Genetic variation of needle morphology and anatomical traits and physiological traits among Pinus tabuliformis geographic populations

Objective Needles are the important organs of physiological activities in pine species, but the relationship between morphological and anatomical characteristics and physiological traits of diffenent geographical populations are still unclarified. Thus, assessing the association between the two kinds of traits could provide a new perspective for understanding the adaptive variation of Pinus tabuliformis.

Method Based on the common garden test of 8 geographic populations which collected in different habitats from the whole distribution area of Pinus tabuliformis, we assessed the variation of morphological and anatomical traits, transpiration and photosynthetic physiological traits of secondary needles of 4-year-old seedlings, and evaluated the correlation between traits.

Result (1) Significant genetic variations were found among geographical populations in needle thickness, vascular bundle, stomatal and resin canal traits; (2) significant genetic diversity of physiological traits was found among geographical populations, except for water use efficiency; (3) the net photosynthetic rate, transpiration rate and intercellular CO₂ concentration were positively correlated with morphological and anatomical traits; (4) the intercellular CO₂ concentration of populations was significantly positively correlated with the annual precipitation and the average temperature of January/ annual precipitation, the stomatal limitation value was significantly negatively correlated with annual precipitation and average temperature of January/annual precipitation; (5) the number of stomatal lines was significantly positively correlated with longitude, while resin canal number was significantly negatively correlated with the longitude but was significantly positively correlated with the altitude. Resin canal area/mesophyll area was significantly negatively correlated with longitude and latitude.

Conclusion Variation of needle traits could reflect the photosynthetic physiological diversity among geographical populations. The number of needle stomata and regulation capacity of stomata would increase with the decreased precipitation, and the change of the number of resin canal mesophyll area. This study provided a theoretical reference for understanding the relationship between the anatomical and anatomical characteristics of the needles and photosynthetic physiological traits, and adaptive evolution of the pine species and genetic improvement.