氮素水平对甜菜功能叶片光合特性的影响越

采用甜研七号(偏高糖型)和甜研八号(偏丰产型)甜菜作为试材，在5个氮素水平(0、60、120、180和240kg/hm2)下，研究了甜菜功能叶片(第15片真叶)在生育进程中和不同叶龄下的叶绿素含量、光合特性的变化动态及其对块根产量、含糖率及产糖量的影响。结果表明：随着生育进程，叶绿素含量、光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)等光合特性指标均为单峰曲线变化，在叶片完全展开后第21天达到最大值，而后逐渐降低，2个品种均表现为这一趋势。单一叶龄(以21d叶龄为例)在0~120kg/hm2施氮水平下，叶绿素含量、光合速率(Pn)随施氮量增加而增加，过量施氮则增长不显著。在生育进程中，叶绿素含量、光合速率(Pn)同块根产量均表现为极显著正相关。以甜研七号为例，相关系数分别为R=083**和R=093**；同产糖量呈显著正相关，相关系数分别为R=085*、R=086*；蒸腾速率(Tr)、气孔导度(Gs)同产质量的相关性基本与光合速率(Pn)相同，胞间CO2浓度(Ci)则与其他光合特性指标均呈极显著负相关；21d叶龄下，两品种的叶绿素含量、光合速率(Pn)同块根产量均表现为显著正相关或极显著正相关。

EFFECT OF NITROGEN LEVEL ON PHOTOSYNTHETIC CHARACTERISTICS IN FUNCTIONAL LEAVE OF SUGAR BEET(Beta Vulgaris L.)

The effects of different nitrogen levels (0,60,120,180 and 240kg/hm2) on dynamic changes of chlorophyll content and photosynthetic characteristic of the 15th leaf(functional leaf), and on beet yield, sucrose content and sucrose yield of two sugar beet varieties (Tianyan 7 and Tianyan 8) were investigated. The results showed that: chlorophyll content, photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) were all expressed in single peak curve, the peak was observed on the 21st day after leaf unfolding. At the certain leaf age (21st leaf age), chlorophyll content, photosynthetic rate (Pn) increased steadily with  increasing of nitrogen levels in the range of 0~120kg/hm2.  Taking Tianyan 7, as an example, chlorophyll content and photosynthetic rate (Pn)  were highly positive correlated to the beet yield, the correlation coefficients were R=083**, R=093**; and chlorophyll content and Pn were also significantly positive with the sucrose yield, the correlation coefficients were R=085* and R=086*. The correlation of transpiration rate (Tr) and stomatal conductance (Gs) with the sucrose content and sucrose yield were similar to photosynthetic rate (Pn). The correlation between internal CO2 concentration (Ci) and the other photosynthetic characteristics were significantly negative. On the 21st leaf age, the correlation between the chlorophyll content, photosynthetic rate (Pn) of two varieties and beet yield were significantly positive.