秦王川湿地滨藜叶脉性状与蒸腾速率关系对种群密度的响应

植物蒸腾速率与叶性状关系的环境响应,对探索植物碳水代谢关系和叶性状构建模式之间耦合的生理生态学机制具有重要的意义。选择甘肃省秦王川国家湿地公园的盐沼湿地为实验地,按研究区域滨藜(Atriplex patens)植株密度设置Ⅰ(16—21株/m~2)、Ⅱ(9—15株/m~2)、Ⅲ(9株/m~2)3个梯度,采用标准化主轴估计(standardized major axis estimation,SMA)方法,以叶脉密度和中脉直径分别表示叶脉性状,研究了种群密度影响下滨藜蒸腾速率与叶脉性状的关系。结果表明:随种群密度减小,滨藜的中脉直径、株高、盖度、光合有效辐射(PAR)、叶面积(LA)均逐渐降低,而叶脉密度、叶干重、蒸腾速率(T_r)和净光合速率(P_n)逐渐增加。在高密度(Ⅰ)和低密度(Ⅲ)中,滨藜的蒸腾速率和叶脉密度之间存在极显著正相关关系(P0.01),与中脉直径之间存在显著的负相关关系(P0.05);在中密度(Ⅱ)中,滨藜的蒸腾速率与叶脉密度呈显著正相关关系(P0.05),与中脉直径不存在相关关系(P0.05)。在小密度样地,蒸腾速率(T_r)较小,滨藜采取减小叶脉密度、增大中脉直径的策略,即在阴生环境中滨藜叶片需要大的中脉直径来支撑,同时较小的叶脉密度亦可满足其蒸腾需求,体现了密度制约下湿地植物的生物量分配格局和资源利用对策。     

Empirical relationship between specific leaf area and thermal dissipation of Phragmites australis in salt marshes of Qinwangchuan

Aims The correlation between specific leaf area (SLA) and thermal dissipation reflects not only the accumulation and dissipation of plant photosynthesis, but also plants’ adaptation to their habitats and changing environment. The objective of this study is to examine the correlation between SLA and thermal dissipation of reed (Phragmites australis) under different soil moisture conditions and salt contents.Methods Our study site was located in the National Wetland Park in Qinwangchuan, Gansu Province, China. Our sampling site extends from the edge to the central of a salt marsh where the reed was the single dominant species. The study site was divided into three zones based on the distance from the water. Within each zone, six 2 m × 2 m sampling plots were randomly located to select six reed individuals in each plot (total = 18). Vegetation height, aboveground biomass, soil moisture, and soil electrical conductivity (EC) were measured, with the six reed individuals taken to the laboratory to measure leaf thickness. Leaf net photosynthetic rate (P_n), transpiration rate (T_r), and other parameters of the reeds were also measured in each plot prior to harvesting. Quantitative measures of chlorophyll fluorescence were taken after 30-min dark adaptation. Quadrat survey method was used to model the empirical relationship between the transpiration rate and leaf characteristics.Important findings Vegetation height and aboveground biomass increased with soil moisture content, but EC and photosynthetically active radiation decreased. Leaf area, T_r and P_n increased along the gradient, leaf thickness showed decreasing, but the increasing trend of SLA switched to a decreasing trend, while leaf dry mass presented an opposite trend. From plot I to III, the quantum yield of regulated energy dissipation (Y(NPQ)) and non-photochemical quenching decreased, the actual photochemical efficiency of PSII and photochemical quenching increased, and quantum yield of non-regulated energy dissipation increased before decreasing. There appeared a highly significant negative correlation (p < 0.01) between SLA and Y(NPQ) at plot I and III, and a less significant negative correlation (p < 0.05) at plot II. Along the soil moisture gradient, reed seemed using light effectively by changing leaf thermal dissipation through adjusting their leaf size and SLA—A potential self-protection mechanism in light of adapting the habitat.     

秦王川盐沼湿地芦苇叶片比叶面积与光合效率的关联分析

植物比叶面积(SLA)与光合效率的关联性分析,有助于理解植物叶片的光合产物分配与能量分配之间的权衡机制。该研究以秦王川国家湿地公园芦苇(Phragmites australis)种群为研究对象,沿芦苇群落末端至水域边缘分别依次设置:(I:土壤电导率(EC) 2.3—2.8 ms/cm)、(II:1.8—2.2 ms/cm)、(III:0.8—1.5 ms/cm) 3个试验样地,研究了秦王川盐沼湿地不同土壤盐分条件下芦苇叶片SLA与光合效率的关系。结果表明:随着土壤盐分含量的降低,湿地群落的高度、地上生物量逐渐增大,密度、光合有效辐射(PAR)呈逐渐减小的趋势;叶面积、株高、净光合速率(P_n)、水分利用效率(WUE)和蒸腾速率(T_r)均呈逐渐增大的趋势,叶厚度逐渐减小,比叶面积呈先增加后减少的变化趋势,叶干重的变化趋势与比叶面积完全相反;芦苇叶片实际光合效率(Y(II))、光化学淬灭系数(Q_P)和电子传递速率(ETR)呈先减少后增大的变化趋势,非光化学猝灭系数(NPQ)、调节性能量耗散的量子产额(Y(NPQ))和最大光化学效率(F_v/F_m)呈先增加后减少的变化趋势,非调节性能量耗散的量子产量(Y(NO))呈逐渐增大的变化趋势。在3个样地中,芦苇SLA与Y(II)和ETR之间均呈极显著负相关关系(P0.01),SMA斜率的绝对值均呈先增大后减少的变化趋势。随土壤含盐量的梯度性变化,芦苇种群适时调整叶片构件模式以改变叶片电子传递速率和实际光化学效率,实现植物光合效率的最大化,反映了盐沼湿地植物的特殊生存策略和叶片构件模式。     

秦王川湿地不同密度柽柳枝-叶性状及其光合特性

枝、叶是植物的两个重要功能器官,密度制约下其异速生长关系不仅是植物个体发育过程的表现,也是植物与环境互相作用的结果。柽柳是干旱区湿地的主要植物之一,密度制约下其小枝与叶的异速生长关系对于理解干旱区湿地环境下植物的资源利用策略具有重要意义。在兰州市秦王川干旱区湿地,将柽柳(Tamarix gansuensis H.Z.Zhang)种群分为Ⅰ(0.1—0.35棵/m~2)、Ⅱ(0.35—0.6棵/m~2)和Ⅲ(0.6—0.85棵/m~2)3个密度梯度,应用标准化主轴估计(standardized major axis estimation,SMA)法,研究了不同密度下,柽柳当年生小枝长度与叶面积、叶数量的生长关系及叶片光合特性。结果表明:随着柽柳种群密度的增加,群落土壤含水量逐渐增加,土壤容重、pH值和电导率逐渐减小;柽柳平均高度、郁闭度、枝长度和叶面积呈逐渐增大趋势,冠幅、基径、分枝角度、叶数量和光合有效辐射呈逐渐减小趋势;叶面积指数、净光合速率、蒸腾速率和气孔导度先增加后减小。枝长度与叶面积、叶数量在不同的密度梯度下显著正相关(异速斜率k0,P0.05),随着密度梯度的增加,枝长度与叶面积的回归斜率逐渐减小(异速斜率0.65≤k≤0.98,P0.05),枝长度和叶数量回归斜率不变(异速斜率k=0.9,P0.01),截距沿着y轴显著的正向移动(截距0.25—1.93)。随着种群密度的增加,柽柳由较小枝长度、叶面积和较大分枝角度、叶数量的枝叶构建模式,发展为较大枝长度、叶面积和较小分枝角度和叶数量的垂直空间拓展模式并提高气孔导度、光合速率和蒸腾速率、降低水分利用效率,反映了该物种在干旱区湿地环境中、密度制约条件下的表型可塑适应机制和资源利用策略。