Chemical fruit thinning has become a popular practice in modern fruit orchards for achieving high quality fruits, reducing costs of hand thinning and promoting return bloom. However, most of the suggested chemical thinners are often concerned for their detrimental effects and environmental problems. 5-Aminolevulic acid (ALA) is a natural, nontoxic, biodegradable, and environment-friendly plant growth regulator. One of its outstanding roles is improving plant photosynthesis and fruit quality. Here, results showed that applying 100-200 mg/L ALA at full bloom stage significantly reduced pear fruit set. Both in vivo and in vitro studies showed that ALA significantly inhibited pollen germination and tube growth. ALA decreased not only cytosolic Ca(2+) concentration ([Ca(2+)]cyt) but also "tip-focused" [Ca(2+)]cyt gradient, indicating that ALA inhibited pollen tube growth by down-regulating calcium signaling. ALA drastically enhanced pollen Ca(2+)-ATPase activity, suggesting that ALA-induced decrease of calcium signaling probably resulted from activating calcium pump. The significant negative correlations between Ca(2+)-ATPase activity and pollen germination or pollen tube length further demonstrated the critical role of calcium pump in ALA's negative effect on pollen germination. Taken together, our results suggest that ALA at low concentrations is a potential biochemical thinner, and it inhibits pollen germination and tube growth via Ca(2+) efflux by activating Ca(2+)-ATPase, thereby thinning fruits by preventing fertilization.

Experiments were conducted in two areas,i.e Sihong County and Xinghua City,Jiangsu Province,with amino-acid fertilizer to explore the effect on plant photosynthetic characteristics,agronomic characters,yield and quality.The results showed that spraying amino-acid fertilizer significantly increased the leaf SPAD value,net photosynthetic rate(Pn),the maximum quantum yield of PSⅡ(φPo)and the probability that a trapped exciton moves an electron into the electron transport chain beyond Q-A(Ψo).However,it depressed heat dissipation(φDo)of PSⅡ reaction center.Among them,φPo value of Sihong soybean variety'Gaofeng 1'increased 9.5%,and Ψo value of Xinghua soybean variety'Dadouwang'increased 23%.It also significantly improved the yield of soybean,100-seeds weight of'Gaofeng 1'increased 10%,yield per plant increased 39%,yield per m2 increased 64%;and 100-seeds weight of'Dadouwang'increased 8.6%,yield per plant increased 22.6%,yield per m2 increased 22%.And the amino-acid fertilizer treatment improved the content of vitamin C,soluble sugars,free amino-acid and protein.

<正>以江苏泗洪县和兴化市两地区主栽的大豆品种"高丰1号"和"大豆王"为材料,研究了喷施氨基酸肥料对植株叶片光合特性、农艺性状、产量与品质的影响。结果表明:氨基酸肥料处理显著增加大豆产量,"高丰1号"的百粒

Spraying with exogenous 5-aminolevulinic acid(ALA)in high concentrations(600,900 and 1 200 mg.L-1)at the late of full blooming could significantly thin flowers of pear(Pyrus pyrifolia Nakai.'Hosui'),and then promote fruit weight and quality at harvest.High concentrations of ALA treatment significantly reduced the stigma fertilizability of pear but increased the production rate of superoxide anion of floral organ,meanwhile,the activities of SOD and CAT were decreased greatly.In vitro,high concentrations of ALA inhibited pollen germination.Measurements of chlorophyll fluorescence showed that although the ALA solution was applied at blooming,leaf photosynthesis was obviously promoted in at least three months.