三叶爬山虎叶片解剖结构和光合生理特性对3种生境的响应

摘要

藤本植物生活环境的时空变化较为剧烈，为适应异质性生境常表现出较大的可塑性，其形态解剖结构及光合生理特征被认为能很好地体现对异质生境的适应。为了明确藤本植物叶片结构和光合作用对不同生境光强的响应策略，以木质藤本三叶爬山虎（Parthenocissus himalayana）为对象，采用光合仪测定和解剖显微观察的方法研究了哀牢山亚热带湿性常绿阔叶林的林外（全光照）、林缘（遮荫）和林内（荫生）3种自然生境中三叶爬山虎的叶片解剖结构和光合生理特征的变化，以期阐述三叶爬山虎对不同光环境的生态适应能力及策略，为森林生态系统的管理和物种多样性的保护及群落优化配置提供理论依据。结果表明：从林内到林外随着生境光强增加，叶片厚度（157.77～299.17μm）、上表皮厚度（21.30～28.40μm）、栅栏组织厚度（30.83～124.65μm）、栅栏组织细胞面积（430.95～652.97μm2）显著增大（P<0.01），栅栏组织细胞长度（29.23～49.54μm）和周长（86.58～155.17μm）、下表皮厚度（16.14～19.01μm）、气孔长度（24.13～27.10μm）和气孔密度（86.20～129.41个·mm-2）呈显著上升趋势（P<0.05）。栅栏组织细胞宽度（19.67～22.81μm）在3种生境中无显著差异。叶片解剖结构性状的平均可塑性值为0.37，其中最大值是栅栏组织细胞长度（0.67），最小值是气孔长度（0.11）。光饱和点（201.27～1299.17μmol·m-2·s-1）、光补偿点（3.86～29.88μmol·m-2·s-1）、饱和光强最大光合速率（2.20～12.03μmol·m-2·s-1）、暗呼吸速率（0.17～2.19μmol·m-2·s-1）、CO2补偿点（83.01～237.26μmol·m-2·s-1）、饱和CO2最大净光合速率（2.07～25.49μmol·m-2·s-1）、光呼吸速率（0.36～7.57μmol·m-2·s-1）、初始羧化效率（0.006～0.035μmol·μmol-1）随着生境光强的增高呈上升趋势，而表观量子效率（0.067～0.031μmol·μmol-1）、CO2饱和点（2062.56～1385.31μmol·m-2·s-1）呈下降趋势。与光合生理参数相关性显著的解剖性状主要是叶片厚度、上表皮厚度及其细胞周长/面积、栅栏组织细胞长度、栅栏组织厚度及维管束占叶脉面积的比例等。研究说明，三叶爬山虎在林外生境中具有明显的阳生叶特征，而在林内生境中具有明显的阴生叶特征，表现出对异质生境很强的适应性，从叶片解剖结构和光合生理特性方面解释了其在林外、林缘和林内均有分布的原因。%Temporal and spatial changes of habitats of vine plants are often intense, so plants should exhibit great plasticity in order to adapt to heterogeneous habitats. The anatomical structures and photosynthetic characteristics of leaves are considered to greatly reflect the adaptation of plants to different environmental regimes. The objective of the present study was to compare the anatomic and photosynthetic properties of the leaves of lianaParthenocissus himalayana grown in different locations (field, forest edge, and forest interior in the Ailao Mountains, Yunnan, China) with paraffin sectioning and Li-6400 photosynthetic apparatus. The reactions ofP. himalayana to different light environments and its survival mechanisms were evaluated. A significant correlation was found between the anatomical structure characteristics and the photosynthesis physiological properties. The intensification of light, from the forest interior to the field, caused a considerable increase in the thickness of the whole leaf and the tissues within upper epidermis, palisade tissue, and palisade cells area, from 157.77 to 299.17μm, 21.30 to 28.40μm, 30.83 to 124.65μm, 430.95 to 652.97μm2, respectively. There was also a significant rise in the length (from 29.23 to 49.54μm) and circumference of palisade cell (from 86.58 to 155.17μm). The thickness of the lower epidermis and the stomatal size and density were substantially increased. There were no significant differences in width of palisade cells (19.67-22.81μm) among different habitats. The average value of plasticity indexes of leaf anatomical characteristics was 0.37, among which the length of palisade cells had the maximum value (0.67) and the size of stoma had the minimum one (0.11). The light saturation point (LSP), light compensation point (LCP), and the maximum photosynthetic rate under saturation light intensity (Pmax) were markedly elevated. Higher were also the values of a number of indicators, including the dark respiration rate (Rd), CO2 compensation point (Ccp), light respiration rate (Rp), and initial carboxylation efficiency (CE). These results indicated thatParthenocissus himalayana have a remarkable light adaptability in heterogeneous habitats in terms of leaf anatomical structure and photosynthetic characteristics.