红海榄木材结构的生态解剖

Ecological wood anatomy of Rhizophora stylosa

红树林是海岸重要生态关键区,在维护生物多样性和沿海地区生态安全等方面发挥着重要作用。红海榄(Rhizophora stylosa)是我国红树林生态系统的建群种之一。为了揭示红海榄次生木质部解剖特征可塑性的生态适应意义,该文测定了海南省东寨港红树林自然保护区6个红海榄种群18个采样点的土壤理化性质,应用显微镜和电镜详细观测了各采样点生长的18株红海榄植株次生木质部的形态解剖特征,并测量了红海榄次生木质部的数量解剖特征。不同样地的红海榄次生木质部都具有纤维状导管和环管管胞、螺旋雕纹和附物、生长轮、薄壁细胞(含淀粉粒)等结构。这些特化结构具有生态适应意义,在潮间带高盐生境中能促进水分输导的安全性。不同生境中红海榄次生木质部数量解剖特征可塑性大,利用逐步回归分析方法分析了土壤理化因子与红海榄次生木质部数量特征的关系。结果表明:土壤全盐含量、土壤Mn2+含量、土壤Na+含量、土壤Cl–含量、土壤Ca2+含量、土壤有机质含量、土壤全磷含量和土壤p H值对次生木质部数量特征的影响达到极显著水平,不同样地红海榄次生木质部数量特征的变化是红海榄适应异质生境的结果。

Aims Mangrove forest is desirable for studying variations in wood structure along an ecological gradient because mangroves are subjected to considerable habitat changes apart from salt stress within a small area.To elucidate the adaptive capability of wood structures towards fluctuating environmental conditions,variations in wood structures were investigated in 18 individuals of Rhizophora stylosa representing 6 populations along a natural soil physicochemical gradient in the National Nature Reserve of Dongzhai Harbor,Hainan Province.Methods Soil physicochemical properties were determined at the sites of 18 sampling trees in six R.stylosa populations.The anatomical characteristics of the secondary xylem were studied in details in the 18 trees by means of light microscopy,laser scanning confocal microscopy,scanning electron microscopy and transmission electron microscopy.Variations in the quantitative wood anatomical features in R.stylosa were assessed in details.Relationships between soil physicochemical variables and the quantitative wood anatomical features were analyzed by means of statistical methods.Important findings Some common specialized wood structures were observed in R.stylosa growing in different habitats,suggesting that these features may function for safely conducting water under high negative pressure and are thus adaptive to intertidal habitats.These common features include the occurrence of：1） some fibriform vessel elements and a few vasicentric tracheids;2） vesturing in pits of vessels and helical structures on vessel walls;3） growth rings;4） starch grains in ray cells and septate fibers.The quantitative anatomical characteristics have great plasticity in response to heterogeneous habitats.Stepwise regression analyses revealed that the total salt,contents of Mn2＋,Na＋,Cl–,Ca2＋,organic matters,and total phosphorus of soils,and soil p H all have significant effects onquantitative wood anatomical features.Variations in the quantitative wood anatomical features in R.stylosa growing at different sites are adaptive to fluctuating environmental conditions in the intertidal areas.