遮荫对金莲花光合特性和叶片解剖特征的影响

以金莲花为材料,系统研究了不同遮荫处理(全光照、40%、60%和80%遮荫)对金莲花叶片光合特性和叶解剖结构的影响,为金莲花引种驯化和抚育管理提供理论依据。结果表明:全光照下金莲花叶净光合速率有明显光合"午休"现象,遮荫处理下"午休"现象不明显。其中,40%遮荫处理显著促进了金莲花叶片净光合速率,80%遮荫处理则起抑制作用;40%和60%遮荫处理促进金莲花叶蒸腾速率和气孔导度的提高,降低了蒸汽压亏缺,有利于光合作用的进行;80%遮荫处理下胞间CO2浓度提高,气孔限制值和蒸汽压亏缺均显著高于其它处理,抑制了金莲花叶蒸腾作用和光合作用;遮荫处理降低了金莲花叶光补偿点和暗呼吸速率,40%和60%遮荫处理下表观量子效率和最大净光合速率提高,说明金莲花有一定耐荫性;金莲花叶光合特性与解剖结构关系密切。遮荫降低了金莲花叶气孔密度和气孔指数,但气孔纵轴长和横轴长显著高于对照。40%和60%遮荫处理下,单叶气孔数量没有明显变化;遮荫下金莲花叶片增厚。栅栏组织厚度和细胞层数减少,栅栏细胞宽度加大,且第二层栅栏细胞有向海绵组织过度的趋势。海绵组织厚度增加,栅栏组织/海绵组织比值减小。随遮荫度增高,栅栏组织和海绵组织细胞间隙增大。该结构有利于提高对光能的利用效率;遮荫处理促进维管束的发育,维管束数量增加,木质部、韧皮部分化明显,其中中脉导管直径和导管数目增加,有利于蒸腾作用和光合作用的进行。

Effects of shading on the photosynthetic characteristics and anatomical structure of Trollius chinensis Bunge

Effect of different shading treatments (0, 40%, 60% and 80% shade) on the photosynthetic characteristics and anatomical structure of Trollius chinensis Bunge was studied to provide some theoretical basis for introduction, domestication and cultivation of the species. The results showed that the significant midday depression of net photosynthetic rate at noon was observed for T. chinensis under the full sunlight treatment, while the depression was not significant under the shading treatments. The net photosynthetic rate increased at 40% shade but decreased at 80% shade. The transpiration rate and stomatal conductance increased while the vapor pressure deficit reduced at both 40% and 60% shade, which was helpful to photosynthesis. The stomata limitation, stomatal conductance and vapor pressure deficit were highest in the 80% shade treatment by comparison with other shade treatments, which suppressed net photosynthetic rate and transpiration rate of the plants. The fact that dark respiration and light compensation point declined in the shading treatments and that the 40% and 60% shading treatments resulted in increase of the apparent quantum efficiency and maximum net photosynthetic rate of the species indicated that T. chinensis had shade tolerance to some extent. The results also showed that there was a close relation between the photosynthetic characteristics and anatomical structure of T. chinensis. Shading treatments resulted in decrease of stomatal density and stomatal index, while increased the stomatal size. The average number of stomata in a leaf did not significantly change at 40% and 60% shade treatments, however, the average size of stomata increased.Leaf thickness also increased. The thickness of palisade tissue and layers of palisade cells reduced, while the breadth of palisade tissue enlarged. In particular, a tendency of palisade tissue changing into spongy tissue was also observed. The thickness of spongy tissue increased and the ratio of palisade tissue to spongy tissue decreased. The gaps between the cells of both palisade tissue and spongy tissue became larger as the increase of shading degree. The above changes of the mesophyll tissue structure were helpful for T. chinensis to improve the utilization of luminous energy. The shading treatment was also able to promote the development of vascular bundle and increase the number of vascular bundle and significantly increased the differetiation of xylem and phloem. The number of catheter in midrib and the diameter of catheters in midrib increased, which was helpful to increase the net photosynthetic rate and transpiration rate.