绝大部分的果树在生产过程中都需要进行疏花疏果，以达到其优质丰产稳产的目的。疏花疏果在果树生产中起着重要的作用，它可以防止和减轻大小年现象，提高优质果比率，使树体保持健壮，延长果树的经济寿命。5-氨基乙酰丙酸(ALA)是叶绿素、亚铁血红素、光敏素以及维生素B12等所有卟啉化合物生物合成的第一个关键前体。并由此展开了大量的研究，结果发现高浓度的ALA可以成为没有毒性、不会造成污染的田间除草剂，其在农业生产中存在主要的潜在应用价值，拥有广泛的应用前景以及市场前景。本研究以翠冠梨为材料，分析了喷布ALA对梨树疏花疏果作用的影响。提出盛花期喷施200 mg·L-1的ALA可以降低坐果率；并进一步解释其疏除机理。主要结果如下： 1. 本研究于2011年至2013年间分别在江苏省徐州丰县大沙河果园和南京农业大学江浦梨园，以‘砀山酥梨’、‘明水’、‘水晶’、 ‘翠冠’等4个品种为材料，花期喷施不同浓度的ALA溶液，都能不同程度地降低了花序坐果率和花朵坐果率。相比而言，盛花期采用200 mg·L-1的ALA溶液处理最为适宜。分析ALA处理后梨花花柱抗氧化特性表明，经ALA处理导致花柱SOD活性降低，超氧阴离子大量产生，丙二醛含量显著增加。荧光显微镜观察表明，ALA处理抑制了梨花花粉在柱头上萌发和花粉管生长。因而，花粉萌发生长受阻和花柱衰老加速可能ALA导致梨花脱落的原因。 2. 以‘翠冠’梨花粉为材料，通过离体培养研究了ALA溶液对花粉粒萌发和花粉管生长的影响。结果表明，5 mg·L-1ALA处理，可以促进花粉萌发与生长。当ALA浓度大于10 mg·L-1时，随着浓度的升高，花粉的萌发率以及花粉管的长度均急剧下降。当培养基中加入适当浓度Ca2+时，可缓解ALA抑制作用。当培养基中添加Ca2+螯合剂EGTA后，Ca2+的缓减作用消失。作者认为，Ca2+对ALA抑制效应的缓减作用可能与花粉中Ca2+-ATPase活性有关。 3. 以‘翠冠’梨花粉为材料，使用低温装载法将钙离子荧光指示剂fluo_3AM完整地装载进花粉粒中,通过激光共聚焦显微技术研究了ALA处理对梨花粉胞内游离Ca2+和H2O2分布的影响。结果表明，经10 mg·L-1ALA处理过之后，花粉内Ca2+荧光强度和H2O2含量都会下降。向其中加入一定浓度Ca2+，花粉内Ca2+荧光强度和H2O2含量均出现平稳状态；若再加入EGTA后又恢复其下降的趋势。这些结果说明，ALA抑制梨树花粉萌发可能通过调节胞内Ca2+和H2O2来实现。

Most fruit trees need to be thin flower and fruit in the process of production, in order to achieve the purpose of the high and stable yield of high quality. Thinning flower and fruit plays an important role in fruit production, it can prevent and reduce biennial bearing, improve the percent rate of the high quality fruit, keep the tree body haleness, extend the economic life of the fruit trees. 5 - aminolevulinic acid (ALA) is the first key precursor of the porphyrin compounds biosynthesis, for examper chlorophyll and heme, photosensitive element and vitamin B12. And we maked a lot of research, which found that high concentrations of ALA can be a herbicide of no toxicity and no pollution in the field, it has potential applications, broad application prospects and market prospects in agricultural production. Using green-coronal pear pollen as material, this study analyzed the effects of the ALA on thinning flower and fruit. It is found that the 200 mg·L-1ALA could reduce the fruit rate in full-blossom period, And explained the mechanism of hydrophobic besides. The main results are as follows: 1. Trees of pear (Pyrus sp. cv. ‘Dangshansuli’, ‘Akemizu’, ‘Suisho’ and ‘Cuiguan’) were sprayed with 5-aminolevulinic acid (ALA) solutions at blooming stage to study the thinning effects in Dashahe Orchard of Feng County, Xuzhou City, and Jiangpu Orchard of Nanjing City from 2011 to 2013. The results showed that 200 mg·L-1 ALA applied at the full blooming stage might be suitable for pear flower thinning. Analysis showed that the superoxide dismutase (SOD) activity in the stigma treated by ALA solution was depressed, compared with the control, but the superoxidate anion production, the content of MDA increased significantly. Observation by microscopes showed that pollen germination and tube growth in the stigma of pear flowers were inhibited by ALA treatment. Thus, the peroxidation stress in stigmas and the inhibition of germination and growth in pollens might be the causes of flower abortion. 2. With pear (Pyrus pyrifolia Nakai cv. ‘Cuiguan’) pollens as material, the effects of ALA on pollen germination in vitro and pollen tube growth were studied in the work. The results indicated that the treatment of ALA in 5 mg·L-1 promoted the pollen germination and pollen tube growth, but when the concentration of ALA was greater than 10 mg·L-1, the pollen germination and pollen tube growth were inhibited as the increase of ALA concentrations. The inhibition of ALA on pollen germination and tube growth could be alleviated by added suitable concentrations of Ca2+, and the Ca2+ effect could be eliminated by added EGTA. The measurement of Ca2+ - ATPase activity in pollen tubes suggested that ALA might affect pollen germination and tube growth thrghou regulating the enzyme activity. 3. Using ‘Cuiguan’ pear pollen as material, the calcium ion fluorescence indicator fluo_3AM was loaded successfully into the pollen grains by low temperature loading method. Laser confocal scanning microscopy was used to study the effect of ALA on cytosolic Ca2+ concentration and H2O2 content in pear pollen grains. It was found that the 10 mg·L-1ALA could decrease the intracellular calcium ion concentration and H2O2 content. To the medium to join a certain concentration of Ca2+, the intracellular calcium ion concentration and H2O2 content remains stable. It would decrease again by addition of calcium. It suggests that the inhibition of ALA on pollen germination and tube growth of pear flowers might be involved in regulation of cytosolic Ca2+ concentration and H2O2 content.