Relationships Between Leaf Area,leaf Shape And Leaf Vein Traits Of Nine Magnoliaceae Species

As an essential organ of plants for photosynthesis,transpiration and maintenance of its own heat balance,leaf needs to perform multiple functions at the same time.However,some functions can conflict with each other,rendering it necessary for plants to make trade-offs among different functions.The trade-off between function and support structures of leaves is the main determinant of leaf physiological activity,so studying the relationships among leaf area,leaf shape and vein structure can provide insight into trade-offs of biomass investment and reveal the adaptation strategies of plants to the external environment.Magnoliaceae is one of the ancient plant groups which differentiated earlier.Modern Magnoliaceae plants still retain many of the original properties,with high scientific value,but also aromatic,medicinal,timber and other economic benefits and greening,beautifying,optimizing the environment and other ecological benefits of plant resources.In this study,the relationships among leaf area,leaf shape and leaf vein traits of nine Magnoliaceae species growing in Nanjing were analyzed to explore the trade-off strategies of leaf biomass allocation.Firstly,the intact leaf vein was obtained by chemical methods,and the leaf vein images were scanned.Then the leaf vein images were processed by Photoshop,Matlab,R and LEAF GUI to obtain the data of leaf traits,and the fractal dimension(FD)of leaf shape was calculated by the box-counting method.Finally,the relationships between FD and leaf width/length(W/L)of the nine species were analyzed;the validity of Montgomery equation,assuming a proportional relationship between leaf area and the product of leaf length and width,was tested;the influence of leaf shape on the relationship between leaf area and midrib length was analyzed;the power function was used to fit the relationships between leaf area and different leaf vein traits,and between reticulate structure and different leaf vein traits.The main results were listed as follows:(1)The leaves of the nine Magnoliaceae species were basically bilaterally symmetrical,and there was a significant positive correlation between FD and W/L,which indicates that the wider the leaf,the greater the FD value.(2)Leaf area was proportional to the product of leaf length and width for each of the nine Magnoliaceae species,and the estimates of the Montgomery parameter(i.e.,the proportionality coefficient of the Montgomery equation)ranges from 0.50 to ?/4.The scaling relationships between midrib length and leaf area were confirmed for the nine Magnoliaceae species.Except Michelia maudiae,the 95% confidence intervals of the scaling exponents between midrib length and leaf area for the remaining eight species include 0.50(8/9).There was a significant positive correlation(P < 0.01)between the coefficient of variation in W/L and the root-square-square error of the linear fit to leaf area vs.leaf length for the nine Magnoliaceae species.(3)The scaling relationship between midrib density mass and leaf area was confirmed for each of the nine Magnoliaceae species.There was a scaling relationships between total areole area and leaf area(5/9),but the scaling relationship between total leaf vein area and leaf area(7/9),and between total vein length and leaf area(8/9)does not hold true for most Magnoliaceae species.Overall,there was no significant correlation between total leaf vein density and leaf area,or only a few species have a weak correlation between total leaf vein density and leaf area.(4)There was a scaling relationship between midrib length and total areole area for each of the nine Magnoliaceae species.The scaling relationships between total leaf vein length and total areole area was confirmed for most Magnoliaceae species(5/9).The relationships between mean areole area and areole density,mean areole area and total leaf vein density for nine Magnoliaceae species were demonstrated to be a power function with a negative exponent.In summary,most Magnoliaceae plants choose to invest more biomass to the construction of vein structure,which is an adapting performance of Magnoliaceae for maximizing their own gains in increasing leaf area via the optimization of the allocation of resources between different functions.The relationships among leaf area,leaf shape and leaf vein traits reflected the trade-offs between function and support structure of leaves,providing a new basis for the strategies of biomass allocation in leaves of Magnoliaceae,and further revealing the adaptation strategies to the external environment.