幼年梨树品种光合作用的研究

 利用CIRAS-1光合仪, 分别于5月下旬和10上旬田间测定了19个梨品种幼树叶片净光合速率( Pn) , 结果表明, 新梢中部叶片Pn值较高且稳定, 不同品种功能叶片平均Pn值以‘中梨1号’最高,达13.13μmol·m^{- 2} ·s^{- 1} , 秋月最低, 仅8.08μmol·m^{- 2} ·s^{- 1} , 其余大多数品种Pn值介于二者之间。分析影响梨树光合作用因素的结果表明, 叶片Pn值并不与枝条长短有直接关系, 而是与其生长状态有关, 未封顶的长梢叶片Pn明显高于已封顶的中梢和短梢。叶片背面受光时的Pn明显低于正面受光, 叶龄长的春梢叶片(约150 d) Pn明显低于健壮的秋梢叶片(约50 d) , 叶片上午Pn值明显高于下午。利用相关分析计算出梨树叶片光合作用的理论光补偿点为59.40 μmol·m^{- 2} · s^{- 1} , 表观量子效率0.038, 暗呼吸速率2.25μmol·m^{- 2} ·s^{- 1} , 最低叶温为13.77℃, 最适叶温为26.86℃, 最高叶温为39.96℃, 最适大气相对湿度为26.50% , 最高为84.23% , CO₂ 补偿点为42.17μmol·mol^{- 1}。

Studies on Leaf Photosynthesis of Young Pear Trees with Various Cultivars

The net photosynthetic rates ( Pn) of young pear ( Pyrus pyrifolia Nakai) trees were determined under field condition with a CIRAS-1 portable photosynthesis system in the late of May and the early of October, respectively. The results showed that Pn of most leaves in the middle of shoots were rather high andstable, while that in the base or top were low. Among 19 cultivars, the highest Pn, 13.13 μmol·m^{- 2} ·s^{- 1} , was found in‘Zhongli 1’, and the lowest in‘Akitsuge’, only 8.08 μmol·m^{- 2} ·s^{- 1} , and the others were the medium between them. The analysis of factors that affected leaf photosynthesis showed that leaf Pn was not dependent on shoot length directly, but on their growth situation. Pn of the leaves on a growing long shoot were significantly higher than that on a terminated middle or short shoot. The Pn when the upper surface of leaves was irradiated were significantly higher than that when the lower surface of leaves was irradiated. The Pn of young healthy leaves about 50-day-age on autumn shoots were significantly higher than that of older leaves about 150-day-age on sp ring shoots. The Pn determined in the morning were higher than that in the afternoon. The theoretical calculation showed that light compensation point of leaf photosynthesis of pear was 59.40μmol ·m^{- 2} ·s^{- 1} , apparent quantum efficiency 0.038, dark respiration 2.25μmol·m^{- 2} ·s^{- 1} , CO₂ compensation point 42.17μmol·mol^{- 1} , the lowest leaf temperature 13.77℃, the optimum leaf temperature 26.86℃, the highest leaf temperature 39.96℃, the optimum atmospheric relative humidity 26.50% , and the highest 84.23%.