Effects Of Leaf Photosynthetic Characteristics And Fruit Quality On Different Apple Tree Shapes

In this study,red Fuji apple was used as the experimental material to study the changes of the Pn-PAR response curve,Pn-CO₂ response curve,fluorescence quenching kinetic curve,leaf anatomical structure,and fruit quality under different tree shapes.The main results are as follows:1.With the increase of photosynthetically active radiation,both the gas exchange parameters and chlorophyll fluorescence parameters show that the high light use efficiency tree shape was better than the small crown sparse layer.The photosynthetic rate of three-bough open-centre was the best,in which the maximum net photosynthetic rate was 20.19 μmol · m^-2 · s^-1,light saturation point was 1443.42μmol · m^-2 · s^-1,light compensation point was 30.00 μmol · m^-2 · s^-1,and the apparent quantum efficiency was 0.107μmol·m^-2·s^-1;the photosynthetic rate of small crown sparse layer is the lowest,in which the maximum net photosynthetic rate was 14.73μmol·m^-2·s^-1,light saturation point was 1041.94μmol · m^-2 · s^-1,light compensation point was 49.00 μmol · m^-2 · s^-1,and the apparent quantum efficiency was 0.082 μmol · m^-2 · s^-1.2.With the increase of CO₂ concentration,the changes of gas exchange parameters and chlorophyll fluorescence parameters show that the high light use efficiency tree shape was better than the small crown sparse layer.Among the characteristic parameters of photosynthesis-intercellular CO₂ concentration,the three-bough open-centre has the best performance,in which the maximum carboxylation rate was 177.60 μmol · m^-2 · s^-1 and the maximum electron transfer rate was 202.13μmol · m^-2 · s^-1,the triose phosphate utilization efficiency was 16.18 μmol · m^-2 · s^-1,the CO₂ compensation point was 55.59 μmol · mol-1,the RuBP carboxylation reaction Mie constant was 1075.66μmol · mol-1,the RuBP oxidation reaction has a Mie constant of 439.41 μmol · mol-1;and the small crown sparse layer has the lowest performance.The maximum carboxylation rate was 121.89μmol · m^-2 · s^-1 and the maximum electron transfer rate was 130.21 μmol · m^-2.· S-1,the triose phosphate utilization efficiency was 13.64 μmol · m^-2 · s^-1,the CO₂ compensation point was 69.70μmol · mol-1,the RuBP carboxylation reaction Mie constant was 1496.60 μmol · mol-1,the RuBP oxidation reaction the Mie constant was 499.82 μmol · mol-1.3.The anatomical structure of the leaves under the high light use efficiency tree shape showed adaptability to high light.As the number of main branches decreased,the leaf thickness gradually increased.The upper epidermal cells in the high light use efficiency tree shape were relatively uniform in size and compact in arrangement,while the upper epidermal cells in the control group were convex and permeable,with poor consistency.The Thickness of palisade tissue in the high light use efficiency tree shape was obviously larger than that in small crown sparse layer,and it was composed of cells arranged orderly and closely.The leaf plasticity is high,especially the palisade tissue is the highest,the spongy tissue and the leaf tissue structure looseness plasticity is very low,the character is relatively stable.4.The fruit yield and quality under the high light use efficiency tree shape were better than that of the small crown sparse layer.As the number of main branches decreased,the fruit quality was better..The fruit quality of the three-bough open-centre is the best in all treatments.The single fruit weight were 361.37 g,and the area yield was 2619.40 kg,the color of the peel was the reddest,the titratable acid content is 0.15%,the soluble solid content is 14.33%,and the content of flavonoids and total phenol in the pulp is 0.87 mg / g and 0.42 mg / g,respectively.The contents of flavonoids,total phenols and anthocyanins in the peel were 6.42 mg / g,2.47 mg / g and 1.20 mg / 100 g,respectively.