyme system of leaves.Compared with the control group.15mmol/L calcium chloride treatment significantly increased the activities of SOD,POD and CAT in melon seedling leaves,and decreased the content of MDA in leaves.The SOD activity measured every 3 days was 62.5%,58.32%.61.17%,48.19%and 43.36%higher than the control.POD activity was 60.62%,75.51%,59.27%,71.29%,42.85%higher than the control.CAT activity was 50.71%,71.24%,59.18%,48.25%,32.41%higher than the control.MDA content was 24.92%,31.22%.30.21%,27.03%and 28.12%lower than the control.3.Compared with the control,25mmol/L calcium chloride treatment significantly increased the plant height,stem diameter and leaf area,and significantly increase the chlorophyll content and net photosynthetic rate of fruit-setting node leaves,which effectively promoted the growth and development of muskmelon plants during the fruit growth period.4.During the growth period of muskmelon fruit,the dry matter content in various organs of the plant was affected by different concentrations of calcium chloride.Compared with the control,leaf spraying of 25mmol/L calcium chloride was beneficial to the accumulation of dry matter content in roots,stems,leaves and fruits,and increased the proportion of dry matter content in fruits in plants.Compared with the control,the root dry matter content measured every 14 days increased by 56.25%.53.86%and 44.19%.Stem dry matter content increased by 39.67%,71.37%and 25.67%.Leaf dry matter content increased by 19.53%,25.06%and 31.18%.Fruit dry matter content increased by 31.49%,30.97%and 29.53%.The results showed that appropriate calcium chloride treatment could significantly increase the dry matter content in various organs of melon plant,and promote the dry matter transfer from stem,leaf and other vegetative organs to fruit.5.During the growth period of muskmelon fruits.different concentrations of calcium chloride treatment had different effects on sugar metabolism of leaf at fruit-setting node.Compared with the control,leaf spraying with 25mmol/L CaCl2 significantly increased the activities of acid invertase(Al).neutral invertase(NI)and sucrose phosphate synthase(SPS)in leaves,and increased the contents of fructose,glucose,sucrose and soluble sugar in leaves,but had no significant effect on the activities of sucrose synthase(SS).Compared with the control,the Al activity measured every 7 days increased by 30.76%,26.23%,24.56%,31.76%and 23.14%;NI activity increased by 33.26%,38.91%,55.69%,29.32%and 13.74%.SPS activity increased by 29.06%,25.43%,30.78%,35.47%and 46.63%.The fructose content increased by 17.37%.21.64%,18,43%,22.07%and 20.82%.Glucose content increased by 41.67%.38.73%.38.93%,41.84%,27.61%.Sucrose content increased by 22.82%,35.71%,12.46%,52.96%,61.75%.Soluble sugar content increased by 25.21%,53.26%.23.73%,31.39%and 28.91%.6.During the growth period of muskmelon fruits.different concentrations of calcium chloride had different effects on sucrose metabolism.Compared with the control,leaf spraying with 25mmol/L CaCl2 significantly increased the activities of acid invertase(AI),neutral invertase(NI)and sucrose phosphate synthase(SPS)in leaves,and increased the contents of fructose,glucose,sucrose and soluble sugar in leaves,but had no significant effect on the activities of sucrose synthase(SS).Compared with the control,the AI activity measured every 7 days increased by 30.76%,26.23%,24.56%,31.76%and 23.14%.NI activity increased by 33.26%,38.91%,55.69%,29.32%and 13.74%.SPS activity increased by 29.06%,25.43%,30.78%,35.47%and 46.63%.Fructose content increased by 17.37%,21.64%,18.43%,22.07%and 20.82%.Glucose content increased by 41.67%,38.73%,38.93%,41.84%,27.61%.Sucrose content increased by 22.82%,35.71%,12.46%,52.96%,61.75%.Soluble sugar content increased by 25.21%,53.26%,23.73%,31.39%and 28.91%.7.Different concentrations of calcium chloride sprayed on the leaf surface during fruit growth period had different effects on fruit quality and yield.25mmol/L calcium chloride treatment could significantly increase the single fruit weight and plot yield,increase the contents of soluble sugar,soluble solids and Vc,reduce the content of titratable acid,and improve fruit quality.Compared with the control,the soluble sugar in fruits increased by 24.06%,the soluble solid content increased by 10.98%,Vc content increased by 25.46%,titratable acid content decreased by 32.24%,plot yield increased by 33.08%. |
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