Seedling Stage Traits Of Pinus Tabuliformis×Pinus Yunnanensis In The High Altitude Habitat

Genetic analyses indicate that P. densata is a natural homoploid hybrid originating from P. tabuliformis and P. yunnanensis. Seedling growth and adaptation traits in seedling stage are essential for the study of seedling adaption. Needle morphological and anatomical features show relative species stability and can be used to identify coniferous species. Comparative analyses of these seedling traits and needle characteristics and phenotypic differences between the artificial hybrids, P. densata, and parental species can be used to determine the genetic and phenotypic evolutionary consequences of natural hybridization. Twelve artificial hybrid families, the two parental species, and P. densata were seeded in a high-altitude habitat in Linzhi, Tibet. Analyzed19seedling growth and adaptive traits of artificial and parental species and P. densata. The needles of artificial hybrids and the three pine species were collected, and24needle morphological and anatomical traits were analyzed. The test results showed that:(1) Needle traits of the artificial hybrids showed different degrees of variation among hybrid families, with relevant large variation existed in resin canals traits between hybrid families; and variance analysis for hybrid families and individuals within hybrid families showed that large variation existed in hybrid families between individuals and within the individual the needle traits were more stable.(2)22traits among species and artificial hybrids were significantly different.13artificial hybrid needle traits were significantly different with P. yunnanensis,5artificial hybrid needle traits were significantly different with P. densata, only needle length and needle cross-sectional area were significantly different between artificial hybrid and P. tabuliformis. The proportion of three needles in a cluster of artificial hybrids is22.92%, and artificial hybrids had very similar needle characteristics with P. tabuliformis and P. densata. (3) Due to the influence of how many needles in bunches, we summed eight relative traits:needle length, the mean number of stomata in sections2mm in length of the convex and flat sides of the needle, mean stomatal density, mesophyll/vascular bundle area ratio, mesophyll/resin canal area ratio, mesophyll/(resin canals and vascular bundles area ratio, vascular bundle/resin canal area ratio, which were similar to the artificial hybrids and P. densata.(4) Seedling traits of hybrid families have a greater degree of variability, instability between hybrid families showing its growth potential difference at high altitude habitats in Tibet, the best-performing hybrid families on the adaptability and growth indicators exceeded P. densata. The second and third year seedlings of artificial hybrids and P. denata existed secondary growth phenomenon, very little P. tabuliformis seedlings appeared secondary growth phenomenon in the third year. Artificial hybrids in the adaption traits are below the P. tabuliformis and exceeded the adaptability of P. yunnanensis, and similar with P. densata; in the growth indicators, artificial hybrids are better than P. tabuliformis, and similar to P. densata and P. yunnanensis.(5) The correlation analysis between the indices indicate that, in addition to the seven traits related to stomata and four needle sectional ratio traits, other needle traits are all positively significant; in the seedling indices, only seedling height, diameter, branch length, stem cell with minority (<8) needle traits are significantly (P<0.05) or highly (P<0.01) significant correlated.