Variation Patterns Analysis Of Leaf Morphological And Anatomical Traits In Two Sympatric Pine Species

Phenotypic plasticity in plants is a universal natural phenomenon,which is the basis for plant adaptation to different environments.The pattern of intraspecific variation in the morphological and anatomical traits of pine needles in southern China and their potential adaptive significance have not been systematically investigated so far.To investigate the patterns of intra-and interspecific variation in needle morphology,anatomical,and sclerophyllous traits of Pinus massoniana and Pinus hwangshanensis and their associations with the environment,this paper investigated natural forests of P.massoniana and P.hwangshanensis in five mountains（Mt.Sanqingshan,Mt.Lushan,Mt.Jinggangshan,Mt.Huangshan,and Mt.Tianmushan）in eastern China.The author measured 6 needle morphological indices,11 needle anatomical indices and two sclerophyllous indices,and used one-way ANOVA,nested analysis,correlation analysis and cluster analysis to investigate the variation patterns of the two pines’needles and their response mechanisms to the environment.The main findings and conclusions are as follows.1.The 6 needle morphological traits of P.massoniana and P.hwangshanensis were highly significantly different between the populations and had extensive variation.The mean values of the coefficient of variation for the 6 needle morphological traits between the two pine populations were 16.13%and 20.58%,respectively.P.massoniana needles had an average leaf length of 13.67 cm（8.40～20.50 cm）,an average specific leaf area of 151.814cm²/g（70.655～424.719 cm²/g）,and an average leaf dry matter content of 0.454 g/g（0.185～0.965 g/g）,while P.hwangshanensis needles had an average leaf length of 9.79 cm（5.62～15.78 cm）,mean specific leaf area 126.267 cm²/g（45.891～247.578 cm²/g）,mean leaf dry matter content 0.362 g/g（0.012～0.956 g/g）.With the exception of leaf length and leaf width,all needle morphological variables showed larger intraspecific variance than interspecific variation.In both pine species,intra-population variation was the primary source of variation because the phenotypic differentiation coefficients(P_ST)between the species were smaller than those inter-populations.Cluster analysis was able to broadly separate the two species based on morphological traits.Redundancy analysis showed that longitude had the greatest influence on the distribution of needle morphological traits in P.massoniana（11.04%explained）and latitude had the greatest influence on the distribution of needle traits in P.hwangshanensis（19.05%explained）,indicating that different environmental factors had different degrees of influence on needle leaf morphological traits in the two pines.2.There was significant variation in the 11 needle anatomical characteristics of P.massoniana and P.hwangshanensis between populations.The mean values of the coefficient of variation for the 11 needle anatomical traits between the two pine populations were 21.95%and 19.47%,respectively.The average number of resin tracts in P.massoniana needles was6.460（3.000～12.000）and the average total resin duct area was 0.015 cm²（0.004～0.035cm²）,while the average number of resin ducts in P.hwangshanensis was 4.585（2.000～8.000）and the average total resin duct area was 0.012 cm²（0.004～0.028 cm²）.The predominant source of variation in anatomical features in both pines was intra-population variation,according to nested analysis and phenotypic differentiation coefficients.The position of resin ducts in P.massoniana needles was exclusively marginal,whereas P.hwangshanensis needles were more varied and could be used with some reliable as a classification of the two pines.Cluster analysis was able to roughly separate the two species based on anatomical traits.Among the environmental factors,the anatomical traits of P.massoniana and P.hwangshanensis were more influenced by latitude,longitude and annual precipitation.3.The average crude protein content of the needles of P.massoniana and P.hwangshanensis was 9.97%（6.92%～12.35%）and 10.03%（7.36%～13.78%）,the average neutral detergent fibre content was 48.34%（40.71%～63.42%）and 48.20%（39.63%～54.73%）,and the average sclerotia index was 4.892 g/g（3.423～8.085 g/g）and 4.902 g/g（2.876～6.547 g/g）,respectively.4.892 g/g（3.423～8.085 g/g）and 4.902 g/g（2.876～6.547g/g）respectively.The lower levels of crude protein content and higher levels of crude protein content in both pines were not conducive to animal feeding and digestion,and that both levels of variation were lower than morphological and anatomical traits.P.massoniana had sclerophylly levels that were fairly low when compared to other sclerophylly speciesand lower than those of P.hwangshanensis.There was covariation between the traits related to sclerophyllous traits in the two pine species and they had their own adaptive significance.At the same time,sclerophyllous traits were strongly influenced by altitude and latitude.A common feature for adaptation to drought,soil nutrient deficiency,and tolerance to pests and diseases was needle sclerophylly.The intra-and interspecific variation patterns of morphological and anatomical features in the needles of P.massoniana and P.hwangshanensis from the same range in eastern China were carefully investigated,revealing the variation patterns of both species.Furthermore,for the first time in China,the sclerophyllous trait（SI）was assessed,and its adaptive importance was discussed.We could provide a theoretical reference for the genetic improvement and production of both pine species,which have high economic benefits,based on the findings of this study.The current study is insufficient for determining needle and leaf features,and future research should incorporate photosynthesis,hydropower,and wood to better understand the adaptation methods of P.massoniana and P.hwangshanensis to diverse habitats.