Juan Li

As an important source of medicine, food, and high-quality wood, Choerospondias axillaris has been widely planted in South China. However, few studies of its growth traits and rhythm and concerning the selection of superior provenances/families were developed. In this study, 77 families from five provenances were studied and grouped. Tree height, diameter at breast height (DBH), and crown width within and between rows were measured. The relevance between growth traits and environmental factors was also analyzed. The results showed the height, DBH, and crown width within and between rows were divided into slow, mean, and fast growth periods, which was significantly related with sunshine hours in earlier months. Next, monthly rainfall showed an extremely positive correlation with the increase in tree height, DBH, and plant volume. Then, the monthly volume increment had a significantly positive correlation with five meteorological factors, excluding sunshine hours with increasing months, while the monthly growth of tree height and crown width within and between rows was significantly negatively correlated with sunshine hours. Based on these results, the superior families No. 15, 76, and 56, which originated from the Raoping provenance, were selected for their fast growth and available adaptation. These results provided the reliable growth rhythm of a young C. axillaris stand, which established a basis for fertilizing and forest tending. During these processes, meteorological factors, especially humidity and sunshine duration, had important effects on growth, implying that the external climate should be paid more attention to promote fast growth and prevent diseases and insect pests. Moreover, selecting superior families was helpful to further breeding and plantation.

Flowering is an important link in the life process of angiosperms, and it is also an important sign of the transformation of plants from vegetative to reproductive growth. Although the flowering regulation network of Arabidopsis is well-understood, there has been little research on the molecular mechanisms of perennial woody plant flower development regulation. Populus tomentosa is a unique Chinese poplar species with fast growth, strong ecological adaptability, and a long lifecycle. However, it has a long juvenile phase, which seriously affects its breeding process. Nuclear factor-Y (NF-Y) is an important type of transcription factor involved in the regulation of plant flowering. However, there are few reports on PtoNF-Y gene flowering regulation, and the members of the PtNF-YC subfamily are unknown. In this study, four key genes were cloned and analyzed for sequence characteristics, gene structure, genetic evolution, expression patterns, and subcellular localization. The plant expression vector was further constructed, and transgenic Arabidopsis and P. tomentosa plants were obtained through genetic transformation and a series of molecular tests. The flowering time and other growth characteristics were analyzed. Finally, the expression level of flowering genes was detected by quantitative PCR, the interaction between PtoNF-YC and PtoCOL proteins was measured using the yeast two-hybrid system to further explain the flowering regulation mechanism, and the molecular mechanisms by which PtNF-YC6 and PtNF-YC8 regulate poplar flowering were discussed. These results lay the foundation for elucidating the molecular regulation mechanism of PtoNF-YC in flowering and furthering the molecular design and breeding of poplar, while providing a reference for other flowering woody plants.