中文摘要：

SPAD（ soil-plant analysis and development ）计是一种快速、方便、非破坏性的诊断植物叶片相对叶绿素或氮含量的仪器，与传统的氮营养诊断方法相比，此仪器节省时间、劳力和资源。本试验通过未遮荫和遮荫的方法观察水稻冠层叶片SPAD值、叶绿素含量、叶绿素荧光、光合参数、叶片厚度和比叶重（叶片干重除以叶片的面积）等生理形态指标的变化，建立SPAD值与光系统II（ PSII）最大量子产量（ Fv/Fm）之间的回归关系。结果表明，遮荫条件下，甬优9号（YY9）和丙9363（B9363）冠层叶片变薄、SPAD值、叶绿素a/b、比叶重、电子传递速率（ETR）降低，但快速光曲线的初始斜率无明显变化；同时，遮荫导致了叶片的呼吸速率、最大净光合（ Pmax）、量子效率、光补偿点和饱和点降低，表明水稻叶片为适应弱光环境，降低光合能力、减少呼吸消耗，以增加对有限光能的利用。不同光照条件下，水稻冠层叶片SPAD值与PSII的Fv/Fm的回归方程呈指数式关系（ YY9 R2＝0.896； B9363 R2＝0.833），表明SPAD计可以快速、无损、有效地评估水稻冠层叶片的光合作用进程，当SPAD值小于35时，其光合过程可能处于受损状态。

英文摘要：

Soil-plant analysis and development （SPAD） meter is a quick, portable,non-destructive diagnostic tool for the measurement of relative chlorophyll or nitrogen （ N） content in leaves.SPAD meter is time, labor and resources saving compared to traditional N nutrition diagnosis methods .The experiment with and without shading treatments was conducted in paddy field with rice cultivars YY 9 and B9363.The physiomorphology indices including leaf SPAD values , chlorophyll contents , chlorophyll fluorescence and photosynthetic parameters , specific leaf weight and blade thickness in rice canopy were measured to establish the regression relationship between SPAD values and the maximum quantum output in photosystem II （ Fv/Fm of PSII） at rice growth stages .The results show that under the shading treatment , there is decline in the leaf SPAD values , chlorophyll a/b ratios, specific leaf weights and electron transport rate .The thickness of leaves becomes thin in rice canopy;the initial slopes of rapid light curves do not change obviously .The respiration rate, the maximum net photosynthetic efficiency （Pmax）, the quantum efficiency , light compensation point and saturation point of leaves are decreased to reduce photosynthetic capacity and consume through breath , and increase the utilization of limited light energy under weak light environment .Under both the shading and without shading treatments , exponential relationships exist between the leaf SPAD values and the Fv/Fm of PSII in rice canopy.For cultivar YY9, the coefficient of determination R2 is 0.896 and for B9363 is 0.833.Therefore, the leaf photosynthetic process in rice canopy can be evaluated quickly , non-destructively and efficiently using SPAD meter , and the SPAD reading of lower than 35 may be used to indicate the impairment in photosynthetic process of rice .