The Relationship Between Leaf Vein Structure And Lamina Size Of Subtropical Broad-Leaved Woody Plants

Leaf is the main organ for photosynthesis,transpiration and respiration.The change of its characters directly reflects the size of plant productivity and the adaptability to the living environment,and also determines the competitiveness of plants.Lamina size is one of important factors affecting the light acquisition efficiency and the carbon acquisition ability of plants.The ecological process determined by lamina size has been paid much attention in recent years.At present,the academic studies on the optimization of lamina size mainly focus on the environment in which plants live and the biomass distribution of plant.Few studies about the variability of lamina size were focusing on the resource allocation within the lamina.The leaf vein is an important channel for the transport of water and nutrients in leaves and has the functions of lamina support and defense.The relationship between the leaf vein architecture and lamina size was studied mainly from the relationship between leaf vein density and lamina size,or the environments that affect this relationship.The article study from the perspective of the comprehensive study about the effects of leaf vein architecture and their internal resource allocation on lamina size,and compare among the different leaf vein sequences species and different life form species.In the current study,42 broad-leaved woody plants within the similar environment were investigated in Tiantong National Forest Park,the relationships between lamina size and leaf vein architecture and the their construction costs were analyzed by standard major estimation(SMA)method.In addition,the traits of lamina size and the growth strategies of vein architecture were compared among different vein sequences(polytopic vein sequence,pinnate arch vein sequence,pinnate straight vein sequence,palmately vein sequence)and different life form(evergreen,deciduous)species.The study results are expected to provide insights into the understanding of the variability of lamina size.The results are shown in the following:(1)The allometric growth relationship of lamina area and leaf mass per area,leaf tissue density,leaf length/width,1° vein density,2° vein density,and each grade of major vein lenghth/minor vein length showed significantly with slopes significantly less than-1.A negative isokinetic growth relationship showed between leaf area and thickness/ lamina area,3° vein density and density of branch point of vein.Leaf tissue density and 1° vein density,2° vein density,3° vein density,density of branch point of vein,lamina length/width and 3° vein/minor leaf vein length showed significantly with slopes significantly less than 1.There was no significant correlation between lamina area and vein density.A isokinetic growth relationship showed between leaf length/width and 1°/minor vein length and 2°/minor vein length.The allometric growth relationship between thickness/leaf area and the length of major vein/minor vein was significantly with slopes significantly greater than 1.These results suggest that lamina size-related characters and leaf vein length,leaf vein density,leaf vein ratios,vein characteristics restricted and supported each other.(2)The allometric growth relationship between lamina area and dry weight of xylem cell wall(DWC)of 1° vein and 2° vein per unit area showed significantly with slopes significantly less than-1.Lamina area and DWC of 3° vein per unit area was not significantly correlated.Lamina area and DWC of petiole,leaf mass per area and DWC of total vein per unit area showed significant allometric relationship with slopes significantly less than 1.It indicated that lamina size was closely related to the distribution of dry weight of xylem cell wall in veins.(3)There was no significant difference in lamina area,lamina thickness,lamina length and leaf tissue density among the four groups of vein sequences.The leaf factor shape of the polytopic vein sequence was the largest.The leaf mass per area,thickness/ lamina area of pinnate vein sequence(straight vein sequence,pinnately camptodrome vein sequence)were significantly larger than those of palmately vein sequence.The petiole length of palmately vein sequence was larger than that of pinnate vein sequence.There was no significant difference in the major vein density between the four groups of vein sequences.The minor vein density of pinnate straight vein sequence was significantly larger than that of the pinnately camptodrome vein sequence.The pinnately straight vein sequence of DWC per unit of 2o vein?3o vein and total vein was larger than those of the palmately vein sequence,but the DWC per unit of 1o vein was smaller.These results suggest that species with different leaf shapes and vein sequences adopted the different leaf vein construction and carbon allocation,but can obtain the same carbon capture potential and lamina support ability.(4)The deciduous species have larger lamina area,leaf circumference,lamina length,lamina width,petiole length,and smaller leaf mass,lamina thickness,each grade of major vein lenghth/minor vein length,(1o+2o veins)DWC per unit than the evergreen species.There was no significant difference between the total vein density and minor vein density of the deciduous species and the evergreen species.It can be inferred from the above results that evergreen species choose a conservative growth strategy with higher major vein density and higher consumption and lower acquisition,while deciduous species adopt a positive growth strategy with increased minor vein ratios and low consumption and high absorption.In a word,leaf vein structure and it's dry weight of xylem cell wall have different effects on leaf characters like lamina size,leaf mass per area,leaf tissue density and lamina thickness.In lamina of different size,the density of leaf veins,the proportion of leaf veins resource and the dry weight of xylem cell wall all use different combinations to optimize the lamina size perfect.The species with different venation and different life forms also adopted different growth strategies to form their own optimal growth patterns.