Effect Of Different Irrigation On Growth,Yield And Quality Of Melon Based On Transpiration Model

Plant transpiration was affected by plant physiological and atmospheric factors,so that it discussed the relationship between daily transpiration and its influencing factors based on the driving effect of environmental factors by correlation and path coefficient analysis in greenhouse.Daily transpiration model of melon was established and verified based on the environmental data and leaf area index.Four levels of irrigation: 80%ET?100%ET?120%ET?140%ET were set in this study to investigate the effect of melon ‘Lvcuibao' on morphological index,photosynthesis,water transport and so on,meanwhile,synthetically evaluated yield and quality,which provided a scientific basis for efficient production and intelligent irrigation of melon in greenhouse.The main results are as follows:1.Leaf area index and environmental factors in greenhouse had significant effects on daily transpiration of melon.Daily transpiration of melon increased with the increasing of leaf area index or daily average temperature showed obvious rising trend,and daily transpiration of melon increased with the increasing of daily average relative humidity showed obvious declined trend.The effect of influencing factors on the transpiration showed that leaf area index>daily average temperature>daily average relative humidity>intensity of solar radiation.Leaf area index and daily average temperature had direct impact on the daily transpiration of melon,and daily average relative humidity and intensity of solar radiation mainly had indirect effects on the daily transpiration of melon.The transpiration model used parameter estimation by the Marquardt method,and analysed multivariate nonlinear regression.The result showed that the daily transpiration model was fitted well.RMSE=41.83 g,RE = 11.4%.2.Different levels of irrigation based on transpiration model had significant effects on morphological and physiological index.Growth of plant height showed a slow-fast-slow trend,and flowering stage was the largest,followed by stretching stage.Growth of plant height was ET4 > ET3 > ET2 > ET1;Growth of stem diameter showed a gradually slowing trend,and stretching stage was the largest,followed by flowering stage.Stem diameter of each treatment was ET4 > ET3 > ET2 > ET1.Net photosynthesis rate,stomatal conductance and chlorophyll increased with the increasing of irrigation showed obvious rising trend,then declined over a certain range.Intercellular CO₂ concentration in flowering stage was higher than that of fruiting stage,and intercellular CO₂ concentration in stretching stage was lower than other times.ET3 had the highest net photosynthetic rate in fruiting stage than ET1,ET2 and ET4 by 36.6%,17.8% and 11.4%,respectively.With the increasing of irrigation,substrate water potential,leaf water potential and hydraulic conductance increased.3.Different levels of irrigation had significant effects on dry matter accumulation and distribution.From stretching stage to fruiting stage,dry matter accumulation in different treatments was ET4>ET3>ET2>ET1.The dry matter accumulation of leaf was ET4>ET3>ET2>ET1,and the dry matter accumulation of fruit in fruiting stage was ET3>ET4>ET2>ET1.The dry matter distribution in stretching stage showed that leaf > stem > root.Proportion of leaf was 68%⁷1%,roportion of stem was 19%²2%,and roportion of root was 8%¹0%.The dry matter distribution in flowering stage showed that leaf > fruit > stem > root.Proportion of leaf was 50%⁵6%,roportion of fruit was 18%²2%,roportion of stem was 16%¹9%,and roportion of root was 7%⁹%.The dry matter distribution in fruiting stage showed that fruit > leaf > stem > root.Proportion of fruit was 58%⁶1%,roportion of leaf was 22%²4%,roportion of stem was 10%¹4%,and roportion of root was 5%⁶%.4.Different levels of irrigation had significant effects on yield and quality.The yield of melon declined in low or high level of irrigation based on transpiration model,and the yield in different treatments was ET3 > ET4 > ET2 > ET1.The yield of ET3 was 1.23kg/plant,which had the highest yield than ET1,ET2 and ET4 by 36.6%,17.8% and 11.4%,respectively.The content of soluble solid,soluble protein and soluble sugar showed a rising trend,and then declined over a certain range.The subordinate function value of fruit quality showed that ET3?4.69?> ET2?3.45?> ET1?3.34?> ET4?2.27?.Comprehensively analyzed from morphological index,photosynthesis,water transport,quality and so on,based on the transpiration model,ET3 was the best.According to the daily transpiration model of melon,the irrigation of 120%ET was the optimal choice.