Effects of L-Proline Foliar Application on the Quality of 'Kosui' Japanese Pear

The effects of L-proline foliar application on young, 4- to 5-year-old, Japanese pear trees grown in containers under greenhouse conditions were investigated. The sugar content of the fruit was increased by the treatment and nitrogen metabolism of the trees was ameliorated in cases where the soil nitrogen level was not in excess. The total nitrogen level and L-glutamic acid contents of new leaves were also increased, while the content of nitrate was decreased. It was suggested that L-proline foliar application promoted the absorption of nitrogen from the fine roots, as well as the production of amino acids and the synthesis of chlorophyll in the leaves in cases where the soil nitrogen level was not in excess. Increase of chlorophyll in the leaves promoted the photosynthesis, resulting in higher sugar contents of the fruit. L-proline foliar application also seemed to ameliorate nitrogen metabolism. These findings may help in producing the high quality fruits.