本研究通过比较基因表达量和有机酸含量，发现了一个P_3A亚家族成员PbPH5基因的表达量与不同梨系统的苹果酸积累呈高度相关，且与白梨系统、西洋梨系统、砂梨系统和秋子梨系统中的相关性分别是0.932**，0.656*，0.900**和0.518*（*P<0.05或** P<0.01）。在梨果实中过表达PbPH5基因后苹果酸含量增加，沉默PbPH5基因后苹果酸含量降低；亚细胞定位结果显示PbPH5定位于液泡膜。此外，系统发育分析结果表明PbPH5基因是PH5的同源基因，与矮牵牛、苹果和柑橘PH5基因归于同一支。综上所述，这些结果表明PbPH5是一个较为保守的基因，而且，梨果实中苹果酸的积累至少部分与PbPH5基因表达量相关。

The soil organic matter and nutrients are fundamental for the sustainability of pear production, but little is known about the spatial distribution of soil organic matter and nutrients in a pear orchard. With the soil of the pear (cv. Dangshansu on P.betulifolia Bunge. rootstock) orchard under clean and sod cultivation models as test materials, the experiment was conducted to evaluate spatial variability of soil organic matter (SOM), total nitrogen (STN), total phosphorus (STP), total potassium (STK), available nitrogen (SAN), and available potassium (SAK) in and between rows at different soil depths (0-60 cm). The SOM, STN, STP, STK, SAN and SAK of the different soil layers under the two tillage models were different in the vertical direction. The SOM, STN, STP and SAN in the 0-20 cm soil layer were higher than those in the 20-40 and 40- 60 cm soil layers. The STK of 40-60 cm soil layer was higher than that in the 0-20 and 20-40 cm soil layers. The STK increased with the depth of soil in the vertical direction in the clean cultivated pear orchard. Variability of the SOM, STN, STP, STK, SAN and SAK of sample sites in between rows of the same soil layer was found in the pear orchard soil in the horizontal direction under clean and sod cultivation management systems, except that STK of all sites did not show the difference in identical soil layers in the pear orchard under clean cultivation. The sod cultivation model improved the SOM, STN, and STK in the 0-20 cm soil layer in the pear orchard, and the three components increased by 12.8, 12.7 and 7.3% compared to clean cultivation, respectively. The results can be applicable to plan collection of orchard soil samples, assess orchard soil quality, and improve orchard soil management practices.

Regrowth traits of alfalfa (Medicago sativa L.) in spring are closely related to its fall dormancy before winter. In order todetermine the relationship between fall dormancy (FD) grade and hormone variation pattern and provide academic referencesfor the variety improvement and production of alfalfa, the variations of gibberellins (GA3), indole-3-acetic acid (IAA), andabscisic acid (ABA) in alfalfa roots during regrowth period in spring were examined by high performance liquidchromatography (HPLC). The study involved seven alfalfa cultivars that belonged to four fall dormant grades, i.e., 2, 4, 6,and 8. The results showed that the differences in spring regrowth among the alfalfa cultivars were partially associatedwith their root hormone levels. The alfalfa cultivars that belonged to the same dormancy grades presented similarvariation trends in endogenous hormone content in their roots during the spring regrowth stage. At the early regrowthstage, cultivars with a higher dormant grade had a higher GA3 concent and a lower ABA content in their roots than thecultivars with a lower dormant grade; and IAA content in roots of non- and semi-fall dormancy cultivars was higher thanthat of fall dormancy cultivars. During the whole period of spring regrowth, the root ABA content of fall dormancy alfalfacultivar is significantly higher than those of semi- and non-fall dormancy cultivars. GA3 contents in the roots of allcultivars under study showed a double-peak dynamic curve; root IAA contents of the studied cultivars presented adownward trend. But the trend did not significantly differed among the different fall dormant cultivars. The higher GA3content and lower ABA content in root of non-fall dormancy alfalfa lead to its earlier regrowth. Regrowth time and rate ofalfalfa can be regulated by exogenous GA3 or ABA at the early regrowth stage to meet producing requirement.