By cloning the BpbZIP36 gene, constructing a plant expression vector, and obtaining stable transgenic birch plants, this study aimed to investigate the drought resistance function of the BpbZIP36 gene.

Using birch as the experimental material, the BpbZIP36 gene was cloned from birch cDNA as the template. Bioinformatics analysis was performed on the gene, and the pROK2-BpbZIP36 plant expression vector was constructed and introduced into birch seedlings to obtain transgenic birch overexpressing BpbZIP36. The transgenic birch plants and wild-type were subjected to drought stress to study the drought resistance function of the BpbZIP36 gene.

A bZIP gene was obtained from the birch genome database, with an open reading frame (ORF) of 1 269 bp encoding 422 amino acids. The results of multiple sequence alignment showed that the BpbZIP36 protein was similar to the bZIP protein of other plants and a conserved bZIP structural domain. qRT-PCR results showed that the BpbZIP36 gene was expressed in roots, stems, and leaves. In stems and leaves, the expression level of BpbZIP36 peaked at 72 h, while in roots, the highest expression was observed at 24 h of stress treatment, indicating that the BpbZIP36 gene could be induced by drought stress. Physiological index and histochemical staining analyses revealed that under drought stress, the transgenic birch overexpressing BpbZIP36 exhibited lower MDA, H₂O₂ content, and relative electrical conductivity compared to wild-type plants, indicating better cell membrane integrity. The SOD, POD and CAT activities, as well as relative water content, were higher in the transgenic birch. DAB staining showed the lightest coloration in the three overexpression lines, suggesting lower H₂O₂ accumulation and reduced cellular damage. These results demonstrated that the drought resistance capacity of the transgenic birch overexpressing BpbZIP36 was stronger than that of wild-type.

Overexpression of the BpbZIP36 gene enhances the drought resistance capability of transgenic birch.

The phenotypic traits of different provenances of Tilia amurensis were analyzed to reveal the pattern of variation and genetic diversity.

126 excellent individual plants were collected from ten provenances of Heilongjiang, Jilin and Liaoning Province. Fourteen phenotypic traits were determined and analyzed by multiple comparisons, correlation analysis, nested analysis of variance, correlation analysis, principal component analysis and (PCA) and cluster analysis.

The results showed that the variation coefficient of 14 phenotypic traits from 10 provenances ranged from 6.68% to 43.73%. The genetic diversity index (H′) ranged from 1.71 to 2.03. The variation within provenances (76.86%) was higher than that among provenances (23.14%). The results of correlation analysis showed that there was a high degree of correlation among leave traits and flower traits. Principal component analysis showed that the cumulative contribution rate of the first five principal components reached 94.10%. The first principal component mainly reflected the indexes of leaves. The second principal component mainly reflected the index of bract. The third principal component mainly reflected the branch growth and vein index. The fourth and fifth principal component reflected the leaf shape and pedicel index. According to the comprehensive evaluation model, the comprehensive ranking of the ten provenances from high to low was Chaihe, Lushuihe, Dongfanghong, Kuandian, Yichun, Jiaohe, Jian, Raohe and Huma. The 10 provenances of T. amurensis were divided into three categories by cluster analysis.

The variation within provenances of T. amurensis was relatively high and was dominant. The results provided theoretical basis for the conservation and development of T. amurensis germplasm resources.