对全光照(遮光率0%,对照)以及遮光率25%、50% 和75% 条件下臭牡丹(Clerodendrum bungei Steud.)生长和光合特性的变化进行了研究。结果表明:随遮光率的提高臭牡丹枝长生长量和比叶面积逐渐增加、枝条直径生长量和比叶质量逐渐减小,叶面积呈波动变化,其中在遮光率25% 条件下叶面积最小。在遮光条件下叶片以及栅栏组织和海绵组织厚度差异不显著,但均显著小于对照。在遮光条件下叶片叶绿素a 和总叶绿素含量以及叶绿素a / b 值总体上随遮光率提高逐渐增加且均高于对照,仅在遮光率25%条件下叶绿素b 以及总叶绿素含量低于对照。在遮光率25%和75%条件下叶片净光合速率(Pn)有明显“午休”现象,Pn 日变化曲线近似于“双峰型”;而在对照和遮光率50%条件下Pn 无“午休”现象,日变化曲线近似于“单峰型”;4 个处理组Pn 峰值的大小以及峰值出现时间有差异。在上午9:00,在遮光率25%和50%条件下叶片气孔导度(Gs)略有降低,而在对照和遮光率75% 条件下Gs 明显升高;此后随时间的延长各处理的Gs 总体上呈逐渐下降的趋势。各处理组叶片胞间CO2 浓度(Ci)的日变化曲线基本一致,均呈早晚略高、中午略低的趋势,谷值均出现在13:00。在对照及遮光率25% 和75% 条件下,叶片蒸腾速率(Tr)的日变化曲线均呈“双峰型”;而在遮光率50%的条件下Tr 呈逐渐降低的趋势,日变化曲线近似于“单峰型”。总体上看,4 个处理组叶片的Pn、Gs、Ci 和Tr 日平均值均无显著差异;且在遮光率25%、50% 和75%条件下臭牡丹叶片的Pn 与Tr 间有显著或极显著相关性。综合分析结果表明:臭牡丹是偏阴生植物, 在栽培中适度遮光有利于臭牡丹的生长发育。

Change of growth and photosynthetic characteristics of Clerodendrum bungei Steud. was researched under conditions of full sunlight (shading rate of 0%, CK) and shading rate of 25%, 50% and 75%. The results show that with enhancing of shading rate, growth increment of branch length and specific leaf area increase gradually, growth increment of branch diameter and specific leaf weight decrease gradually; and leaf area appears a fluctuant change with the smallest leaf area under shading rate of 25%. Under shading conditions, thickness of leaf, palisade tissue and sponge tissue has no significant differences, but that is significantly smaller than that of the control. Under shading conditions, contents of chlorophyll a and total chlorophyll and ratio of chlorophyll a / b increase generally with enhancing of shading rate and are higher than those of the control, but only contents of chlorophyll b and total chlorophyll are lower than those of the control under shading rate of 25%. Under shading rate of 25% and 75%, net photosynthetic rate (Pn) of leaf has an obvious “midday depression”with a Pn daily change curve similar to “two-peak pattern”, while under the control and shading rate of 50%, Pn has no “midday depression”with a Pn daily change curve similar to “single-peak pattern”; and range and appearance time of Pn peak value are different among four treatment groups. At 9: 00, stomatal conductance (Gs) of leaf decreases slightly under shading rate of 25% and 50%, but increases obviously under the control and shading rate of 75%, and then Gs under all treatment conditions appears a trend of gradually decreasing with prolonging of time. Daily change curve of intercellular CO2 concentration (Ci)of leaf in all treatment groups is basically identical with a trend of slightly high in the morning and evening and slightly low at noon, and Ci valley value all appears at 13:00. Daily change curve of transpiration rate (Tr) all displays “two-peak pattern”under the control and shading rate of 25% and 75%, but Tr appears a gradually decreasing trend under shading rate of 50% with a daily change curve similar to “ single-peak pattern”. Generally, Daily average values of Pn, Gs, Ci and Tr have no significant differences among four treatment groups, and there is significant or extremely significant correlations between Pn and Tr of C. bungei leaf under conditions of shading rate of 25%, 50% and 75%. Comprehensive analysis result suggests that C. bungei is a partial shade plant, and appropriate shading is beneficial to its growth and development in cultivation process.